la-13278-pr progress report 1 l aboratory- 9 directed ... · and nitride thin films 18 texture...

LA-13278-PRProgress Report

1 L ABORATORY-9 DIRECTED

EVELOPMENT°$

Los AlamosN A T I O N A L L A B O R A T O R Y

Los Alamos Laboratory is operatedStates Department of Energy unde

the Univeontract W-

ABSTRACT

This report summarizes the FY 1996 goals and accomplishments ofLaboratory-Directed Research and Development (LDRD) projects. Itgives an overview of the LDRD program, summarizes work done onindividual research projects, and provides an index to the projects' princi-pal investigators. Projects are grouped by their LDRD component: Indi-vidual Projects, Competency Development, and Program Development.Within each component, they are further divided into nine technicaldisciplines: (1) materials science, (2) engineering and base technologies,(3) plasmas, fluids, and particle beams, (4) chemistry, (5) mathematicsand computational sciences, (6) atomic and molecular physics, (7) geo-science, space science, and astrophysics, (8) nuclear and particle physics,and (9) biosciences.

FRONT COVER

The background graphic is anatomic force microscope image ofthe slip bonds on a stressed iron-silicon-boron magnetic ribbon(M. Haw ley, "Scanning ProbeMicroscopy Competency Develop-ment"). The superimposed upper-left image shows the trajectory ofa single deuterium-tritium fusionalpha particle through a magne-tized target plasma (R. Kirkpatrick,"Generation and Compression ofa Target Plasma for MagnetizedTarget Fusion"). To the right aretwo scattered-light images showingthe effect of a low-density plasmaon a high-intensity laser probe(J. Cobble, "High-Intensity MatterInteraction Physics"). The equa-tion describes the transport ofvorticity in turbulent fluid flow intwo-dimensional Cartesian space.

UC-900Issued: May 1997

1 L ABORATORY-9 D IRECTED9 R ESEARCH AND6 D EVELOPMENT

'••>•'-s€ ;*" ,>, '<i ' " •.

FY1996 PROGRESS REPORT

COMPILED BYJOHN VIGIL AND JUDY PRONO

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Government or any agency thereof.

MASTER

DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

Los AlamosLos Alamos, New Mexico 87545

Published by Los Alamos National Laboratory

Laboratory Director: Sig Hecker

Director for Science and Technology Base Programs: Al Sattelberger

Office Leader for Laboratory-Directed Research and Development: Ed Heighway

Scientific Editor: John Vigil

LDRD Office Team: Shelly Cross, Jo McCarthy, and Leonard Salazar

Managing Editor: Judy Prono (CIC-I)

Editors: Deborah Bacon, lleana Buican, Marty DeLanoy,Anne Garnett, Jennifer Graham, Sheila Molony,Kathleen Park, Amy Reeves,and James Russell (CIC-I)

Editorial Support: Eileen Patterson (CIC-I)

Cover Design:Susan Carlson (CIC-I)

Layout, Composition,and Production: Wendy Burditt (CIC-I)

Printing Coordination: CIC-I 7 Printing Team

The previous reports in this unclassified series are LA-12680-PR,LA-12880-PR, and LA-131 10-PR.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither TheRegents of the University of California, the United States Government nor any agency thereof, nor any of their employ-ees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, complete-ness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would notinfringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name,trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, orfavoring by The Regents of the University of California, the United States Government, or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of The Regents of the University ofCalifornia, the United States Government, or any agency thereof. Los Alamos National Laboratory strongly supportsacademic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse theviewpoint of a publication or guarantee its technical correctness.

iv Los Alamos FY1996 LDRD Progress Report

DISCLAIMER

Portions of this document may be illegiblein electronic image products. Images areproduced from the best available originaldocument*

LDRD Program Overview—FY 1996

Individual Projects

Contents

Materials Science

9 Origin of Radiation Damage in Potassium TitanylPhosphate

10 Development of a Fundamental Understanding ofChemical Bonding and Electronic Structure inSpinel Compounds

11 Phase Stability of Transition Metals and Alloys

12 Theoretical and Experimental Investigation on theLow-Temperature Properties of the NbCr2 LavesPhase

14 Nanostructured Materials: Growth and Patterning

Using Hyperthermal Materials Chemistry

14 Inorganic-Organic Composite Nanoengineered FilmsUsing Self-Assembled Monolayers for DirectedZeolite Film Growth

15 Rigid Molecular Foams

15 Materials Research for Optical Refrigeration

16 Innovative Composites through ReinforcementMorphology Design—A Bone-Shaped Short-FiberComposite

18 New Deposition Processes for the Growth of Oxide

and Nitride Thin Films

18 Texture Characterization for HE Design

19 Interfacial Charge Transport in Organic ElectronicMaterials: The Key to a New ElectronicsTechnology

19 Thermodynamic and Electrodynamic Studies of

Unusual Narrow-Gap Semiconductors

20 A Molecular Architectural Approach to Novel

Electrooptical Materials

21 Characterization and Manipulation of Broken-Symmetry Materials at Phase Boundaries

Engineering and Base Technologies

23 Development of New and Efficient Hard-RockMining Methods Using Pulsed-Laser Excavation

23 Virtual Reality and Telepresence Control of RobotsUsed in Hazardous Environments

24 Nuclear Magnetic Resonance Imaging with

Hyperpolarized Noble Gases

25 The Development of Fullerene-Based Hydrogen

Storage Systems

25 Optical Imaging through Turbid Media Using aDegenerate, Four-Wave, Mixing Correlation TimeGate

26 High-Average-Power, Intense Ion Beam forMaterials Modification and Other Applications

Contents

Individual Projects (cont.)Engineering and Base Technologies (cont.)

27 Multichip Module Technology Development

27 Magnetic Resonance Force Microscope

Development

28 Femtosecond Scanning Tunneling Microscope

29 Exploration of Technologies for Improving CivilSecurity

30 Fiber-Optic Communications Using Solitons

(FOCUS)

30 New Applications for Zeeman Interferometry

31 A Comprehensive Monitoring System for DamageIdentification and Location in Large Structural andMechanical Systems

31 Quantum Cryptography for Secure

Communications to Low-Earth-Orbit Satellites

32 Application of Intense Surface Discharge VUV

Light Sources to Photoresist Ashing in

Semiconductor Manufacturing

33 All-Solid-State Four-Color Laser

34 Material Processing for Self-Assembling MachineSystems

34 Diode Laser Development for Quantum

Computation

35 Designing a Micromechanical Transistor

35 High-Sensitivity, Solid-State Carbon MonoxideSensor Development

35 Acoustic Resonance Spectroscopy

36 Liquid-Metal, Focused-Ion-Beam EtchSensitization and Related Data TransmissionProcesses

36 Experimental Validation of Superconducting

Quantum Interference Device Sensors

Plasmas, Fluids, and Particle Beams

37 High-Power, High-Frequency, Annular-Beam Free-Electron Maser

38 Determination of Optical Field-IonizationDynamics in Plasmas through Direct Measurementof the Optical-Phase Change

39 Delta-f and Hydrodynamic Methods forSemiconductor Transport

40 A Compact Compton-Backscattering X-RaySource for Mammography and CoronaryAngiography

40 Equation of State of Dense Plasmas

41 Turbulence and Turbulence Spectra in ComplexFluid Flows

41 A Water-Filled, Radio-Frequency AcceleratingCavity

42 A Target Plasma Experiment for Magnetized TargetFusion

43 Developing Electron-Beam Bunching Technologyat Subpicosecond Pulse Lengths for ImprovingPhoton Sources

44 High-Intensity Laser-Matter Interaction Physics

vi Los Alamos FY1996 LDRD Progress Report

Individual Projects (cont.)Chemistry

45 New Fullerene-Based Mixed Materials: Synthesis

and Characterization

46 Uses of Novel Selenium-Containing ChiralDerivatizing Agents: Potential Catalysis for theChiral Oxidation of Simple Alkenes and Chiral-Promoted Aldol Reactions

47 Metal-Ligand "Multiple" Bonding: Revelations in

the Electronic Structure of Complexes of High-

Valent f-Elements

48 Chemistry and Catalysis in Supercritical Media

50 Decay of Surface Nanostructures Via Long-Time-

Scale Dynamics

51 Solvation and Ionic Transport in Polymer

Electrolyte Membranes

51 Heterogenization of Homogeneous Catalysts:The Effect of the Support

52 Photoredox Reactions: Energy Storage and

Halocarbon Degradation

52 Reactivity at Metal Centers Bound to Water-

Soluble Catalysts

53 Cyclodextrin-Based Chemical Microsensors for

Volatile Organic Compounds (VOCs)

54 Binding of Hydrocarbons and Other ExtremelyWeak Ligands to Transition-Metal Complexes thatCoordinate Hydrogen: Investigation of Cis-

Interactions and Delocalized Bonding InvolvingSigma Bonds

55 Asymmetric Catalysis in Organic Synthesis

56 Temperatures and Vibrational Frequencies ofLiquid N2/O2 and CO/O2 Mixtures Shock-Compressed to 10 GPa and 2000 K

57 Catalysts for Hydrocarbon Oxidation

57 Fundamental Studies of Polymer Filtration

58 Modification of Heterogeneous Chemistry byRealistic Substrate Complexity

59 Ionically Conducting Polymers for High-Energy-Density Batteries

59 Advanced Polymer Chemistry of Organometallic

Anions

60 Reaction Kinetics Relevant to the RecycleHydride-Dehydride Process for PlutoniumRecovery

60 Ultrafast Laser Studies of Solution Reactivity

Mathematics and Computational Sciences

61 Parallel Three-Dimensional Spherical-Harmonics 63Transport Methods

61 Adaptive, Composite, Overlapping Mesh 64Algorithms on Message-Passing Architectures

62 A Self-Consistent Multiscale Theory of Internal- 64Wave, Mean-Flow Interactions in the Ocean

62 Geometry in the Large and Hyperbolic Chaos 65

63 Industrial Processing of Complex Fluids: 65Formulation and Modeling

Dispersive Water Waves in One and TwoDimensions

Mimetic Difference Approximations of PartialDifferential Equations

Wavelet Transforms as Solutions of PartialDifferential Equations

Dispersive, Internal, Long-Wave Models

Solution-Adaptive Methods for Low-Speed andAll-Speed Flows

Contents VII

Individual Projects (cont.)Mathematics and Computational Sciences (cont.)

66 Combinatorics, Geometry, and Mathematical

Physics

66 The Fundamental Role of Solitons in Nonlinear

Partial Differential Equations

67 Elliptic Solvers for Adaptive Mesh Refinement

Grids

67 Studies of Structure of Turbulence by High-Resolution Simulation and Theory

68 Computational Three-Dimensional Inversion forSeismic Exploration

68 Super-Speed Computer Interfaces and Networks

69 Particles and Patterns in Cellular Automata

69 High-Quality Finite-Difference Schemes for PartialDifferential Equations and Discrete Vector andTensor Analysis

70 Modeling Mesoscopic Phenomena in ExtendedDynamical Systems

Atomic and Molecular Physics

71 State-to-State Photodetachment in the Two-

Electron Hydrogen Ion

71 Transient Quantum Mechanical Processes

72 Calculation of Satellite Line Structures in HighlyStripped Plasmas

73 Optical Wave Packets (Optical Bullets): A New,Diffraction-Free Form of Light Travel

74 Nonlinear Atom Optics

74 Dynamics of Quantum Wave Packets

Geoscience, Space Science, and Astrophysics

75 Low-Energy Neutral Atom Imager

76 Nonlinear Processes in Earthquakes

78 Lead Immobilization in Thermally Remediated

Soils and Igneous Rocks

78 Experimental Studies of Auroral-Arc Generators

79 Fundamentals of Laser Ablation in the Analysis ofGeological Materials

80 Integrating Chemistry into Three-DimensionalClimate Models: Detailed Kinetics in theTroposphere and Stratosphere of a Global ClimateModel

80 Using Microspheres as Tracers for Flow in

Geologic Media

81 Theoretical Research on Dwarf and ClassicalNovae

81 Micro/Macroscale Coupling in MagnetosphericPlasmas

82 Numerical Simulations of Convection Experiments

and Earth's Interior

83 High-Velocity Neutron Stars

83 Sedimentary Basin Response to Strong Motion in

Populous Regions

84 Heterogeneous Processing of Bromine Compoundsby Atmospheric Aerosols: Relation to the OzoneBudget

viii Los Alamos FYI996 LDRD Progress Report

Individual Projects (cont.)Geoscience, Space Science, and Astrophysics (cont.)

85 Coronal Mass Ejections in the Solar Wind

85 Modeling Core-Collapse Supernovae in Three

Dimensions

86 Deriving the Structure of Presupernovae and Delta

Scuti Stars Using Nonradial Oscillations

88 Magmatic Tritium

90 Minerals of Earth's Deep Interior

91 Striation-Image Monitoring of Plasmaspheric,L-Resolved Electrodynamics (SIMPLE)

91 Coupled Ocean-Atmosphere Model System forStudies of Interannual-to-Decadal ClimateVariability over the North Pacific Basin

92 Particle Acceleration from Reconnection in theGeomagnetic Tail

93 Fluxes of Water and Energy in Physically

Heterogeneous Environments

94 Hare Star Monitoring with a New Single-Photon-

Counting Imaging Detector

95 Close Encounters of Asteroids and Comets to

Planets

95 Isotopic Prediction of Eruption Volume at

Continental Volcanoes

96 Experimental Cosmology: The Early Universe

98 Cosmology with Massive Neutrinos

98 Global Climate Effects of the Emerging ChineseTransportation System

99 Regge Geometrodynamics in Support of GravityWave Astronomy

99 Remote Sensing of Thundercloud Electric-Field

Airglow

100 Accretion onto Black Holes: The Power-Generating Mechanism

102 Thermal Rocketing and the Laser Geodynamic

Satellite (LAGEOS-1)

102 Plasmasphere Refilling: New Numerical and

Observational Tools

Nuclear and Particle Physics

103 Time-Reversal Tests in Polarized Neutron Reactions

104 Exploring and Testing the Standard Model and Beyond

104 L3 Physics at the Z Resonance and a Search for theHiggs Particle

105 Neutrinos and Theory of Weak Interactions

106 Weak Interaction Measurements with OpticallyTrapped Radioactive Atoms

108 Neutrino Physics at Fermilab

108 A Continuous Watch of the Northern Sky above40 TeV with the CYGNUS Array

108 Neutron Measurements to Optimize Treatment ofCancer Patients with Fast Neutrons

109 Antiquark Distributions in the Proton

109 Nucleon-Nucleon Data Analysis

110 Solar Neutrino Physics

111 Chiral Symmetry in Finite Nuclei

111 Simulating the Decays of Bottom and Charm

Mesons

112 Nonequilibrium Dynamics of the Quark-GluonPlasma in Heavy-Ion Collisions

113 Determination and Study of Cosmic-RayComposition above 100 TeV

114 Nonperturbative Estimates of the Standard ModelParameters

Contents IX

Individual Projects (cont.)Biosciences

115 Biotechnology Approaches to Stable-Isotope

Labeling for Biomolecular Structure/Function

Studies

116 Preparation and Utilization of 13C- and 15N-LabeledDNAs for the Determination of Unusual DNAStructures Relevant to the Human Genome Projectby Nuclear Magnetic Resonance Spectroscopy

116 Applications of Strand-Specific In Situ

Hybridization

117 Computer Simulation of Protein Solvation,Hydrophobic Mapping, and the Oxygen Effect inRadiation Biology

117 Electromagnetic Inverse Applications forFunctional Brain Imaging

118 Gene Shuffling Using Flow Cytometry

118 Identification and Characterization of a HumanDNA Double-Strand Break Repair Complex

119 Determining the Role of the Telomere on theSeverity of Birth Defects

119 Development of an Ultrasensitive and Rapid DNA

Repair Assay

120 Structure and Thermodynamics of Surface

Recognition

120 Neutron Structural Biology

121 Sum-Frequency Generation Studies of MembraneTransport Phenomena

121 Engineering Sequence-Specific RNA and Single-

Stranded-DNA Binding Proteins

122 Theoretical Studies of Allosteric Changes andDNA Binding of a cAMP-Dependent TranscriptionActivation Protein

122 Engineering the Specificity of xylR: A Bacterial

Protein that Detects Chemicals in the Environment

123 Optimization and Monitoring of Hollow-FiberBioreactors

124 Optimal Screening Designs for BiomedicalTechnology

126 Nuclear Magnetic Resonance (NMR) Spectroscopyof Unusual DNA Structures and FunctionsAssociated with Human Disease

127 Emerging Pathogens: Dynamics, Mutation, and

Drug Resistance

127 Optical Measurement of Drug Concentrations in

Tissue

128 Stable-Isotope Labeling of Oligosaccharide Cell-

Surface Antigens for Structural Studies

129 Protein Motions that Determine the Efficiency of

Photosynthesis

129 Studying Properties of Cell Suspensions withElastic Scattering

130 Numerical Simulations of Biochemical Self-Organization: Calcium Wave Propagation andMicrotubule Growth

Los Alamos FYI996 LDRD Progress Report

Competency Development ProjectsMaterials Science

135 Actinide Crystal Structures with an Emphasis on

Plutonium Alloys

136 The Implications of Diffraction In Situ LoadingMacrostrain Measurements in Composites andFinite-Element Interpretations

137 Chemical and Physicochemical Properties of

Submicron Aerosol Agglomerates

137 Characterization of Bioactive Materials Using

Neutron Reflectivity and Atomic Force Microscopy

138 Bulk Amorphous Materials

139 Characterization of Advanced Electronic Materials

140 Neutron Scattering Studies on Shear-InducedStructure in Polymers

140 Structural and Magnetic Characterization ofActinide Materials

142 Equation-of-State, Thermodynamic, and Structural-Mechanical Properties of Intermetallic Compounds

142 Neutron Scattering from Correlated-ElectronSystems

143 Advanced Deformation Process Modeling

144 Scanning Probe Microscopy CompetencyDevelopment

145 Design and Implementation of an X-Ray StrainMeasurement Capability Using a Rotating AnodeMachine

146 Computational Modeling of Materials Processingand Processes

146 Nanometer-Scale Materials

147 Science and Technology of Reduced-DimensionalMagnetic Materials

147 Complementary Neutron Diffraction andComputational Micromechanics Studies ofPolycrystalline Deformation in Advanced Materials

148 Characterization of Active Sites in Zeolite Catalysts

149 New Initiatives in Materials Characterization,

Modeling, and Synthesis

149 Dynamics of Polymers at Interfaces

150 Understanding and Controlling Self-Assembly

151 Role of Charge Localization in the Basic High-

Temperature Superconductivity Mechanism

152 Measurement by Neutron Diffraction of Strains inAdvanced Engineering Structural Materialsincluding AlSiC and AlTiC

153 Chemistry and Microstructure of High-Temperature

Superconductor Interfaces

154 Texture Science and Technology

154 Microstructures of Transition Metal OxidesCharacterized by Neutron and X-Ray Scattering

155 A Thermodynamically Consistent, Damage-Dependent, Interface Debonding Model forComposites

155 Zircon as a Host Phase for Plutonium Disposition

156 Many-Body Theory Research

157 Alloy Design and Phase Stability of the Ternary

Alloy Ti-Al-Nb

158 Synthesis and Characterization of Correlated-

Electron Materials

159 Tailoring the Interfacial Electronic Structure ofOrganic Electronic Materials and Devices

159 Controlling Function of Polar Organic Multilayers

160 Pinning Vortices and Enhancing High-Temperature

Superconductor (HTS) Critical Currents

161 Nonlinearity in Structural and Electronic Materials

163 High-Resolution Electron Microscopy of AdvancedMaterials

Contents

Competency Development Projects (cont.)Engineering and Base Technologies

167 Molten Salt and Molten Lead Systems Studies

168 Advanced Measurements and Techniques in High

Magnetic Fields

168 Dynamic High-Strain Deformation of Materials:Experiments, Advanced Constitutive Modeling,and Computational Implementation

169 Ultrasensitive Sensors for Weak ElectromagneticFields Using HTS SQUIDs for Biomagnetism,NDE, and Corrosion Currents

170 Short-Pulsed Electric-Discharge Degradation

of Toxic and Sludge Wastes

171 Laser-Sheet Imaging of HE-Driven Interfaces

171 A Neural-Network-Based System for DamageIdentification and Location in Structural andMechanical Systems

172 Development of Inexpensive Continuous-EmissionMonitors for Feedback Control of CombustionDevices to Minimize Greenhouse Gases, ToxicEmissions, and Ozone-Damaging Products

173 Distortion, Residual Stress, and Thermal GradientIssues for Plutonium Gravity Casting in Ambient-Temperature Molds

174 Radiation Resistance Measurements of Rare-EarthPermanent Magnet Material for High-IntensityLinac Applications

174 Molten Salt and Separations TechnologiesEvaluation

175 Neutron Metrology for Stockpile Stewardship atLANSCE


177 High-Energy Test of Proton Radiography Concepts

177 Comparison of Cyclotrons and Linacs for High-Intensity-Beam Applications

178 A 1-kW-Power Demonstration from the AdvancedFree-Electron Laser

179 Advanced Techniques for Producing, Polarizing,

and Storing Ultracold Neutrons

179 Development of Ion-Beam Techniques for theStudy of Special-Nuclear-Materials-RelatedProblems

180 Generation and Compression of a Target Plasmafor Magnetized Target Fusion

182 Advanced Modeling of High-Intensity Accelerators

Chemistry

183 Binding Carbon Dioxide in Mineral Form: A CriticalStep toward a Zero-Emission Coal Power Plant

183 Foreign Nuclear Test Radiochemical Diagnostics

184 The Characterization of Atmospheric Aerosols:Applications to Heterogeneous Gas-Particle Reactions

185 Kinetic Studies of Competitive AdsorptionProcesses Related to Automobile CatalyticConverters

185 Investigations of Biomimetic Light-Energy-Harvesting Pigments

xii Los Alamos FYI996 LDRD Progress Report

Competency Development Projects (cont.)Mathematics and Computational Sciences

187 Nuclear Futures Analysis and Scenario Building

188 New Numerical Models for Global Ocean

Modeling

188 Lie Group Applications to the Solution of

Differential Equations

189 Lithospheric Processes

189 Geometrically Compatible 3-D Monte Carlo and

Discrete-Ordinates Methods

190 Adaptive Monte Carlo Methods for RadiationTransport

191 High-Perf ormance Computing of ElectronMicrostructures

192 Modeling Complex Phenomena: Multiple Lengthand Time Scales in Extended Dynamical Systems

192 Continuing Benchmarking of Ocean-Circulation

Models

193 Simulation Methods for Advanced Scientific

Computing

193 Adaptive Mesh Refinement Algorithm

Development and Dissemination

194 Neutron Transport Methods for 3-D Cartesian

Adaptive Meshes

194 Applications of Nonlinear and Stochastic

Dynamics

195 Theoretical Foundation for Adaptive Monte Carlo

196 Advanced Three-Dimensional Eulerian

Hydrodynamic Algorithm Development

198 Phase Transitions, Nonequilibrium Dynamics, and

Critical Behavior of Strongly Interacting Systems

198 Numerical Simulations of Disordered

Superconductors

199 Transactional Memories: A New Abstraction forParallel Programming

199 Development of an Integrated System forEstimating Human Error Probabilities andModeling Their Effects

200 Novel Monte Carlo Algorithms for StatisticalMechanics

200 Advanced Computational Science

201 Development of an Automated Core Model forNuclear Reactors

201 Density Function Estimation for Monte CarloSimulations

202 Self-Organization and Pattern Formation

203 Application of Discrete Mathematics

204 Theory and Modeling of Correlated-Electron

Materials


207 Modeling the Heat Flow and Resulting Dynamicsin Earth's Interior

208 Remote Sensing Science Thrust: New Concepts

209 Subsurface Noble Gas Transport at the NevadaTest Site

210 Analysis and Visualization of GlobalMagnetospheric Processes

211 Neutron Star Evolution and Emission

212 Remote Sensing Science Thrust: Laser RemoteSensing

Contents XIII

Competency Development Projects (cont.)

Geoscience, Space Science, and Astrophysics (cont.)

213 Development of the First Nonhydrostatic, Nested-

Grid, Grid-Point Global Atmospheric Modeling

System on Parallel Machines

213 Production and Application of High-Specific-

Activity Si-32

214 Remote Sensing Science Thrust: Hyperspectral

Sensing

216 Studies of Dynamical Processes Affecting Global

Climate

218 Transport Processes in Space Plasmas

220 Physical Properties and Mantle Dynamics


223 Advanced Research Capabilities for NeutronScience and Technology—Neutron Polarizers

Biosciences

225 Solution Structure of the cAMP-Dependent Protein

Kinase

225 Development of Biosensors and Bioprobes Basedon Spectroscopic Monitoring of Enzymes andOther Proteins Encapsulated in Sol-Gel Glasses

226 Molecular Characterization of Flow-Sorted

Mammalian Centromeres

226 Advanced Biomolecular Materials Based onMembrane-Protein/Polymer Complexation

227 Similarity Landscapes: An Improved Method forScientific Visualization of Information fromProtein and DNA Database Searches

227 Formation of Drug-Bearing Vesicles in MixedColloids of Bile Salts and Phosphatidylcholine

228 Structural Biology of Disease-Associated DNARepeats and Protein-DNA Complexes Involved inthe Repair of DNA Damage

229 Applications of Optical Trapping toSingle-Molecule DNA Sequencing

230 Microbial Acquisition of Iron from Iron-BearingMinerals

230 The Biology of Novel Animal Genes: MouseAPEX Gene Knockout

231 Competency Development in Antibody Productionfor Cancer Cell Biology

232 Covariation of Mutations: A ComputationalApproach for Determination of Function andStructure from Sequence

233 Structure, Dynamics, and Function of Biomolecules

234 Advanced NMR Technology for Bioscience andBiotechnology

234 Nonlinear Analysis of Biological Sequences

235 Indigenous Bacteria as Hosts for Proteins forBioremediation

236 Landscapes and Dynamics of Proteins

237 Engineering Haloalkane Dehalogenasefor Bioremediation

xiv Los Alamos FYI996 LDRD Progress Report

Program Development Projects

Materials Science

241 Fundamental and Applied Studies of HeliumIngrowth in Plutonium

241 Cost-Effective Development of Thin Films for

Hat-Panel Displays

242 Development of High Magnetic Fields for Energy

Research

242 Advancing the Technology Base for High-Temperature Membranes

243 Giant Magnetoresistance Materials for MagneticRecording Technology

243 Characterizing Mechanical Effects of AgingDamage

244 High-Magnetic-Field Research Collaborations

244 Ceramic/Polymer, Functionally Graded Material

(FGM), Lightweight Armor System

245 New Anion-Exchange Polymers for ImprovedSeparations in Nuclear and Industrial Applications


247 Detection of Underground Structures and Tunnels

247 Active Noise and Vibration Control for VehicularApplications

248 Study of Possible Detector Geometries for

Detection of Radioactivity in Moving Vehicles

248 Environmentally Conscious Coal Combustion:Development of Process Monitors and ImprovedNumerical Models

249 Establishing the Operational Durability of Polymer

Light-Emitting Diodes

249 Helium-3 Targets for Tritium Production in FissionSystems

250 Explosives Detector Using the Optical Signature ofDeflagrating Explosive Particulates

250 Directed-Light Fabrication—A Laser Metal-Deposition Process for Fabrication of Near-Net-Shape Components

251 Modeling and Assessment of Concrete and theEnergy Infrastructure

251 Global Nuclear Material Monitoring

252 Frequency-Resolved Optical Gating: A Diagnosticfor the Characterization of OptoelectronicMaterials and Devices

253 Neutron-Based, Land-Mine Detection SystemDevelopment

254 Development of the Transient-Reactor Analysis

Code (TRAC) for Real-Time Applications

254 Rapid Prototyping of Hazardous Materials Usingthe Directed-Light Fabrication Process

255 Reactor-Based Tritium Production

255 Methods for the Rapid On-Line Detection ofBiological and Chemical Weapons

256 Night-Vision Device Technology Development

256 Integrated Approach to Advanced Machining

Contents xv

Program Development Projects (cont.)


259 Subsurface, Directed-Energy Methods for

Groundwater Treatment

260 Plasma Source Ion Implantation for Advanced

Manufacturing

260 Magnet Design Concepts for the 100-MeVIsotope-Production Facility

261 Advanced Ignition of Jet Turbine Engines

262 Removal of Transuranic Materials from

Contaminated Equipment Using Plasma

Decontamination

262 Supporting Technologies for a Long-PulseSpallation Source

Chemistry

265 Advanced Oxidation Technologies for Chemical

Demilitarization

266 Advanced Nuclear Fuel Processing

267 Chemical-Biological Treatment of HeterogeneousWastes

267 Radionuclide Separations Using Pillared Layered

Materials

268 Integration of Advanced, Nuclear MaterialsSeparations Processes

269 Catalysis for Alternative Feedstocks

270 Separation Science and Technology: Membrane-Based Separations and Destruction Processes

271 Microwave Processing Improvements for Methane

Conversion to Ethylene

Mathematics and Computational Science

273 Data Resources and Sample Applications for

Information Analysis in Chemical and BiologicalWarfare Defense

273 Information-Handling/Data-Fusion Technologies toExtract and Analyze Export Information

274 Intelligent Controllers for Battlefield Simulations

274 Visualization Capability for Nonproliferation andEmergency Training: A "Poor Man's" Virtual-Reality System

275 Modeling for Environmentally ConsciousManufacturing

275

276

278

278

Low-Speed Flow Hydrodynamics

A New Model to Estimate Regional EmissionsInventories

Improving Industrial Performance throughIntegrated Process Simulation, Control, andOptimization: Modeling Atoms to Enterprise

National Environmental/Economic InfrastructureSystem Model

279 Global Nuclear Material Flow Model


281 Measurement Criteria Analysis for Krypton, Xenon,and Hydrogen (Hydrogen/Deuterium/Tritium)Isotopes and Concentration Variability at Distance

xvi Los Alamos FYI996 LDRD Progress Report

Program Development Projects (cont.)


283 The Carpinteria Reservoir Redevelopment Project

284 Satellite-Based Laser Windsounder

284 Conditioning Geological Reservoir Realizationswith Time-Dependent Data

285 Improved Atmospheric Transport for Risk

Assessment in Complex Terrain

285 Reservoir Enhancement on the ImpermeableMargins of Productive Geothermal Fields:Integrated Resource Development andManagement


287 Disposition of Plutonium as Nonfertile Fuel forWater Reactors

288 An Ultracold Neutron Facility at the ManualLujan Jr. Neutron Scattering Center

288 Measurement of Fissile Material in Spent Fuel and

Alternate Nuclear Materials

Biosciences

289 A Consortium for Biomedical Applications ofSingle-Molecule Detection

290 Cancer Risk Assessment

290 Human Brain Mapping: Experimental andComputational Approaches

291 Universal Biological-Agent Point-Sensor ProgramDevelopment

291 Sensors for Point Detection of Chemical and

Biological Warfare Agents

292 Molecular Medicine for the 21 st Century: AComputational Basis for Design and Critiqueof Vaccines and Therapeutics

293 Distributed Telemedicine for the NationalInformation Infrastructure Testbed

293 Deformable Human Body Model Development

294 Detection and Characterization of Biological-Weapons Agents by Matrix-Assisted LaserDesorption/Ionization Mass Spectrometry

294 Novel Gene Complex Structure Determination by

Neutron and X-Ray Scattering

295 In Situ Bioremediation of Trichloroethylene-Contaminated Groundwater

299 Index of Principal Investigators

Contents xvii

Overview

LDRD Program Overview—FY 1996

Ed Heighway and John Vigil

The Laboratory-Directed Researchand Development (LDRD) Program isauthorized by Congress to fundinternally proposed research anddevelopment that extends theLaboratory's science and technologycapabilities in support of its mission.There are three ways in which LDRDhelps extend these capabilities. First,the research explores new ways oftackling mission problems, therebyidentifying opportunities to executethe Laboratory's mission in a cheaper,faster, or better way. Second, theresearch invests in new core capabili-ties needed to fulfill the mission,perhaps adding a multidisciplinaryapproach that provides new insight.And third, but by no means least,LDRD invests in the fundamentalscience and technology base thatunderpins the Laboratory's ability toexecute its mission.

All three types of research arerepresented in the Los Alamos LDRDprogram. Projects are chosen based ontheir innovation and scientific merit ina mission context, and as a result thework leads to a large number ofpublications, patents, and externalawards. These in turn result in greatervisibility for the Laboratory's scienceand technology, and LDRD becomesa vehicle for attracting the bestscientists and engineers.

The primary mission of Los AlamosNational Laboratory is "to reduce thenuclear danger," and there are fourmajor pieces of that mission: ensuringthat the nation's nuclear stockpile isreliable and safe, managing theproduction and use of nuclearmaterials, ensuring that the environ-ment is both restored from pastnuclear activities and is minimallyimpacted by future activities, and

developing technology to helpeliminate proliferation of nuclearmaterials and weapons. To show howthese activities are supported at LosAlamos, a breakdown of theLaboratory's FY 1996 funding bymajor programs is shown in Fig. 1.

Program Structure

LDRD is a formally managedprogram that imposes accountabilityin the processes of selecting, conduct-ing, and documenting projects. Allprojects are selected competitivelythrough review by peers or scientificmanagers. Innovation and scientificexcellence are key selection criteria.All projects must be in science andtechnology areas that support theLaboratory's mission.

The LDRD program at Los Alamoshas three components—IndividualProjects (IP), Competency Develop-ment (CD), and Program Develop-ment (PD)—each with slightlydiffering goals. The IP component isintended to fund the most far-reaching

WFO-DODWFO-DOE 5%

6%Other DOE

4%

WFO-Federal Agencies Other WFO

Nonproliferation &International Security

9%

Energy Research6%

Environmental Restoration &Waste Management

15%

Fig. 1. Funding for major programs at Los Alamos National Laboratory during FY 1996.

Overview

and fundamental research proposedby technical staff members to extendthe Laboratory's core science andtechnology base. The CD componentinvests in large multidisciplinaryactivities that tackle significantproblems from several approaches,often combining theory and experi-ment. The PD component is intendedto invest in nearer-term research for aspecific sponsor that requires someexploration of feasibility or otherconfidence-building demonstration. InFY 1996, the LDRD program funded356 projects at a total expenditure of$54.9 million. The funding distribu-tion among the three components isshown in Fig. 2.

Individual Projects. This compo-nent funds basic research whosepotential is high but whose payoffmay be distant. Often mappinguncharted territory, these projects aremore exploratory than those of theother two components. Proposals areevaluated and ranked by peer-reviewteams (one team for each of ninetechnical disciplines), and the mosthighly ranked and relevant ones are

selected for funding. These projectsare generally funded for three years. InFY 1996, 166 projects were funded.

Competency Development. Thiscomponent funds the key science andtechnology competencies that supportthe Laboratory's missions and enableit to respond to new Department ofEnergy (DOE) and national issues. CDprojects are intended to be cross-cutting: that is, they draw on theresources of several Laboratorydivisions and have clear institutionalvalue beyond the strategic interest ofany single division. CD projects areproposed by the scientific staffthrough their technical division andprogram offices, are reviewed both fortechnical content and strategic value,and are ultimately selected by theLaboratory Director. In FY 1996,117 CD projects were funded.

Program Development. Thiscomponent funds research that allowsthe Laboratory to examine novel waysof meeting extended or future needs ofprogram sponsors. Generally explor-atory or demonstrational, this researchassesses the feasibility of new scien-tific approaches or technologies and

establishes a technical path toadvanced solutions of existingproblems. PD projects are generallyof shorter duration than those in theother two components, typically beingfunded for only one or two years.Proposals are solicited, reviewed, andselected by scientific managers andtechnical staff within the Laboratory'seight program offices. In FY 1996,73 PD projects were funded.

The high quality of science sup-ported by all three LDRD componentsis attested by the number of relatedscientific publications, patents, andawards. In 1996, LDRD projectsgenerated 27% of all Laboratorypublications, 39% of its patentawards, and half of the Laboratory'sR&D 100 Awards—with only 5.5% ofthe budget. In addition, the LDRDprogram is a significant testingground for the talent attracted to theLaboratory through its postdoctoralprogram. In 1996,150 postdoctoralstaff members worked on LDRDprojects. Of these, many will go on tobecome permanent Laboratoryemployees and contribute to corescientific missions.

Program Development Competency Development

Individual Projects

Fig. 2. Distribution of FY 1996 LDRD funding among the three program components.

1 Los Alamos FY 1996 LDRD Progress Report

Highlights of LDRD Support ofNational Security

LDRD projects tend to be cutting-edge research and contribute broadlyto the science and technology basethat supports the Laboratory'smission. They contribute to nuclearweapons science and technology, tononproliferation, counterproliferation,and arms control, and to nuclearmaterials characterization and defensewaste disposal, as well as to othernational security areas such asmaterials, detectors, and computa-tional tools for military applications.In this year's summary, we havechosen to highlight just a few LDRDcontributions related to nationalsecurity.

Nuclear Weapons Science andTechnology. Without nuclear testing,a fundamental understanding ofnuclear weapons performancebecomes paramount. LDRD research-ers are developing new ways to makethe measurements needed for stock-pile certification and for improvingthe modeling capability of nuclearweapons codes.

Recently, LDRD researchersidentified a promising new approachfor using high-energy protons to makehigh-resolution radiographs of veryrapid events in high-density materials.Proton radiography's advantages arehigh spatial resolution, sensitivity todensity variations, and the ability tocapture the time history of an implo-sion. The LDRD program funded aproof-of-principle test that producedproton radiographs of a dense, statictest object. Researchers are nowdeveloping the capability to makedynamic radiographs of dense objectsunder explosive compression.

The tendency of adjacent but dis-similar liquid layers to mix (interfaceinstability) is a problem of centralimportance to nuclear weaponsperformance and simulation. Inparticular, the interfacial instability ofa thin fluid layer driven by shockcompression is a fundamental issue inturbulent mixing in nuclear weapons.LDRD researchers are developing anew measurement technique to obtain

"snapshots" of the evolving instabil-ity, leading to more accurate simula-tion models and improvedcalculations.

Understanding the effects of agingon nuclear weapon components,particularly plutonium and polymers,is an important aspect of science-based stockpile stewardship. LDRDresearchers are making majorcontributions to this understandingthrough theoretical, computational,and experimental analyses. Usingtransmission electron microscopy,small-angle neutron scattering, andother advanced techniques, LDRDresearchers are investigating alpha-decay-generated helium bubbles thatform in aged plutonium metal. Theyare also developing computer simula-tion tools to evaluate the effects ofthis and other aging phenomena onproperties that are germane to nuclearweapons safety and performance.

Degradation of polymers as theyage is probably the most importantfactor limiting the lifetimes ofstockpiled weapons. LDRD research-ers are using both experiment andtheory to link the large span of scalesneeded to accurately predict howchanges in chemical structure,physical structure, and stress affectthe mechanical properties of materi-als. Although aspects of each of thesize scales (atomic, molecular, micro-,meso-, and macroscales) have beenstudied in the past, this LDRD work isone of the first attempts to link such awide range of scales into a coherentpicture that can be used to understandthe behavior of polymeric elastomers.

Advanced ManufacturingProcesses for the Weapons Program,LDRD researchers have developed anew fabrication process calleddirected-light fabrication (DLF), andthey are exploring its application tonuclear weapons fabrication (beryl-lium, uranium, and plutoniumcomponents). DLF is an automated,rapid, one-step method of makingcomplex metal parts by fusing metalpowder in the focal zone of a laserbeam. The resulting parts are fullydense, have excellent structural

properties, and are shaped to within afew thousandths of an inch of finaltolerance without the use of a mold,pattern, or forming die. The process isideal for low-volume production ofprecision parts for both defense andcivilian applications.

LDRD researchers have alsodeveloped and benchmarked com-puter simulations that predict distor-tion, residual stress, and thermalmanagement in cast plutonium parts.Advances in these areas will benefittwo DOE initiatiatives—AdvancedDesign and Production Technology(ADaPT) and the AcceleratedStrategic Computing Initiative(ASCI).

Advanced ComputationalCapability and Nuclear WeaponsSimulation. In the absence of nucleartesting, the ability to predict theperformance of nuclear weaponsbased on computer simulations is oneof the key requirements for maintain-ing a safe, secure, and reliablestockpile. Computer simulations ofthe complex phenomena that occur ina nuclear explosion continue to taxavailable state-of-the-art capabilities.

Past LDRD work has produced thediscrete ordinates method for radia-tion transport, the particle-in-cellmethod for hydrodynamics, and othercomputational tools that are now usedwidely in both military and civilianapplications. Today, LDRD research-ers are providing the technology toimplement these tools on the newgeneration of massively parallelsupercomputers. They are also ex-tending the capability of these toolsthrough such developments as acomplex geometric representationcommon to both Monte Carlo anddiscrete ordinate codes.

Computer simulations of nuclearweapons require not only the mostpowerful computers available, butalso the ability to transfer hugeamounts of computational data anddisplay the data in forms that can beeasily digested and analyzed. LDRDresearchers have advanced the state ofthe art in fast data-transfer networksby inventing the high-performance

Overview

parallel interface (HIPPI), whichsupports local networks at data-transfer rates of 800 megabits/s(equivalent to transmitting onehundred 250-page books per second).Adopted as a standard by theAmerican National StandardsInstitute, HIPPI has been imple-mented by many vendors and iscurrently the high-speed interface ofchoice for supercomputers. Buildingon this LDRD work, researchers havedeveloped a synchronous opticalnetwork (SONET) gateway that canlink supercomputers at HIPPI speedsover very large distances. Work isnow under way to extend the networkbandwidth to the 5 to 10 gigabits/srange.

Nonproliferation, Counter-proliferation, and Arms Control.LDRD researchers are advancing thetechnology required to verify andmonitor arms control treaties and todetect clandestine production ofnuclear, chemical, or biologicalweapons.

Earth-orbiting satellites havedetected transionospheric pulse pairsthat are similar to the signature of anuclear explosion. LDRD researchershave shown that these pulses can beexplained by a runaway electronmechanism near thunderstorms thatcauses upward-propagating dis-charges called "sprites." Their newtheory agrees with measurements ofradio-frequency "chirp" pairs, as wellas with optical and x-ray emissionsassociated with this phenomenon.This understanding will allowscientists to more accurately identifysignals from clandestine nuclearexplosions.

LDRD researchers are developingtechnology for detecting (withsurrogates) chemical and biologicalwarfare agents. The detection technol-ogy is based on the combination ofmembrane introduction and ion-trapmass spectrometry, and preliminarymethods for continuous surrogatedetection have been successfullydeveloped. The surrogates includechlorobenzene, cyclohexanol,dimethyl methyl phosphonate, and

dimethyl sulfoxide and have beendetected at approximately 100 ppb byvolume in air.

Global proliferation of weapons-grade plutonium and highly enricheduranium has become one of theforemost threats to the security of theUnited States and the entire world.LDRD researchers are characterizingand modeling, from a global perspec-tive, the management, control, andflow of weapons-grade nuclearmaterials. The objective of thisresearch is to provide a computer-based tool capable of (1) capturingand enumerating data concerning theglobal inventory of nuclear weaponsmaterials, (2) providing a global viewof the management and control ofnuclear materials, (3) undertakingmacrosystem simulations of safe-guards accounting surety and resourceestimation, and (4) visually represent-ing the nuclear materials information,including both inter- and intracountryflows.

Nuclear Materials. LDRD-fundedactivities at Los Alamos have con-tributed significantly to advancedmethods for processing and recover-ing plutonium, to recovery of acti-nides and toxic metals from a varietyof process streams, and to develop-ment of sensors for monitoringspecial nuclear materials.

LDRD researchers are exploringactinide crystal chemistry to learnwhy the ideosyncratic structures ofplutonium metal occur. They aredoing this by examining the crystalstructures of several actinide alloys:neptunium-uranium, plutonium-thorium, and plutonium-zirconium.Such additional structural data mayvery well lead to a solution of theplutonium structure problem.

LDRD researchers are performinga series of laboratory-scale experi-ments to enhance the operation andsafety of a new process for recoveringmetallic plutonium from nuclear

weapons. The hydride-dehydriderecycle process eliminates theenvironmental hazards associatedwith other plutonium recoverymethods. It takes advantage ofplutonium's strong affinity forhydrogen gas. In the hydriding step,hydrogen reacts with the plutonium toform plutonium hydride powder,which is collected and then reheatedto release the hydrogen (thedehydriding reaction), forming ametal powder. This metal powder isthen melted to form storage-readyingots.

LDRD researchers have developedand evaluated water-soluble chelatingpolymers for recovering actinide andtoxic metals from a variety of processstreams, as well as polymer filtrationfor recovering precious metals fromindustrial process streams. The highcost associated with the long-termstorage of radioactive and toxicwastes mandates separating thesecomponents in a process waste streambefore the waste is packaged andstored. A portable polymer filtrationsystem that recovers zinc and nickelions from electroplating rinse waterswon an R&D 100 Award in 1995.LDRD researchers are now investi-gating membrane-based separationtechnologies for removing plutoniumand americium from nuclear-materi-als-processing waste water, fission-product separations using cobaltdicarbolide for solvent extraction,hollow-fiber membrane modules forseparating gases and nuclear materi-als, and selective waste remediationusing in situ photocatalytic reactors.

Los Alamos FYI996 LDRD Progress Report

Other National Security Research.LDRD contributions to other nationalsecurity research include developmentof materials, detectors, and computa-tional tools for conventional militaryapplications, as well as sensors forenvironmental monitoring.

Intelligent computer-generatedforces are an area of growing model-ing importance within the Departmentof Defense (DoD). LDRD researchersare successfully using intelligentcontrol and adaptive systems technol-ogy as well as advanced simulationsoftware to develop, test, and demon-strate new intelligent actor capabilityin warfare simulations.

Resonant ultrasound spectroscopy(RUS) was originally used as adiagnostic tool in an LDRD projectthat studied the properties of high-temperature superconducting crystals.It was quickly determined that RUScould be used for nondestractivelytesting crystals for structural imper-

fections. The technique was furtherapplied to detect cracks and otherflaws in commercial and militaryhardware. RUS is now being used fornondestructively testing militarycomponents (aircraft landing assem-blies, turbine disks, helicopter rotorparts, and ball bearings) and foridentifying the contents of chemicalmunitions. Exploratory work is underway for using RUS to study theeffects of aging on hemisphericallyshaped explosive charges as part ofthe Laboratory's stockpile steward-ship mission.

Using molecular self-assemblytechniques, LDRD researchers havedeveloped a compact, robust, surface-acoustic-wave-based chemicalmicrosensor for remote, real-timesensing of volatile organic com-pounds. The microsensor is reversibleand can be used to monitor continu-ously changing concentrations of acontaminant over an extended periodof time. This capability is relevant toenvironmental monitoring of defensewastes and to detecting environmentalindicators of weapons production.

LDRD Project Summaries

In the following sections, we havegrouped project summaries by LDRDcomponent—IP, CD, and PD—andthen subdivided them into ninetechnical disciplines:

Materials Science



Chemistry

Mathematics and ComputationalSciences


Geoscience, Space Science, andAstrophysics


Biosciences

A list of related publications writtenby project team members is includedwith the summaries. An index to theprojects' principal investigators isprovided at the end of this report.

Overview

Individual Projects

Individual Projects (IPs) are staff-initiated R&D aimed atstrengthening the Laboratory's science and technology baseand fostering a stimulating research environment. Theseprojects play a key role in maintaining the expertise and state-of-the-art technologies that underpin the Laboratory's scientificand engineering excellence. IPs accounted for 38% of thisyear's LDRD budget and 46% of all projects, and they sup-ported research in all nine technical disciplines.

Examples of subjects investigated by IPs include nonlinearatom optics, dynamics of quantum wave packets, chemistryand catalysis in supercritical media, microsensors for volatileorganic compounds, quantum cryptography, optical imagingthrough turbid media, nonlinear processes in earthquakes,three-dimensional climate models, nanoengineered films,phase stability of transition metals and alloys, particles andpatterns in cellular automata, high-speed computer interfacesand networks, antiquark distributions in the proton, weakinteraction measurements using optically trapped radioactiveatoms, high-intensity laser-matter interactions, turbulence incomplex fluid flows, the structure and dynamics of surfacerecognition, and the role of the telomere in birth defects.

Materials Science

Origin of Radiation Damage in PotassiumTitanyl Phosphate

D. Wayne Cooke

Potassium titanyl phosphate (KTP)is the most widely used material fornonlinear optical applications such asoptical parametric oscillators andlaser frequency-doublers. However,its use is limited to low-powerapplications because of laser-induceddamage incurred at high power. Theorigin of this damage is presentlyunknown.

Recent investigations of radiationdamage in KTP showed that thematerial emits bursts of light uponheating or cooling over a broadtemperature range (4-675 K). Thisemission is believed to result from thedevelopment of a large surfaceelectric field that discharges into theambient environment. The fieldevolves from a change in spontaneouspolarization as a function of tempera-ture, a phenomenon called pyroelec-tricity. This observation implies thatlaser excitation of KTP may cause achange in its temperature, therebyinducing large electric fields thatmight contribute to the optical-damage threshold in KTP. Theconsensus is that reduction of Ti4+toTi3+ ions in KTP is responsible for thedamage and that two-photon absorp-tion or other electronic mechanismsare involved.

We believe that laser-inducedthermal mechanisms may be relevant.Specifically, our objective was todemonstrate that electrons could beproduced in KTP by thermal ratherthan optical excitation. That is,excitation with a CO2 laser, which hasa wavelength 10 times that of aneodymium-based laser and thereforecannot excite electrons across theband gap, may in fact produce

electrons via ionization as a result ofthe pyroelectric effect in KTP. Weexcited the KTP sample with CO2

laser radiation and, with an opticalmultichannel analyzer, measuredbursts of light coincident with thelaser pulse. By attaching electrodes totwo surfaces of the crystal, we alsomeasured current pulses.

Shown in the accompanying figureis the current generated in KTP at295 K by a CO2 laser pulse. Themaximum current occurs during theon-off cycle of the laser, whichcorresponds to the maximum changein the crystal's spontaneous polariza-tion. Simultaneous with this peakcurrent is the occurrence of opticalbursts of light, implying surface

200

100

r o

electric fields of approximately30 kV/cm. These results agree withwhat we expected based on pyroelec-tricity in KTP; the surface fieldshould be proportional to dPsldt or,equivalent^, to (dPs/dT)(dT/dt),where Ps is spontaneous polarization,T is temperature, and t is time. Fromthe second factor, dTldt, we see thatfields evolve from a large rate ofchange in temperature, as induced bythe laser on-off pulse. Observation ofpyroelectricity in KTP provides animportant new insight into thepossible origin of optical damage inthese materials.

Publications

Cooke, D.W., B.L. Bennett, R.E.Muenchausen, et al., "Pyroelectricityand its Role in Radiation Damage ofPotassium Titanyl PhosphateCrystals," in Proceedings of the SPIE(SPIE, Bellingham, Wash., in press).

o-100

22

I -200'5

-300

-400

cn o

A ^\

if

\(

1

-

T - 295 *P ~ 0.1 K,

•

f

Is

_ -

10 20 30 40 50

Time (s)

60 70 80 90

Current generated in KTP at 295 Kby a CO2 laser pulse. The continuous-wavelaser is turned onatt = 10 s and off at t = 30 s, as shown by the dashed profile.The approximate crystal heating rate during this time interval is 0.1 K/s.

Individual Projects—Materials Science 9

Development of a Fundamental Understanding of ChemicalBonding and Electronic Structure in Spinel Compounds

Kurt E. Sickafus

Our objective is to investigate therole of chemical bonding and pointdefects (both extrinsic point defectsand cation-disorder antisite defects)on structural stability and electronicstructure in compounds with thespinel crystal structure. Experimen-tally, we assess structural and elec-tronic properties of spinel samplesusing electron energy-loss spectros-copy (EELS) and electron, x-ray, andneutron diffraction techniques. Weperform total-energy electronic-structure calculations to determinestructural stability, band structure,density of states, and electrondistribution.

This year we prepared, by sol-gelsynthesis routes, oxide compounds in

the composition field MgOAl203

through MgOCr203 from magne-sium, aluminum, and chromiumnitrate precursors. We are using thesesamples to measure electron-lossnear-edge structure (ELNES) by theEELS technique (see plot of energyloss vs electron intensity). ELNES isproportional to the density of states atthe bottom of the conduction band ofthe material being examined.

We performed neutron diffractionexperiments on single crystals ofstoichiometric (equimolar) spinel(MgOAl203) and nonstoichiometric(nonequimolar) single crystals ofspinel (Mg03Al203). Crystal-structure refinements of the diffrac-tion data revealed that point defects

accommodating deviations from theequimolar spinel composition resideon both tetrahedral and octahedralcation sites.

We completed total-energy elec-tronic-structure calculations forMgOAl203 and MgO»Ga2O3 in bothnormal and inverse structures (seeplots of E - EF vs D(E) forMgOAl203). We demonstratedexcellent agreement between theoryand experiment in basic structuralparameters. By analyzing the bandstructure, we have identified alumi-num-related sp bands pulled down outof the valence band in the inversestructure as the source of the extrapeak observed in the EELS/ELNESspectra.

2000

lits

rary

ur

biti

iten

sit)

ron Ir

1600

1200

800

400

LU

77 7J 79

Al -1-2,3 edge MgAI2O4 spinel

I I I !80 81 82Energy Loss (eV)

83 84 85

Aluminum in octahedrally coordinated sites

Aluminum in tetrahedrally coordinated sites

EELS spectra obtained using a dedicated scanning transmission electron microscope. In these spectra we examine theELNES in magnesio-aluminate spinel, MgO*Al2O3. The peak just below 80 eV is at the onset of the aluminum L23

absorption edge and reflects the aluminum contribution to the density of states of the conduction band from octahedrallycoordinated aluminum ions. Following neutron irradiation to a high dose, a substantial fraction of aluminum atoms inthe lattice relocate from octahedral to tetrahedral sites. This relocation is manifested in EELS analyses by anenhancement of the ELNES peak at 78 eV. In a perfectly ordered, "normal" spinel crystal, this additional ELNES peakwould not exist. Quantitatively, the occupation of tetrahedral sites by aluminum atoms increases from about 20% togreater than 50% following neutron irradiation.

10 Los Alamos FY1996 LDRD Progress Report

0.010 15

E-EF(eV)

Calculated valence site, E - EF, vs projected density ofstates, D(E), for the normal structure ofMgO*Al2O3,wherein all of the aluminum cations reside onoctahedrally coordinated lattice sites. Contributions tothe density of states from the different lattice sites areindicated by the different shadings.

10 15E - EF (eV)

Calculated valence site, E - EF, vs projected density,D(E), of states for the inverse structure ofMgO*Al2O3. In this case the aluminum cations aredistributed equally between octahedral andtetrahedral lattice sites. A prominent new feature inthe density of states for inverse spinel appears near8 eV. This structure is absent in the density of statesfor normal spinel. It is probable that this new bandof states arises primarily from tetrahedral aluminumand is responsible for the additional peak that weobserve in the ELNES spectra at 78 eV.

Phase Stability of Transition Metalsand Alloys

Robert Hixson

Our objectives were to study thephase transitions in transition metalsand to attempt to move the transitionpressure by alloying with d-electrondonor metals. Such a study will lead toa better understanding of the phasediagrams of both pure transition metalsand alloys. Furthermore, this study isessential for a complete understandingof the physical properties of materialsunder varying conditions. We alsomade progress in the areas of theory,metallurgy, and experiment.

Theory. We have calculated thevirtual crystal approximation of the

structural stability of pure titaniumand its alloys. The results confirm thefirst year's results that the omegaphase occurs as a result of one-electron band filling. As comparedwith Ti-V alloys, tantalum andtungsten decrease the structuraltransition pressure.

Metallurgy. We have preparedsamples of hafnium and molybdenumalloys. In addition, we preparedsamples of Mo-Re (10%), Mo-Re(30%), and Mo-Re (40%) withsufficiently fine grain structure to beused in the diamond anvil cell (DAC).

The Mo-Re (40%) buttons shatteredupon rolling as a result of the pres-ence of sigma-phase material.Samples of Hf-Nb (1%), HF-Nb(3%), and pure hafnium were pro-duced.

Experimental. Our work hascontinued on defining the alpha-to-omega transition pressure in puretitanium, which has turned out to bemore difficult than anticipated. Puretitanium and the Ti-V material studiedin previous years have very close tothe same free energy, and our experi-mental work shows a very similaralpha-omega transition pressure.Because this result was surprising, wehave spent the last year perfecting ourtechnique for growing single crystalsin the DAC. This work shows atransition pressure close to 90 kbar forboth pure metal and Ti-V alloy.

Individual Projects—Materials Science I I

Theoretical and Experimental Investigation on theLow-Temperature Properties of the NbCr2 Laves Phase

Dan Thoma

Laves phases are the most abundantyet least utilized intermetallic phases.Because of some unique properties(including superconductivity, mag-netic properties, hydrogen-storagecharacteristics, high melting tempera-tures, high strength, reasonableoxidation resistance, and excellentcreep properties), they have unusuallyhigh potential for a wide variety ofapplications that are directly related toenergy sciences. For example, inaddition to high-temperature struc-tural applications (heat exchangers forcoal conversion and gas turbineengine materials), Laves phases alsohave significant nonstructuralapplications: (Tb,Dy)Fe2 is used as amagnetoelastic transducer because ofits giant magnetorestriction,(Hf,Zr)V2 has been used for specialsuperconductivity requirements,Zr(Cr,Fe)2 has been utilized forhydrogen-storage applications, andthe Mo(Co,Si)2 Laves phase contrib-utes to the wear-resistance of"Tribaloy" materials. Unfortunately,the overall potential of Laves phaseshas not been exploited, largelybecause of their tendency for low-temperature brittleness.

We are focusing on experimentaland theoretical alloy design method-ologies in order to elucidate andoptimize deformation mechanisms asa function of defect structure for theC15 Laves phase NbCr2 (C15 refers tothe crystal structure). Our resultsshould provide a scientificmethodology—from atomic to bulkscale—that will improve the low-temperature ductility and toughness ofLaves phases. As a result, an in-creased application of the largest classof materials will be available for avariety of energy-related technologi-cal fields.

We have made substantial progressin the past year to achieve theseproject objectives. Our accomplish-

ments include (1) preparing materials (2) measuring physical propertiesfor single-crystal growth and me- such as elastic parameters (seechanical testing (see photograph), accompanying spectrum),

NbCr,

NbCr,

Nb45Cr55

I I l l I0 1 in 2 in

Arc-melted buttons and rods ofNbCr2 and NbCr2-based composites.

1000 1050 1100 1150FREQUENCY (kHz)

1200

A portion of a resonant ultrasound spectrum ofC15 NbCr2 taken at roomtemperature. This spectrum is used to determine the elastic parameters ofC15NbCr2. The units of amplitude are arbitrary.


(3) establishing ternary phasediagrams for Nb-Cr-M (M = Ti, V,and Be), such as the two diagramsshown, (4) determining the defectstructures/mechanisms and alloyingbehavior in C15 NbCr2-based Lavesphases, (5) performing first-principles

total-energy and electronic-structurecalculations for the C15 NbCr2 Lavesphase, and (6) developing an alloydesign scheme for the C15 NbCr2

Laves phase based on the combinedexperimental and theoretical investi-gations.

Cr

Ti Nb

Nb 90 80 70 60 50 40 30 20 10

Publications

Chu, E, Y. He, et al., "ElasticConstants of the C15 Laves PhaseCompound NbCr2," Sen Metal. Mater.33, 1295 (1995).

Chu, E, A. Ormeci, T. Mitchell, et al.,"Stacking Fault Energy of the NbCr2

Laves Phase," Philos. Mag. Lett. 72,147 (1995).

Chu, E, DJ. Thoma, Y. He, et al.,"Resonant Ultrasound Spectroscopy:Elastic Properties of SomeIntermetallic Compounds," inNondestructive Evaluation (NDE) andMaterials Properties (III), P.K. Liawet al., Eds. (The Materials Society,Warrendale, Pa., in press).

Kotula, P.G., I.M. Anderson, E Chu,et al., "ALCHMEI of NbCr/V CIS-Structured Laves Phase," Proc. ofMicroscopy and Microanalysis 19961996, 554 (1996).

Ormeci, A., E Chu, J. Wills, et al.,"Electronic Structures andMechanical Properties of C15 LavesPhase Compounds: NbCr2 and HfV2,"Phys. Rev. B 54,12753 (1996).

Thoma, D.J., E Chu, et al., "AlloyingEffect in NbCr2 and Nb(Cr,V)2 C15Laves Phases" (to be published inMater. Sci. Eng.).

Thoma, D.J., E Chu, et al.,"Comparison of NbCr2 and HfV2 C15Laves Phases," in High TemperatureOrdered Intermetallic Alloy•s-VII,MRS Symposium Proceedings, C.C.Koch et al., Eds. (Materials ResearchSociety, Boston, Mass., in press).

Ternary phase diagrams ofNb-Cr-Ti and Nb-Cr-V, indicating the phase field ofthe ternary Laves phase based on NbCr2-


Nanostructured Materials: Growth andPatterning Using Hyperthermal MaterialsChemistry

Mark Hoffbauer

In the next century, high-densitycompact disks, large and bright flat-panel displays, fast computers, andmany other microelectronic deviceswill rely on our ability to producenanostructured thin-film materials.These thin-film materials are pro-duced atom-by-atom for the purposeof controlling their atomic-layerproperties. Our research goal is toproduce nanostructured thin-filmmaterials that will make electronicand optical products run longer, faster,and more efficiently than thosepresently available.

At the Laboratory, we have recentlydeveloped a facility for producingnanostructured thin-film materialsusing hyperthermal materials chemis-try, in which we selectively activatedesired chemical reactions using thekinetic energy of one or more keyatomic species incident upon a thin-film surface. The advantage ofhyperthermal materials chemistry isthat coveted electronic materials can

be easily produced at low surfacetemperatures, avoiding commonproblems such as thermal degradation,defect formation, and chemicalimpurities that are associated withexisting high-temperature processes.

We are using hyperthermal materi-als chemistry to grow wide-band-gap,thin-film nitride materials (such asgallium, indium, aluminum, andcarbon nitrides). Using a beam ofhigh-kinetic-energy nitrogen atoms,we have grown gallium nitride filmson GaAs. Analysis of these filmsusing x-ray photoelectron spectros-copy has shown that nitrogen com-pletely replaces the arsenic. Earlyindications are that we have synthe-sized thick gallium nitride films(>20 nm) of very high quality at lowsurface temperatures.

We have also grown nitride films atlow surface temperatures on indium,aluminum, silicon, diamond, andsapphire surfaces. Our preliminaryanalysis indicates significant nitrogen

incorporation into the surfaces in spiteof the thick oxide layers alreadypresent on some of the surfaces. Forexample, thick nitride films grow onindium and aluminum surfaces, andsilicon forms silicon nitride andsilicon oxynitride. Detailed analysisof the quality of these nitride filmswill enable us to further optimize thegrowth process. Analysis of thediamond surfaces indicates that wehave incorporated significant amountsof nitrogen into the surface. If furtheranalysis demonstrates that we haveformed a crystalline carbon nitridefilm, we will be the first to havesynthesized this substance, which istheoretically predicted to be harderthan diamond.

We have achieved significantprogress toward improving nitridethin-film growth using hyperthermalatoms. The next step will be toprocess selected areas of materialsusing direct patterned thin-filmgrowth and etching. These processesare necessary for electronic deviceproduction. Our goal is to usehyperthermal atom beam sources toperform carefully controlled process-ing on length scales of < 100 nm. Wewill then be able to createnanostructured devices of unprec-edented quality.

Inorganic-Organic CompositeNanoengineered Films Using Self-AssembledMonolayers for Directed Zeolite Film Growth

Robert Dye

The objective of the project is toattempt the directed growth of azeolite (aluminosilicate) cage crystalfrom an organic template deposited asa Langmuir-Blodgett (LB) film on asilicon wafer substrate. This worksupports fundamental research onmaterials synthesis of an inorganicmaterial from a tailored organicprecursor film (biomimetic synthesis).We ran two phases of this projectconcurrently: synthesis of the targetamphiphile containing a quaternary

ammonium group which couldnucleate the crystallization of ZSM-5zeolite, and preparation of LB films ofselected model compounds onto atreated silicon wafer.

We took the organic synthesis of amonosubstituted norbornadiene trimerto the ethyl carboxylate stage. Thenwe developed a large-scale syntheticmethod to make the norbornadienetrimer in good yield, using selectivesublimation and recrystallizations toobtain pure trimer from a mixture of

dimer, trimer, tetramer, and theirisomers. We prepared the ethyl carboxy-late as the precursor to further chemicalreactions which should produce thetargeted quaternary ammonium salt.Several attempts at producing the freecarboxylic acid failed. Our last try wasonly moderately successful.

Deposition of LB films usingequipment at the Advanced MaterialsLaboratory in Albuquerque resulted inhigh-quality films that could be used forour purposes. Under appropriatereaction conditions, we used one ofthese model films to produce whatappeared to be ZSM-34 zeolite on thesurface. Making the experiment safer byusing a high-pressure bomb instead of asealed glass jar resulted in our not beingable to reproduce the first success.


Rigid Molecular Foams

Warren P. Steckle

Carbon foams have been findingmany applications in recent years.Applications include fuel-cellelectrocatalysts, general catalystsupports, porous adsorbents, and foamelectrodes for use in batteries andcapacitors for energy efficiency andconservation. We prepared a series ofrigid hypercrosslinked foams, usingsimple, rigid polyaromatic hydrocar-bons such as benzene, biphenyl,m-terphenyl, diphenylmethane, andpolystyrene, with p-dichloroxylene asthe crosslinking agent. After dryingthe gels, we found the resulting foamsrobust and rigid. Their densities rangefrom 0.3 to 0.5 g/cm3. Upon carbon-ization the densities of these foamsincreased to a range from 0.6 to1.0 g/cm3.

As catalyst supports, these carbon-ized foams can retain their integrity

and porosity to temperatures greaterthan l,000°C in nonoxidizingatmospheres. We also investigated thehypercrosslinked foams and thecarbonization of these materials fortheir ability to chelate metals.

We prepared polymeric crownethers by the polycondensation ofdibenzo-18-crown-6. Crown etherscan chelate certain metals within theirring. Supported crown ethers havebeen of interest for the past severalyears in environmental clean-up andremediation. We also prepared otherpotential candidates for metal uptakeby the sulfonation of other aromatichypercrosslinked foams. To elucidatethe structure of these hypercross-linked materials, we used nitrogen-adsorption, surface-area analysis,transmission electron microscopy, andsolid-state, nuclear magnetic resonance

experiments. Pore size distributionsranged from 5 to 1000 A, dependingon starting materials.

Publications

Steckle, WP. Jr., "Carbon FoamsPrepared from HypercrosslinkedPolymer Foams" (submitted to RecentAdvances in Polymeric Foam andTechnology, Am. Chem. Soc. Books).

Steckle, W.P. Jr., "Carbon FoamsPrepared from HypercrosslinkedPolymeric Foams," Polymer Preprints37 (2), 777 (1996).

Steckle, W.P. Jr., M.A. Mitchell, andP.G. Apen, "HypercrosslinkedPolmeric Foams Prepared by Friedel-Crafts Polycondensation," PolymericMater. Sci. Eng. 74, 344 (1996).

Steckle, W.P. Jr., M.A. Mitchell, andP.G. Apen, "Tailoring the Pore Size ofHypercrosslinked Polymer Foams" (tobe published in Mater. Res. Soc.Symp. Proc: Microporous andMacroporous Mater.).

Materials Research for OpticalRefrigeration

Richard Epstein

Our objective is to characterize andtest a variety of crystals and glasses fortheir usefulness as optical refrigerants.Depending on the operating conditionsto which they are subjected, numerousmaterials can be useful opticalrefrigerants. In particular, the optimalrefrigerant material will depend uponoperating temperatures and type ofdiode lasers used. Our research issignificant because of its greatpotential for allowing the developmentof cryocoolers that operate efficientlybetween a few tens of kelvins up tofood-freezer temperatures.

This year, we confirmed theoreticalpredictions that some ytterbium-dopedfluoride glasses may effectively cool at

100 K. This was the first demonstra-tion of a solid-state cooling processthat works below 150 K, and it laidthe groundwork for developing apractical cryogenic device. Addition-ally, we have created a list of candi-date cooling materials that may besuperior to ytterbium-doped fluorideglasses. In particular, we are lookingfor materials that will cool at lowertemperatures and have better thermaland mechanical properties thanytterbium-doped fluoride glasses. Wehave characterized the spectralproperties of seven materials (fiveytterbium-doped crystals, an ytter-bium-doped glass, and ruby). Wefound that one material, BaYYbF, has

very promising absorption andfluorescent spectra. The initialcalorimetric measurements, however,showed that the particular sample wewere studying does not cool at roomtemperature because of impuritycontamination. We will be working tocorrect that problem by using purerBaYYbF crystals in our experiments.

Publications

Fajardo, J.C., G.H. Sigel Jr., B.C.Edwards, et al., "ElectrochemicalPurification of Heavy Metal FluorideGlasses" (to be published in /. Non-Cry st. Solids).

Mungan, C.E., M.I. Buchwald, B.C.Edwards, et al., "Laser Cooling of aSolid by 16 K Starting from RoomTemperature" (to be published inPhys. Rev. Lett.).


Innovative Composites throughReinforcement Morphology Design—ABone-Shaped Short-Fiber Composite

Yuntian T. Zhu

The objective of this project is toimprove the strength and toughness ofconventional short-fiber composites byusing innovative "bone-shaped," shortfibers as reinforcement. We have madesignificant progress in the fabricationand characterization of a prototypecomposite and in the understanding ofthe toughening mechanisms throughnumerical modeling. Our accomplish-ments on the experimental frontinclude the following: (1) We havedemonstrated that the strength andtoughness of a bone-shaped, short-fiber composite improve by 34% and200%, respectively, over that of aconventional short-fiber composite (asshown in the first figure). (2) We haveautomated the fabrication of bone-shaped fibers with a fiber productionrate of 2400/h. (3) We have establisheda procedure to form nodules alongNicalon fibers (see second figure).When chopped, these nodular Nicalonfibers play a similar role as the bone-shaped fibers. (4) We have establisheda facility and procedure to makecomposite samples with short fibersrandomly distributed and aligned as inthe third figure.

Using the finite-element method(FEM), we are studying the load-transfer mechanism of bone-shapedfibers and searching for better fibergeometrical design. We have foundthat there is a critical fiber lengthabove which bone-shaped fibers aresuperior in strength as compared withstraight-fiber composites.

On the modeling front, we havetailored the composite lattice springfailure-analysis model (CLASFAM) tofacilitate both chopped, straight, andbone-shaped fibers randomly distrib-uted in an elasto-plastic matrix withfiber failure strength following theWeibull distribution. We accounted forthe fiber shape in the model by using

different load-transfer functions asdetermined by FEM.

Publications

Taylor, S.T.,Y.T. Zhu, etal.,"Characterization of Nicalon Fiberswith Varying Diameters. Part I:Strength and Fracture Studies"(submitted to /. Am. Ceram. Soc).

Taylor, S.T., Y.T. Zhu, et al , "SomeNew Perspectives on the Strength andFracture of Nicalon Fibers," Third Int.Conf. on Composite Engin. Proc, 837(1996).

Zhu, Y.T., WR. Blumenthal, and T.C.Lowe, "Determination of Non-Symmetric 3-D Fiber Orientation andAverage Fiber Length in Short-FiberComposites" (to be published in J.Composite Mater.).

Zhu, Y.T., WR. Blumenthal, and T.C.Lowe, "On the Tensile Strength ofShort-Fiber Reinforced Composites"(to be published in J. Mater. ScL).

Zhu, Y.T., W. R. Blumenthal, et al.,"Modeling of Statistical TensileStrength of Short-Fiber Composites,"in Modeling of Composites:Processing and Properties, S.P. Chen,and M.P. Anderson, Eds. (TMS,Anaheim, Calif., 1996), pp. 11-21.

Zhu, Y.T., W. R. Blumenthal, et al.,"Modeling of Young's Modulus ofComposites Reinforced with 3-DOriented Short Fibers" (TMS AnnualMeeting, Anaheim, Calif., February4-8, 1996).

Reinforced with straight fibersReinforced with straight fibersReinforced with bone-shaped fibersReinforced with bone-shaped fibersReinforced with bone-shaped fibers

10 15 20

strain%

Stress-strain curves of composite samples, which are made of polyester matrixreinforced with straight nickel fibers (bottom two dotted lines) or bone-shapednickel fibers (upper three solid lines). Nickel fiber length = 2.5 mm, diameter =76.2 mm, and fiber volume fraction = 3.3%. The average strength andtoughness (area under the stress-strain curve) of the bone-shaped, short-fibercomposite samples improve by 34% and 200%, respectively, over that ofconventional short-fiber composite samples.


A Nicalon fiber with nodules obtainedby high-temperature oxidation ofcommercial Nicalon fibers.

J ' H , = 1

Fibers are aligned and randomlydistributed in a glass-fiber-reinforced,polyester-composite sample.


New Deposition Processes for the Growthof Oxide and Nitride Thin Films

Kevin Hubbard

The general goal of this effort is toapply an integrated approach todevelop and understand the details ofthe deposition process for metaloxides and nitrides from homolepticmetal amido precursors. This under-standing will lead to new routes forthe production of high-qualitymaterials that have wide application.Organometallic chemical vapordeposition (OMCVD) has been slowin gaining acceptance for coatingsapplications despite the possibilitiesfor significant advantages over metal-halide-based CVD processes. Themajor underlying limitation is the lackof understanding of the chemistryimportant to the deposition process.

Control of the fundamental chemistryof a deposition process is the key toadvancement of the OMCVDtechnique.

Recently, the efficient transamina-tion of homoleptic metal amides[M(NR2)X] with ammonia to yieldhighly reactive metal amido/imidointermediates has been used todevelop low-temperature, high-growth-rate processes for the deposi-tion of high-purity metal nitrides andoxides. The purpose of this project isto improve our understanding of thedeposition mechanisms for theseprecursors and to expand the list oftechnologically important materialsthat can be deposited from them.

This year we successfully com-pleted a low-pressure CVD reactor forthe deposition of pure and doped GaNthin films and synthesized homolepticamido precursors for the Ga and forthe Zn dopant. We also successfullydeposited pure and Zn-doped GaNfilms at low temperatures (250°C-550°C) and developed synthesisroutes for homoleptic amido precur-sors for the deposition of A1N, InN,and In2O3, as well as their alloys. TiNand Zr3N4 were deposited usingplasma-enhanced CVD. We depositedthe TiN on Kevlar fibers to improvetheir performance under compressivestress and studied Zr3N4 for itsdielectric properties.

Publications

Atagi, L.M., J.A. Samuels, et al.,"Plasma Enhanced Chemical VaporDeposition of Zirconium Nitride ThinFilms," Mat. Res. Soc. Symp. Proc.410, 289 (1996).

Texture Characterization for HE Design

Sheila Schiferl

The objective of this project is todevelop the capability to investigatethe effects of crystallographic texture(the preferred orientation of single-crystal grains in a polycrystallinematerial) on the behavior of high-explosives (HEs). Preferred orienta-tions are consequences of metal-working and other thermomechanicalprocesses and result in both strengthand elastic anisotropies. This researchincludes three components: state-of-the-art survey, model development,and implementation of models indesign code. Our research willimprove the predictive capabilitiesthat became an essential part ofstockpile stewardship after under-ground nuclear testing was banned.

We used crystallographic-texturemodeling concepts from both the

open and secure literature, and weextended methods that we haddeveloped for conventional weapons.In our modeling, textured materialsare treated as polycrystals. Individualgrains deform by shears on severalslip systems (a slip system is com-posed of a particular shear plane plusa particular direction in that plane),each slip system has a critical stress,and a maximum work criterion selectsfive independent systems. For a givenstrain, the model obtains the tensoryield strength by averaging thestresses over all the grains and thenfits the resulting yield "points" to ananalytic function. The textures weinvestigated are typical for processingweapons materials. We normalizedthe yield functions using experimentaldata.

We can adapt these techniques toanisotropic elasticity by averagingelastic constants over the grains. Weincorporated a texture-based model ofanisotropic strength into a two-dimensional Lagrangian code.Capabilities of this new code includean axisymmetric polar decompositionfor rotations, a directional yieldfunction, and a geometric-"normal"iterative return to the yield surfacethat is performed in a fixed materialframe.

Publications

Maudlin, P.J., and S.K. Schiferl,"Computational Anisotropic Plasticityfor High-Rate Forming Application,"Comput. Methods Appl. Mech. Engin.131, 1 (1996).

Schiferl, S.K., and P.J. Maudlin,"Evolution of Plastic Anisotropy forHigh-Strain-Rate Computations" (tobe published in Comput. MethodsAppl. Mech. Engin.).

18 Los Alamos FYI996 LDRD Progress Report

Interfacial Charge Transport in OrganicElectronic Materials: The Key to a NewElectronics Technology

Darryl Smith

Organic electronic materials anddevices are poised to revolutionizemajor technological areas, such asinformation display and opticalcommunication, because of theirprocessing advantages, the tunabilityof their electronic properties, and theirmaterials and design flexibility. Wecan make the complex structuresnecessary for the technology cheaplyand easily. We can modify theelectronic properties of these materi-als in a controlled way by makingsystematic changes in their molecularstructure. We would have manydesign options at both the molecularand mesoscopic scales for organicelectronic materials and devices if wehad a better fundamental understand-ing of their properties. Becauseinterfaces are the essential activeelements in every organic electronic

device, we must understand interfacialcharge transport to realize thepotential of these materials anddevices. Our primary goal is todevelop this basic scientific under-standing.

In this first year of the project, wehave developed a theory to describethe electronic structure of metal/polymer interfaces. This theorypredicts the behavior of Schottkyenergy barriers at these interfaces.We have also taken a series ofelectroabsorption and internalphotoemission measurements oninterfaces between the conjugatedpolymer MEH-PPV (a derivative ofpoly[phenylene vinylene]) and aseries of metals. We were able tosuccessfully interpret these measure-ments in terms of our theoreticalmodel.

Publications

Albrecht, J.D., L. Cong, P.P. Ruden, etal., "Resonant Tunneling in (100) and(111) Oriented Double BarrierHeterostructures," J. Appl. Phys. 79,7763 (1996).

Campbell, I.H., P.S. Davids, J.P.Ferraris, et al., "Probing ElectronicState Charging in Organic ElectronicDevices Using ElectroabsorptionSpectroscopy," Synth. Metals 80, 105(1996).

Davids, P.S., A. Saxena, and D.L.Smith, "Bipolaron Lattice Formationat Metal-Polymer Interfaces," Phys.Rev. B 53, 4823 (1996).

Heller, CM., I.H. Campbell, B.K.Laurich, et al., "Solid StateConcentration-Effects on the OpticalAbsorption and Emission of Poly (p-phenylene vinylene) RelatedMaterials," Phys. Rev. B 54, 551(1996).

Smith, D.L, and S.M. Kogan, "Theoryof Ballistic Electron EmissionMicroscopy of Buried SemiconductorHeterojunctions," Phys. Rev. B 54,10354 (1996).

Thermodynamic and ElectrodynamicStudies of Unusual Narrow-GapSemiconductors

Albert Migliori

Cryogenic solid-state refrigeratorsbased on the Ettingshausen effect(heat transport by carriers in amagnetic field) can provide vastlysuperior performance to Peltierdevices, and can thus create newmarkets in electronics, superconduc-tor, and medical applications. Thegoals of this project are to design andcreate new materials, to study theirtransport and thermodynamic proper-ties to determine if they are appropri-ate for such devices, and to optimizetheir performance. Our specific

objective is to select from suchmaterials those of highest perform-ance. In parallel we are developing acomprehensive theory to be used totune the selected systems (Bi-Sbsystems) to produce maximumtransverse thermopowers below200 K.

We have eliminated many of thehybridization-gap semiconductors andskutterudites from consideration anddiscovered a possible new explanationfor the high mobilities in Bi-Sb alloysthat may make certain little-studied

variants the best choices for anEttingshausen cooler. We have alsoadvanced the state of the theory of theEttingshausen effect and have shownit to be fundamentally different fromthe Peltier effect. Ettingshausencoolers, unlike Peltier coolers, canapproach Carnot efficiency whenphonon thermal conductivity iscontrolled. We have also constructedand used an apparatus to make all thenecessary measurements. Thesemeasurements (resistivity, Hallresistivity, thermopower, transversethermopower, and thermal conductiv-ity) were made on single crystals ofBi, Bi-2%Sb, Bi-8.5%Sb-0.05%Sn,Bi-14%Sb, SmB6 and other materials.We found astonishingly high trans-verse thermopowers in BiSb alloys atsmall magnetic fields (less than 2 T)at temperatures near 50 K.


A Molecular Architectural Approach toNovel Electrooptical Materials

DeQuan Li

Optical devices are used in a varietyof applications, including opticalcomputing, data storage, and opticalcommunication. A number of opticaldevices contain electrooptical (EO)materials—materials in whichapplying an electric field changes theindices of refraction—that are used tomanipulate light. Improving theperformance of EO materials, andthus increasing the amount ofinformation transmitted by the opticaldevices, is a constant concern.

The goal of our project is toconstruct polar multilayers with EOcoefficients much larger than those ofclassical inorganic crystals such aspotassium dihydrogen phosphate orquartz. Our approach incorporatesionic and covalent bonding amonglayers that contain preassembledchromophores—highly aligned dipolearrays that have stable and efficientEO properties. Furthermore, weintend to determine the fundamentalmechanisms controlling the formationof polar self-assembled multilayers sothat we can design advanced materialswith high performance.

In this first year, we focused on thefundamentals of molecular self-assemblies, in which molecularcomponents spontaneously organizeinto ordered structures. Thesefundamentals included the efficientinterlayer bonding, the functionalitieswithin molecular building blocks, andnew techniques for monitoringmultilayer growth. We took twoapproaches to tackle the interlayerbonding issues: (1) covalent bondformation at mild conditions and(2) multiple electrostatic-chargeinteractions between layers.

First, we synthesized various long-chain surfactants [BrCH2-(CO)-O-(CH)n-SiCl3 and BrCH2-C6H4-(CH2)i6-SiCl3]. The advantages ofthese surfactants are that the activebromine group can react with pyridylgroups at room temperature and thatthe long alkyl chains will provide in-plane ordering effects in the self-assembled monolayers. Second, wecarried out the multilayer growth byalternating an electron-rich buildingblock, nickel phthalocyaninetetrasulfonate (NiPc), with a slightlyelectron-deficient building block,poly(diallyldimethyl)ammonium(PDDA). The ionic bonds formed veryrapidly. We were able to manually growthin films of NiPc and PDDA with asmany as 100 bilayers (x-rayreflectivity/thickness = -0.08 um;spectroscopic ellipsometry/nfllm = -1.7).The accompanying plots show the x-ray reflectivity data from four of ourfilms.

Publications

Li, D., and O. Ramos Jr., "MolecularSelf-Assemblies as AdvancedMaterials" in Electrical and OpticalPolymer Systems, D.L. Wise, Ed.(World Scientific, in press).

Li, D., C.T. Buscher, and D.McBranch, "Understanding theRelationship between SurfaceCoverage and Molecular Orientationin Polar Self-Assembled Mono-layers," J. Am. Chem. Soc. 128 (12),2950 (1996).

Li, D., X. Yang, and D. McBranch,"Molecular Architectural Approachesto Nonlinear Optical Materials,"Technical Digest, Opt. Soc. Am. 11,409 (1996).

Li, D., X. Yang, and D. McBranch,"Molecular Architecture ofCalixarenes and Their Self-Assembled Mono- and Multilayersfor Nonlinear Optical (NLO)Applications" (to be published inSynth. Met.).

Li, D., X. Yang, et al., "MolecularArchitecture of Calixarenes and TheirSelf-Assembled Mono- andMultilayers for Nonlinear Optical(NLO) Applications" (InternationalConference on Science andTechnology of Synthetic Metals '96,Snowbird, Utah, July 28-August 2,1996).

Yang, X., D. McBranch, et al.,"Synthesis and NLO Properties ofPolar Self-Assemblies of MolecularPyramids Covalently Bound on OxideSurfaces," Angew. Chem. 35 (5), 538(1996).

Yang, X., L. Smilowitz, C. Buscher, etal., "Molecular ArchitecturalApproach to Self-AssembledMonolayers as NLO materials,"Mater. Res. Soc. Symp. Proc. 413, 241(1996).


!io2

100.1 0.2 0.3 0.4 0.5

10

0.1 0.2 0.3 0.4

0.10 0.20 0.30

X-ray reflectivity data (diamonds) andtheoretical fit (solid line) for thesubstrate (top left), 3 bilayers (topright), 9 bilayers (bottom left), and 27bilayers (bottom right). The verticalaxis measures the intensity of thereflected x-ray, and the horizontalaxis measures the momentum (qz) ofthe x-ray along the z-direction. Thenumber of fringes clearly increases asthe number of layers increases.

Characterization and Manipulation of Broken-SymmetryMaterials at Phase Boundaries

Robert Donohoe

The goal of this project is tounderstand the magnetic properties oflow-dimensional materials. Magneticparameters can help determine boththe ground- and defect-state proper-ties and the photodynamics of solid-state materials. These measurementscan reveal important physical proper-ties that we can relate to the chemicalcomposition of materials and therebybetter control a material's electronicand photophysical properties.

Our focus is to gain a fundamentalunderstanding of ground-stateinstabilities induced in the spindensity wave (SDW) and weak chargedensity wave (CDW) materials by theapplication of magnetic fields. Wehave primarily used Raman/magnon

scattering from samples in the bore ofthe 20-T magnet at the National HighMagnetic Field Laboratory at LosAlamos in this investigation.

We are attempting to manipulateSDW or other non-Peierls distortedquasi-one-dimensional solids com-posed of halogen-bridged linearchains (MX) into new ground statesby applying concerted and indepen-dent variations of the temperature andmagnetic field. The experimentalapproach includes the detection ofinelastic scattered light from the MXmaterials within a magnetic field withthe objective of detecting phasetransitions by observation of changesin Raman vibrational features andmagnons.

We examined both of these featuresfor a weak CDW material (PtI) andfor the SDW NiBr MX chain. Inneither instance was there a clearindication of phase transition as afunction of applied magnetic fields(0-18 T). We could not conclusivelydemonstrate detection of a magnon inthe NiBr material, although weobserved a weak, broad band near1500 cm"1 that exhibited sometemperature dependence in accordwith the expected behavior for suchan excitation.


Engineering and BaseTechnologies

Development of New and EfficientHard-Rock Mining Methods UsingPulsed-Laser Excavation

David Cremers

We are investigating the applicationof pulsed lasers to hard-rock mining.We believe that pulsed-laser excava-tion will be a more efficient methodof hard-rock mining than eitherconventional mining methods orinefficient laser techniques based onthermal processing. The new pulsed-laser techniques that we investigatedinclude hydraulic trapping of laserpulse energy at the rock surface (laserpulse/hydraulic effect) and resonantamplification of the shock wavesinduced through repetitive pulsing.We are also working to develop amethod to deliver high-power laserpulses through a fiber-optic cable.We will in part use the results of thiswork to design a hard-rock mininginstrument based on pulsed-laserexcavation.

This year we investigated the effectof sampling geometry (lens focallength, angle-of-incidence, lens type,and lens-to-sample distance) on thecoupling of laser-pulse energy in asolid matrix (soils and metals).Sampling geometry has practicalapplicability to laser-based hard-rockmining. We found that the laser plumetemperature, emissions signals, andmass ablated from the solid werestrongly dependent on geometry, andwe determined the optimum values ofthese parameters.

We also investigated energycoupling into a solid sample locatedunder water. Our experiments verifiedthat a water layer several millimeters

thick produced strong coupling of thelaser-pulse energy into the sample.This strong coupling efficiencyproduced high rates of materialablation. On the other hand, highlaser-pulse repetition rates reducedenergy coupling because the forma-tion of bubbles on the surfaceduplicated laser ablation in air, which

characteristically has low rates ofmaterial ablation.

Publications

Multari, R.A., L.E. Foster, et al.,"Effect of Sampling Geometry onElemental Emissions in Laser-Induced Breakdown Spectroscopy,"Appl. Spectrosc. 50,1483 (1996).

Pichahchy, A.E., D.A. Cremers, andM.J. Ferris, "Elemental Analysis ofMetals Under Water Using Laser-Induced Breakdown Spectroscopy"(to be published in SpectrochimicaAda B).

Virtual Reality and TelepresenceControl of Robots Used inHazardous Environments

John W. Elling

The objective of this project is todevelop virtual reality and tele-presence control for robots used inhazardous environments. Such controlof manipulators would allow opera-tors to work on hazardous materialswhile being completely removed fromthe danger of exposure. However, thesimulated environment in which theoperators would work must be asrepresentative of the actual hazardousenvironment as possible. Our methodallows for component-based genera-tion of software, which greatlyreduces system implementation anddevelopment costs.

We developed a method to incorpo-rate learning and adapting capabilitiesinto traditional rule-based descrip-tions of environments. The learningand adapting capability is critical torobot programming for highlyunstructured and variable environ-ments such as inside glove boxes. Webased our method on a hybrid expertsystem technology called expertnetworks and developed it with theassociated knowledge capturetechniques. Users will be able toapply our method to establishedsimulation packages for virtual realityand telepresence control.

Individual Projects—Engineering and Base Technologies 23

Nuclear Magnetic Resonance Imagingwith Hyperpolarized Noble Gases

David Schmidt

Our objective is to demonstratenuclear magnetic resonance (NMR)imaging of gas pressure distributionsor porosity size distributions ofobjects containing a noble gas. Inconventional magnetic resonanceimaging (MRI), the signal is derivedfrom nuclei that are thermallypolarized in the presence of a largemagnetic field. In contrast, the nucleiof noble gases can be hyperpolarizedthrough laser-driven spin exchange.Furthermore, these gases have both astrong signal and a large diffusioncoefficient. We exploited this fact intwo different experiments and madegreat progress in our goal of demon-strating diffusion imaging.

First, we inverted the polarization ina thin central section of a cylinder ofhyperpolarized 3He gas and made aseries of one-dimensional (1-D)images of the cylinder over time inorder to see the diffusion of the twopopulations of nuclei (see first figure).We measured a diffusion coefficientof D = 12.3 ± 0.2 mm2/s.

The second experiment was tomake diffusion-weighted images ofthe gas. We calculated a diffusioncoefficient at each point in the imageby taking the ratio of the imageintensities with and without a previ-ous magnetic field gradient in place.We show this process in the secondfigure, where the effects of tempera-ture and of boundaries are reflected inthe diffusion images.

Just as the relaxation parameters Tx

and T2 are used to highlight differ-ences in physical environments inNMR and MRI, we believe that thediffusion coefficient D can be used tohighlight environmental differences.Possible applications include charac-terizing porosity of materials anddynamically imaging pressuredistributions in biological or acousti-cal systems.

The series of 1-D images of the 3He gas in the cylinder over a period of 5 s, oneimage every 0.2 s. The polarization in the central portion of the cylinder isbeing filled in by other nuclei diffusing into this section, rather than by thermalrepolarization, which is what would happen in water, for example.

Without Temperature GradientDiffusion Weighted I

With Temperature Gradient

(a)

Disto-ce Alcnq Cel

(b)

Two 1-D diffusion images of the 3He gas. (a) A diffusion image with the gas atthermal equilibrium at room temperature. The diffusion coefficient away fromthe ends of the cylinder matches that measured earlier by a completely differentdiffusion-inflow method. The lowering of the diffusion coefficient near the wallsof the cylinder is due to the walls restricting the diffusion in this area, (b) Adiffusion image when the cylinder had a thermal gradient produced by holdingthe right-hand end of the cell in a liquid-nitrogen exhaust plume. For an idealgas, the diffusion coefficient is proportional to the square root of the absolutetemperature. The thermal gradient is nicely represented by the diffusiongradient in this image. Again, the lowering of the diffusion coefficient at theends is due to restricted diffusion.


The Development of Fullerene-BasedHydrogen Storage Systems

Shimshon Gottesfeld

The objectives of our project are toevaluate hydrogen uptake of fullerenesubstrates and to probe the potentialof the hydrogen/fullerene system forhydrogen fuel storage. We have madesignificant progress in demonstratingconditions for substantial andreversible hydrogen uptake/release byfullerenes. We have completed andtested a system for measuringhydrogen uptake that is capable ofhandling both a vacuum of1 x 106 torr and pressures greaterthan 200 bars. Operation of thesystem is fully automated andcontrolled by computer.

We obtained the first promisingresults using fullerene-rutheniumsamples prepared by reactingfullerenes with ruthenium carbonyland then annealing the samples at

600°C under high vacuum to removeresidual carbonyl groups. This formof modified fullerene was designed toprovide effective hydrogenationcatalysis as well as increased intermo-lecular gaps in solid fullerenes. Weused a hydrogen pressure cycle (0 to140 to 0 bars) to measure reversiblehydrogen uptake/release by thefullerene-ruthenium sample atconstant temperature. The thresholdtemperature for significant hydrogenuptake was somewhat over 200°C,and reversible uptake/release levelsmeasured for the fullerene-rutheniumsample were 1.2% at 270°C and 2.0%at 350°C. Later, we discovered that anunmodified fullerene exhibits similarhydrogen uptake/release behaviorunder similar pressure-swing condi-tions when hydrogenation is catalyzed

by a platinum strip located above thefullerene sample. Reversible isother-mal hydrogen uptake levels for theunmodified fullerene were 0.9% at200°C, 1.4% at 300°C, and 2.6% at400°C.

We suspect that hydrogenationproceeds by incipient sublimation offullerenes, as indicated by our thermo-gravimetric analysis measurements.These results provide original, signifi-cant data on the extent and mecha-nism of hydrogen uptake/release byfullerenes and, consequently, on theviability of the hydrogen/fullerenesystem for hydrogen storage. Ofparticular interest is our demonstra-tion of reversible uptake/release atlevels exceeding 2% for isothermal-pressure-swing conditions. We hopeto increase hydrogen uptake furtherby optimizing the composition andstructure of the catalyzed fullerenesample.

Optical Imaging through Turbid MediaUsing a Degenerate, Four-Wave, MixingCorrelation Time Gate

Irving Bigio

There is a significant need for asafer alternative to x-ray imaging forapplications such as mammography,dentistry, and brain imaging, andnear-IR optical diagnostics could fitthe bill. However, because tissuestrongly scatters light, resulting indiffuse or fuzzy images, a method isneeded for selecting and amplifyingonly the small number of photons thathave traveled nearly unscatteredthrough the tissue medium. Practi-cally, this is equivalent to detectingonly those photons that have taken thestraightest (that is, the shortesttemporal) path through the medium.

The goal of this project is todevelop an optical imaging diagnosticbased on the nonlinear optical

technique of degenerate four-wavemixing as a very fast correlation timegate. This method generates a short,well-defined optical gate for theimaging signal, which ensures thatonly the least-scattered photons aredetected and imaged.

This year we designed and as-sembled a tunable near-IR laser(CrLiSAF) and explored the use ofnew nonlinear media, identifying aspecific dye solution in toluene thatimproves the signal-to-noise ratios. Inaddition, we generated the firstimages of a crosshair test pattern, atwavelengths appropriate for imagingin tissue, through 2 cm of scatteringmedium. We improved the configura-tion of the optical system and refined

our component specifications toobtain excellent resolution of thecrosshair images. Finally, we alsobegan designing a cesium-vapor cellfor the nonlinear medium, which weexpect to provide several orders ofmagnitude further improvement in thesignal-to-noise ratio.

Publications

Zerkle, D.K., I.J. Bigio, and N. Nogar,"Imaging through Turbid Media witha Nonlinear-Optical Correlation TimeGate," OSA Trends in Optics andPhotonics 2, 103 (1996).


High-Average-Power, Intense Ion Beamfor Materials Modification and OtherApplications

Harold A. Davis

We are developing a 1- to 2-Hzrepetitive, intense, ion-beam sourcefor materials studies (see figure).Specifications call for a beam energyof 200-250 keV, a beam current of10-15 kA, and a pulse length 1 ms.The beam will be produced in amagnetically insulated diode with anactive plasma anode. Applications forthe source include (1) materialssurface treatment through rapid meltand resolidification, (2) coating athigh rates through vaporization oftargets and deposition onto substrates,

(3) a diagnostic neutral beam for thenext generation of tokamaks, and(4) an intense pulsed-neutron sourcefor detecting land mines and produc-ing medical isotopes.

The major accomplishments thispast year have been in the area ofdesigning and fabricating the ion-beam system. We have designed alayout of components for the high-voltage modulator, sized the overallbeam and power supply system, andcompleted design of the diode andvacuum system (including the anode-plasma generation system, thevacuum interface, the diode vacuumchamber, the beam transport andmaterials processing chamber, and thevacuum pumps, valve mounting, andplasma diagnostic vacuum chamber).Fabrication of these parts is underway. The first attempt to encapsulatethe active plasma, high-voltage coilwas unsuccessful, requiring a rede-sign; fabrication on this part is out forbid now. We also built and tested theplasma-anode and puff-valve drivecircuits.

In addition, we have successfullymodeled the thermal transport in theplasma coil with a finite-element codeand determined cooling requirementsfor the anode-plasma induction coil.We have modeled and optimized the

accelerator and fast-coil circuits, andwe have also modeled the plasmaformation and acceleration processwith a snowplow model (i.e., coupled-circuit and momentum equations).

Publications

Davis, H.A., et al., "Intense Ion BeamTreatment of Materials," Bull. Mater.Res. Soc. 21 (8), 58-62 (1996).

Davis, H.A., et al., "Progress Towarda Microsecond Duration, RepetitivelyPulsed, Intense Ion Beam," in Proc.11th Int. Conf. High Power ParticleBeam (Tiskarna, K., Ltd, Prague,Czech Republic, 1996), Vol. 1,p. 263.

PlasmaInduction^Coil-

Davis, H.A., et. al., "Progress Towarda Microsecond Duration, Repetitive,Intense Ion Beam for ActiveSpectroscopic Measurements onITER," Rev. Sci. lustrum. 68, 332-335(1997).

Jiang,W., et al, "Thermal ImagingExperiments on the Anaconda IonBeam Generator," in Proc. 11th Int.Conf. High Power Particle Beam(Tiskarna, K., Ltd, Prague, CzechRepublic, 1996), Vol. 2, p. 890.

Rej, D.J., et al, "Materials Processingwith Intense Ion Beams" (to bepublished in/ . Vac. Sci. Technol).

Rej, D.J., et al., "Materials Processingwith Intense Pulsed Ion Beams"(submitted to J. Vac. Sci. Technol.).

MagneticFluxSurfacesN

CathodeCones

Design for intense ion-beam source.

InsulatingFieldCoils


Rej, D.J., et al., "Preparation ofDiamond-like Carbon and BoronNitride Films by High-IntensityPulsed Ion Beam Deposition," inProc. 3rd Int. Conf. on Applications ofDiamond Films and RelatedMaterials, A. Feldman et al., Eds.(National Institute of Standards andTechnology, Gaithersburg, Md.,1995), p. 723.

Rej, D.J., et al., "Surface Modificationof AISI-4620 Steel with IntensePulsed Ion Beams" (to be published inNucl. Instrum. Methods Phys. Res. B).

Yatsui, K., et al., "Preparation of ThinFilms by Ablation with the AnacondaIon Beam Generator," in Proc. 11thInt. Conf. High Power Particle Beam(Tiskarna, K., Ltd, Prague, CzechRepublic, 1996), Vol. 2, p. 894.

Multichip Module Technology Development

Jon Kapustinsky

In this project we are exploringwhether several instruments underdevelopment at Los Alamos could beminiaturized using new multichipmodule (MCM) technology for theelectronics and instrument readout. Tothat end, we addressed the problemsassociated with getting dies of therequired precision. We worked with avendor and used a prototype PHENIXsilicon preamplifier, analog memory,

analog-to-digital converter (ADC),and control chips to produce a small(approximately 5- to 10-die) MCM.

We successfully created specifica-tions for the small MCM, designed it,and submitted it for fabrication. Toaccomplish this process we had toengage in significant amounts ofcommunication and collaborationwith the fabrication team, and wedemonstrated that the Los Alamos

design tools can generate files thatcan be transferred to the MCMfoundry as planned. Our Oak RidgeNational Laboratory collaboratorstransferred technical informationabout the PHENIX preamplifier,analog memory, ADC, and controlchips that we incorporated into thedesign. We procured bare die parts,and we also developed the conceptualdesign of bare die testing. We willtake measurements of the completedmultichip modules so that we candetermine the accuracy to which thosetests must be performed to ensureacceptable yields.

Magnetic Resonance Force MicroscopeDevelopment

P. Chris Hammel

Our central objective is to build atool applicable to a wide range ofstudies of technologically importantsystems, specifically layered magneticand semiconductor systems. We haveaccomplished four important goals inour program to apply the emergingcapabilities of the magnetic resonanceforce microscope (MRFM). We have(1) quantified the sensitivity andresolution of the MRFM in a pub-lished article; (2) applied the MRFMto ferromagnetic resonance (FMR)studies of microscopic ferromagneticsamples and thus opened up a newarena of study; (3) developed a newapproach to MRFM that will enablethe use of novel, high-performance

resonators (the subject of a patentapplication in preparation); and(4) developed new RF hardwareespecially appropriate for MRFM.

These last two advances are directlyin support of our ongoing work withour California Institute of Technologycollaborators on development of thenext-generation high-performancemicroresonators and on incorporationof these resonators into the MRFMinstrument. These accomplishmentsare crucial steps in our program toapply the emerging MRFM technol-ogy to important technologicalproblems in interface science.Potential applications include buriedinterfaces in layered microelectronicand magnetoelectronic devices.

Publications

Hammel, P C , Z. Zhang, et al., "Sub-Surface Imaging with the MagneticResonance Force Microscope," /. LowTemp. Phys. 101, 59 (1995).

Zhang, Z., P.C. Hammel, and G.J.Moore, "Application of a NovelRF Coil Design to the MagneticResonance Force Microscope," Rev.Sci. Instr. 67, 3307(1996).

Zhang, Z., P.C. Hammel, and P.E.Wigen, "Observation of Ferro-magnetic Resonance in a Micro-scopic Sample Using MagneticResonance Force Microscopy," Appl.Phys. Lett. 68, 2005 (1996).

Zhang, Z., M.L. Roukes, and P.C.Hammel, "Sensitivity and SpatialResolution for Electron-Spin-Resonance Detection by MagneticResonance Force Microscopy," /.Appl. Phys. 80, 6931-6938 (1996).


Femtosecond ScanningTunneling Microscope

Antoinette Taylor

By combining scanning tunnelingmicroscopy with ultrafast opticaltechniques, we are developing a noveltool to probe phenomena on atomictime-and-length scales. The goal ofthis project is to build the firstfemtosecond scanning tunnelingmicroscope (STM). The <l-pstemporal resolution of this STM willexploit the tip-sample nonlinearity.We will undertake research tocharacterize and understand thephysics of the tip-sample interactionunder transient conditions for avariety of sample materials tooptimize the temporal resolution,sensitivity, and dynamic range thisultrafast STM.

We have assembled a custom STMand optical system that permits a widerange of flexibility to accommodatethe task of developing and optimizingultrafast tunneling microscopy. Wehave examined various methods fordemonstrating ultrafast time resolu-tion of tunneling currents:• direct laser rectification of the

femtosecond pulse,• the application of an ultrafast bias

using a novel near-field, biased,terahertz emitter, and

• the incorporation of a photocon-ductive switch in the STM circuit,as shown in the first figure.

The use of the photoconductiveswitch has produced the best transientdata (see second figure). In thismethod one of the laser beamsprovides the time-gate for tunneling

signal by briefly illuminating thephotoswitch, which is fabricated fromradiation-damaged GaAs and has an"open" time on the order of 600 fs.We have obtained a time resolution of2.5 ps with a few tens of picoamps ofaverage transient tunneling current.Presently we are working to under-stand and optimize the technicalaspects of this method.

Publications

Rodriguez, G., and A.J. Taylor,"Screening of the Bias FieldiromTerahertz Generation fromPhotoconductors," Opt. Lett. 21,1046(1996).

Taylor, A.J., and G. Rodriguez,"Ultrafast Field Dynamics in GaAsPhotoconductors" (submitted to Appl.Phys. Lett.).

Input laser pulseLock-in amplifier

Modulated tunnelingcurrent

Raw tunneling current

Positioningvoltage

Computer &electronics

-STM tip

Silicon-on-sapphire stripline

Femtosecond STM schematic: The feedback loop applies voltage to the STMpiezoelectric actuator based on the raw tunneling current, in order to positionthe tip at a constant distance of a few angstroms from the metal striplinesurface. The laser pulse train, consisting of50-fs laser pulses at 100 MHzrepetition rate, is split into two beams: one generates a subpicosecondelectrical pulse which propagates down the stripline under the STM tip, and theother gates the STM measurement by briefly opening the radiation-damagedGaAs photoconductive switch. Lock-in detection occurs at the sum of the twochopping frequencies, thus indicating only that portion of the total tunnelingcurrent that is due to both the electrical transient on the stripline and the gatingpulse. Scanning the time delay of the gating pulse with respect to the striplineexcitation results in a time-resolved tunneling measurement.


Ultrafast tunneling signal,demonstrating picosecond resolutionof the femtosecond STM: (a) Tipcrashed into sample, (b) Tip weaklycontacting sample (total resistance ofGaAs switch and tunneling junction is10 M). (c) True tunneling with atotal resistance ofl6M. (d) Truetunneling with total resistance of33 M. Note that the waveform of atrue tunneling signal is the derivativeof the signal obtained with the tip incontact with the sample (a).

w

EccoQ.

O

co

-20 -15 - 5 10 15 20

Time Delay (psec)

Exploration of Technologies for ImprovingCivil Security

Eugene Farnum

Of the utmost importance to oursecurity forces and to our governmentis the security of civilians, and newtechnologies for improving securityare continually sought. Our project isaimed at increasing civilian protectionby exploring the use of flexible-tiletechnology for bomb disposalcontainers, protective vests, andportable armor and then evaluatinghow the tiles, when combined withfunctional graded ceramics andballistic modeling codes, can be usedto improve security systems. Afterinterviewing civil security forces,both state and Laboratory, to deter-mine issues and needs, we reviewedthe state of the art in security-systemmaterials and contacted potentialcollaborators.

Work this year focused on themerits of using flexible tiles forimproving bomb disposal containers,protective vests, and portable armor.During our investigation of bomb

disposal containers, two companiesthat were interested in having usevaluate their technologies fabricatedsuch containers, which did notincorporate our flexible-tile technol-ogy, and delivered them to LosAlamos for testing. The companies'involvement was sponsored by theIndustrial Partnership Office. Testresults suggested that our flexible-tiletechnology would substantiallyimprove explosive containmentdevices and led to a Los Alamosproposal to the National Institute ofJustice for further technologydevelopment.

During our study of protectivevests, we learned that Kevlar™ vestscan be penetrated by ice picks. Acollaboration with the New MexicoState Police established that ourflexible-tile technology will signifi-cantly increase the protection offeredby ballistic vests against ice picks andother pointed weapons without adding

undue weight and that it may be usedby civilian police forces. StructuralLaminates, a company with which weestablished a collaboration, donatedsome aluminum/fiberglass laminatethat we used in experiments on ClassHa ballistic vests donated for testingby the New Mexico State Police. Thetile-protected vests were successful indefeating hand thrusts with sharpenedice picks. We also designed an ice-pick test fixture capable of meetingthe California Department of Correc-tions Penetration Standard.

Finally, for portable armor wedesigned an armored blanket that willprovide portable protection of policevehicles from rifle fire. For theblanket, we acquired off-the-shelfceramic/cermet tiles (similar to thosepreviously used at Los Alamos indeveloping armor for the C-141aircraft) and a bolt of appropriateKevlar™ cloth, but lack of sufficientresources prevented us from complet-ing and testing the blanket.


Fiber-Optic CommunicationsUsing Solitons (FOCUS)

Darryl D. Holm

The telecommunications industry iscurrently developing soliton-basedoptical-fiber networks in the hope ofsending many scores of gigabits persecond of digital data over fiber-opticlinks between computers and intohomes and businesses. These soliton-based optical-fiber networks woulduse solitons (stable nonlinear opticalpulses in nearly transparent fibers) asinformation bit carriers. Suchnetworks would take advantage of theintrinsic stability of soliton solutionsof the nonlinear Schrodinger equa-tion, which to leading order describesthe evolution of optical pulses in alossless fiber. However, even in thehighest-purity fibers, unavoidableenergy losses cause soliton pulses todecay and disperse, thereby limitingdata transmission rates. Reversing thisdispersion, and thereby improving therate of information transmission,requires devices that can reshapepulses. In this project we are design-ing and developing these devicestheoretically and numerically by usingand extending a general mathematicalframework for analysis of nonlinearpulse transmission in optical-fibernetworks.

This year we designed and analyzeda novel pulse recovery scheme usingnonlinear optical loop mirrors.Because of the initial success of ourresults and the potential for theirapplication in optical-fiber networks,the University of California decidedto seek a patent on our pulse recoveryscheme. We also invented a way ofusing nonlinear optical loop mirrorsto generate high-quality soliton pulsetrains. (Of course, a method of

reliably generating soliton pulses is aprecondition for their use in opticaltransmission systems.) We have alsodeveloped a new perturbation tech-nique for the study of optical-fiberamplifiers that should help guidefuture design developments andfacilitate benchmarking of numericalsimulation results. Next year we planto continue our study of pulse-reshaping devices and apply ourperturbation technique to the develop-ment of numerical methods andalgorithms for accurately computingsoliton pulse propagation in opticalfibers.

Publications

Cruz-Pacheco, G., and B.P. Luce,"The Relationship between PeriodicWavetrains and Solitary Waves inOptical Fiber Communications" (to bepublished in Phys. Lett. A).

Gabitov, I., D.D. Holm, and B.P.Luce, "Generation of Soliton PulseTrains from Sinusoidally ModulatedCW Beams with NonlinearAmplifying Loop Mirrors" (to bepublished in Opt. Lett.).

Gabitov, I., D.D. Holm, and B.P.Luce, "Low-Noise Picosecond SolitonTransmission Using ConcatenatedNonlinear Amplifying Loop Mirrors"(to be published in J. Opt. Soc. Am. B).

Gabitov, I., D.D. Holm, et al.,"Recovery of Solitons with NonlinearAmplifying Loop Mirrors," Opt. Lett.20, 2490 (1996).

New Applications forZeeman Interferometry

Roger Johnston

Our objective is to develop andexplore new applications for theZeeman Refractive Index (RI)Detector, which received an R&D 100Award in 1992. The RI of a sample isthe ratio of the speed of light invacuum to the speed of light as itpasses through the sample. Ourinstrument detects and measureschanges as small as one part in abillion in the RI of a time-varyingsample, such as a flowing gas orliquid. We developed the Zeeman RIDetector initially for monitoring air orgas samples for small changes incomposition or contamination.Among the new applications for thetechnology explored in this project isa detector for gel electrophoresis, adetector for chromatography, andultrasensitive thermooptic spectros-copy (a type of ultrasensitive spectro-photometry).

This year we made significantprogress in devising new applicationsfor the technology, in making theinstrumentation simpler, and indiscovering new ways to use theinstrument for ultrasensitive specia-tion. These new methods mayultimately prove to be patentable.Progress made during this project hasled to two new cooperative researchand development agreements(CRADAs), one of which is forpollution and process monitoring.

Publications

Johnston, R.G., "On the Matter of'Ratioing'" (to be published in Am.Stat.).


A Comprehensive Monitoring System forDamage Identification and Location inLarge Structural and Mechanical Systems

Charles R. Farrar

It would be very helpful if we couldidentify damage to large structuresand mechanical systems at the earliestpossible stage, before permanentdamage to the structure or system, orinjury to individuals, occurs. For thisproject we are developing andexperimentally verifying a softwarepackage comprising state-of-the-artstructural monitoring/damage-detection algorithms.

During the past two years of thisresearch effort, we have reviewed theexisting state-of-the-art methods ofstructural damage identification bymeasuring changes in the vibrationcharacteristics of civil, mechanical,and aerospace structures; we alsodeveloped new algorithms that betterdetect damage. We are in the process

of assembling these algorithms into ainteractive computer code.

This year we developed robustdamage identification algorithmsthrough numerical and experimentalsimulations. To quantify and locatedamage using global vibrationresponse measurements, we primarilylooked at changes in strain energystored in the structures; we deter-mined the strain energy changes fromchanges in the mode shape curvatureof the structures. We also developedand implemented statistical analysismethods whereby we can distinguishbetween changes in measuredparameters caused by damage andthose caused by random experimentalerror. This feature of our damageidentification procedure is unique, and

it enhances our ability to detectdamage in structures and mechanicalsystems.

Publications

Doebling, S.W., and L.D. Peterson,"Computing Statically CompleteFlexibility from DynamicallyMeasured Flexibility" (submitted to /.Sound Vib.).

Doebling, S.W., L.D. Peterson, andK.F. Alvin, "Estimate of ReciprocalResidual Flexibility from Experi-mental Modal Data," AIAA J. 34,1678-1685 (1996).

Doebling, S.W., L.D. Peterson, andK.F. Alvin, "ExperimentalDetermination of Local StructuralStiffness by Disassembly of MeasuredFlexibility Matrices" (submitted to /.Vib. and Acoustics).

Farrar, C.R., "System Identificationfrom Ambient Vibration Measure-ments on a Bridge" (submitted to J.Sound Vib.).

Quantum Cryptography forSecure Communications toLow-Earth-Orbit Satellites

Richard Hughes

Cryptanalysis techniques andalgorithms are advancing rapidly andby the start of the twenty-first centurywill necessitate the development anduse of new encryption technologies toensure secure communications tosatellites. The aim of our project is todevelop quantum cryptography toprovide absolutely secure encryptionof communications to low-Earth-orbiting satellites. We will developand demonstrate the cryptographictechnology to a stage where it can befeasibly incorporated into newsatellites.

Quantum cryptography uses singlephotons to create and transferinformation in a way that utilizes thelaws of quantum mechanics to affordabsolute security. Our calculationsshow that with quantum cryptography,completely secure, random "seeds"(cryptographic keys) can be generatedbetween a ground station and satellitein real time. By eliminating any priorrecord of a key, quantum cryptogra-phy removes the possibility of hostileinterception of communications,making the entire encryption processboth simpler and more assured.

During the past year, we havedesigned, constructed, and tested aquantum cryptography system thatcreates and transmits—using single-photon transmissions—cryptographicrandom numbers between a sending-and-receiving instrument within ourlaboratory. The system is based on thepropagation and detection of non-orthogonal polarization states ofsingle photons in free space at awavelength (771 nm) for which theatmosphere has a very low attenua-tion. We are now taking the stepsrequired to preserve the intellectualproperty rights to this inventionbefore publishing papers or makingpublic presentations about our systemand its performance.


Application of Intense Surface DischargeVUV Light Sources to Photoresist Ashingin Semiconductor Manufacturing

Robert Sze

This project deals with the develop-ment of a sliding-arc light source thatwould have sufficient intensity in theultraviolet spectral region to domaterial processing over a very largearea. The ability to melt thin-filmmaterials in a single shot can have amajor impact (for example, on the flatpanel display industry) in suchapplications as the conversion ofamorphous to polysilicon circuits onglass substrates used in liquid-crystalflat panel displays and in the activa-tion of phosphors on electrolumines-cent flat panel displays.

The device we designed has a6-in. x 6-in. discharge area on adielectric surface for studies that havebeen made on alumina, teflon, andplate glass. At a charge voltage of30 kV, the system stores some 2 kJ inpulse power. At this operating pointwe have shown a surface intensityuniformity of better than 5% acrossthe entire surface area of the lightflash. Integrated light-energy outputson the surface from 200 nm to theinfrared have been measured atgreater than 800 mJ/cm2. Preliminaryattempts to crystallize amorphoussilicon were unsuccessful, butcrystallization was attempted atdistances very far from the flashsurface.

This year we focused our experi-mental efforts toward obtainingdetailed light spectra of the flash. Wehave obtained instrumental distortion-corrected spectra from 160 to 735 nm

in helium, neon, argon, and krypton,as well as typical KrF and ArFexcimer-laser gas mixtures andfluorine-containing gas mixtures inattempts to maximize uv productionin these sliding-arc discharges. Thefirst accompanying figure gives anexample of such a study in argon. Thesecond figure gives a comparison inthe 160- to 360-nm UV range forargon and krypton. Krypton showshigher UV content, although therising slope in UV light from black-body radiation is judged similar inboth gases. The third figure showsthat energy deposition into thedischarge is greatly enhanced withincreasing pressure as a result ofincreasing discharge impedance.

Publications

Hatanaka, H., and R.C. Sze,"Development of an Intense SurfaceDischarge Pumped VacuumUltraviolet Lamp" (Tenth IEEEElectron Devices Pulse PowerConference, Albuquerque, N. Mex.,July 1995).

Sze, R.C., "Intense UV Light Sourcefor Semiconductor and Flat PanelDisplay Processing" (Conference onLasers and Electrooptics, Baltimore,Md., May 1995).

Sze, R.C.,"Large-Area SurfaceDischarge UV Light Source forMaterials Processing Applications"(to be presented at Gas and ChemicalLasers Conference, San Jose, Calif.,February 17, 1997).

1500

1000-

Wavelength (nm)

Flash spectra in 1000-torr argon gas on alumina dielectric from 160 to 735 nm.


Flash spectra comparison at 1000-torr pressure between argon andkrypton in the 160- to 360-nm UVrange on alumina dielectric.

1400-

1200

1000

160 180 200 220 240 260 280 300 320 340 360

Wavelength (nm)

Flash spectra in argon at 500-, 750-and 1000-torr pressure on aluminadielectric.

700

260 460

Wavelength (nm)

All-Solid-State Four-Color Laser

Timothy R. Gosnell

The goal of this project is todevelop a solid-state laser thatproduces visible output wavelengths,including the commercially compel-ling blue wavelength. The deviceconsists of a single-mode optical fiberdoped with Pr3* and Yb3+ ions. Whenthe ions are simultaneously pumpedwith a near-infrared laser (860 nm),complex energy-transfer processesinvolving multiple excited ions lead topopulation of a high-lying energylevel of Pr3+.

Our main accomplishment this yearwas to verifiy and quantify the natureof the energy-transfer processes, inparticular a "photon avalanche"process, responsible for the efficientpopulation of the upper laser level.These results will be used to design anew geometry for the optical fiber,which was initially unoptimized, inorder to enhance device performance.


Material Processing forSelf-Assembling Machine Systems

Klaus Lackner

We are developing the foundationfor a new technology based on self-reproducing machine systems. Of thenumerous issues that need to beconsidered and resolved before ourvision of the new technology can beimplemented, material extraction isone, and it is the focus of our project.Limitations in energy and nonrenew-able resources and the need to controldeleterious side effects of humanactivities on the environment aremajor problems for the comingdecades. Self-reproducing machinesystems could be their solution.

Machine systems that build andmaintain themselves promise anincrease in industrial productivity asdramatic as that of the industrialrevolution. A system that can builditself must procure all raw materialsfrom its natural surroundings. Thus,next to automation, one of the most

critical issues in developing the newtechnology is the design of a processthat will extract all the importantchemical elements from raw dirt. Thisprocess differs from conventionalextraction metallurgy in that it usesonly abundant elements, becausealmost the entire mass of the self-replicating system is channeledthrough the process. However, suchextraction processes are of interesteven to conventional metallurgybecause they do not involve use ofexpensive and sometimes hazardousmaterials.

This year, we have successfullycollected a set of sample materials—for example, basalts—that are typicalfor the basic extraction process.However, most of our work to datehas been performed on pure oxidesand minerals. Because our newextraction processes occur at high

temperatures, we have been designingand building special, small, low-costfurnaces. We have reduced ironoxides and pure iron silicates withmetallic silicon at 1600°C in air.Avoiding the need for a protectiveatmosphere is a major achievementbecause it greatly simplifies theultimate design of the extractionprocess for self-replicating machines.We succeeded in extracting small ironpellets from raw materials. At thesame time, our experimental resultspoint to the need for a careful choiceof the material for the containmentvessel, which tends to be attacked bythe melted charge. We have tested anumber of materials and are optimiz-ing our choice. Discover magazine(October 1995) referred to ourconcept as one of seven ideas thatcould change the world.

Publications

Lackner, K.S., and C.H. Wendt,"Exponential Growth of Large Self-Reproducing Machine Systems,"Math. Comput. Modelling 21, 55-81(1995).

Diode Laser Developmentfor Quantum Computation

Richard Hughes

Quantum computation is muchmore powerful than classical compu-tation because it allows computingwith quantum-mechanical superposi-tions of many numbers at once. In aquantum computer, binary numberswill be represented by quantum-mechanical states ("qubits")- We havebeen developing a quantum computa-tional device in which the qubits willbe two electronic states of calciumions that have been cooled with alaser to rest at a particular location inthe ion trap. We will then performquantum logical operations with alaser beam that is resonant with thequbit transition frequency and isdirected at individual ions. Titanium-sapphire lasers are a proven

technology for this application, butthey are expensive, require a laserexpert, use over 40 kW of power, andfill an entire laser table. The objectiveof our project is to develop diodelasers for this application becausethey are easy to use, low in cost, andcompact.

This year, we have developed diodelasers at the 866-nm and 794-nmwavelengths that are required forcooling calcium ions. (In the next fewmonths, we will double the frequencyof the 794-nm light to obtain 397-nmlight.) We have assembledexternal-cavity diode laser systemsand, with a prototype, demonstratedlocking to an existing frequencystandard. We have developed

frequency-offset techniques usingmodulators and/or ultrastable cavitiesto reference the 866-nm and 397-nmwavelengths to stable atomic lines.Typically, the wavelength of the lightemitted by the laser must be con-trolled with respect to a referencewavelength, which is near to thedesired wavelength. For our diodelasers, we can reference light wave-lengths to an absolute atomic standardor to a very stable optical cavity thatresonates at a very well definedfrequency.

At the same time, we have workedwith two companies to determine ifthe frequency-doubling cavities thatthey market would give the necessaryamount of output power and wouldprovide adequate beam quality for our397-nm wavelength requirements.Finally, we have studied theDrever-Hall stabilization techniquefor external-cavity lasers as a meansfor producing laser linewidths ofbetter than 100 kHz.


Designing a Micromechanical Transistor

Ronnie Mainieri

Micromechanical electronicsystems are chips with moving parts.They are fabricated using the sametechniques for manufacturing elec-tronic chips, sharing their low cost.Micromechanical chips can alsocontain electronic components. Thecombination of mechanical parts andelectronic parts makes it possible forchips to process signals mechanically.To achieve designs comparable withthose obtained with electroniccomponents, it is necessary for these

chips to have a mechanical device,i.e., a mechanical transistor, that canchange its behavior in response to asmall input.

Large responses caused by smallchanges are the hallmark of chaoticdynamics so most of the transistordesigns we have considered corre-spond to chaotic systems. The chaosis in the ray dynamics of soundpropagation. When we tried tocompute the resonances of systemswith chaotic ray dynamics, we

discovered that the numericallycomputed resonances had errors thatgrew exponentially fast with theresonance number. The errors alsofollow a universal curve independentof the shape of the device. The errorsin the resonances imply an error forthe time evolution of the system andmay also be present in other equa-tions. This exponential growth inerrors makes it impossible to usetraditional numerical techniques, andwe are now characterizing theproblem and approaching its solutionusing methods developed for thestudy of nonlinear dynamical systems.The basic idea is to combine MonteCarlo data with analytic methods.

High-Sensitivity, Solid-State CarbonMonoxide Sensor Development

Fernando Garzon

Carbon monoxide gas (CO) is adeadly, colorless, odorless gas thatresults from incomplete combustionof typical fuels. It is the most com-mon form of death due to asphyxiantgases in the United States. Better

sensor technologies for this gas areneeded to protect people in theirworkplaces and homes. Our objectiveis to develop simple, low-cost,electrochemical sensors for thedetection of CO in air with tens of

Acoustic Resonance Spectroscopy

Randy S. Roberts

US government agencies havesuccessfully applied AcousticResonance Spectroscopy (ARS) to theproblem of noninvasive classificationof chemical munitions. The classifica-tion technique compares templatesformed from the acoustic signature ofknown munitions to acoustic signa-tures of unknown munitions. Oneproblem with this approach istemplate construction—specifically,determining which combination ofsignatures yields the best template.The objective of this project was todevelop a technique to determine thebest set of signatures to construct atemplate.

We have developed an approachthat appears to be a promisingsolution to this problem. The ap-proach involves successively addingnew signatures to the template andmonitoring discrepancies betweensuccessive templates. At this point weare evaluating the technique onseveral data sets. Additional work onthis project included reporting aliquid-solid discrimination algorithmand exploring the application of ARSto such areas as gas-bottle inspectionand pit surveillance. We obtainedpromising results in the formerapplication, and results are forthcom-ing in the latter.

parts per million sensitivities, goodselectivity, and fast response times.The current commercial sensortechnologies cannot detect carbonmonoxide below dangerous thresholdlevels—tens of parts per million—nordo they respond quickly at thehundreds of parts per million levels.

We have produced, tested, andoptimized solid-state electrochemicalsensors that use thin-film perovskite-or fluorite-structure catalysts assensing electrodes deposited onoxygen-ion, conducting solid electro-lytes for monitoring carbon monoxidein air. Our sensors show excellentsensitivity: the ability to detect lessthan 1 ppm CO, rapid response time,and good return to baseline character-istics. They also show good long-termdurability—over 1000 hours ofoperation under a variety of condi-tions.

We have studied the cross sensitiv-ity of these sensors to carbon dioxide,water vapor, propane, methane,ethanol, and hydrogen. We have alsodemonstrated that variants of thistechnology can be used to sense othergases, such as hydrocarbons, sulfurdioxide, and nitric oxides. Our tech-nology may replace semiconductor-based sensors currently in use becauseof the new devices' superior responsecharacteristics. We have filed a patentapplication for this invention.


Liquid-Metal, Focused-lon-BeamEtch Sensitization and RelatedData Transmission Processes

Bruce Lamartine

Ultrahigh-vacuum focused-ion-beam micromilling is a method ofrecording data permanently at veryhigh density. The process can poten-tially be significantly improved byion-beam sensitization to wet or dryanisotropic chemical etch reactions.The objective of this project is toexplore the general phenomenon ofion-beam etch sensitization in severalmedia—e.g., silicon (100), galliumarsenide, and tantalum oxide ontantalum—for optimal pixel or bitcontrast and to search for optimal

media and transmission formats forrapid digital transfer. In addition, weintend to explore, in hardware, thefeasibility of a charge-coupled-devicedata transfer scheme that can senddata at video rates.

The ion-beam micromillingprocess, while already successful, canbe enhanced by ion-beam sensitiza-tion to wet or dry anisotropic chemi-cal etch reactions. Ion-beamsensitization differs from conventionallithography in that many levels offeature depth are potentially available

(depending on the local, spatial iondose) and that no organic or inorganicresist is required. We developed theseunique features sufficiently during thepast year to file several patent actionson applying this process to theproduction of both digital and human-readable grayscale data on archivalmedia such as silicon and other singlecrystals or amorphous coatings.Furthermore, we showed that severalmicromachined data media can beused for human-readable formats(either pictures or print): silicon (100)can be read by a phase-sensitiveinterference microscope, silicon (100)and silicon (111) can be read by alaser intensity feedback microscope,and tantalum oxide can be read by aconventional scanning-electronmicroscope.

Experimental Validation ofSuperconducting QuantumInterference Device Sensors

Robert Kraus

Along with Sandia NationalLaboratories (SNL) and the Univer-sity of New Mexico, we have sup-ported the collaborative developmentof two critical components for a hand-held, low-field magnetic sensor basedon superconducting quantum interfer-ence device (SQUID) technology. Thetwo components are a digital signalprocessing (DSP) algorithm forbackground noise rejection and asmall, hand-held, dewar cooled by acryocooler (supplied by SNL).

We reported the results of the DSPalgorithm implementation at the 10thInternational Conference onBiomagnetism. Traditionally SQUIDshave been operated in magneticallyshielded rooms, costing approxi-mately $500,000 or more, to reduce

background fields sufficiently thatthey will not overwhelm the dynamicrange of the SQUID. We implementedthis novel approach developed as partof this LDRD project in a prototypesystem that enables cancellation ofmore than 99% of the backgroundmagnetic field at the SQUID. We usedthe principle of superposition ofmagnetic fields.

Using state-of-the-art electronicsand digital circuits, we anticipatebeing able to cancel at least 80 dB(99.99%) of the background signal.This level of background cancellationat the SQUID makes applicationssuch as monitoring head trauma orcardiac function in the field a realisticprospect and one that we will develop.

The hand-held SQUID sensorsystem is nearing completion as of thewriting of this report. The battery-powered cryogenic cooler has beenprocured by SNL and the last parts ofthe dewar are in fabrication. Thedewar design uses a thick aluminumwall for eddy-current cancellation ofall but low-frequency signals,reducing further the ambient back-ground at the SQUID, while allowingmost of the biomagnetic frequenciesof interest through the wall to theSQUID sensor.

A second hand-held dewar has beendesigned using G-10 glass-epoxycomposite that will allow the entireelectromagnetic spectrum to passthrough to the SQUID. The aluminumdesign will enable use of the proto-type DSP background cancellationsystem, since it is less reliant oncomplete removal of the background.The composite dewar will requirehighly efficient background rejection.


Plasmas, Fluids, andParticle Beams

High-Power, High-Frequency,Annular-Beam Free-Electron Maser

Michael Fazio

Free-electron masers (FEMs)operating in the microwave regimehave demonstrated both high beam-to-RF power extraction efficiencies(-30%) and high output power(~GWs). In addition, FEMs arepotential candidates for drivingadvanced particle-beam acceleratorsat relatively high frequencies (greaterthan 10 GHz). However, current FEMtechnology does not lead to adequatephase stability for this application.Furthermore, high output power hasbeen demonstrated only with FEMsdriven by induction accelerators athigher voltage than practical fordriving long accelerators. Such ahigh-power RF source would enablethe construction of future linearcolliders that are simply too expensiveto build with existing technology.

The objectives of this project are to(1) demonstrate high output power(0.5 GW) at high frequency (17 GHz),using a high-current but relativelylow-voltage electron beam, and

(2) demonstrate a phase-stabilityscheme in which the RF phase of theoutput power is not affected by smallfluctuations in the electron beamvoltage. We have derived theoreticalphase-stability criteria and designed ahigh-power FEM using the axial FEMinteraction that satisfied these phase-stability criteria.

Most recently we have concentratedon prototyping and fabricatingcomponents for a high-power experi-ment. Because of the uniqueness ofthis experiment, completely newdiagnostic techniques and RFmatching components are needed. Inparticular, we have designed and builtan input coupler, a high-power load, aslow-wave structure, directionalcouplers, and high-power calorim-eters. We are now assembling thehigh-power experiment.

Publications

Carlsten, B.E., "Axial Free-ElectronLaser Interaction between an AnnularElectron Beam and an AxisymmetricTM Mode," IEEE J. QuantumElectron. 31, 1753 (1995).

Carlsten, B.E., "Enhanced PhaseStability for a Raman Free-ElectronLaser Amplifier in the ExponentialGrowth Regime," Phys. Plasmas 2,3880 (1995).

Carlsten, B.E., CM. Fortgang, J.M.Potter, et al., "Microwave Axial Free-Electron Laser with Enhanced PhaseStability," Nucl. lustrum. MethodsPhys. Res. A 375, 171-174 (1996).

Carlsten, B.E., W.B. Haynes, and R.L.Sheffield, "Particle Acceleration bythe Inverse Axial-Free-Electron LaserInteraction," Particle Accelerators 51,121-133 (1995).

Input SectionRippled-Wall

Structure

DirectionalCoupler 6 Port

Input Coupler

A schematic of the high-power free-electron maser experiment.BeamDump

Load andCalorimeter

Individual Projects—Plasmas, Fluids, and Particle Beams 37

Determination of Optical Field-lonizationDynamics in Plasmas through DirectMeasurement of the Optical-PhaseChange

Antoinette Taylor

The interaction of ultrashort, high-intensity laser pulses with solid andgas targets is a field of growinginterest. Highly ionized, atmospheric-density plasmas are a potential sourceof coherent visible-ultraviolet andx-ray light, as well as a potentialmedium for charged-particle accelera-tion. The interaction of a high-intensity,ultrashort pulse with a solid target is ofinterest both scientifically and as asource of ultrashort x-ray pulses.

New, quantitative experimentaldiagnostics compatible with ultrafasttime scales are needed to measure theionization and the subsequent plasmadynamics that give rise to theseconditions. The goal of this project isto develop a technique for characteriz-ing laser-plasma interactions withfemtosecond resolution based on thedirect measurement of the phase

change of an optical pulse. We canthen use this technique to investigatefemtosecond field-ionization dynam-ics in atomic and molecular gases andto study solid-target laser-plasmainteractions.

This year, we developed this noveltechnique and used it to investigatefemtosecond field-ionization dynam-ics in atmospheric-pressure noblegases. We focused an intense (1014 to1016 W/cm2), ultrafast (100-fs) pulseinto a cell containing a noble gas at apressure of 1 atm or less; this pulseionized the gas. We then measured thechange in the optical phase andamplitude induced by the presence offree electrons in the ionized gas usingthe technique of frequency-resolvedoptical gating. With this setup wedetermined the evolution of theionization dynamics in helium, neon,

argon, krypton, and xenon as afunction of pressure and pumpintensity (see plot of phase vs time)and measured strong-field ionizationrates of these gases. We modeled theionization dynamics using strong-fieldtunneling theories—both Keldysh andAmmosov-Delone-Krainov (ADK)—and compared the results with ourmeasurements (see plot of density vstime).

Publications

Clement, T.S., G. Rodriguez, et al.,"Characterization of UltrafastInteractions with Materials throughDirect Measurement of the OpticalPhase," Proc. Soc. Photo-Instrumentation Eng. 2701, 229(1996).

Kane, D.J., T.S. Clement, et al.,"Simultaneous Measurement of TwoUltrashort Laser Pulses from a SingleSpectrogram in a Single Shot" (to bepublished in J. Opt. Soc. Am. B).

Wood, W.M., M. Cyza, et al.,"Determination of Strong FieldIonization Rates through DirectMeasurement of the Optical Phase,"in Ultrafast Phenomena X (Springer-Verlag, Berlin, in press).

0.5 —

0.4 —

0.3 —

0.2

0.1 -

0.0

Phase Changesin Neon

-300 -200 -100 0 100 200Time ffs)

300

Measurement of the phase change ofthe optical pulse due to the creationof the plasma in neon gas reveals thatthe magnitude of the effect scales withpressure, as expected. Consistent withtheory, the onset of ionization occursrapidly in the early stages of thepulse.


We analyzed the phase measurementsfrom the other figure to yield the free-electron density as a function of time.The results are compared withcalculations from both the Keldyshand ADK theories. The measuredresults demonstrate higher ionizationrates earlier in the pulse than eitherof the theories suggests.

oZ

1.0

0.8 —

0.6 —

0.4

0.2

0.0

-200

Intensity

\ Keldysh Theory

\ ADK Theory

\ W M M H Measured: 10 torrI\ - - - - Measured: 20 torr

\

\ Density vs Time1 Neon

200Time (fs)

Delta-f and Hydrodynamic Methodsfor Semiconductor Transport

Lester E. Thode

The most sophisticated simulationtechnique for semiconductor carriertransport is the Monte Carlo method.Unfortunately, the Monte Carlomethod is computationally costly. Inthis work we are investigatingwhether the delta-f method, developedwithin the magnetic fusion commu-nity, can be successfully applied tosemiconductor transport. In addition,we are working to develop a singlearchitecture to allow users to selectfluidlike models, a Monte Carlomodel, or a delta-f model.

Development of a C++ prototypeplug-and-play code (PCUBED) isnow complete. PCUBED allows theintegration of different code lan-guages within a single architecture,including C++, C, and FORTRAN

codes. PCUBED utilizes advancedinput and output capabilities andincludes interactive graphicaldebugging.

We imported the code MINIMOSinto PCUBED to provide the drift-diffusion, energy-balance, andhydrodynamic models for thefluidlike part of the delta-f method.For the particle-tracking part of thedelta-f method, we imported a newC++ object-oriented Monte Carlocode into PCUBED. We also devel-oped new approaches to solve thenonlinear Poisson equation. Tocalculate moments of the distribution,we developed a general particleaccumulation approach. To reducenoise, we are investigating higher-order particle-weighting schemes.

The plug-and-play nature ofPCUBED has allowed use of the codein new areas such as neutron trans-port, brain tomography, and gas-corenuclear rocketry. Finally, we haveshown that existing FORTRAN codescan be standardized with respect toinput, output, restart, and graphics,which, if implemented, would lead toincreased productivity of designefforts.

Publications

Gray, M., T. Booth, et al., "Multi-Comb Variance for Monte CarloSemiconductor Simulators"(submitted to IEEE Trans. ElectronDevices).

Thode, L., R. Hotchkiss, C. Snell, etal., "Plug-and-Play Environment forAlgorithm Development" (U),(Nuclear Explosives Code DevelopersConference, San Diego, Calif.,October 1996).


A Compact Compton-BackscatteringX-Ray Source for Mammography andCoronary Angiography

Dinh C. Nguyen

We are developing a compact,tunable, monochromatic x-ray sourcefor applications in medical imagingsuch as mammography and coronaryangiography. Using monochromaticx-rays in such applications willreduce the x-ray dose to patients andat the same time enhance the filmimage by reducing unwanted scatter.Our technical goal is to demonstratethe generation of a large flux ofmonochromatic x-rays in the keVenergy range. We accomplish thisgoal by colliding a visible laser beamagainst a relativistic beam of electronsin a process known as Comptonbackscattering.

The experimental setup forCompton-backscattering x-raygeneration includes a linear accelera-tor to produce the relativistic electronbeam, a high-powered laser, and anoptical resonator to trap the laserbeam and to increase its intensity. Fordetecting the x-rays, we use ascintillator coupled to a light pipe thatdirects the visible fluorescence fromthe scintillator to a photomultipliertube. These components are shown inthe accompanying figure. In ourexperiments, the laser beam is used togenerate electrons through a photo-emission process, and the trajectory ofthe electrons is timed so that theycollide with the laser beam at a knownposition.

We have successfully tested thescintillation x-ray detector and foundthat it exhibits good sensitivity andgood spatial discrimination againstbackground radiation. We used apicosecond streak camera coupled toa charge-coupled device camera tooverlap the electron beam and thelaser beam in both space and time.Although the x-ray detector registereda positive reading, we could notconclusively demonstrate that the

signal arose from the Compton-backscattered x-rays because it didnot completely go away when the

several approaches to increase theyield of x-rays via Compton backscat-tering in order to meet our objectives.

Publications

Nguyen, D.C., and B.E. Carlsten,"Amplified Coherent Emission fromElectron Beams Prebunched in aMasked Chicane," Nucl. Instrum.Methods Phys. Res. Sect. A 375, 597

laser was blocked. We are working on (1996).

ElectronAccelerator

CollisionBeam Point

Transport

X-rays

/ A

BeamDump

Li!The major components of theCompton-backscattering experiment.

Equation of State of Dense Plasmas

John Benage

The goal of our project is tomeasure the equation of state of adense aluminum plasma. We willaccomplish this goal by using a laserto produce a shock in a uniformaluminum plasma plume. We willmeasure the velocity of the shock, thedensity in front of and behind theshock, and the temperature. Fromthese measurements, we will deter-mine the equation of state.

In the past year, we designed andcompleted the construction of the newcapacitor bank which we will use toproduce our plasma. The laser we willuse to produce x-rays for the densitymeasurements is operational, and wehave begun tests on the production ofthese x-rays. We are just beginning

preliminary tests of the new capacitorbank; when these tests are completed,we will begin tests on the productionof the aluminum plasma plume.

We also did a series of simulationsof this experiment to determine therequirements for the laser that will beused to produce the shock in theplasma. These calculations showedthat we need a 0.53-um laser with apulse width of 1-2 ns and an intensityat the plasma of 10 TW or greater.From these results, we designed alaser system which takes advantage ofthe system we already possess and,with a minimum cost, gives us thelaser we need. We expect this laser tobecome operational by the middle ofnext year.


Turbulence and Turbulence Spectrain Complex Fluid Flows

Timothy Clark

Turbulence possesses a rich spec-trum of time and length scales thatdefy direct computation because of theinability of foreseeable computers toresolve all scales. Turbulence stronglyaffects flows—e.g., mixing rates ofpollutants, fuel in a combustor, orconstituents in an inertial confinementfusion capsule. We are developingtheoretical models of turbulence inparallel with direct numerical simula-tions of flows to produce tractable,accurate models for use in computercodes. We proceed from spectralmodels that describe turbulence interms of a range of length scales. Byexploiting emergent self-similarities of

the model predictions, we reducethese models to tractable approxima-tions for engineering calculations.

This year we have developed acomputer program to simulateinhomogeneous turbulence. We thenused this program to isolate effects oftriple- and pressure-velocity correla-tions from mean-flow effects. Theresulting database is unique in theamount and quality of informationregarding these correlations. We usedthis data to determine the necessity ofmaintaining certain tensorial andphysical properties of the abovecorrelations. Our simulations wereuniquely appropriate to evaluate the

A Water-Filled, Radio-FrequencyAccelerating Cavity

Rickey J. Faehl

The objective of this project is tostudy water-filled resonant cavities asa high-energy-density source to drivehigh-current accelerator configura-tions. Basic considerations lead to theexpectation that a dielectric-filledcavity should be able to store up toe/e0 (the ratio of the material to thevacuum dielectric constant), as muchenergy as a vacuum would with thesame dimensions, and thus be capableof accelerating a proportionatelylarger amount of charge before cavitydepletion occurs.

During this period, we confirmedthat water-filled cavities with e/eo =60-80 did indeed behave with theexpected characteristics, in terms ofresonant TM modes and cavity Q. Weaccomplished this result with numeri-cal cavity eigenvalue codes, with fullyelectromagnetic, two-dimensional,particle-in-cell codes, and mostsignificantly with scaled experimentsperformed in water-filled aluminumcavities. The low-power experiments

showed excellent agreement with thenumerical results. Simulations of thehigh-field, high-current mode ofoperation indicated that charged-particle loss on the dielectric win-dows, which separate the cavity fromthe beamline, must be carefullycontrolled to avoid significantdistortion of the axial fields.

Publications

Faehl, R.J., R.K. Keinigs, and E.WPogue, "Dielectric-filledRadiofrequency Linacs," in BEAMS96, 11th Intl. Conf. on High PowerParticle Beams Proc, K. Jungwirth,and J. Ullschmied, Eds. (Academy ofSciences of Czech Republic, Prague,1996), pp. 636-639.

Faehl, R.J., R.K. Keinigs, E.W. Pogue,"New Initiatives for Producing HighCurrent Electron Accelerators" (to bepublished in AIP 14th Intl. Conf. Appl.Accel, in Ind. & Res. Proc).

various models of the correlations. Wehave analyzed the self-similarityobserved in spectral model calculationsof a free-shear layer. Computationswith more-advanced models of triplecorrelations yielded more-complicatedand physically accurate self-similarforms; these results will assist us inimproving engineering models. This isthe most complete rigorous applicationof spectral theory to an inhomoge-neous turbulence yet accomplished.The geometry is consistent with oursimulations. The formulation employsan elegant methodology for specifyingeigenstates for a wide variety ofgeometries.

Publications

Sandoval, D.L., J.J. Riley, and T.T.Clark, "Buoyancy-Generated Variable-Density Turbulence," in IUTAMProceedings of the Low-SpeedVariable-Density Flow Conference(Kluwer Academic Publishers, Boston,in press).

Steinkamp, M.J., T.T. Clark, and F.H.Harlow, "Two-Point Description ofTwo-Fluid Turbulent Mixing, Part 1:Model Formulation" (submitted to Int.J. Multiphase Flow).

Steinkamp, M.J., T.T. Clark, and F.H.Harlow, "Two-Point Description ofTwo-Fluid Turbulent Mixing, Part 2:Numerical Solutions" (submitted toInt. J. Multiphase Flow).

Turner, L., "The Driven-DissipativeEuler's Equations for a Rigid Body: AChaotic System Relevant to FluidDynamics," Phys. Rev. £54, 5822(1996).

Turner, L., "EDQNM Model ofEvolution of Homogeneous, AnisotropicTurbulence in a Helicity Representation"(submitted to Phys. Rev. E).

Turner, L., "Remarks on StatisticalMechanics of Discrete and ContinuousMedia with MagnetohydrodynamicDynamo" (to be published in J. PlasmaPhys.).

Turner, L., "A Tractable Model ofIncompressible, InhomogeneousTurbulence" (submitted to Phys. Rev. E).


A Target Plasma Experimentfor Magnetized Target Fusion

Frederick Wysocki

Achieving controlled fusion is ascientific "grand challenge" thatmankind has been pursuing for over40 years. Fusion energy would helpsatisfy the long-term energy needs ofthe growing population on Earth.Magnetized target fusion (MTF) is anapproach to controlled fusion inwhich a premagnetized, preheatedtarget plasma is near-adiabaticallycompressed to fusion conditions. Theobjective of this project is to developthe ability to generate suitable targetplasmas for MTF, the first criticalmilestone in the development path forachieving fusion with the MTFconcept. Our approach involvesdriving a fast-rising electrical currentreaching 1-2 MA through a fiber ofcryogenically frozen deuterium about200 urn in diameter. The fiber rapidlyturns to plasma, heats, and expands tofill a plasma-containment chamber,thus becoming confined by the wallsof the chamber. This project reliesheavily on existing facilities andequipment at the Laboratory that areadapted to our needs.

This year, we designed and con-structed a power-flow-channel andplasma-chamber system, and weincorporated this system into theLaboratory's Colt capacitor-bankfacility. The capacitor bank has amaximum stored energy of 0.25 MJ,and it delivers a maximum of 3 MAof current with a rise time of 2-3 us.We have performed initial plasma-formation experiments using a staticfill of hydrogen gas. The diagnosticsthat we have fielded include an arrayof 12 B-dot probes used to determine

plasma current, a 1.3-um laserinterferometer to determine plasmadensity, an optical framing camera, agated optical multichannel analyzerfor visible spectroscopy, a visible tonear-ultraviolet monochromator withtime resolution for spectral timehistory, photodiodes to measure lightemission, and the usual capacitor-bank monitors.

The data show that we are generat-ing a plasma that lasts 10-20 us withno obvious signs of impurities.Further analysis of the data isongoing. The results from the 1.3-uminterferometer show that we need togo to a shorter-wavelength laserinterferometer to reduce beamdeflection caused by density gradientsin the plasma and to reduce theoverall sensitivity of the system. Inaccordance, we have borrowed aHeCd laser, purchased the supportingoptics, and assembled and bench-tested the new interferometer. We willinstall the new interferometer on theactual plasma chamber in the upcom-ing weeks. We are also refurbishingthe cryostat used for making thecryogenically frozen deuterium fibersand will be installing it on the plasmachamber in the next two months.

Publications

Idzorek, G., and R. Kirkpatrick,"Analysis of Filtered Silicon DiodeData from the MAGO 2 and MAGO3" (Seventh International Conferenceon Megagauss Field Generation,Sarov, Russia, August 1996).

Kirkpatrick, R., and D. Smitherman,"Energetic Alpha Transport in aMagnetized Fusion Target" (to bepublished in Fusion Technol).

Kirkpatrick, R., P. Sheehey, et al.,"Proposed Generation andCompression of a Target Plasma forMTF" (Tenth IEEE InternationalPulsed Power Conference,Albuquerque, N.Mex., July 10-13,1995).

Lindemuth, I., R. Reinovsky, et al.,"Target Plasma Formation forMagnetic Compression/MagnetizedTarget Fusion," Phys. Rev. Lett. 75,1953 (1995).

Sheehey, P., R. Faehl, et al.,"Computational Modeling ofMagnetically Driven Liner-on-PlasmaFusion Experiments" (SeventhInternational Conference onMegagauss Magnetic FieldGeneration, Sarov, Russia,August 1996).

Sheehey, P., J. Guzik, et al.,"Calculations of ProposedMagnetized Target FusionExperiments" (Tenth BiennialNuclear Explosives Design PhysicsConference, Los Alamos, N.Mex.,October 1995).

Sheehey, P., J. Guzik, R. Kirkpatrick,et al., "Computational andExperimental Investigation ofMagnetized Target Fusion" (to bepublished in Fusion Technol.).


Developing Electron-Beam BunchingTechnology at Subpicosecond PulseLengths for Improving Photon Sources

Bruce Carlsten

The purpose of this project is toextend the current electron-bunchcompression technology by develop-ing a small experiment to study theessential physics associated withsubpicosecond bunch compression,and to probe the fundamental limitsassociated with compression. Inparticular, our goal was to bunch 1 nCof charge to less than 1 ps, whichwould represent more than an order ofmagnitude increase in compressionover previous experiments.

In previous years, we analyzed thedominant emittance growth mecha-nism and designed a second-ordercompressor. We also built a sub-picosecond compressor on a newaccelerator that was constructed fora plasma light-source. Using thiscompressor, we demonstratedcompression of 0.1 nC from 20 to0.25 ps and compression of 1.1 nCfrom 20 to 0.75 ps. These levels ofcompression far exceed previousresults and provide important guid-ance to advanced compressor designs.

This year we used this compressedelectron beam to generate as short as22-nm-wavelength ultraviolet light,demonstrating tremendous improve-ment in an associated photon source.We analyzed additional compressioneffects in radio-frequency photo-injectors, and theoretically derivedimportant formulas describing thenonlinear coherent synchrotronradiation force and the noninertialspace-charge force that lead toemittance growth in compressorsystems. Finally, we developed a newroot-mean-square emittance diagnos-tic that can be used to study theemittance growth from these nonlin-ear effects.

Publications

Carlsten, B.E., "Calculation of theNoninertial Space-Charge Force andthe Coherent Synchrotron RadiationForce for Short Electron Bunches inCircular Motion Using the RetardedGreen's Function Technique," Phys.Rev. E 54, 838 (1996).

Carlsten, B.E., "NonlinearSubpicosecond Electron-BunchCompressor," Nucl. lustrum. MethodsPhys. Res. A 380, 505 (1996).

Carlsten, B.E., and J.C. Goldstein,"Emittance Growth of a ShortElectron Bunch in Circular Motion"(to be published Nucl. lustrum.Methods in Phys. Res. A).

Carlsten, B.E., and D.C. Nguyen,"Electron Bunch Compression Due toRF Forces in an RF Photoinjector forSmall RF Launch Phases" (to bepublished in Part. Accel.).

Carlsten, B.E., and SJ. Russell,"Subpicosecond Compression of0.1-1 nC Electron Bunches with aMagnetic Chicane at 8 MeV," Phys.Rev. E 53, 2072 (1996).

Carlsten, B.E., D.W. Feldman,J.M. Kinross-Wright, et al.,"Subpicosecond CompressionExperiments at Los Alamos NationalLaboratory," AIP Conf. Proc. 367, 21(1996).


High-Intensity Laser-MatterInteraction Physics

James A. Cobble

During the first year of research, weemployed the short-pulse capability ofthe Trident laser at Los Alamos tomeasure the penetration of a high-intensity beam through a 1-mm scalelength plasma. The highest laserirradiance was 7 x 1018 W/cm2. Theplasma density depends on the delaybetween a low-intensity plasmaformation beam and the high-intensityprobe in striking the plastic target.The critical plasma density is oneabove which the plasma oscillatesquickly enough to reject the penetra-

tion of the light. Our experiment usedplasmas of 1% to 5% of the criticaldensity. The probe beam was focusedwith an f/2.5 parabola. We found thatthe beam f number increased uponpassing through the plasma. It wasmore collimated because of itsinteraction with the plasma. In orderto measure this effect, we allowed thetransmitted beam to strike a diffuserplate behind the target. A cameraimaged the scattered light from theplate to produce the data shown in thefigure.

We also measured the reflected andtransmitted light for different delays(plasma densities). Even at the low-plasma densities used, transmissionwas less than expected. There appearsto be an anomalous absorption that ispossibly related to the ultrahighirradiance of the probe laser beam.We are pursuing this possibility withtheoretical studies to model thebehavior of the beam in the plasma.We are planning more experiments forthe coming year.

Publications

Cobble, J.A., R.P. Johnson, and RJ.Mason, "Exploded Foil TransmissionExperiments with an Ultra-IntenseLaser," 26th Annual AnomalousAbsorption Conf. Proc. 26, 116(1996).

The f number of the probe beam isapproximately doubled on passagethrough a 3% critical density plasma.The case with no plasma is shown in(a); the case with a plasma is shownin (b). Each frame is a 250 x 250pixel array.


Chemistry

New Fullerene-Based Mixed Materials:Synthesis and Characterization

Duncan McBranch

Our goal is to develop novelcomposites of derivatized C60

(fullerene) in inorganic glass hosts.We seek to (1) understand thenonlinear optical properties of thefullerenes and (2) form optimizedsolid-state materials with propertiesthat allow rapid change of opticaltransparency as a function of lightintensity (for protection of eyes andsensors from harmful pulsed lasers).

We have formed glass compositescontaining C60 and soluble derivativesusing our patented sol-gel techniques.We have demonstrated that thefullerene concentration in theseglasses can be controlled over a widerange and that the resulting materialscan be polished to high-qualitysurfaces and have optical damagethresholds much higher than those ofplastic host materials.

We have observed enhanced opticallimiting in solutions of a derivatizedfullerene. Our transient absorptionmeasurements determined the spectraland temporal regions of interest foroptical limiting in C60 and derivativesand predicted enhanced limiting atlonger wavelengths. Intensity-dependent transmission measurementsconfirmed these results. The increasedsolubility and broadened ground-stateabsorption of the functionalized C60

make it a more effective limiter in thered and near-IR spectral regions thanthe pure C60 (see accompanyingfigure).

We also used transient absorption to(1) determine the magnitudes of theexcited-state cross sections as afunction of wavelength and (2) dem-onstrate that the morphology of thefullerene molecules in the solid state

is a crucial parameter in the optical-limiting effectiveness for nanosecondpulses. Fullerene/sol-gel glasses areone of the most promising solid-stateoptical limiters in the near-IR spectralrange.

Publications

Klimov, V., et al, "Femtosecond toNanosecond Dynamics in Fullerenes:Implications for Excited-StateNonlinearities" (to be published inRes. Chem. Intermed.).

Klimov, V., et al, "Strong OpticalNonlinearities in Porous FemtosecondNonlinear Transmission Study," Phys.RevB. 62, 16989(1995).

McBranch, D., et al, "FemtosecondExcited-State Absorption Dynamicsand Optical Limiting in FullereneSolutions, Sol-Gel Glasses, and ThinFilms" (to be published in SPIEFullerenes and Photonics III).

McBranch, D., et al, "OpticalLimiting in Fullerene Solutions andDoped Glasses," SPIE Fullerenes andPhotonics II2530, 196 (1995).

Smilowitz, L.S., et. al., "EnhancedOptical Limiting in DerivatizedFullerenes," Opt. Lett. 21, 922 (1996).

Incident fluence (J/cm )

Intensity-dependent transmission (T)for C60 at 532 nm (open squares, low-intensity transmission, T = 80%) and 700 nm (solid squares, T = 80%) and forthe monosubstituted fullerene 6,6phenyl-C61-butyric cholesteryl acid at 700 nm(open circles, T = 80%; solid circles, T = 50%). The solid line indicates lineartransmission of 80%.

Individual Projects—Chemistry 45

Uses of Novel Selenium-Containing ChiralDerivatizing Agents: Potential Catalysis forthe Chiral Oxidation of Simple Alkenesand Chiral-Promoted Aldol Reactions

Louis A. Silks

The last frontier for chemicalcatalysis is the design of chiral andenvironmentally benign chemicalprocesses. Our goals are to develop(1) a new oxidative catalytic processto generate chiral allylic alcohols and(2) new chiral aldol reactions. We areusing derivatives of selone reagents aschiral derivatizing agents (CDAs) forboth goals. The arrangement ofphenyl and methyl groups on theseCDAs allows us to produce chiralproducts with predictable chiralityfrom nonchiral starting materials.

Simple allylic chiral alcohols areprecursors of many pharmaceuticalsand agrochemicals. The successfulsynthesis of these alcohols wouldbenefit chemical industry because themethod would be catalytic, an easilyrecoverable co-oxidant could be used,and low levels of byproducts wouldbe produced and, therefore, wastewould be minimized. We success-fully made the CDA adducts,

Synthesis of the starting adducts ofthe selone CDAs from a chiral seloneand an allylic bromide. The upperproduct (adduct) is a phenylglycinol-derived selone, and the lower productis a norephedrine-derived selone.

phenylglycinol- and norephedrine-derived selone, by reacting an allylicbromide with a chiral selone (see firstset of reactions). We then oxidizedthese CDAs with m-chloroperbenzoicacid (MCPBA) to produce the allylicalcohol (see second reaction).Because the optical purity of theoxidation reaction was low, we areevaluating other oxidants and lowertemperatures.

Chiral aldol reactions are anotherproductive area for developing newmethods for chiral inductions. Forexample, we can form two new chiralcenters by enolizing an acylatedselone with di-n-butylboron triflate (aLewis acid) to generate an £-enolatethat has boron chelated to both theoxygen anion and the selenium atom(see third set of reactions). We have

SeLI JK. Alkyl Halides

N O

R1 R"

trapped the enolate with two differentaldehydes. Although di-n-butylborontriflate is useful for generating thealdol product, the di-n-butylboron isdifficult to remove from our desiredproduct. To get around this problem,we replaced di-n-butylboron triflatewith a boron-based Lewis acid thatdegrades in the presence of water.

More interesting is the use oftitanium tetrachloride as the Lewisacid. From the proton nuclear-magnetic-resonance spectra, we knowthat the stereochemistry of thetitanium-promoted aldol productsdiffers from that of the boron-promoted products. This differenceshows that we can reverse the productof the aldol reaction at the b-carbonatom by changing the acid compo-nent. In an effort to rigorouslydetermine the stereochemical out-come of the reactions, we are cur-rently attempting to grow crystalsand obtain x-ray structures of ourtitanium- and boron-promoted aldolproducts.

Ph

Se

NO

Ph

R',R" = alkyl and aryl groups

80-90% yield

Se MCPBA HO-50%

Ph

Ph The oxidation reaction that produces the allylic alcohol.


Publications

Wu, R., L.A. Silks, et al., "HighlySensitive Spectroscopic Detection ofChiral Molecular Stractures by 77SeNMR Spectroscopy," Spectroscopy 11(6), 37 (1996).

Wu, R., G. Hernandez, L.A. Silks, etal., "Simple Enantiomeric ExcessDetermination of Amines UsingChiral Selones: Unusual N-H-SeBonding Detected by HMQC 1H/77SeNMR Spectroscopy," /. Chem. Soc.,Chem. Commun., 1125 (1996).

n-Biu •n-Bu

R1Se

R= methyl, O-benzyl

R'= alkyl, arylThe aldol reaction that generates a productcontaining two new chiral centers. Di-n-butylborontriflate is the Lewis acid used.

Metal-Ligand "Multiple" Bonding:Revelations in the Electronic Structure ofComplexes of High-Valent f-Elements

Carol Burns

Complexes of the f-elementscontaining multiply bonded functionalgroups (e.g., oxo, sulfido, imido, andphosphinidene groups) are importantin actinide environmental science,waste management, and actinidematerials chemistry research. Forexample, actinide hydrolysis yieldingoxo- and hydroxide-containingspecies is important in dilute aqueoussolution under certain pH conditions,and binary oxides and nitrides areimportant solid-state phases as bothnuclear fuels and, in the case ofoxides, as potential waste forms.Little is known, however, about theenergetics and chemical behavior ofthese functional groups at actinidemetal centers (important to theevaluation of the nature of interac-tions between f-metals and maingroup elements such as carbon,nitrogen, and oxygen). The goal ofour project is to extend the develop-ment of the field of metal-ligandmultiple bonding in coordinationchemistry to include f-elementanalogs.

During the final year of this project,we have demonstrated importantdifferences between the chemistry ofthe actinide elements and that ofd-transition metals in bonding to maingroup elements. We have developednew multiple-electron-transfersynthetic pathways to preparecomplexes with organoimido and oxofunctional groups, which are uniqueto actinide elements. Theoreticalstudies suggest that f-orbitals mayplay a significant role in stabilizingmultiply bonded functional groups.We have exploited these samemultiple-electron-transfer pathways inexamining coupling reactions ofalkynes at actinide centers. Importantdifferences exist between the reactiv-ity of actinide and d-transition metalanalogs, suggesting that organo-actinide complexes may have uniquevalue in organic synthesis.

Publications

Arney, D.S.J., R.C. Schnabel, et al.,"Preparation of ActinidePhosphinidene Complexes," J. Am.Chem. Soc. 118, 6780 (1996).

Barnhart, D., CJ. Burns, et al.,"Synthesis of Neutral and AnionicUranyl Aryloxide Complexes," Inorg.Chem. 34, 4079 (1995).

Burns, C.J., and D.S.J. Arney,"Synthesis and Properties of High-Valent Organouranium Complexes," J.Am. Chem. Soc. Ill, 9448 (1995).

England, A., R. Schnabel, J. Huffman,et al., "Structure-Reactivity Relation-ships in Elimination Reactions:Solution and Solid State Structuresof Cp2Zr(Me)(o-MeOC6H4) andCp*2Th(Me)(o-MeOC6H4)"(submitted to Organometallics).

Radu, N.S., S.L. Buchwald, et al.,"Carbon-Hydrogen Bond Activationof Aromatic Imines by (Cp*2SmH)2,"Organometallics 15, 3913 (1996).

Warner, B., C J. Burns, "Synthesis ofUranium (VI) Imido Complexes by aUranium (II) Synthon and the FourElectron Reduction of Azobenzene"(submitted to /. Am.Chem. Soc).


Chemistry and Catalysisin Supercritical Media

William Tumas

Our aim in this research is toexplore the potential of supercriticalfluids as reaction media for stoichio-metric and catalytic chemical trans-formations in an effort to developnew, environmentally friendlymethods for chemical synthesis orprocessing. This approach offers thepossibility of opening up substantiallydifferent chemical pathways, increas-ing selectivity while enhancingreaction rates, facilitating downstreamseparations, and mitigating the needfor hazardous solvents.

We investigated a number ofcatalytic processes for which carbondioxide represents a viable solventreplacement. In several cases we haveobserved significant enhancements inselectivity and/or reactivity relative toconventional organic solvents. Wehave investigated the followingcatalytic processes: (1) selectiveoxidation including dihydroxylationand epoxidation, as shown in the firsttwo figures, (2) asymmetric hydroge-nation (see third figure) and hydro-gen-transfer reduction (see fourthfigure), (3) Lewis acid-catalyzedacylation and alkylation, and (4) cou-pling of amines with carbon dioxideto make isocyanates.

Publications

Burk, M.J., S.G. Feng, M.F. Gross, etal., "Asymmetric Hydrogenation inSupercritical Carbon Dioxide," / . Am.Chem. Soc. 117, 8277-8278 (1995).

Morgenstern, D.A., R.M. LeLacheur,D.K. Morita, et al., "SupercriticalCarbon Dioxide as a SubstituteSolvent for Chemical Synthesis andCatalysis," in Green Chemistry, P.T.Anastas, and T.C. Williamson, Eds.(American Chemical SocietySymposium Series 626, Washington,D.C., 1996), pp. 132-151.

liq-COj

Time T(°C) Conversion Products

CH3- H-

nCH3CH2CIfc- H-

CHj- CHj-

CH3-

CH3-

24h 25°C

24h 2S'C

14h 2S°C

24h 2S°C

24h 25°C

(85*) (15%)

>99%

L»,R =

cat T^OiPr)^ L*

liq. COj, ffluOOH/(2000psi, 0°C 72 h

Conversion

oC OR

* _ H-jfOH-• - H O - ^ H

C OR

6

Selectivity

(CH3)2CH- >99% 89% 87.4%

Selected results from the epoxidation catalysis: (top) vanadium-catalyzedepoxidation ofprochiral allylic and homoallylic alcohols using VO(Oi-Prj3

and t-butylhydroperoxide; (bottom) enantioselective epoxidation of 2-hexenolusing titanium catalysts containing chiral tartrate ligands.

OH

60

55

50

45

40

35

30

CO—#—FelTFPPICI_ .* . . . FefTFPPfirjCI

acetonitrile

60

55

50

45

40

35

30

Fluorinated ironporphryin air-oxidation ofcyclohexene: muchhigher selectivities toepoxide (cyclohexeneoxide) are observedin supercritical car-bon dioxide relativeto conventionalorganic solvents.

10 15 20 25 30 35 40

dielectric constant


Table illustrates Rh-DuPhosenantioselective hydrogenation ofenamides: higher enantioselectivity insupercritical carbon dioxide isobserved for several substrates.Structures shown below the tableillustrate the generality of highenantioselectivity for asymmetrichydrogenation in supercritical carbondioxide.

Et

CO2Me 1 (02 mol %)

N(H}Ac5

CO2Me

N(H)Ac7

scCO2/H2(5000psig)40 °C, 24 h

1 (0.2 mol %)•

seCO2/H2(S000psig)

40°C,24h

N(H)Ac6

CO2Me

N(H)Ac

8

Substrate Catalyst%ee

MeOH hexane Supercritical CO2

5S77

lalblalb

62.667.481.195.0

69.570.476.291.2

84.788.496.892.5

Hydrogenation of p.P-disubstituted a-enamides with catalysts I"

N(H)Ac97.2% ee

N(H)Ac94.2% ee

N(H)Ac95.6% ee

MeCO2Me

N(H)Ac97.0% ee

N(H)Ac96.8% ee

73% ee

N(H)Ac

95.2% ee

HCO2H +N(H)Ac

5

1 or 2/NEt3

SCCO2

24 h

+ CO2

N(H)Ac

6

Substrate

5a

Sa

5b

Sc

5d

H

H

Ph

TemperatureHexane

Et

55

35

55

55

55

no reaction

no reaction

89.6

SCCO2

95.6

96.5 Asymmetric hydrogen transferreduction of a-enamides using(r)-BINAP-ruthenium catalystsusing formic acid/triethylamine.


Decay of Surface NanostructuresVia Long-Time-Scale Dynamics

Arthur Voter

The main goal of this project is todevelop a method for simulatinginfrequent molecular dynamics (MD)events even when the subsequentstates of the system following theevents are not known in advance. Wehave achieved a breakthrough thisyear and have in place a new workingmethod. This method, which we term"hyper-MD," significantly extends thetime period over which we cansimulate classical molecular dynam-ics. To achieve this end, we aug-mented the true potential energyfunction with a bias potential thatraises the energy in regions other thanat the saddle points.

For strongly coupled, solid-statesystems, we can construct such a biaspotential from the local gradient andHessian for the potential. An MDsimulation performed on this modi-fied potential allows transitions frombasin to basin to occur at an acceler-ated pace, while the total time evolvedbecomes a statistical property of thesystem. This hyper-MD methodshould be most useful when the timescale of interest cannot be accessedwith direct (or conventional) MDsimulation, which is typically limitedto a few nanoseconds, and whenfuture events cannot be inferred fromsimple models.

We are presently testing the methodby applying it to the diffusion of asilver atom on the Ag(100) surface.

Time evolution of the x and z positionsof atom 1, which is initially theadatom. After hopping for about1.1 us, atom 1 exchanges with a top-layer substrate atom, which becomesthe new adatom. For the remaining1.9 us, atom 1 simply vibrates aboutits equilibrium position in thesubstrate.

Both adatom-hopping events andadatom substrate-exchange eventsoccur at rates that are verified againstexact calculations. The system isshown in the first figure. The evolu-tion of the hypertime at T = 400 K isshown in the second figure, corre-sponding to a boost factor of 1500.

14.0

10.6 -

AG/AG(100) t=0

The initial adatom executes diffusivehops for about 1.1 us, at which time itexchanges with a substrate atom asshown in the third figure. This 2.9-nssimulation took four days on a scalarworkstation, but would require almost ayear of computer time with direct MD.

Publications

Voter, A.F., "A Method forAccelerating the Molecular DynamicsSimulation of Infrequent Events"(submitted to /. Chem. Phys).

Surface-normal (z) view of theAg/Ag(100) system. Atoms interactthrough an embedded-atom-method(EAM) potential. The system isperiodic in the x and y directions.The top three layers are allowed tomove during the dynamics, whiletwo more-rigid layers belowmaintain the fcc(100) structure.The adatom is shaded for clarity.

12.0

Evolution of the calculatedboosted time (or "hypertime ")during the hyper-MD simulation.The system reaches 2.9 /us after2 ns ofMD time, for a boost ofabout 1500. Because each hyper-MD step requires about 20 timesmore work than a simple MDstep, the net computational gainis a factor of 1500/20 = 75.

ra.

3.5

3.0

2.5

2.0

t.5

1.0

0.5

0

L~T'-~T-r/

Ag/Ag(100). > j i i i i I i i i

J/

/

. . 1 . . . . 1 . . .

T=400K

-_

-_

i , , , , i , , , ,'z

10Ag/Ag(100) T=400K

0.5 1.0 1.5

MD time (ns)2.0 2.5

1.0 1.5 2.0hypertime

0 3.5


Solvation and Ionic Transportin Polymer Electrolyte Membranes

Thomas Zawodzinski

In this project we have studied thefundamentals of ion and solventtransport in polymer electrolytemembranes. Such membranes are avital tool in separation and filtrationprocesses that can be used in thenuclear complex, particularly inenvironmental aspects of thosemissions. In addition, these materialsare of key importance in emergingbattery and fuel-cell technologies.Our ability to radically changeperformance is greatly increased bygaining an understanding of thesefundamentals.

We have begun calculations onmodel systems to develop two aspectsneeded for the final theory approach:

(1) good electronic structure calcula-tions of appropriate models of theNation side-chain as one input for thetheory, and (2) refinement of thedielectric continuum approach for thedescription of confined water layers.We carried out electronic structurecalculations in trifluoromethanesulfonic acid (triflic acid), the anion(triflate), and several examples ofclusters of a water molecule.

We also developed Monte Carlomethods to simulate water-oil-polymer mixtures. We expect thatthese techniques will allow us toconstruct physically reasonablemodels of hydrated Nation mem-branes. Finally, we implemented

multigrid techniques in the dielectricsolvation model to enable the study ofthe solvation of larger molecules.

We developed the needed tech-niques for the determination of thehigh-frequency (1-1000 GHz)dielectric response of ion-exchangepolymers. Measurements on mem-branes of variable hydration staterevealed features in the gigahertzrange that are attributable to waterrelaxation. This is the first such resulton a highly conducting system at suchhigh frequencies. The electrophoreticnuclear-magnetic-resonance methodwill allow us to isolate the transport ofindividual ions in mixed ionic ormixed solvent systems, and thusobtain their mobilities and transfer-ence numbers. We have recently builta new apparatus that allows us tostudy membranes. We also designedand constructed an electrochemicalsystem with well-defined electrodeprocesses for mobility measurements.

Heterogenization of HomogeneousCatalysts: The Effect of the Support

William Earl

The goal of our project is tocovalently bind known solution(homogeneous) catalysts to thesurfaces of high-surface-area, solidmaterials and to investigate the effectsdue to binding. We vary the structureof the solid surface and the chemicallink between the catalyst and surfaceand measure the catalytic activity.This allows us to determine if there isa correlation between the finalstructure and catalytic activity. Thisproject includes two phases ofinvestigating heterogeneous catalysis.The first is to duplicate unusual datathat already exists, as reported in theliterature, and the second is to usesimilar compounds and syntheses tounderstand these results.

In the past year, we made progressin establishing the infrastructure andin synthesizing the starting materialsrequired for the project. The first stepwas to synthesize the substrate to beused in the catalysis reactions. Al-though this was a relatively straight-forward synthesis, the compoundswere not commercially available andit was a multistep synthesis. Thehomogeneous catalyst used was fairlyeasy to synthesize. The difficult stepin this work was modifying thehomogeneous catalyst to allowlinking it to the surfaces. The prepara-tion process reported in the literaturedid not work as presented. We alsoacquired several zeolites and mademinor modifications to them to allow

linking the homogeneous catalysts tothem. In addition, we started theprocess of synthesizing high-surface-area silica with controlled pores. Wewill use these synthesized silicainstead of commercial silica. Eventu-ally, the solid materials will becharacterized using a number ofdifferent spectroscopic probes. Duringthe past year, we began some of thesetechniques, but the samples are, asyet, only partially characterized.

We ran several homogeneousreactions before Unking the catalyst tothe surface, and we established themethods to measure catalytic activity.These methods are applicable tohomogeneous solutions and will bemodified as we proceed to supportedcatalysts. At present, we are unable toquantitatively reproduce the literatureresults.


Photoredox Reactions: Energy Storageand Halocarbon Degradation

William Woodruff

Our project had five objectives:(1) to characterize the structures andthe structural dynamics of the singletand triplet states of selected metal-metal bonded systems; (2) to charac-terize the postexcitation, intra-molecular electron-transfer reactionsof these complexes; (3) to investigatestrongly adiabatic photo-oxidativeaddition reactions, including theaddition of halocarbons to theelectronically excited complexes andtheir hydrogen-evolving reactions;(4) to seek effective reductant systemsthat will function in catalytic cyclesand regenerate the original, reduceddimer; and (5) to explore the chemis-try of metals less expensive thaniridium or platinum with regard totheir potential for photochemicalreactivity.

Our results include studies oftungsten and molybdenum clusterswith potential multielectron excited-state redox reactivity, metal-metalbonded dimers sequestered in liquid-crystal environments, d7 dimers withlong-lived photocycles, and photo-chemically produced oxygen-fluorinesystems. These results have beenreported in three research articles.

Publications

Abney, K., P. Eller, M. Eastman, etal., "Thermal DecompositionReactions of Gaseous DioxygenDifluoride and Dioxygen Fluoride atAmbient Temperature," J. FluorineChem. 73 (2), 137-46 (1995).

Chisholm, M., G. Christou, K.Folting, et al., "Solution Studies ofRu2(O2CR)4

n+ Complexes (n = 0, 1;O2CR = Octanoate, Crotonate,Dimefhylacrylate, Benzoate, p-Toluate) and Solid-State Structures ofRu2(O2C-/?-tolyl)4(THF)2,[Ru2(O2C-p-tolyl)4(THF)2]

+[BF4], and Ru2(O2C-/?-tolyl)4(CH3CN)2: Investigations ofthe Axial Ligation of the Ru2 Core,"Inorg. Chem. 35 (12), 3643-58(1996).

James, C , D. Morris, S. Doom, et al.,"Photochemistry of Deca(acetonitrile)Dirhodium(II) Cation: Evidence forKilosecond-lived PhotoinducedCharge Separation," Inorg. Chim.Ada 242 (1-2), 91-96 (1996).

Schoonover, J., T. Zietlow, D. Clark,et al., "Resonance Raman Spectra of[M6X8Y6]

2- Cluster Complexes (M =Mo, W; X, Y = Cl, Br, I)," Inorg.Chem. 35 (22), 6606-13 (1996).

Reactivity at Metal CentersBound to Water-Soluble Catalysts

Nancy Sauer

We are examining water-solublepolymers as supports for homoge-neous catalysts. Our approach is tocovalently attach the catalyst precur-sors to these soluble polymers. Theresulting macromolecular materialswill mitigate loss of precious metalsby modifying the solubility of thehomogeneous catalyst. This approachwill permit more benign solvent to beused and potentially will engenderunusual substrate selectivity in thecatalytic systems. The initial focus ofthe project has been incorporation ofphosphine ligand onto water-solublepolymers as ligands for catalyticallyactive metals such as rhodium. We areexploring the rate and selectivity ofthese systems.

Our work this year has focused onthe attachment of phosphine ligandsto the polymers. To demonstrate thereactivity of soluble supported metalcenters, we have devised methods toprepare phosphine-functionalizedpolymers for incorporation ofcatalytically active metals into oursoluble polymer systems. The workbegan with rhodium-phosphinehydrogenation catalysts that are activein aqueous solution. Accomplish-ments for this year include (1) prepa-ration and screening of the baselinecatalyst: [Rh(NBD)(PPh3)2]

+(NBD isNorbornadiene); (2) synthesis andcharacterization of the molecularsystem with the chelating diphosphine

2,3-bis(diphenylphosphino)maleicanhydride(L); (3) development of methodologyfor attaching the chelating ligand L toorganic nucleophiles; (4) synthesisand characterization of the molecularsystem with ring-opened chelatingdiphosphines 2,3-bis(diphenyl-phosphino)maleic acid monoethylester (L2) and 2,3-bis(diphenyl-phosphino)maleic acid mono-ethylenediamine amide (L3); and(5) screening of hydrogenationactivity and selectivity for rhodiumcomplexes with the three phosphineligands L, L2, and L3.


Cyclodextrin-Based ChemicalMicrosensors for Volatile OrganicCompounds (VOCs)

DeQuan Li

The goal of this project is toconstruct thin films of well-con-trolled, assembled nanotubes as novelsensing materials for chemicalmicrosensor applications. Thesenanotubes provide a well-defined,hydrophilic porosity suitable fordetecting small VOCs (such asbenzene, toluene, chloroform, andtrichloroethylene) that may contami-nate water supplies. We can use oursensing materials for chemicalseparations and environmentalcleanup, applications that are essentialboth for improving our health andsafety and for saving money andresources. Our microsensor technol-ogy received an R&D 100 Award in1995. The accompanying figureshows a schematic drawing of thesensor configuration.

To reach the targeted goals, weused modified cyclodextrins ("hostcompounds," so called because theyare able to bind and surround smaller"guest" molecules) as the basicbuilding units. We functionalizedthese building blocks with variousorganic groups, including linear alkylchains and aromatic rings. Thesefunctional groups allow thecyclodextrins to self-assemble intotubular structures. We are currently inthe process of purifying the buildingblocks that will self-assemble intonanotubes.

In another approach to constructingour thin films of nanotubes, we usedcharge interactions (the attraction ofpositive to negative charges) toassemble surface-receptors. Wefabricated thin films from cyclodextrin

derivatives with charged functionalgroups and measured the sensors'responses to vapors containing knownconcentrations of VOCs. The resultsof these measurements indicate that itis feasible to construct sensor arraysto identify a wide variety of VOCs.

Publications

Li, D., J. Shi, et al., "MicrosensorsBased on Self-AssembledCyclodextrin Host Thin Films forVolatile Organic Compounds"(Spectrum '96, Seattle, Wash., July1996).

Swanson, B., and D. Li,"Cyclodextrin-Based Microsensorsfor Volatile Organic Compounds"(1996 American Chemical SocietyNational Meeting, Orlando, Fla.,August 1996).

Swanson, B., and D. Li, "Smart FilmSensor for Halogenated Hydrocarbonsand Volatile Organic Compounds"(Incineration and Thermal TreatmentTechnologies, Savannah, Ga., May1996).

Sensing LayerOxide Layer

| ElectrodesReflectors

Side View FunctionalizedCyclodextrin/Calix[n]areneSensing Layer

Host-GuestInteractionsInside Cavity

Top View

Surface AcousticWave Thin-FilmChemical Microsensors

Schematic illustration of a chemical microsensor based on surface-bound receptormolecules. This illustration shows an example of a cyclodextrin sensing layer on a surfaceacoustic device.


Binding of Hydrocarbons and Other Extremely Weak Ligandsto Transition-Metal Complexes that Coordinate Hydrogen:Investigation of Cis-Interactions and Delocalized BondingInvolving Sigma Bonds

Gregory Kubas

At the forefront of chemistry areefforts to catalytically transform gas-or oil-derived hydrocarbons intouseful products such as gasoline withmetal compounds that chemicallybind and break the inert carbon-hydrogen sigma bonds. Our first goalis to bind hydrocarbons, silanes, andgermanes to metal complexes via theirH-Y bonds (where Y is carbon,silicon, or germanium), analogous toour discovery of hydrogen (H2)binding to metals. Studies of theseunique "sigma complexes" (M—H-Y,where M is a transition metal) will aidin developing new catalyst, sensor,and separation technologies. A secondgoal is to probe atom exchangebetween sigma-bonded molecules andother atoms bonded to the metal withtechniques such as inelastic neutronscattering (INS). Such atom transfers,typically involving hydrogen, are theheart of catalysis, the lifeblood of thechemical industry and many biologi-cal processes.

We studied several transition-metalsystems, including the molybdenumcomplex Mo(CO)(PP)2, the manga-nese complex [Mn(CO)(PP)2]

+, andthe platinum complex [PtH(PR3)2]

+.In these complexes, PP isPh2PC2H4PPh2 (where Ph is phenyl),and R is isopropyl. The platinumcomplex weakly binds the hydrogen-hydrogen bonds of H2 and the carbon-chlorine or carbon-iodine bonds ofhalocarbons such as methylenechloride and iodobenzene (see firstfigure). The binding between theplatinum and the carbon-hydrogenbonds is too weak to be observed.

In the molybdenum and manganesecomplexes, however, the metalinteracts with intramolecular (inter-nal) carbon-hydrogen bonds (seesecond figure). These carbon-hydrogen bonds are reversiblydisplaced by H2, N2, and silanes,which bind weakly to the positivelycharged manganese center. We havesupported the manganese cation onalumina, and our calculations showthat this material can be used to bindand separate hydrogen isotopes (H2,D2, and T2) at room temperaturerather than at the extremely lowtemperatures now used. This tech-nology could be useful in tritiumprocessing.

In the course of our study, we wereable to prepare the first germanecomplex, Mo(CO)(PP)2(GeH4), whichrelates to our discovery of the SiH4

binding that models methane binding.We also studied H2 rotation on

CMObl

Cll2bl

[Mn(H2)(CO)(PP)2]+and

RuH2(H2)2[P(cyclohexyl)3]2 by INS,which allowed us to probe atomexchange and interactions betweenhydride and H2.

Publications

Butts, M.D., G.J. Kubas, and J.C.Bryan, "Temperature-DependentBehavior of Agostic ComplexesW(CO)3(PR3)2. Structures of Productsof N2, Ethylene, and Silanes" (to bepublished in Inorg. Chem.).

Butts, M.D., B.L. Scott, and G.J.Kubas, "Synthesis and Structure ofAlkyl and Aryl Halide Complexes ofthe Type [(PiPr3)PtH(ri1-XR)]BArf andAnalogues with Et,O, THF, and H2

Ligands," J. Am. Chem. Soc. 118,11831 (1996).

C!2I CI3I

Ct11bl

C(9b)

CtHol

CIBal

Molecular x-ray crystal structure of [PtH(P-i-Pr3)2(PhI)]+ showing iodobenzene(Phi) binding to platinum. P-i-Pr3 is tri-isopropylphosphine. This platinumcomplex is stable to air, a rare feature for such weak molecular binding but afeature that is highly desirable for sensor and separation technologies.


Eckert, J., A. Albinati, et al., "Nature ofthe Rh-H2 Bond in a DihydrogenComplex Stabilized Only by NitrogenBonds. Inelastic Neutron ScatteringStudy of TpRhH2(r|

2-H2) (Tp =Hydrotris(3,5-dimethylpyrazolyl)borate),"Inorg. Chem. 35,1292 (1996).

Kubas, G.J., "Metal-SilaneComplexes" in McGraw-HillYearbook of Science and Technology,S.P. Parker, Ed. (McGraw-HillProfessional Book Group, New York,1996), pp. 350-351.

Limbach, H.-H., S. Ulrich, S. Sabo-Etienne, et al., "NMR and INSLineshapes of Transition MetalHydrides in the Presence of Coherentand Incoherent DihydrogenExchange" (submitted to J. Am.Chem. Soc).

Rodriguez, V., S. Sabo-Etienne, B.Chaudret, et al., "SpectroscopicStudies and Reactivity of the Bis-Dihydrogen ComplexRuH2(H2)2(PCy3)2 in Freons andCHC13. Synthesis of a Ruthenium IVDihydride: RuH2Cl2(PCy3)2"(submitted to Inorg. Chim. Actd).

Molecular x-ray crystal structure of [Mn(CO)(Ph2PC2H4PPh2)2]+ showing theinteraction (dotted lines) of the manganese(I) center with two carbon-hydrogenbonds located on separate phenyl (Ph) rings of the diphenylphosphine (PPh2)groups. Multiple carbon-hydrogen interactions are rare. The analogous zero-valent molybdenum complex has only one such interaction.

Asymmetric Catalysis in OrganicSynthesis

John Watkin

This research project is aimed atdeveloping new catalysts for theenantioselective formation of organicmolecules that may be used in a widerange of industrial applications. Ourprimary goal is to develop lanthanide-based catalyst systems that featurechiral alkoxide or Schiff-basesupporting ligands.

During the past year, we havesystematically examined the use of awide range of lanthanide complexescontaining chiral diolate and Schiff-base ligands as catalysts for the

asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of acetophe-none to a secondary alcohol. In onecase, we have employed a Schiff-baseligand, prepared from norephedrineand 2-hydroxynaphthaldehyde,chelated to a gadolinium-metal centerto perform the MPV reduction with anoptical purity of 52%. Other lan-thanide metals such as samarium,neodymium, and erbium were foundto give somewhat lower optical purityin analogous reactions. The commer-cially available Jacobsen ligand used

in the same reaction gave better yieldsthan the simple Schiff-base ligand, butthe optical purities of the productwere rather low, reaching a maximumof 38% in the case of erbium.

We have also examined the use ofchiral diolate ligands chelated to alanthanide-metal center for the MPVreduction. In this case, the yields werevery good (>85%), but the opticalpurity was low (<20%), which webelieve was due to the lack of rigidityin the diolate ligands. The resultsobtained to date have providedextensive information that will help usdesign more effective chiral ligands inthe future.


Temperatures and Vibrational Frequenciesof Liquid N2/O2 and CO/O2 MixturesShock-Compressed to 10 GPa and 2000 K

Stephen C. Schmidt

The purpose of this project was toexperimentally determine the tem-peratures and vibrational frequenciesof N2/O2 and CO/O2 mixtures thathave been shock-compressed topressures of -10 GPa and tempera-tures of -2000 K. The results obtainedare used to improve the equation ofstate that describes mixtures atconditions characteristic of theexpansion of explosive products. Themeasured molecular vibrationalfrequency shifts can be used to helpdevelop molecular-potential functionsthat will allow calculations ofthermodynamic equations of state.

We used a two-stage light-gas gunand single-pulse, multiplex, coherentanti-Stokes Raman scattering (CARS)to obtain vibrational spectra of carbonmonoxide, nitrogen, and oxygen forseveral high-temperature, dense-fluid

carbon monoxide/oxygen andnitrogen/oxygen mixtures. Theexperimental spectra were comparedwith synthetic spectra calculated witha semiclassical model for CARSintensities and using best-fit vibra-tional frequencies, peak Ramansusceptibilities, and Raman linewidthsfor each mixture component. Up to amaximum shock pressure of 7 GPafor the carbon monoxide/oxygenmixtures and 13 GPa for the nitrogen/oxygen mixtures, the CO, N2, and O2

vibrational frequencies were all foundto increase monotonically withpressure and depended on the carbonmonoxide/oxygen and nitrogen/oxygen mixture ratios. The transitionintensity and linewidth data suggestthat thermal equilibrium of thevibrational levels is attained in lessthan 10 ns at these shock pressures.

The vibrational temperatures obtainedfor the nitrogen/oxygen mixtures wereused to improve the oxygen potentialfunction that is used to calculateequation-of-state pressures andtemperatures. The measuredlinewidths for CO, N2, and O2 weredifferent for the different mixtures,but did not appear to depend signifi-cantly on mixture ratios. The broaden-ing of all spectral lines suggested thatthe vibrational dephasing time foreach species decreased to a fewpicoseconds at the highest-pressureshock states.

The accompanying figure showsrepresentative CARS spectra of aliquid 67% CO/33% O2 mixtureshock-compressed to 6.8 GPa at atemperature of 1286 K.

Publications

Schmidt, S.C., D.S. Moore, and M.S.Shaw, "Coherent Anti-Stokes RamanSpectroscopy of Shock-CompressedLiquid Carbon Monoxide/Oxygen andNitrogen/Oxygen Mixtures" (to bepublished in / . Chem. Phys.).

1.0

c3

S

-2200 -2100 -1600

Raman Shift (cm"1)

-1500

Representative coherent anti-Stokes Raman spectra of a liquid67% CO/33% O2 mixture shock-compressed to 6.8 GPa at atemperature of 1286 K. The tallsharp features are the spectra ofunshocked carbon monoxide andoxygen, and the lesser peaks arethe vibrational progressions fromthe shocked fluids. The solidcurves are the experimental data,and the dotted curves arecomputed spectra.


Catalysts for Hydrocarbon Oxidation

Kevin Ott

We are investigating the structureand reactivity of site-isolated catalyststhat selectively oxidize hydrocarbonsubstrates. As the starting point forour studies, we are examining aprototypical site-isolated oxidationcatalyst, TS-l.TS-1 selectivelyoxidizes hydrocarbon substrates touseful products using hydrogenperoxide as the oxidant. TS-1 is amicroporous silicate with a smallpercentage of the silicon atomsreplaced by titanium.

The titanium ions promote theoxidation chemistry via hydroperox-ide intermediates. We are incorporat-ing additional metal ions capable ofactivating and utilizing molecularoxygen into the structure of TS-1 andsimilar compounds. It is necessary toknow the placement of secondarymetal ions such as cobalt, iron,manganese, and chromium withrespect to the titanium ions. Becausex-ray diffraction techniques are notuseful in determining the location of

titanium, we have used neutrondiffraction to determine that there is asurprising nonrandom distribution oftitanium in the lattice.

We are applying a novel techniquecalled Pair Distribution Function(PDF) to zeolites. PDF is an analysisof diffuse neutron scattering to obtaininformation about local structure ofmaterials rather than the long-rangeorder afforded by more conventionaldiffraction experiments. We areprimarily interested in the localstructure of the titanium ions in TS-1.Preliminary results indicate the PDFdata include shifts to larger distancesrelative to the published data onsilicalite, a material analogous toTS-1 but that does not containtitanium. We believe these shifts arelikely due to Ti-0 bond lengths thatare longer than Si-O bond lengths.Knowledge of the structure of theactive site is fundamental to under-standing the function of any catalyst.We have designed and constructed a

catalytic reactor to be installed thisfall into the High Intensity PowderDiffractometer, an instrument fordetermining the structure of materials,at the Los Alamos Neutron ScienceCenter. This catalytic reactor willallow us to obtain diffraction and PDFdata on catalyst structures duringreaction.

Publications

Szanyi, J., and M. Paffett, "TheAdsorption of NO and Reaction ofNO with O2 on H-, NaH-, CuH-, andCu-ZSM-5: An In Situ FTIRInvestigation," J. Catal. 194,232-245(1996).

Szanyi, J., and M. Paffett,"Coadsorption of Nitriles and CO onCu-ZSM-5: An In Situ FTIRSpectroscopic Study" (to be publishedin Mater. Res. Soc, Symp. P Proc).

Szanyi, J., and M. Paffett, "AFTIRInvestigation of the Coadsorption ofAcetonitrile and CO on Cu-ZSM-5"(to be published in FaradayTransactions of The Chem. Soc).

Fundamental Studies of Polymer Filtration

Barbara F. Smith

The objectives of this project are todevelop an enhanced fundamentalunderstanding of the coordinationchemistry of hazardous-metal-ioncomplexation with water-solublemetal-binding polymers and to exploitthis knowledge to develop improvedseparations for analytical methods,metals processing, and waste treatment.

We investigated features of water-soluble metal-binding polymers thataffect their binding of and selectivityfor selected transition metal ions. Weevaluated backbone polymers usinglight-scattering and ultrafiltrationtechniques to determine the effect ofpH and ionic strength on the molecu-lar volume of the polymers. First, we

incrementally functionalized thebackbone polymers with a metal-binding ligand. Then we developed aprocedure and analytical method todetermine the absolute level offunctionalization and correlated theresults with the elemental analysis,viscosity, and molecular size. We willuse these results as a quality assur-ance measure for these polymers oncewe transfer them to our industrialpartner for commercialization.

Next, we performed a large-scalesynthesis of the optimized polymersto confirm that there were no prob-lems with scale-up of the synthesis.Both large- and small-scale synthesisproduced the same materials. We did

further troubleshooting with ourindustrial partner to help get a large-scale pilot unit of the polymerfiltration technology installed in alarge electroplating facility. Theproblem addressed involved determin-ing the effect of chromium(VI) onnickel(II) binding to the polymers.

Publications

Smith, B.F., T.W. Robison, et al.,"Polymer Filtration: A NewTechnology for Selective MetalsRecovery" (SUR-FIN95 Conferenceof the American Electroplaters andSurface Finishers Society, Baltimore,Md., June 26-29, 1995).


Modification of Heterogeneous Chennistryby Realistic Substrate Complexity

Bryan Henson

This project explores a set ofchemical reactions on porous surfacesthat play an important role in theobserved depletion of stratosphericozone over Antarctica every polarspring. We specifically study a seriesof coupled heterogeneous reactions ofchlorine nitrate (C10N02) that are ofconsiderable current interest in polarozone depletion:

C10N02 + H2O -> HOC1 + HNO3

HOC1 + HC1 -» Cl2 + H2OC1ONO2 + HC1 -» Cl2 + HNO3

These reactions proceed on polarstratospheric clouds which formduring the winter, releasing Cl2 gasthat subsequently attacks ozone whensunlight returns during the spring.

We have developed a model ofheterogeneous reactivity based onphysical adsorption. This modeldescribes how the observed relativehumidity affects the reactivity ofC1ONO2 with H2O and HC1 onsulfuric acid tetrahydrate (SAT) ice

l.OOE-01

surfaces and with H2O on nitric acidtrihydrate (NAT) surfaces. For a givensystem, we model the laboratory datausing only two parameters: themeasured reaction probability on aneat ice surface and a constant fromBrunnauer-Emmett-Teller (BET)theory. This theory describes thefraction of an acid-hydrate surfacecovered by water as a function ofrelative humidity. The agreementbetween calculations of reactionprobability based on this model andlaboratory measurements is shown inthe accompanying figure.

We have used a surface-specificlaser technique to quantify thecoverage of water on a porous NATsurface. Thus, for the hydrolysis ofC1ONO2 on NAT, all parameters inthe model are fixed by laboratorymeasurements. The model indicatesthat C1ONO2 reactivity with both H2Oand HC1 on SAT and with H2O onNAT is controlled by the surfacecoverage of H2O. Our model suggests

that the reported reactivities of HC1with C1ONO2 on NAT may beunderestimated by as much as a factorof 10.

Publications

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Chlorine NitrateReactivity on Simulated PolarStratospheric Cloud Surfaces" (211thAmerican Chemical Society Meeting,New Orleans, La., March 1996).

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Modeling the RelativeHumidity Dependence of C1ONO2

Reactivity on Ices" (1996 Inter-national Symposium on the Physicsand Chemistry of Ice, Hanover, N.H.,August 1996).

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Modeling the RelativeHumidity Dependence ofHeterogeneous Reactions on PolarStratospheric Clouds" (1995 FallMeeting of the American GeophysicalUnion, San Francisco, Calif.,December 1995).

Henson, B.F., K.R. Wilson, and J.M.Robinson, "A Physical AdsorptionModel of the Dependence of C1ONO2

Heterogeneous Reactivity," Geophys.Res. Lett. 23,1021 (1996).

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Thermodynamics ofHeterogeneous Surfaces fromNonlinear Light Scattering" (NewMexico Chapter of the AmericanVacuum Society Annual Meeting,Albuquerque, N.Mex., April 1996).

1.00E-060 0.5 1

Relative Humidity P/Po

The hydrolysis ofClONO2 on NAT and SAT surfaces. The dataare plotted by reaction probability as a function of fractionalrelative humidity. The curve through the NAT data is calculatedfrom our physical adsorption model with no variableparameters. The curve through the SAT data is a best fit usingthe same model, which predicts that the coverage of water onSAT is parameterized by the BET constant, c = 0.2. The dataare from several different laboratories, as referenced in Hensonet al, Geophys. Res. Lett. 23, 1021 (1996).


lonically Conducting Polymers forHigh-Energy-Density Batteries

Robert Hermes

Using polymer synthesis andelectrochemical characterizationtechniques, we set out to understandthe ionic transport chemistry of thepolyelectrolyte component of solid-state lithium batteries. Lithium-iontransport is the mechanism by whichcharge is carried through the poly-electrolyte.

This year we synthesized severaloligooxyethylene-modified poly-phosphazenes and tested them forelectrical conductivity and lithium-iontransport characteristics, each atseveral lithium-imide-salt loadingsand temperatures, under dryboxconditions. With fresh batches of

polyelectrolytes, we reproduced theoutstanding electrical conductivityresults achieved in 1995 and wereable to double the room-temperatureconductivity from 1.1 xlO"4 S/cm to2.2 x 10"4 S/cm with two newlysynthesized polyelectrolytes.

This result has validated the essenceof our original hypothesis: mixedether side-chains for increasedmobility and decreased lithium salttogether induce crystallinity. Weobtained Raman spectra from varioussalt/polyelectrolyte compositions.

This spectroscopic technique helpedus correlate the ion-pairing thresholdof lithium salts with the electricalconductivity results. We also investi-gated lithium nuclear magneticresonance as a tool to estimate ionicdiffusion coefficients.

In the three years of this project, wehave developed techniques that can beused to predict the interaction oflithium and lithium-imide salt withthe polyelectrolytes we synthesized inour laboratory. We also achieved thehighest room-temperature conductiv-ity for an "unplasticized" solidpolyelectrolyte.

Advanced Polymer Chemistryof Organometallic Anions

Rebecca M. Chamberlin

The objective of the project was toprepare and characterize new poly-mers incorporating the cobaltdicarbollide anion, [Co(C2B9Hn)2]~.Cobalt dicarbollide is well known asan extraction agent for removingradioactive cesium and strontiumfrom nuclear waste. Polymerscontaining cobalt dicarbollide in themain chain are expected to have novelapplications in ion exchange, cataly-sis, and medical radiotherapy.

During this year we characterizedthe scope and stereochemical outcomeof the twofold deprotonation andnucleophilic substitution reactions of[Co(C2B9Hn)2]" and generated apublication on this topic. We alsosynthesized several reactive mono-mers using nucleophilic substitution

reactions, most notably a dicarboxylicacid, [Co(C2B9H10)2(COOH)2]-. Thedicarboxylic acid forms organometal-lic polymers via condensation withamines such as hexamethylenediamine, by two different routes. Thefirst route is conversion of thedicarboxylic acid to a di(acid chlo-ride), which reacts with the diaminein solution to form an insoluble, redpolyamide. The second route is directreaction of the dicarboxylic acid withthe diamine, forming an amine salt.The amine salt is thermolyzed in athermogravimetric analysis/differen-tial thermal analysis (TGA-DTA)experiment to form the polymer whilereleasing water.

Publications

Balaich, G.J., S.A. Fino, et al.,"Synthesis of an OrganometallicPolyamide of Cobalt Dicarbollide"(submitted to Inorg. Chem.).

Chamberlin, R.M., B.L. Scott, et al.,"Butyllithiurn Deprotonation VersusAlkali Metal Reduction of CobaltDicarbollide: A New Route to C-Substituted Derivatives" (to bepublished in Inorg. Chem.).


Reaction Kinetics Relevant to the RecycleHydride-Dehydride Process for PlutoniumRecovery

John Haschke

Objectives of this project were toexpand fundamental knowledge ofplutonium chemistry and to developinformation for enhancing plutoniumrecovery methods and weapons safety.Plutonium oxide monohydride,PuO(H), is a novel, but incompletelycharacterized, compound that formswhen plutonium metal is exposed towater. Like other compounds ofplutonium(III), it is expected to behighly reactive with oxygen and canpromote reactions between metal andair in a manner similar to thatobserved for plutonium hydride.

Therefore, formation of an oxidehydride layer by reaction with watermay catalytically enhance theoxidation of plutonium while avoid-ing safety problems associated withusing hydrogen in the recycle process.

We used pressure-volume-tempera-ture experiments to produce a surfacelayer of PuO(H) by aqueous corrosionof plutonium metal. We then testedthe behavior of moist and driedsamples by rapid exposure to oxygenand air. Results of these kineticstudies demonstrate that the monoxidemonohydride is pyrophoric when dry

and acts as an initiator for hydride-catalyzed reaction of the metal withair. This process consumes bothoxygen and nitrogen and continuesuntil reactants are depleted. Thecatalyzed corrosion rate of plutoniumis 108 times faster than the corrosionrate of the metal in dry air. Thehydride-catalyzed reaction transformsplutonium into a fine oxide nitridepowder with a high potential foraerosolization and environmentaldispersal. Catalyzed reaction withoxygen produces plutonium dioxide,the chemical form needed to preparemixed-oxide fuel for nuclear-powergeneration, and is potentially appli-cable as a method for direct recoveryof plutonium as PuO2. Wet PuO(H) isnonpyrophoric, and the safety hazardposed by formation of oxide hydrideis reduced if the material remainsmoist.

Ultrafast Laser Studiesof Solution Reactivity

William Woodruff

Fast chemical dynamics generallymust be initiated photochemically.This fact limits the applicability ofmodern laser methods for followingthe structural changes that occurduring chemical and biologicalreactions to those systems that havean electronic chromophore thatproduces a significant yield ofphotoproduct when excited. Ourproject has developed a new andentirely general approach to ultrafastinitiation of reactions in solution:laser-induced temperature jump. Thisapproach opens entirely new fields ofstudy of ultrafast molecular dynamicsin solution.

We have demonstrated the tempera-ture-jump technique on timescales of50 ps and longer and have applied itto the study of fast events in protein

folding. We have found that a generallifetime of alpha-helix formation isabout 100 ns and that tertiary folds (inapomyoglobin) form in about 100 us.This work has been reported in twopublications.

Publications

Gilmanshin, R., S. Williams, R.Callender, et al., "Fast Events inProtein Folding: Relaxation Dynamicsof Secondary and Tertiary Structure inNative Apomyoglobin" (to bepublished in Proc. Nat. Acad. Sci.).

Williams, S., T. Causgrove, R.Gilmanshin, et al., "Fast Events inProtein Folding: Helix Melting andFormation in a Small Peptide,"Biochem. 35 (3), 691-97 (1996).


Mathematics andComputational Sciences

Parallel Three-DimensionalSpherical-Harmonics Transport Methods

Jim Morel

Solution of the Boltzmann transportequation is essential in modeling awide variety of physical phenomena.The standard angular discretizationtechnique used in production transportcodes is the Sn, or discrete-ordinates,method. However, this method doesnot preserve the rotational invarianceof the transport operator, and hencegives rise to nonphysical "ray effects."Such ray effects make the Sn dis-cretization unsuitable in problemswith localized sources and opticallythin regions. In addition, fundamental

difficulties arise in applying the Sn

discretization on finite-elementmeshes because many cells in typicalmeshes are re-entrant. The Pn, orspherical-harmonics, method is theonly deterministic method thatpreserves the rotational invariance ofthe analytic transport operator. ThePn method does not suffer from rayeffects and can be applied on finite-element meshes.

The primary goal of our project isto develop three-dimensional,unstructured-mesh radiation transport

algorithms and an associated parallelcode based upon a Pn, or spherical-harmonics, discretization in angle.Such a capability is unique to LosAlamos as well as to the entire DOEcomplex.

This year we completed a parallelPn code for the Connection Machine 5computer. This code is based upon anew self-adjoint form of the transportoperator that offers significantadvantages over previous forms. Wealso generalized our parallel algo-rithm, which used unstructuredtetrahedral meshes, to use unstruc-tured meshes of arbitrary combina-tions of hexahedra and degeneratehexahedra, e.g., wedges, pyramids,and tetrahedra.

Adaptive, Composite, OverlappingMesh Algorithms on Message-Passing Architectures

David L. Brown

We have developed computationalmethods and a programming frame-work for adaptive, composite,overlapping meshes to be used onserial and parallel computers. Theneed for high-level tools to aid in themodeling of large-scale, complex,physical processes described incomplex geometries by fluid-flowequations prompted this research.Parallel tools are based on object-oriented, message-passing techniques.We used an object-oriented approachbased on the C++ language to createthe Overture programming framework

in which relatively high-level compu-tational objects may be assembledinto solvers for partial differentialequations (PDEs). With this frame-work users can create solvers that areportable across a wide variety ofcomputer architectures and seam-lessly incorporate software that usesadaptive, composite overlappingmeshes.

We developed a number of C++class libraries as part of this project.The A++/P++ library handles basicarray operations required in scientific

codes. Parallel infrastructures arehidden from the user of this library.The Overture framework containsC++ class libraries that handleoverlapping meshes, arrays of data onthose meshes, and difference opera-tors. We developed PDE codes forcompressible and incompressible flowproblems as well as an "all-speed"solver that handles flows with a rangeof Mach numbers from near zero toMach 1 using these class libraries.

Publications

Brown, D.L., and W.D. Henshaw,"Overture: An Advanced Object-Oriented Software System for MovingOverlapping Grid Computations"(NASA Computational AerosciencesWorkshop, Ames, Calif., August1996).

Individual Projects—Math and Computational Sciences 61

A Self-Consistent Multiscale Theory ofInternal-Wave, Mean-Flow Interactionsin the Ocean

Darryl D. Holm

This research is directed towardapplications of nonlinear dynamicsand kinetic theory in developing newmodel equations and better analysistools for nonlinear problems, such asocean dynamics, involving multipletime- and length-scales. At present itis not feasible to resolve all of thesescales and their interactions innumerical simulations. We propose afundamental approach for describingthe effects of these interactions bydeveloping a self-consistentmultiscale theory of internal-wave,resolved-flow interactions. To do this,we take advantage of the remarkablestatistical homogeneity of the internalwave field observed nearly every-where in the ocean—the empiricalGarrett-Munk spectrum.

We have derived a hierarchy ofapproximate models of wave, mean-flow interaction (WMFI) for model-ing ocean dynamics by usingasymptotic expansions. One smallparameter for these expansions is theratio of time scales between internalwaves at most wave numbers and themesoscale mean-flow of an inviscid,stratified, rotating fluid. This "adia-batic ratio" is small and is comparableto the ratio of space scales for theclass of initial conditions that supportinternal waves. Another smallparameter available in these expan-sions is the ratio of the internal-waveamplitude to its wavelength.

The new self-consistent WMFIequations are derived in two ways:first, by requiring Euler's equations topreserve the wave, mean-flowdecomposition to linear order in thewave amplitude; and second, bysubstituting this decomposition intoHamilton's principle for Euler'sequations and applying asymptoticexpansions and phase averaging to thedecomposition. The derivation from

Hamilton's principle shows that theresulting equations possess a Kelvincirculation theorem, conserve apotential vorticity, and are Lie-Poisson Hamiltonian dynamicalsystems in the Eulerian variables. Thederivation from Euler's equationsconfirms the validity of the derivationfrom Hamilton's principle. Passage tothe Lie-Poisson Hamiltonian formula-tion brings the WMFI theory into aframework in which formal andnonlinear stability analysis can beapplied.

We have also found relations ofthese results to the Charney-Drazinnonacceleration theorem, Whifhamaveraging, Wentzel-Kramers-Brilluoin(WKB) stability theory, andLagrangian-mean fluid equations for

prescribed wave displacements, suchas those of Andrews and Mclntyre.

Publications

Allen, J.S., and D.D. Holm,"Extended-Geostrophic HamiltonianModels for Rotating Shallow WaterMotion," Physica D 98, 229-248(1996).

Gjaja, I., and D.D. Holm, "Self-Consistent Wave-Mean FlowInteraction Dynamics and ItsHamiltonian Formulat," Physica D98, 343-378 (1996).

Holm, D.D., "Hamiltonian BalanceEquations," Physica D 98, 379^14(1996).

Holm, D.D., "The Ideal Craik-Leibovich Equations," Physica D 98,415^41 (1996).

Camassa, R., D.D. Holm, and CD.Levermore, "Long-Time Effects ofBottom Topography in ShallowWater," Physica D 98, 258-286(1996).

Geometry in the Large andHyperbolic Chaos

Brosl Hasslacher

Chaos theory continues to becentral to the modeling and under-standing of complex mathematicaland real systems, and the tools beingdeveloped to model these systemscontinue to expand. This project isaimed at providing an important newcapability to better understand suchsystems. In strongly chaotic systems,one common difficulty is that thecalculation of useful observables isoften blocked by the lack of aworkable orbit classification for suchsystems. This is because globalgeometrical information from the

original dynamical system is en-tangled in an unknown way through-out the orbit sequence.

This year we have successfully usedgeometrical methods from modernmathematics and recent connectionsbetween global geometrical andmodern quantum field theory to studythe natural geometrical objectsbelonging to hard chaos, i.e., hyper-bolic manifolds. In this way we canbetter interpret global geometricalinformation and so ultimatelycalculate useful observables in chaoticsystems that otherwise would not bepossible.


Industrial Processing of Complex Fluids:Formulation and Modeling

James Scovel

Many commercial materials such astextile fibers, plastics, and fiber-opticcable are produced by cooling com-plex fluids to form a solid. We aredeveloping models that can be used tooptimize the macroscopic propertiesof such materials and to identify andthus minimize sources of defects.

The objective of our project is toderive constitutive laws of complexfluids in which the relaxation modesare determined geometrically by thedifferent micro-, meso-, and macro-scale structures, and thus the modescouple not only through the dissipa-tive term but through geometricalrelations. In addition, the couplingshould evolve through the solidifica-tion phase.

We developed a model for the two-scale system (where the two scales arefine and coarse) based on a state-space representation in which thetransition equation must be modifiedso that the observation equationcorresponds to the mapping from thefine to the coarse scale. The tradi-tional state-space representationconsists of two components: the firstcomponent is a state vector thatcannot be observed but for which thedynamics (the transition equation) isunderstood. The second component isa mapping from the state vector to avector of observable quantities. Forlinear equations of motion, solutionsof this system can be found by usingthe Kalman filter when the equations

of motion on the fine scale are known.When these equations are not pre-cisely known, they can be determinedwithin a particular class by combiningthe Kalman filter with a maximum-likelihood technique that we havedeveloped. However, how to applythis technique in the case of nonlinearequations of motion has not beendetermined.

To test our maximum-likelihoodtechnique, we applied it to theunsolved problem of disaggregationof time series. We developed andtested an algorithm for the disaggre-gation of time series on severalclasses of data generated by AutoRegressive Integrated MovingAverage (ARIMA) processes. Wefound that we can successfullyestimate the parameters of the modelgenerating the original data from theaggregate data alone. In addition, ourestimates of the disaggregate data aresuperior to a naive estimate com-monly used in multigrid methods.

Dispersive Water Waves inOne and Two Dimensions

Darryl D. Holm

With applications in mind forgeophysical ocean dynamics, we areusing multiple-time-scale perturbationtheory to derive new equations for thelong-time asymptotic behavior ofdispersive shallow-water flow in athin domain over a varying bottom inone and two dimensions. This pastyear we continued to analyze our newshallow-water equations and relatedsystems of equations while develop-ing new directions for the mathemat-ics underlying the integrability ofthese systems. In particular, weapplied the generating equationmethod to create and study newintegrable systems of nonlinear partialdifferential equations related to ourshallow-water equations. We alsoinvestigated the solutions of thesesystems of equations on a periodicspatial domain by using methods from

the complex algebraic geometry ofRiemann surfaces.

We developed several aspects ofthe required mathematical tools inthe course of this investigation:(1) inverse scattering with degeneratepotentials, (2) asymptotic reductionof the angle representations, (3)geometric singular perturbationtheory, and (4) modulation theory andsingularity tracking for completelyintegrable equations.

We also studied models that admitweak solutions, i.e., solutions withdiscontinuous derivatives in the formof corners or cusps. These appeareven though the models we arestudying are integrable, a propertythat is often incorrectly assumed toimply smooth solution behavior. Wealso derived new shallow-waterequations in two dimensions. Theseequations provide an estimate of the

long-time asymptotic effects ofslowly varying bottom topographyand weak hydrostatic imbalance onthe vertically averaged, horizontalvelocity of an incompressible fluidwith a free surface moving under theforce of gravity. In this work weconsidered the regime in which theFroude number is much smaller thanthe aspect ratio of the shallowdomain.

Publications

Alber, M., R. Camassa, et al., "On theLink Between Umbilic Geodesies andSoliton Solutions on NonlinearPDEs," Roy. Soc. Proc. 450, 677-692(1995).

Camassa, R., D. Holm, and C.Levermore, "Long-Time Effects ofBottom Topography in ShallowWater," Physica D 98, 258-286(1996).

Camassa, R., and C. Levermore,"Layer-Mean Quantities, LocalConservation Laws, and Vorticity,"Phys. Rev. Lett. 78, 650 (1997).


Mimetic Difference Approximationsof Partial Differential Equations

James Hyman

The goal of this research has beento construct local, high-order differ-ence approximations of differentialoperators on nonuniform grids thatmimic the symmetry properties of thecontinuum differential operators.Partial differential equations solvedwith these mimetic differenceapproximations automatically satisfydiscrete versions of conservation lawsand of analogies to Stake's theorem;because these versions are true in thecontinuum, they are more likely toproduce physically faithful results.Continuum symmetries are easilypreserved by local, discrete high-orderapproximations on uniform grids, butthey are difficult to retain in high-order approximations on nonuniformgrids. The approximations must alsobe local and use only function valuesat nearby points in the computationalgrid; these methods are especiallyefficient on computers with distrib-uted memory.

We have derived new, mimetic,fourth-order, finite-differencediscretizations of the divergence,gradient, and Laplacian on nonuni-form grids. The discrete divergence is

the negative of the adjoint of thediscrete gradient, and consequentlythe Laplacian is a symmetric negativeoperator. The new methods we arederiving are local, accurate, reliable,and efficient difference methods thatmimic symmetry, conservation,stability, the duality relationships, andthe identities between the gradient,curl, and divergence operators onnonuniform grids. These methods areespecially powerful on coarsenonuniform grids and in calculationsin which the mesh moves to trackinterfaces or shocks, such as inmodeling fluid dynamics.

Publications

Hyman, J., and M. Shashkov, "AdjointOperators for the Natural DiscreteDivergence, Gradient, and Curl" (tobe published in Appl. NumericalMath.).

Hyman, J., and M. Shashkov,"Natural Discretizations for theDivergence, Gradient, and Curl onLogically Rectangular Grids" (to bepublished in Comput. Math. Appl.).

Hyman, J., M. Shashkov, and S.Steinberg, "The Numerical Solutionof Diffusion Problems in StronglyHeterogeneous Non-IsotropicMaterials" (to be published in J.Comp. Phys.).

Hyman, J., M. Shashkov, and S.Steinberg, "Problems withHeterogeneous and Non-IsotropicMedia or Distorted Grids," inProceedings of Finite Volumes forComplex Applications, Problems andPerspectives, F. Benkhaldoun and R.Vilsmeier, Eds. (Hermes, Paris, 1996),pp. 249-260.

Hyman, J., J. Castillo, et al., "High-Order Mimetic Finite DifferenceMethods on Nonuniform Grids," inProceedings Third InternationalConference on Spectral and High-Order Methods, A.V. Ilin and R R.Scott, Eds. (Houston Journal ofMathematics, Houston, Tex., 1996),pp. 347-361.

Hyman, J., J. Castillo, et al., "TheSensitivity and Accuracy of FourthOrder Finite Difference Schemes onNonuniform Grids in One Dimen-sion," Comput. Math. Appl. 30 (8),41-55 (1995).

Shashkov, M,. and S. Steinberg,"Solving Diffusion Equations withRough Coefficients in Rough Grids,"/. Comp. Phys. 129, 383-405 (1996).

Wavelet Transforms as Solutionsof Partial Differential Equations

George Zweig

A significant recent development inapplied mathematics is the study ofwavelet transforms, both continuousand discrete. Like Fourier transforms,wavelet transforms express functionsin terms of simple building blocks; inparticular, wavelet transforms de-compose functions into componentswith respect to a set of expansionfunctions that are dilations andtranslations of a single function called

the "parent wavelet." Such wavelettransforms are useful in representing"transients" whose time and fre-quency structure reflects the dynamicsof an underlying physical system.Speech sound, pressure in turbulentfluid flow, or engine sound in automo-biles are excellent candidates forwavelet analysis.

We made significant progress intwo areas: (1) methods for choosing

the parent wavelet for a continuouswavelet transform in pattern recogni-tion applications were developed, and(2) the computation of continuouswavelet transforms was made moreefficient by understanding therelationship between discrete wavelettransforms and discretized continuouswavelet transforms.

Publications

Zweig, G., and C.A. Shera, "TheOrigin of Periodicity in the Spectrumof Evoked Otoacoustic Emissions," /.Acoust. Soc. Am. 98, 2018-2047(1995).


Dispersive, Internal, Long-Wave Models

Roberto Camassa

This work is a joint analytical andnumerical study of internal, dispersivewater-wave propagation in a stratifiedtwo-layer fluid, a problem that hasimportant geophysical applications.Two-layer models can capture themain baroclinic (density dependent)effects. They also support the ob-served large-amplitude, internal wavemotion at the interface between layersas well as a large shear in the velocityfield, which cannot be described bythe simpler barotropic (verticallyintegrated) models.

We have derived model equationsfor two-layer, stratified fluid in thefully nonlinear regimes for finite andinfinite depth of the lower layer. Byconsidering the weakly nonlinearregimes in various limits of the ratio

between upper and lower layerdepths, and by assuming uni-directionality of wave propagation,we have shown that our modelequations reduce to the known casesof coupled Boussinesq, intermediatelong-wave, and Benjamin-Onoequations. We have implementedfinite-difference and pseudo-spectralcodes for solving numerically thetraveling wave solutions for the one-dimensional version of the model andalso carried out simulations of inter-acting waves.

One breakthrough made possible byretaining the full nonlinearity of thefundamental dynamics of the two-layer fluid finally clarifies experimen-tal observations that have been leftunexplained for more than 15 years. It

is now evident that the traditionalweakly nonlinear models are unableto deal with most regimes encoun-tered experimentally. However, theseregimes can be accurately describedby our new equations, with minimalloss of simplicity with respect to theknown models.

Publications

Camassa, R., and W. Choi, "LongInternal Waves of Finite Amplitude,"Phys. Rev. Lett. 77,1759 (1996).

Camassa, R., and W. Choi, "NonlinearInternal Waves in a Two-Layer Fluid,"J. Fluid Mechanics 313, 83 (1996).

Camassa, R., and D. Levermore,"Layer-Mean Quantities, LocalConservation Laws, and Vorticity" (tobe published in Phys. Rev. Lett).

Choi, W., "On the Fission ofAlgebraic Solitons" (to be publishedin Proc. R. Soc. Lond. A).

Solution-Adaptive Methods forLow-Speed and All-Speed Flows

Jeffrey S. Saltzman

We are developing solution-adaptive methods for efficientlycomputing fluid problems that involvelow-speed flows and problems thatare a mixture of low-speed and high-speed flows. A solution-adaptivemethod switches to different solversand/or algorithms as needed indifferent regions of the problemdomain. In regions where the flow isslightly compressible (low-speed), weuse a scheme based on efficient andaccurate methods that have beenrecently developed for incompressible

flows. In regions of the domain wherethe flow is compressible, we switch toan existing high-quality shock-capturing method. As anotherpossibility, there may be parts of thedomain where only sound waves arepresent, and in this case we would usea method that is optimized for thewave equation of acoustics.

We have developed and are nowcomparing two promising approachesfor all-speed flow solvers. The first isbased on a novel Godunov-Projectionalgorithm for incompressible flows

that we have extended to treat flows atall Mach numbers. The secondapproach uses a semi-implicitdiscretization for low Mach numbersthat requires the solution of only onescalar Poisson equation. The lattermethod switches to a standardcompressible solver when the Machnumber becomes sufficiently large.We used the "Overture" class librariesto write the solvers; the Overturelibraries provide a high-level interfacefor solving partial differentialequations on moving, overlappinggrids. This method provides forsignificant reuse of code between thesolvers, meaning that future solverswill be easier to write. The require-ments of the solvers have alsoinfluenced the design and capabilitiesof the Overture library.


Combinatorics, Geometry,and Mathematical Physics

William Chen

Combinatorics and geometry areamong the most active areas ofmathematics today, and this project isparticularly focused on the areas ofunitary symmetry and combinatorics,q-extensions of hypergeometricfunctions, and Hopf algebras. Theseareas of mathematics will continue tobe important for the next severaldecades because of the power theybring both in new techniques and inthe linkages that have emergedbetween them and several establishedfields. In this work, we extend theselinkages to an area of mathematicalphysics dealing with symmetry andthe quantum description of many-particle systems. As a result, we haveidentified a specific area of appliedmathematics with applications tophysics, chemistry, and perhapsbiology.

During the two years of this project,we have advanced our goal ofbringing combinatorics to bear onphysical problems by the publicationof six papers (three in 1995) dealingwith these subjects and by five morepapers accepted by refereed journals.These papers are in each of the statedareas of unitary symmetry andcombinatorics, q-extensions ofhypergeometric functions, and Hopfalgebras. We expect that these lattertwo "hot topics" will feed back to thefirst one and advance that subject.Finally, we have in advanced stages ofpreparation nine more papers comingunder the purview of our proposal,about half of which have resulted inrequests to present our work in invitedtalks at scientific conferences. Wehave made and are still makingsubstantive contributions in the cross-fertilization of combinatorics and itsapplications.

Publications

Beyer, W.A., and J.D. Louck,"Transfinite Function Iteration andSurreal Numbers" (to be published inAdv. Appl. Math.).

Chen, W.Y.C., and Z.G. Liu,"Parameter Augmentation for BasicHypergeometric Series, I" (RotafestConference, Cambridge, Mass., April1996).

Chen, W.Y.C., and Z.G. Liu,"Parameter Augmentation for BasicHypergeometric Series, II" (submittedto SIAMJ. Math. Anal).

Chen, W.Y.C., and J.D. Louck, "TheCombinatorial Power of theCompanion Matrix," Linear AlgebraAppl. 232, 261-78 (1996).

Chen, W.Y.C., and J.D. Louck,"Interpolation for SymmetricFunctions," Adv. Math. 117,147-56(1996).

Chen, W.Y.C., and J.D. Louck,"Necklaces, MSS Sequences andDNA Sequences" (to be published inDiscrete Math.).

Louck, J.D., "Conway Numbers andIteration Theory" (to be published inAdv. Appl. Math.).

Louck, J.D., "MacMahon's MasterTheorem, Double Tableau, andGroups," Adv. Appl. Math. 17,143-68(1996).

The Fundamental Role of Solitons inNonlinear Partial Differential Equations

James Hyman

Numerical simulations and math-ematical analysis have proved crucialto understanding the fundamental roleof solitons in the evolution of generalinitial data for quasilinear, dispersivepartial differential equations, such asthe Korteweg-de Vries (KdV)nonlinear Schrodinger and theKadomtsev-Petviashvili equations.These equations have linear disper-sion, and the solitons have infinitesupport.

Recently, we discovered a new classof solitons with compact support forsimilar equations with nonlineardispersion. These 'compactons'display the same modal decomposi-tions and structural stability observedin earlier integrable partial differentialequations. They form from arbitraryinitial data, are nonlinearly self-stabilizing, and maintain theircoherence after multiple collisions,even though the equations are notintegrable.

This year we discovered a newmultiple-humped, pulsating solitonfor a related fifth-order KdV equation.This multihumped solitary waveshares many of the properties of thetraditional single-humped solitonspreviously seen in KdV-like equa-tions. We have observed multi-humped solitary waves, with up toeleven humps, that are dynamicallystable in multisoliton collisionsemerge spontaneously from initialdata.

We also began a new researchproject to investigate a new nonlineardispersive equation based on aLagrangian approach to another fifth-order KdV-like equation. The solu-tions of this new family of equationspossess a rich variety of compact andnoncompact solitons. This research isthe opening for a far-reaching andnew understanding of the central roleof solitons in nonlinear dispersion.


Elliptic Solvers for AdaptiveMesh Refinement Grids

Daniel Quinlan

We are developing multigridmethods that will efficiently solveelliptic problems with anisotropic anddiscontinuous coefficients on adaptivegrids. The final result will be a librarythat provides for the simplifiedsolution of such problems. Thislibrary will directly benefit efforts inscientific computing, geoanalysis,fluid dynamics, mathematicalmodeling and analysis, radiationtransport, and others. The focus ofthis work is research on serial andparallel elliptic algorithms and theinclusion of our black-box multigrid

techniques into this new setting. Theapproach applies the Los Alamosobject-oriented class libraries thatgreatly simplify the development.

We focused on the extendeddevelopment of the software tools forparallel adaptive mesh refinement andtheir application to a simplifiedadaptive mesh refinement. The initialapplication involved the Fast AdaptiveComposite and Asynchronous FastAdaptive Composite solution methodsusing Multigrid single-grid solvers.We demonstrated that Multigridsolvers (an important component of

Studies of Structure of Turbulence byHigh-Resolution Simulation and Theory

Shiyi Chen

This project is a study of thestructures of fluid turbulence throughhigh-resolution, direct numericalsimulation and the development oftheory based on those simulations.Significant advances have been madein the study of fundamental fluidturbulence through our numerical andtheoretical work.

Using the equations of motion, wehave predicted analytically the scalingexponents for anomalous diffusioninvolving fluid turbulence, and wehave verified these exponents througha large-scale simulation with 8,192mesh points. This research is the firstinstance in which anomalous scalingexponents for a turbulence problemhave been deduced from the equationsof motion.

We carried out high-resolution,direct numerical simulations of three-dimensional (3-D) Navier-Stokes

turbulence with normal and hypervis-cosity to study inertial-range statis-tics. We found that both the scalingsand the probability distributionfunctions are independent of thedissipation mechanism, while thenear-dissipation-range fluctuations(smaller-scale motions) show signifi-cant structural differences.

We studied the statistics andstructures of pressure field, vorticity,and dissipation in 3-D, incompress-ible, isotropic turbulence. We alsoinvestigated the statistical relationsamong pressure, vorticity, dissipation,and kinetic energy using a conditionalaveraging process. Finally, we studiedthe conditionally averaged velocityincrements as a function of the locallyaveraged dissipation. Our resultsprovide direct evidence that supportsthe refined similarity hypothesis.

the adaptive solvers) can run inparallel using the P++ array class(parallel array class); we originallydeveloped the solvers in the serialenvironment using the A++ arrayclass (serial array class). This demon-stration illustrated the usefulness ofthe simplified application develop-ment environment provided by theobject-oriented A++/P++ classlibraries. We completed extendingP++ for use with adaptive meshrefinement and tested its robustnesson different parallel environments.

As part of the AMR++ work(AMR++ is an object-oriented libraryfor adaptive mesh refinement meth-ods), we installed a sophisticatedgraphics and visualization system thatpermits simplified debugging andinterpretation of adaptive results. Thiswork has proved to be an importanttool in the research on numericalalgorithms for problems difficult toanalyze.

We have nearly completed addi-tional work on parallel load balancingspecific to adaptive mesh refinement.This work has focused on fast optimalcomplexity algorithms for the loadbalancing and distribution of theadaptive refinement grid across alarge number of processors. Thealgorithms are specific to structuredgrid adaptive mesh refinement, andwe expect them to be applicable tomany other parallel structuredapplications as well.

Publications

Shapira, Y., "Black-Box MultigridSolver for Definite and IndefiniteProblems," in Algebraic Multi-LevelIteration Methods with Applications,O. Axelsson and B. Polman, Eds.(University of Nijmegen, Nijmegen,The Netherlands, 1996), pp. 235-250.

Shapira, Y., "Domain DecompositionMultigrid for Unstructured Grids"(Ninth International Conference onDomain Decomposition Methods,Ullensvang, Norway, June 3-8, 1996).

Shapira, Y, "Multigrid for RefinedTriangle Meshes" (submitted to BIT).


Computational Three-DimensionalInversion for Seismic Exploration

Eugene Gavrilov

We are working to develop andimplement a three-dimensionalcomputational inversion tool forseismic exploration that will signifi-cantly improve the effectiveness ofcurrent seismic technology. Ourtechnique allows more efficient datagathering and analysis and, mostimportant, automates the currentinversion process, eliminating thecurrent need for human "interpreters."In addition, our technique has thepotential to dramatically improvemedical imaging technology forshortwave diagnostics.

We modified a three-dimensionalacoustic code for the massively parallel

computer, Cray T3D, that was imple-mented at the Advanced ComputingLaboratory; the code will serve as a testtool that we can use to solve theforward problem, whose solution iscritical to solving the inverse problem.We used the three-dimensional forwardcode to explore three different methodsfor solving the inverse problem, or theinversion process.

Unfortunately, the first method,based on the inverse matrix, wasunstable for three-dimensional casesand did not produce the expectedresults. The second method, three-dimensional computational acousticholography, allowed us to convert

seismic (acoustic) records into avisual representation of the exploredmedium. This method was stable androbust, and although it did not providean accurate velocity distributionbecause of a phase shift, it neverthe-less captured the major features of thevelocity structure. In fact, thismethod could be of great use inultrasound medical imaging. The thirdmethod we explored was based on thecoupled-phase (eikonal) and ampli-tude equations. With this method wewere able to recover the phase fromrecords and then solve the amplitudeequation for the whole investigateddomain, thereby achieving an accuratemathematical representation of theundistorted velocity in three dimen-sions. Our initial results from thismethod are very promising, but wemust explore it further to verify itsusefulness and effectiveness.

Super-Speed ComputerInterfaces and Networks

Donald Tolmie

Researchers studying super-speedcomputer interfaces and networkshave focused on identifying the net-working requirements of computation-intensive applications that are criticalto DOE programs. In particular, boththe Energy Research, High-Perfor-mance Computing Research Centers(HPCRCs) and the Defense Programs,Accelerated Strategic ComputingInitiative (ASCI) have plannedapplications that will require largeincreases in network bandwidth. In

this project we were working toidentify and understand criticalrequirements and to explore ways todevelop super-speed networks. Whenthe necessary network componentsbecome available, we plan to conductearly experiments on network switchand diagnostic techniques.

According to application developersat Los Alamos and other researchinstitutes, the new super-speednetwork requirements fall in the 5- to10-Gbit range. We have also identified

another parameter, network latency, asbeing critical to these applications.For the applications to perform well,we estimate that a network latency ofless than 1 us is the upper bound.

For this project we have performedan exhaustive evaluation of currentnetwork technologies. Based on thecriteria above, we found that no singletechnology meets all of the require-ments. This finding triggered acollaboration of Los Alamos research-ers with computer and networkingvendors to develop a 6.4-Gbit networkspecification called HIPPI-6400. Weare leading the effort to develop theHIPPI-6400 specification as anAmerican National Standard. We havealso started to develop a tester toverify and measure the performanceof HIPPI-6400 implementations.


Particles and Patternsin Cellular Automata

Erica Jen

We developed a general methodol-ogy to study particles and domains inone-dimensional cellular automata.A cellular automaton is a discretedynamical system that consists of alattice of sites whose values evolvethrough a local interaction rule.Newly obtained results in the math-ematics of one-dimensional cellularautomata promise to provide for thefirst time a method for analyzing therelationship between an automaton'smicroscopic-level specification

through its rule table, and certainmacroscopic features—includingpattern formation and computationalcapabilities—that characterize itsevolution. The central point is thatthese automata are characterized bytheir generation of mesoscopicstructures that can be viewed asparticles and backgrounds, and theglobal behavior of the automata maybe described through a reformulationof the automaton in terms of collisionrules on this mesoscopic scale.

On the basis of this methodology,an atlas was generated of the range ofbackgrounds, particle types, andparticle for one particular elementarylocal interaction scheme. Based onthis atlas, an appropriate filter wasconstructed to study the patternevolution, self-organization, andcomputational characteristics of thissystem. Finally a deterministicdescription of the filtered system wasderived that permits the characteriza-tion of interactions resulting in(1) annihilation of particles bybackgrounds, (2) annihilation ofbackgrounds by particles, and (3)spatial translation of particles inducedby collisions with backgrounds.

High-Quality Finite-Difference Schemesfor Partial Differential Equations andDiscrete Vector and Tensor Analysis

Mikhail Shashkov

Our primary goal in this project isto develop new, general techniques forperforming large-scale numericalsimulations based on approximatingthe solution of partial differentialequations. The basis of these newtechniques is the design of discreteoperators that preserve certainessential properties of, and relation-ships between, their correspondinganalytic operators. The techniqueswill significantly extend the well-known and useful finite-volumemethods and are designed to morefaithfully represent important proper-ties of physical processes and thecontinuum mathematical models forsuch processes. Algorithms based onthese techniques can be used formodeling high-speed flows, porous-media flows, diffusion processes, andgeophysical flows.

This year we constructed discreteanalogs of the invariant first-orderoperators—div, grad, and curl—on alogically rectangular grid and proveddiscrete analogs of the main theoremsof vector analysis related to these

operators. Using discrete analogs ofdivergence and gradient, we devel-oped new finite-difference schemesfor two-dimensional diffusionequations with a discontinuous,nondiagonal matrix of coefficients ona logically rectangular grid. We alsotested our new schemes on practicalproblems. We analyzed problemsinvolving the conservation laws andthe presence of parasitic modes inLagrangian codes, formulating theseproblems in terms of vector andtensor analysis. Our goal is to find therelationship between the desiredproperties of finite-differenceschemes (i.e., maintaining conserva-tion laws but suppressing parasiticmodes) and the properties of theobjects of vector analysis.

Publications

Castillo, J., J. Hyman, et al., "High-Order Mimetic Finite-DifferenceMethods on Non-Uniform Grids,"Houston J. Math., Special Issue, 347(1996).

Hyman, J., and M. Shashkov, "TheAdjoint Operators for the NaturalDiscretizations of the Divergence,Gradient, and Curl on LogicallyRectangular Grids" (submitted toIMACS J. Appl. Num. Math.).

Hyman, J., and M. Shashkov,"Discrete Analogs of Invariant First-Order Operators on LogicallyRectangular Grids" (to be publishedin Int. J. Comput. Math. Appl.).

Hyman, J., M. Shashkov, and S.Steinberg, "The Numerical Solutionof Diffusion Problems in StronglyHeterogenous Non-IsotropicMaterials" (to be published in /.Comput. Phys.).

Hyman, J., M. Shashkov, and S.Steinberg, "Problems withHeterogenous and Non-IsotropicMedia or Distorted Grids," Proc. FirstInt. Symp. Finite Volumes for ComplexApplications, 249 (July 19, 1996).

Shashkov, M, and S. Steinberg,"Solving Diffusion Equation withRough Coefficients in Rough Grids"(to be published in J. Comput. Phys).


Modeling Mesoscopic Phenomenain Extended Dynamical Systems

Alan Bishop

Our research goals were to developappropriate analytical and numericaltechniques to describe the formationand dynamics of collective, coherentstructures in extended nonlineardynamical systems and their role inmacroscopic space-time complexity.The influence of nonlinearity,classical and quantum stochasticity,and lattice discreteness has also beenaddressed and classified in somecases.

Our major achievements were asfollows:

• We have obtained classes ofnonlinear solutions on curvedgeometries that demonstrate anovel interplay between topologyand geometric frustration relevantfor nanoscale systems.

• We have analyzed the nature andstability of localized, oscillatorynonlinear excitations (multiphononbound states) on discrete nonlinearchains, including demonstrationsof successful perturbation theories,existence of quasiperiodic excita-tions, response to external statisti-cal time-dependent fields and pointimpurities, robustness in thepresence of quantum fluctuations,and effects of boundary conditions.

• We have demonstrated multi-timescale effects for nonlinearSchrodinger descriptions and haveshown the success of memoryfunction approaches for goingbeyond these approximations.

• In addition we have developed ageneralized rate-equation frame-work that allows analysis of theimportant creation/annihilationprocesses in driven nonlinear,nonequilibrium systems.

Publications

Bishop, A.R., "Disorder-InducedBreakdown of Soliton and PolaronParticles in Nonlinear Systems," inNoise, Nonlinearity and FluctuationPhenomena, A.R. Bishop et al., Eds.(World Scientific, Singapore, 1995).

Cai, D., A.R. Bishop, N. Gronbech-Jensen, "Perturbation Theories forPerturbed Ablowitz-Ladik NonlinearLattices," Phys. Rev. 53,4131 (1996).

Cai, D., A.R. Bishop, N. Gronbech-Jensen, "Spatially Localized,Temporally Quasiperiodic DiscreteNonlinear Excitations," Phys. Rev. E53,1202(1996).

Cai, D., A.R. Bishop, N. Gronbech-Jensen, et al., "Interaction of a Solitonwith Point Impurities in anInhomogeous Discrete NonlinearSchroedinger System" (to bepublished in Phys. Rev. B.).

Christiansen, P.S., N. Gronbech-Jensen, et al., "Oscillations ofEccentric Pulsons" (submitted toPhysica Scripta).

Dandoloff, R., A. Saxena, A.R.Bishop, "Violation of Self-Duality forTopological Solitons due to Soliton-Soliton Interaction," Phys. Rev. Lett.74, 813 (1995).

Gronbech-Jensen, N., P. S. Lomdahl,M. Cirillo, "Uniform Coupling ofMicrowaves to Nonlinear ResonantModes in Josephson Junctions," Phys.Rev. B 51, 11690(1995).

Kenkre, V., S. Raghavan, et al.,"Memory Function Approach toInteracting Quasiparticle-BosonSystems," Phys. Rev. B 53, 5407(1996).

Kenkre, V., S. Raghavan, et al.,"Relation between DynamicLocalization in Crystals and Trappingin Two-Level Atoms," Phys. Rev. A 54(R), 1781 (1996).

Konno, H., and P.S. Lomdahl,"Generalized Birth-Death StochasticProcesses in Nonequilibrium OpenSystems," /. Phys. Soc. 64,1936(1995).

Konno, H., and P.S. Lomdahl,"Stochastic Process of Annihilationand Creation of Solitons in OpenSystems," (1995 InternationalSymposium on Nonlinear Theory(NOLTA '95), Las Vegas, Nev.,December 10-14, 1995).

Salkola, M., A.R. Bishop, et al.,"Coupled Quasiparticle-BosonSystems: The SemiclassicalApproximation and NonlinearSchrodinger Equation," Phys. Rev. B52 (R), 3824 (1995).

Salkola, M., A.R. Bishop, et al.,"Coupled Spin-Boson Systems Farfrom Equilibrium" (to be published inPhys. Rev. B.).

Villain-Guillot, S., R. Dandoloff, etal., "Toplogical Solitons andGeometrical Frustration," Phys. Rev.A 52,6712(1995).

Wang W.Z., J.T. Gammel, et al.,"Quantum Breathers in a NonlinearLattice," Phys. Rev. Lett. 76, 3598(1996).


Atomic andMolecular Physics

State-to-State Photodetachmentin the Two-Electron Hydrogen Ion

Charlie E. M. Strauss

Experimental observation of thenegative hydrogen ion, which consistsof only two electrons and a proton, isfundamentally important to thedevelopment of three-body quantummechanics. We have observed thenegative hydrogen ion in a regime inwhich the optical electric fields arebecoming comparable to the bindingfields of the ion (that is, high-fieldphysics). The principal objective ofobserving the low-field one-photonspectroscopy of the negative hydrogensystem was overshadowed by ourobservation of two new physicalprocesses.

First, the negative hydrogen systemexhibited multiphoton excitation to a

detachment resonance. This is the firsttime that a multiphoton detachmentresonance has been seen in a negativeatomic ion. The analogous process inneutral atoms, multiphoton ionization,differs from multiphoton detachmentresonance because ions exhibit a long-range coulombic binding potential.The yield (as a function of laserwavelength) of electrons ejected withkinetic energy in excess of the single-photon energy showed a pronouncedFano-profile-shaped peak, consistentwith theoretical predictions. Second,we observed nonresonant excessphoton detachment with photons ofenergy exceeding the ion's bindingenergy. Nonresonant excess photon

detachment in competition with thesingle-photon process was previouslyunknown in either ions or neutrals.

This year, we also assembled avacuum ultraviolet (VUV) laser withwhich to examine, as a function ofVUV wavelength and electron energydistribution, the Feschbach and Shaperesonances in the negative hydrogenion near 113 nm. Our collaboratorsfrom the University of New Mexicoare continuing research on bothmultiphoton and VUV spectroscopy,and they are searching for similarphenomena in the deuterium ana-logue.

Publications

Zhao, X.M., M.S. Gulley, H.C.Bryant, et al., "Nonresonant ExcessPhoton Detachment of NegativeHydrogen Ions" (to be published inPhys. Rev. Lett).

Transient Quantum Mechanical Processes

Lee Collins

The principal objective of this projectis the theoretical investigation oftransient quantum mechanical eventssuch as coherent control of molecularprocesses and artificial atoms. Rapidadvances in laser technology havemade control of quantal processespossible. Since the duration of laserpulses has become much shorter thanthat of many molecular interactions, alaser will act as a strobe that probes theevolution of the system. Electronspassing through layers of compositematerials that are many nanometersthick also behave as quantum mechani-cal entities, despite the large-scalenature of the medium. However, thestudy of such transient processes

requires the development of sophisti-cated, large-scale computationalapproaches to solve the time-dependentSchrodinger equation, which representsthe basic physics of these fleetingencounters. One major goal of ourproject involves modeling variousmolecular-control experiments con-ducted at Los Alamos.

This year, we have developed andextensively tested two independentmethods for efficiently and accuratelysolving the time-dependent Schrodingerequation for these processes. Themethods are based on the real-space-product and discrete-variable-representation formulations, respec-tively. We first applied the methods to

the interaction of a short-pulse laserwith a dimer of potassium in order tostudy the interference effects betweenvibrational wave packets in differentelectronic states. Initial calculationsusing simple models for the molecularinteractions yielded qualitative agree-ment with experiment. They indicated aclear correlation between the signal andthe vibrational motion of the wavepacket. To improve the agreement, wehave begun calculating better molecularparameters such as potential energycurves and coupling matrix elements.

Publications

Collins, L., R. Walker, and J. Kress,"Quantum Control of MolecularProcesses," Bull. Am. Phys. Soc. 41,1145(1996).

Individual Projects—Atomic and Molecular Physics 71

Calculation of Satellite Line Structuresin Highly Stripped Plasmas

Joseph Abdullah Jr.

Recently developed high-resolutionx-ray spectrographs have made itpossible to measure satellite linestructures from various plasmasources with great detail. These areweak, optically thin lines caused bythe decay of autoionizing states andgenerally accompany the resonancelines of hydrogen-like and helium-likeions. The goal is to use Los Alamosatomic physics and nonequilibriumkinetics codes to calculate the linestructure and compare it with high-resolution experiments. Consequently,we are able to interpret and under-stand the physical processes inplasma. The results can be used todevelop plasma temperature anddensity diagnostics using the signa-ture of satellite structures. Suchdiagnostics will have wide applicationto Laboratory programs. The studyalso provides a fundamental under-standing of the atomic physicsprocesses in different plasma environ-ments. Collaborations with A. YaFaenov, T. A. Pikuz, and S. A. Pikuzof Russia add tremendous value to theresearch.

The accomplishments for this yearinclude the analysis of satellitespectra taken from various plasmasources, including a silicon spectrummeasured at the Los Alamos BrightSource Facility. We studied data fromaluminum X-Pinch experimentsperformed at Cornell University thatshowed a strong dependence onelectron-beam effects. Data onmagnesium have been taken from theRussian Multicharged Ion SpectraData Center carbon dioxide laserfacility and the Los Alamos Tridentlaser. The observed satellite structuresshow strong dependence on hotelectrons for both the Russian and theTrident laser (500 fs, 1054 nm)measurements. We have determinedelectron densities, thermal tempera-tures, and hot-electron fractions by

matching the experimental resultswith calculations.

Model calculations were performedusing an electron distribution consist-ing of a thermal Maxwellian part anda nonthermal, high-energy Gaussianpart to determine if hot electronscould be responsible for the anoma-lous structure of satellite lines ob-served in the Trident experiments. Thefirst figure is a comparison of thecalculated spectra for magnesiumshown with and without hot electrons

at an electron temperature near200 eV and a electron density of1022/cm3. The number of hot electronsis fixed at 10% of the electron density.Note the significant differencebetween the relative intensitiespredicted for the two different cases.The second figure shows the goodagreement of the measured Tridentspectrum with calculations thatinclude the effect of hot electrons.

Publications

Abdallah, J. Jr., A. Ya Faenov, D.Hammer, et al., "Electron BeamEffects on the Spectroscopy ofSatellite Lines in Aluminum X-PinchExperiments," Phys. Scr. 53,705(1996).

13301332 1334 1336 1338 1340 1342Photon Energy (eV)

1344 1346 1348 1350

1330 1332 1334 1336 1338 1340 1342Photon Energy (eV)

1344 1346 1348 1350

(Top) A comparison of calculated spectra for magnesium showing the effect ofhot electrons at an electron temperature near 200 eV and a density of 1022

electrons per cubic centimeter. (Bottom) A comparison of the calculated spectrumincluding the effect of hot electrons with the observed Trident spectrum.


Optical Wave PacketsNew, Diffraction-Free

(Optical Bullets): AForm of Light Travel

David J. Funk

In this work we study the propaga-tion of self-confined packets of lightthrough the atmosphere. At suffi-ciently high intensities, pulses of lightwill not only self-focus, but maypropagate indefinitely without activeoptics or guiding media in the form ofa fine filament until the intensity ofthe pulse falls below a measurablecritical value.

We are analyzing the phase andstructure of the pulse above, near, andbelow that critical intensity tounderstand the origin of this phenom-enon. We are also investigating theuse of the filament path as awaveguide for low-intensity laserpulses. The ability to focus intenselight at large distances and collect thescattered light may revolutionizeactive remote sensing and long-rangeenergy transmission. Applicationsinclude remote sensing and rangefinding in battlefield conditions, long-range energy transmission, andguiding lightning discharge.

Our studies have concentrated onthe demonstration and understandingof the fundamental physics associatedwith this phenomenon and the proofof the existence of these wave packetsin air. We have successfully (1) gener-ated filaments, (2) set up a frequency-resolved, optical-gating analysisstation, (3) measured the energy in thefilament as a function of traveldistance in the laboratory, (4) exam-ined the effect of chirp on the pulse(both on filament formation distanceand conical emission), as shown in thefirst figure, and (5) spectrally dis-persed and autocorrelated the filamentas a function of distance traveled inthe laboratory.

We have also found that the pulsesplits into two pulses as it propagates,as predicted by various theories thatfold in the nonlinear interaction ofintense electromagnetic fields withmatter (see second figure). Our goalis to be able to control this phenom-

Publications

Zhao, X.M., R.J. Jones, D.J. Funk, etal., "Evolution Characteristics andControl of Self-Filamentation in theAtmosphere" (submitted to Opt.Lett.).

enon and turn it into a useful tool forcontrolling lightning discharge (as anexample) by providing an ionizationpath for the lightning to dischargealong.

o

I

20

15

10

5

0

— . .1 i \ : ; i j

; • : Experiment i : ; /A Calculation : i \ /

- ! f ! j : J /

- j '•• ; i i j / .

.——

<

- ' I

1 i 1 I i

-2 4 6Chirp (AWd)

10

Effect of chirp on filament formation distance. The graph shows that the pulseforms most readily when blue light precedes red light (large Al/ldj as expectedfrom a simple, group-velocity dispersion analysis.

.a

1500-

1000-

500-

0 -

i

i

: i j

: ] 4

* • i

iE : I* • •

> i

i

: *!

O L=3'4m :M L=12m :

: •» L=20m:3K L=27m

: : t:

S ; • *

-10 -6 -4 -2 0 2Chirp (Al/ld)

10

Effect of chirp on pulse splitting as a function of propagation distance L. Thegraph shows that the pulse splits most readily when blue light precedes redlight (large Al/ld), as expected from a simple, self-phase modulation and group-velocity dispersion analysis.

Individual Projects—Atomic and Molecular Physics 73

Nonlinear Atom Optics

Peter Milonni

The objective of this project is todevelop the quantum field theory ofatom optics and, in particular, toexplore the possibilities for realizingnonlinear wave effects in atom optics.Our progress in the basic physics andin the development of very promisingapplications has been rapid. We arefocusing on nonlinear atom-opticaleffects including wave phenomenasuch as self-focusing, solitary-waveformation, wave mixing, and phaseconjugation, which can arise fromlong-range dipole-dipole interactions.Such effects occur when more thanone atom can occupy a single "mode"of the many-body wave function, a

situation of particular interest in"lasers for atoms" with whichrelatively intense atom waves, ratherthan photon waves, will be produced.

We have outlined the basicstructure of a coherence theory ofatom optics, along the lines of theoptical theory of coherence. A fewissues involving the treatment ofatom-atom interactions remain to beworked out before the theory iswritten up and submitted for publica-tion. One of the issues is the modifi-cation of atom-atom interactions inthe case of cold atomic samples thatare of interest in atom optics. For thecase of ground-state atoms, we have

analyzed the modification of van derWaals interactions in both thermal andlaser fields.

The natural framework for themany-particle system of interest,including the two-body dipole-dipoleinteractions and the quantum statis-tics, is quantum field theory. In thiscase, the requisite formalism isnonrelativistic, and it leads tocomputationally workable, coupled,nonlinear wave equations. We havedeveloped this formalism and arepreparing it for publication, followingthe numerical simulation of a fewexamples based on the formalism. Wehave also begun to study the applica-tions of this theory to the recentlyobserved Bose-Einstein condensationin cold atom traps.

Dynamics of Quantum Wave Packets

Timothy R. Gosnell

The time-domain investigation oflocalized vibrational wave functionsin diatomic molecules is possible withfemtosecond laser sources. In ourexperiment, a femtosecond pumppulse creates a wave packet on anexcited potential surface of gas-phaseK2 molecules. The packet oscillateswithin the well, much as one expectsclassically, but then disperses as aresult of rotational effects anddispersion within the the weaklyanharmonic potential well. Thepurpose of the experiment is not justto create and observe such packets butto alter their shape by manipulating

the time and spectral content (orchirp) of the pump pulse. The ultimategoal is to develop a broader tool setfor controlling chemical reactionswith laser light.

This year we improved the signal-to-noise ratio in our wave-packetdetector and confirmed chirp-inducedeffects on the shape of the packets. Atheoretical investigation helped clarifywave-packet dynamics, but continuedtheoretical studies are needed tounderstand the specific wave-packetshapes and decay patterns observed inour experiments.


Geoscience, Space Science,and Astrophysics

Low-Energy Neutral Atom Imager

Herbert 0. Funsten andDavid J. McComas

Remote imaging from space iscontributing more and more to ourunderstanding of the space environ-ment around Earth. Sensing ofmagnetospheric plasma ions that havebeen neutralized by charge exchangewith geocoronal neutral atomspromises to be the next majordiagnostic of magnetospheric physicsand may provide global snapshots ofthe structure and dynamics of theterrestrial magnetosphere.

The goal of this project is to fly thefirst low-energy neutral atom (LENA)imager capable of imaging neutralatoms with energies less than 30 keV.As shown in the accompanying figure,the imager consists of (1) alternatelybiased collimator plates to rejectambient plasma particles, (2) anultrathin, 50-A foil that ionizes afraction of the neutral atoms thattransit the foil, (3) electrostatic energyanalyzer plates that measure the

CHARGECONVERSION

FOIL

HEMISPHERICALANALYZER

Start Foil

Los Alamos low-energy neutral atom (LENA) imager.

LENA energy, and (4) a detectorsubsystem that provides trajectory andcoincidence measurements.

In this first year we have success-fully completed the design, procure-ment, and fabrication of imagercomponents. We assembled and testedthe collimator, door, and detectorsubassemblies. As a demonstration ofnew technology, the LENA imageruses thin-walled, hemispherical,electrostatic energy analyzer platesthat were formed by electroplating,which is considerably less expensivethan traditional machining.

The LENA imager, which will befully flight qualified, is positioned tofly on the first ride of opportunity.The LENA imager will provide thefirst neutral atom measurements forits energy range with image integra-tion times of several minutes.

Publications

Funsten, H.O., DJ. McComas, andM.A. Gruntman, "Mechanisms forNeutral Atom Imaging" (submitted toAm. Geophys. Union MonographSeries, Measurement Techniques forSpace Plasmas).

Hesse, M., D. Mitchell, E. Roelof,et al., "Neutral Atom Imaging of thePlasma Sheet: MeasurementPredictions" (submitted to Geophys.Res. Lett.).

McComas, D.J., H.O. Funsten, andE.E. Scime, "Advances in LowEnergy Neutral Atom Imaging"(submitted to Am. Geophys. UnionMonograph Series, MeasurementTechniques for Space Plasmas).

Individual Projects—Geoscience, Space Science, and Astrophysics 75

Nonlinear Processes in Earthquakes

Eric Jones

Characterizing the source ofseismic signals is important both fordistinguishing clandestine nucleartests from earthquakes and forunderstanding the mechanisms ofearthquakes. However, geologicstructures near the source and alongthe propagation path can modify theseismic signals and complicate sourceanalyses.

We applied a three-dimensional,elastic-wave-propagation code, knownas the AFD code, to model anearthquake near the upper boundaryof a subducting slab. As shown in the

three-dimensional seismograms, thedifferences between the syntheticseismograms calculated with andwithout the slab are significant. Ourcollaborators at the University ofTexas planned to use existing analysistechniques to show that inferredseismic moment tensors wouldcontain non-double-couple compo-nents. However, by midyear werealized that we first needed todevelop methods to utilize seismichistories at the outer boundaries of thenumerical grid. Our initial numericalresults were used in a proposal

£ °-X

- 1 -

- 2 -

A'- -

•j _

cc

X °"X

- 1 -

- 2 -

Station 40

40 60 80 100 120 40 60 80 100 120

submitted to the National ScienceFoundation.

We also applied the AFD code tostudy path effects on seismic signalsin Western China, and we completed aparameter study to isolate the effectsof major geologic features along thepath, such as the Tarim Basin and theMoho root of the Himalayas (seediagram of the major geologicfeatures in this region). As shown theaccompanying vertical-velocityseismograms, the low-velocity basinis particularly effective in convertingcompressive (P-wave) energy from anexplosive source into the shear wave(S-wave) energy characteristic of anearthquake.

x 0-x

-1-

-2-40 60 80 100 120

2-, , , , 2

H 1 1 !-M 1cc

40 60 80 100 120 40 60 80 100 120

•

•

1 I J

*;

M•

-

- / ^

11,111

rJ I -

2

1

°-1

-2

-

-

-

r.

•)\j

40 60 80 100 120

N °-1

-2

•

•

-

-

Mi

40 60 80 100Time

120

cc0 -

-1

-240 60 80 100

Time120

2-

1-

-1

-2

f\ „

40 60 80 100Time

120

Three-component synthetic seismograms showing the diagonal (xx, yy, zz) components of the moment tensor, observed450 km from a source 50 km deep in a subducting slab with a 10% velocity contrast. For each component, the bold line isa finite-difference result for the case with the subducting slab, and the dashed line is for the "no-slab" case. Z, R, and Tcorrespond to vertical, radial, and tangential displacements. Differences in phase and amplitude for the slab and no-slabcases indicate that standard, flat-layer analysis techniques of the synthetic seismograms would produce inaccuratesource characterizations.


-5.0x10

axsooo

-1.0x10

-1.5x10

0.00

5.0x10^ 1.0x10X Coordinate (m)

1.5xio6

The geologic structures along a path from the Chinese nuclear test site at Lop Nor (left) to a seismic station in northernPakistan (right). The major features include the low-velocity Tarim Basin, which lies between 100 and 400 km from LopNor, and the deep Moho depression underneath the Tibetan Plateau from 1100 km to the right side of the computationalregion.

niiex! z-vel time 3.sac _

^4*4 ,^»M-«V

i 1 ! I r~

nilex? z-vel time 7.sec _

X 10+2

Vertical-velocity seismogram atx = 1100 km for a case not including (top) and including (bottom) the Tarim Basin. Inthe upper portion of the figure, the first arrival from an explosive source is at about 140 seconds and is a compressivewave which travels mostly through the high-velocity mantle material. Arrivals starting at 190 seconds representcompressive energy ducted in the crust. In the lower portion of the figure, the arrivals between 200 and 225 secondsrepresent compressive-to-shear (PS) energy conversion at the upward sloping edge of the basin between x = 600 km andx = 1000 km, and the arrivals between 340 and 360 seconds represent PS conversions on the downward slope of thebasin between x = 100 and x — 500. The large-amplitude arrivals after 400 seconds represent surface waves created inthe basin. In a simpler geologic setting, the shear-wave arrivals would be characteristic of an earthquake source and notan explosive source.


Lead Immobilization in ThermallyRemediated Soils and Igneous Rocks

Donald D. Hickmott

Cleanup of rocks, soils, andaquifers contaminated with mixturesof lead and organic or high-explosivewastes is a problem of considerableimportance across the nation. Thisproject is designed to (1) investigatethe speciation of lead in soils andigneous rocks; (2) use numericaltechniques to investigate phases thatmay immobilize lead; and (3) performlaboratory-scale experiments in whichlead is immobilized by thermaltreatment of soils. Our project willresult in an understanding of factorsthat control whether the mobility oflead in soil can be minimized bythermal treatments.

In this review period we havesuccessfully identified lead phos-phates as the most likely phasessuitable for using thermal-treatment

methods to immobilize lead. Wemodeled the thermodynamics andkinetics of the precipitation of leadimmobilizers at both ambient andhigh temperatures. Experimentsdetermined that Na2HPO4 amendmentof lead chloride can produce leadphosphates at high temperatures(400°C) but that lead carbonate andlead oxide are stable relative to leadphosphate in most bulk compositionsat the temperatures investigated.

Clearly, kinetic factors influenceour ability to produce thermodynami-cally stable, lead-phosphate-bearingassemblages in thermal remediationexperiments. Further investigation ofthe dissolution/precipitation kineticsof lead-immobilizing phases isrequired before thermal immobiliza-tion of metals in soils can be imple-mented on a wide scale.

Publications

Eppler, A.S., D.A. Cremers, D.D.Hickmott, et al., "Matrix Effects inthe Detection of Pb and Ba in Soilsusing LIBS," Appl. Spectrosc. 50,1175(1996).

Hickmott, D.D., J.M. Herrin, R.A.Abell, et al., "EnvironmentalApplications of Nuclear Micro-probes" (submitted to Nucl. lustrum.Phys. Res. B).

Larocque, A.C.L., C.E. Chapin, et al.,"Metal-Residence Sites in MineTailings in the Magdalena District,New Mexico," in Mineral Deposits,Pasava, Kribek, and Zak, Eds., (A.A.Balkema, Rotterdam, Netherlands,1995), pp. 661-664.

Stimac, J.A., D.D. Hickmott, R.A.Abell, et al., "Redistribution of Pb andOther Volatile Trace Metals duringEruption," J. Volcanol. Geotherm.Res. 73, 245 (1996).

Experimental Studies ofAuroral-Arc Generators

David Suszcynsky

The focus of our project was thepreliminary analysis of all-sky andsatellite data and the identification ofphenomena/events for future studies.We completed two analyses. The firstwas a survey of the satellite andground data to identify signatures ofdiscrete auroral arcs at geosynchro-nous orbit. The second analysischaracterized the geosynchronousenvironment during pulsating auroraand black-aurora events.

In the effort to identify signaturesof discrete auroral arcs, we discoveredthat although specific conditions atgeosynchronous orbit could beassociated with the occurrence of

general discrete arc activity, nospecific features in orbit could beassociated with individual arcstructures. This information leads usto conclude that the fine structure ofdiscrete arcs is generated at loweraltitudes than the equatorial magneto-sphere.

In characterizing the geosynchro-nous environment during pulsatingaurora and black-aurora events, welearned that the geosynchronous orbitis dominated by electron pitch-angleanisotropies (pancake distributions)and fluxes, as predicted by leadingpulsation theories. As expected, weobserved that the pulsations occurred

during the recovery phase ofsubstorms and often became re-energized during the growth phase ofsuccessive substorms. This observa-tion supported the idea that theprecipitating particles are supplieddirectly by injection events. We foundthat a black aurora, a rarely observedand studied phenomenon, wasassociated with counterstreaming 0.2-to 2-keV ions and is much morecommon than previously reported.

Publications

Suszcynsky, D.M., J.E. Borovsky,et al., "Coordinated Ground-Basedand Geosynchronous Satellite-BasedMeasurements of Auroral Pulsations"(Twenty-third Conference on OpticalMethods for Atmospheric Research,Kiev, Ukraine, September 2-6, 1996).


Fundamentals of Laser Ablationin the Analysis of Geological Materials

Aaron Koskelo

Our goal is to determine theparameters that contribute to matrixeffects in laser ablation of materials.Laser ablation underlies many of themethods that hold promise for real-time materials recognition and rapidchemical analyses of environmentalsamples. However, laser ablation hasnot yet gained widespread use as amethod of analysis nor regulatoryacceptance because of matrix effects.Different sample types exhibitdifferent sensitivities under laserablation. This effect arises from thecomplex and not-yet-understoodablation process itself, particularly inmixed or inhomogeneous materials.We are developing new techniques toexamine the causes of the differencein sensitivity of different materials,with particular emphasis on funda-mental measurements of processesinvolved in the laser ablation ofgeological materials and soils

This year we developed the use ofcorrelations in laser-induced break-down spectroscopy (LIBS) spectra toexamine the inhomogeneity of soilsand mine tailings. We obtained aseries of single-shot LIBS spectra andcalculated interwavelength correlationmatrices that reveal the correlationbetween different species emitting inthe laser ablation plume. The workreveals that some Resource Conserva-tion and Recovery Act (RCRA) metalscorrelate well with iron-containingcomponents of the soil matrix but notwith titanium components.

We have also seen indications thatatomic and ionic lines in the laserablation plume are anticorrelated, asshown in the accompanying figure.Strong correlation to the titanium ionemission line at 3360.96 A occurs forevery ionic line in this emissionspectrum. Every atomic line in thespectrum—regardless of atomicspecies from which the lineoriginates—exhibits anticorrelation to

the ionic line. This effect is explainedby a shot-to-shot change in electrondensity in the plume. There are alsoindications that the degree of anti-correlation depends on how easily theelement is ionized.

This year we also gained experiencein the use of infrared pump-probetechnology for monitoring bondbreaking in materials. We expect toextend this technology to use incomplex materials like geologicalmaterials.

We studied the photodecompositionof diazo-Meldrum's acid in a polym-efhyl methacrylate (PMMA) matrixand found that the intermediate keto-ketene appeared within 20 ps of thephotoexcitation. This work indicatesthat the path through the keto-keteneis the primary reaction pathway to thestable carboxylic acid. It is thecarboxylic acid that makes this systemuseful for base-soluble photoresists.

Publications

Koskelo, A., and T. Gamble, "LaserAblation of Geological Materials"(Federation of Analytical Chemistryand Spectroscopy Society, October1996).

Koskelo, A., T. Gamble, and T.Lippert, "Laser Induced BreakdownSpectroscopy of GeologicalMaterials" (Winter Conference onPlasma Spectroscopy, January 1996).

Koskelo, A., C. Mahan, et al., "DirectChemical Analysis at Los AlamosNational Laboratory (SPIE NationalMeeting, Denver, Colo., August1996).

Lippert, T., A. Koskelo, and P.Stoutland, "Direct Observation of aPhotoinduced Wolff Rearrangement inPMMA Using Ultrafast InfraredSpectroscopy," J. Am. Chem. Soc.118, 1551 (1996).

Lippert, T, A. Koskelo, and P.Stoutland, "Laser-induced Reactionsin a Deep UV Resist System: Studiedwith Picosecond InfraredSpectroscopy," Mater. Res. Soc. Proc.397, 661 (1996).

J3240 3260 3280 3300 3320 3340 3360

WAVELENGTH (A)

3380 3400 3420 3440

Correlation spectrum obtained from a sample of mine tailings from Butte,Montana. The spectrum shown is the average of 910 spectra taken as thesample moved continuously under repetitive laser sparks. Each data point is thecorrelation coefficient of the wavelength channel to that of a channelcorresponding to Ti(II) emission. Note the strong correlation to Ti(II) for allother Ti(II) lines. Atomic emission lines do not have a strong correlation to theTi(II) lines and, indeed, do exhibit some anticorrelation.


Integrating Chemistry into Three-Dimensional Climate Models:Detailed Kinetics in the Troposphere and Stratosphere of aGlobal Climate Model

Chih-Yue J. Kao

Several atmospheric gases, includ-ing ozone and methane, are bothradiatively and kinetically active.They influence global climate but arethemselves controlled by photochemi-cal processes. The role of suchmolecules in the global system hasgenerally been simulated either in lowdimensionality or with chemistrydecoupled from dynamics. Three-dimensional chemical models havefurther sacrificed integrity by focusingeither above or below the tropopause.

The goal of our research is toalleviate these restrictions by incorpo-rating kinetics interactively into boththe troposphere and stratosphere of aglobal climate model (GCM) so thatthe chemical and thermodynamiceffects of important atmosphericgases can be comprehensivelymodeled and used by decision-makersin coping with the changing earth-atmosphere system. We expect tocreate the first truly interactive, three-dimensional, chemical climatesimulations. Our work on this projecthas applications to photochemistry,environmental sciences, chemicaltransport, and monitoring.

This year we implemented theparameterization of aerosol formationand chemical heterogeneous reactionsin our photochemical module to studythe influence of aerosol on ozoneconcentrations. In particular, weinvestigated the heterogeneouschemistry occurring on the sulfateparticles from volcanic eruptions. Wecompared the simulated ozonedepletions with documented data fromeruptions such as El Chichon andPinatubo.

Publications

Elliott, S., C.-YJ. Kao, F. Gifford, etal., "Free Troposphere OzoneProduction after Deep Convection ofDispersing Tropical Urban Plumes"(to be published in Atmos. Environ.).

Elliott, S., M. Shen, C.-YJ. Kao, etal., "A Streamlined Family Photo-chemistry Module ReproducesMajor Nonlinearities in the GlobalTropospheric Ozone System," J.Comput. Chem. 20, 235-259 (1996).

Zhao, X., R.P. Turco, et al., "AerosolInduced Chemical Perturbations ofStratospheric Ozone: Three-Dimensional Simulation and Analysisof Mechanisms" (submitted to /.Geophys. Res.).

Zhao, X., R.P. Turco, et al., "NumericalSimulation of Dynamical Response tothe Arctic Vortex to Aerosol-AssociatedChemical Perturbations in the LowerStratosphere," Geophys. Res. Lett. 12,1525-1528 (1996).

Using Microspheres as Tracersfor Flow in Geologic Media

Bruce A. Robinson

The goal of this study is to developmicrospheres as groundwater tracers.This capability will allow us toinvestigate the movement of colloidalcontaminants in groundwater and togain insight into the movement ofdissolved and colloidal contaminantsin fractured rock. We used polysty-rene latex and silica microspheres(0.25 to 1 um in diameter) taggedwith fluorescent dyes in laboratoryand field groundwater-tracer experi-ments to (1) obtain insights intocolloidal contaminant transport ingeohydrologic systems, and (2)characterize geohydrologic systemsmore thoroughly than we could usingonly dissolved tracers.

We have measured microsphereconcentrations in groundwatersamples at two to three orders ofmagnitude below natural backgroundconcentrations, using the uniquecapabilities of the flow cytometrylaboratory at Los Alamos. Preliminaryresults suggest that the use ofmicrospheres in tracer experimentscan provide valuable insights into

colloid-transport mechanisms andretardation/attenuation mechanisms ofsolute contaminants in saturatedgroundwater systems. Laboratoryexperiments revealed that negativelycharged, carboxylate-modifiedmicrospheres provided the mostmobile surface-charge characteristicsin natural groundwater systems. Fieldstudies of fractured granite supportedour theory that microspheres travelslightly faster than dissolved tracers inforced-gradient tests. However,attenuation, possibly caused bysettling, also affects the field results.

This work has resulted in severalmaster's and doctoral theses at twouniversities.

Publications

Reimus, P.W., B.A. Robinson, et al.,"Simultaneous Transport of SyntheticColloids and a Nonsorbing Solutethrough Saturated Rock Fractures,"Mat. Res. Soc. Symp. Proc. 353,363-370 (1995).


Theoretical Research onDwarf and Classical Novae

Warren Sparks

Previous simulations of accretingwhite dwarfs (WDs) have been one-dimensional. The recent identificationof the two-dimensional (2-D) beltstructure on the WD surface in VWHyi demands more realistic simula-tions using a 2-D model, which weare developing. To allow the model tohave time steps exceeding the limit setby the Courant condition (the sound-crossing time in a grid cell inside thedegenerate WD), the code has to beimplicit for numerical stability. Usingan energy criterion of shear mixingcharacterized by the Richardsonnumber, we find that the forcedconvection is most efficient along theequipotential surface of the differen-tially rotating WD atmosphere. To

simulate this effect, we developed anew time-dependent zoning scheme inwhich the time-dependent gridfollows the equipotential surfaces.

The standard alpha-model theorypredicts that during a dwarf novaoutburst, the boundary layer betweenthe WD surface and the inner diskradiates away one-half of the accretedenergy from a small area of the WDstellar surface and has an effectivetemperature as high as 500,000 K.Recent observations show that duringa dwarf nova outburst, a significantportion of the gravitational energyaccreted onto the WD may not beradiated away instantly from a narrowboundary layer as predicted by thestandard disk theory. In collaboration

with Villanova University, we havefound various means of transportingthis energy deeper into the star andextending the radiative region. Thus,we may account for the long-puzzlingmissing boundary layer when weconsider the response of the WD tothe accretion.

In collaboration with the Universityof Wyoming, we investigated thecause of the high and low accretionstates in AM Herculis binaries (AMHers). We proposed a model in whichthe WD's rotation acts like an angularmomentum storage battery for thebinary orbit. The accreted materialfrom the Roche lobe-overflowingsecondary charges up this battery,whereas the magnetic torque of theWD on the secondary discharges itback into the binary's orbit. TheRoche lobe's volume becomesalternately larger and smaller than thesecondary's volume. This alternationcauses the mass flow to vary betweena high and low rate.

Micro/Macroscale Coupling inMagnetospheric Plasmas

S. Peter Gary

Microscale plasma processes cansignificantly affect the large-scaledynamics of a plasma, whereas large-scale computer models of spaceplasmas cannot directly model kineticprocess and require special algorithmsto adequately represent small-scaleeffects. Our goal is to develop newscaling relations for proton param-eters that allow good quantitativerepresentation of the consequences ofmicrophysical processes that takeplace in the magnetosphere.

We have recently developed thefirst scaling relation for the hot-proton-anisotropy upper bound inmagnetospheric plasmas and haveused it as an algorithm in a computermodel of the magnetotail to demon-strate that it qualitatively affects thepredictions of that model. We are

using plasma theory, hybrid simula-tions, and spacecraft data analysis todevelop additional new scalingrelations for the consequences ofsmall-scale instabilities in themagnetosphere. These relationshipssignificantly improve the predictivecapabilities of the models.

We have recently published twoimportant results. The first, which wasobtained through the use of two-dimensional computer simulations, isthat the whistler anisotropy instabilityimposes an upper bound on thetemperature anisotropy of electronsthat have bi-Maxwellian velocitydistributions. This result is fullyanalagous with the upper bound wehave demonstrated for ion tempera-ture anisotropies. The second impor-tant result is that the scaling relation

for the properties of anisotropicprotons near 10 eV (i.e., "warm"protons) in the outer magnetosphereprovides an approximate upper boundfor a selected set of warm-protontemperatures observed at geosynchro-nous orbit.

Publications

Convery, P.D., and S.P. Gary,"Electromagnetic Proton CyclotronRing Instability: Threshold andSaturation" (to be published in J.Geophys. Res.).

Gary, S.P., M.E. McKean, and D.Winske, "Proton TemperatureAnisotropy in the Magnetosheath:Hybrid Simulations," Geophys. Res.Lett. 21, 2887 (1996).

Gary, S.P., M.F. Thomsen, J. Lee,et al., "Warm Protons at Geo-synchronous Orbit" (to be publishedin J. Geophys. Res.)

Gary, S.P., and J. Wang, "WhistlerInstability: Electron AnisotropyUpper Bound," J. Geophys. Res. 101,10 (1996).


Numerical Simulations of ConvectionExperiments and Earth's Interior

Gary Glatzmaier

Our project is targeted at providingnew insights and explanations aboutthe origin, structure, and evolution ofEarth's magnetic field through thedevelopment of a dynamicallyconsistent, three-dimensional com-puter model of the geodynamo—theconvective mechanism in Earth'souter fluid core that generates andmaintains the geomagnetic field. Wehave successfully developed the firstsuch model and have used it in asimulation that has maintained anEarth-like magnetic field for asimulation length of more than200,000 years.

Our simulated magnetic field has anintensity and a dipole-dominatedstructure that are very similar toEarth's (see accompanying figure).Our simulation also has a westwarddrift of about 0.2 degrees/year of thenondipolar structures of the field atthe core-mantle boundary; this drift issimilar to that measured on Earth. Inour simulation, the solid inner corerotates about 2 to 3 degrees/yearfaster than the mantle. This prediction

A snapshot of the computer-simulated geomagnetic field.Magnetic field lines are drawn outto two Earth radii. The complicatedinterne field occurs in the fluid outercore where the field is generated;the field outside the outer core is asmooth potential field. The axis ofrotation is vertical in this image.

we made for the core's rotation wasrecently supported by two indepen-dent seismic analyses. The radius ofthe inner core grows at about 3 cm percentury as iron in the fluid alloyabove freezes onto the core. If oneassumes the heat flow out of Earth'score has remained relatively constant,the simulated growth rate implies thatthe age of the solid inner core is onlyabout one-fourth the age of Earth.

In the past year, we also conductedcomputer simulations of the geophysi-cal fluid-flow cell experiment thatwas flown aboard the NASA spaceshuttle Columbia in November 1995.This experiment will improve ourunderstanding of convection inrotating planetary interiors.

Publications

Glatzmaier, G.A., and P.H. Roberts,"An Anelastic Geodynamo SimulationDriven by Compositional andThermal Convection," Physica D 97,81 (1996).

Glatzmaier, G.A., and P.H. Roberts,"The Growth, Topography, Rotationand Magnetism of Earth's InnerCore," Science 274,1887 (1996).

Glatzmaier, G.A., and P.H. Roberts,"On the Magnetic Sounding ofPlanetary Interiors" (to be publishedin Physics of the Earth and PlanetaryInteriors).


High-Velocity Neutron Stars

Edward Fenimore

The following three recent discov-eries could revolutionize our under-standing of high-energy astrophysicaltransients: many neutron stars havesufficient velocity to escape thegalaxy; soft gamma repeaters (SGRs)come from high-velocity neutronstars; and one high-velocity neutronstar may have produced a gamma-rayburst. Our project goal is to under-stand these phenomena and determineunder what conditions the observedhigh-velocity neutron-star properties(when applied to the local group ofgalaxies) can reproduce all of theproperties of high-energy transients;

namely, an apparent isotropic distribu-tion and uniform density of gamma-ray bursts, a lack of events from theAndromeda Galaxy, the association ofSGRs with population I material, andthe fact that a young neutron star wasable to produce both SGRs andgamma-ray bursts.

During this year we completedthree steps in understanding gamma-ray bursts from galactic high-velocityneutron stars. First, since the March5th burst event (which was thebrightest event ever observed), wehave searched for fainter versions thatmight have come from nearby

Sedimentary Basin Response toStrong Motion in Populous Regions

Paul Johnson

An important origin of damage inmodern metropolitan areas duringlarge earthquakes is the amplificationof seismic shear waves. The amplifi-cation is due to both basin-geometry-induced resonance and local siteresonances. Examples of amplifica-tion include all of the most damagingearthquakes of the latest decade,including the 1985 Michoacan(Mexico), the 1989 Loma Prieta(California), the 1994 Northridge(California), and the 1995 Kobe(Japan) earthquakes. These earth-quakes cost thousands of lives, mostlyresulting from structural failure, andcost tens of billions of dollars instructural damage. Consequently,understanding and mitigating theeffect of the uppermost sedimentarylayers on ground motion and theresulting response of engineeredstructures is of paramount impor-tance.

In the past year, we focusedprimarily on obtaining high-quality,

strong-motion data from the mainshock and aftershocks of theNorthridge earthquake to study siteeffects. Our preliminary analysisshows strong nonlinear-inducedresonance changes at several strong-motion sites in the Los Angeles basin.A three-day conference at LosAlamos regarding preliminaryprogress was held in September 1996with all project participants. Anexhaustive analysis of all strong-motion sites has begun as a result ofobservations and discussions.

Simultaneously, we began workingwith groups that are creating whole-basin, finite-element differencemodels of the Los Angeles basin. Wewill incorporate observations andnonlinear response models beingdeveloped at Los Alamos into basinmodels. We also recently obtaineddata, for additional studies, on theKobe earthquake and on severalearthquakes in Taiwan.

galaxies. For example, the Burst andTransient Source Experiment canobserve March 5th-like bursts out to5 Mpc, a volume that contains70 galaxies. No events were found,showing that they are less frequentthan the rate seen in our galacticneighborhood.

Second, we investigated whatwould be necessary to detect gamma-ray bursts from the AndromedaGalaxy in anticipation of possibleNASA gamma-ray-burst satellites thatwould attempt to detect bursts fromAndromeda. We published an analysisbased on our models of high-velocityneutron stars, which showed that onlyone class of models can be tested witha next-generation satellite (the"delayed turn-on" models), whereasthe other models (based on beaming)cannot be tested.

Third, we evaluated what relativis-tic motion would be required to allowthe escape of the observed very highenergy photons from a neutron star.We found that much slower relativis-tic motion could be present (Lorentzfactors of only 5 rather than 50). Theslower motion will allow a widerrange of high-velocity neutron-starmodels.

Publications

Duncan, R.C., and H. Li, "The HaloBeaming Model for Gamma-RayBursts" (submitted to Astrophys. J.).

Fenimore, E.E., CD. Madras, and S.Nayakshin, "Expanding RelativisticShells and Gamma-Ray BurstTemporal Structure," Astrophys. J.473, 998 (1996).

Li, H., and E.E. Fenimore, "Log-Normal Distributions in Gamma-RayTime Histories," Astrophys. J. Lett.469,115(1996).

Li, H., E.E. Fenimore, and E.T. Liang,"Detectability of Gamma-Ray BurstExcess toward M31," Astrophys. J.Lett. 461, 73 (1996).


Heterogeneous Processing of BromineCompounds by Atmospheric Aerosols:Relation to the Ozone Budget

Jeanne M. Robinson

In this project we have studied theadsorption of halogenated gases onice aerosols and the potential contri-bution to ozone depletion. Before thediscovery of the "ozone hole," theseheterogeneous processes were ignoredin atmospheric chemistry models.Field measurements supported bylaboratory experiments and modelinghave confirmed the pivotal role ofreactions of photoinactive (reservoir)chlorine and nitrogen gases on ice andnitric acid ice aerosols in the Antarcticpolar vortex. It was subsequentlyrecognized that heterogeneousprocessing on the background sulfuricacid aerosols distributed worldwide atmid-latitudes presented a potentialthreat for global ozone depletion.

Attention is now turning to brominecompounds that undergo the analo-

gous reactions and likely play asignificant role in ozone depletion inthe Arctic boundary layer. We use anonlinear optical probe, secondharmonic generation (SHG), tomeasure the thermodynamic behaviorof porous ice films and adsorption ofbromine compounds on the ice. Ourformalism allows us to measure theadsorption isotherm for an adsorbate/ice system and quantify the adsorp-tion on these heterogeneous substratesin terms of the multilayer structureand adsorbate coverage. We have usedSHG to measure the uptake of HBr bywater ice at low temperatures and tomonitor the phase behavior of HBrhydrates as a function of temperature.The adsorption isotherm shown hereresembles our results for HC1 adsorp-tion at slow introduction rates.

Publications


Heterogeneous Reactions," Geophys.Res. Lett. 23, 1021 (1996).

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Porous HNO3(H2O) IceFilms: Adsorption and SurfaceThermodynamics Measured bySecond Harmonic Generation"(submitted to J. Phys. Chem.).

Robinson, J.M., B.F. Henson, andK.R. Wilson, "Second HarmonicGeneration Studies of Porous IceFilms: Quantitative Measurement,"Nonlin. Opt. Mater. Fund. Appl. 1996Tech. Dig., 11, 391 (1996).

Wilson, K.R., B.F. Henson, JJ. Kim,et al., "Equilibrium Thermodynamicsof HC1 Adsorption on Water Ice"(211th American Chemical Soc.Meeting, New Orleans, March 1996).

Annealing Spectra 75 torr HBr on 0.5gWater Ice

1 3 0 180 230 -

Temperature (K)

2 8 0

Adsorption Isotherm: HBr on H20 @18OK

4 T

& = 2 -

o> o -fc=«*f5 10

COVERAGE HBr

15

HBr adsorption into a porous waterice substrate. The upper panel showsthe SHG intensity as a function oftemperature for a water ice with 0.7monolayers HBr adsorbed. The lowerpanel shows an adsorption isothermfor HBr at 180 K, which can beanalyzed using Brunnaer-Emmett-Teller multilayer adsorption theory.


Coronal Mass Ejections in the Solar Wind

John Gosling

Coronal mass ejections (CMEs) arespectacular solar events in whichlarge amounts of material from thesolar atmosphere are ejected intointerplanetary space. The processesthat trigger the release of CMEs fromthe sun and the factors that determinetheir sizes, their speeds, and theirevolution in interplanetary space areonly poorly understood. In this projectwe are studying CMEs in the solarwind near Earth's orbit.

Our overall goals are to distinguishand understand the physical processesgoverning CME evolution in inter-planetary space and to learn how bestto identify CMEs in solar windplasma and magnetic field data. Ofparticular interest is investigating therole that three-dimensional (3-D)magnetic reconnection plays indetermining the overall magnetictopology of these vital interplanetaryobjects. We are analyzing andinterpreting solar wind plasma andmagnetic field data archived at LosAlamos from a variety of spaceprobes.

Our review of transient solar windflows showed that 3-D reconnectionprovides a logical framework forexplaining a diverse set of solar andsolar wind observations related toCMEs. One new insight is that it isthe plasma beta (ratio of plasma tomagnetic pressures) within a CMEthat determines if 3-D reconnectionwill produce the nearly force-freestructure characteristic of "magneticclouds," which form an importantsubset (about one-third) of all CMEsobserved in the solar wind nearEarth's orbit.

We also found that -20% of allCMEs previously identified in thesolar wind near Earth contain eitheropen or completely disconnectedmagnetic field lines, suggesting thepresence of sustained 3-D recon-nection in at least these events. Ourpreliminary calculations show that theforces associated with rarefactionsproduced in front of slow CMEs areinsufficient to explain observedaccelerations of such CMEs in thesolar wind.

Publications

Gosling, J.T., "Corotating andTransient Solar Wind Flows in ThreeDimensions," Annu. Rev. Astron.Astrophys. 34, 35 (1996).

Gosling, J.T., "Physical Nature of theLow-Speed Solar Wind," in RoboticExploration Close to the Sun:Scientific Basis, S.R. Habbal, Ed.(American Institute of Physics, NewYork, N.Y., in press).

Gosling, J.T., and P. Riley, "TheAcceleration of Slow Coronal MassEjections in the High-Speed SolarWind," Geophys. Res. Lett. 23, 2867(1996).

Gosling, J.T., M.F. Thomsen, et al.,"Observations of MagneticReconnection at the LobeMagnetopause," J. Geophys. Res. 101,24765 (1996).

Roberts, D.A., and J.T. Gosling, "InSitu Measurement Requirements for aSolar Probe," in Robotic ExplorationClose to the Sun: Scientific Basis,S.R. Habbal, Ed. (American Instituteof Physics, New York, N.Y., in press).

Modeling Core-Collapse Supernovaein Three Dimensions

Michael Warren

The deaths of massive stars insupernova explosions are the mostviolent events ever witnessed byhuman beings. As a consequence,understanding core-collapse supemo-vae represents a fascinating challengewhich requires the convergence ofsuch varied areas of expertise asnuclear physics, neutrino transport,and hydrodynamics. In addition, theextreme conditions of density,temperature, and gravity which reign

at the heart of supernovae make thema natural laboratory in which to testideas about physics that are otherwisedifficult to investigate on Earth.

We have previously established thatthe mechanism which powerssupernova explosions relies on large-scale convection driven by neutrinoheating. However, determining thepattern of this convection demandsthree-dimensional simulations, whichhave not yet been performed. Using

our combined expertise in parallelcomputing and supernovae theory, weare beginning to carry out suchsimulations. We will then use theresults to estimate the kick velocityimparted to neutron stars at birth,which has far-reaching implicationsfor models of gamma-ray burstsources. We have thus far extended anexisting parallel, smooth-particlehydrodynamics code into a full-fledged supernova code. We have alsobegun developing a parallel, multidi-mensional, mesh-refined, shock-capturing method that should providesignificantly improved simulationcapability.


Deriving the Structure ofPresupernovae and Delta ScutiStars Using Nonradial Oscillations

Joyce Guzik

We are modeling the evolution andpulsation of luminous blue variables(LBVs) and delta Scuti stars. TheLBVs are massive stars and Type IIsupernova progenitors, while the deltaScuti variables are slightly moremassive than the sun. Both types ofstars pulsate in multiple radial andnonradial modes that have significantamplitudes throughout the stellarinterior. We are improving the modelphysics and comparing predicted andobserved pulsation properties toconstrain the interior structure ofthese stars (see the first figure). Thestudy of stellar interiors can contrib-ute to the understanding of fundamen-tal physics, such as equations of state(EOSs) and opacities of denseplasmas, energy transport, andturbulent mixing.

x

IQ3CT

i£s

1o

it•o

o

32.5

2

1,5

1

0.5

0

-0.5

-1

-1.5

-2

-2.5

-3

-3.5

-4

i 1

: \ \

1 v \

i i

i

U-i

2000 2500 3000 3500

Calculated Frequency (uHz)

4000

and possible turbulent mixing belowthe solar convection zone. We areapplying this code to model the morerapidly rotating delta Scuti stars.

Publications

Bradley, P.A., and J.A. Guzik,"Seismological Modeling of the DeltaScuti Star FG Vir," Bull. Am. Astron.Soc. 27, 1430 (1995).

Guzik, J.A., "What Have We Learnedabout the Solar Interior from SolarOscillations?" (The Sun and Beyond,Ho Chi Minh City, Vietnam, October23-27, 1995).

Guzik, J.A., and P.A. Bradley,"Models and Mode Identifications ofthe Delta Scuti Star FG Vir," BalticAstron. 4, 442 (1995).

Guzik, J.A., A.N. Cox, and F.J.Swenson, "The Last Few Microhertz,"Bull. Am. Astron. Soc. 27, 1454(1995).

Guzik, J.A., A.N. Cox, and FJ.Swenson, "Using Solar Oscillations toConstrain the Equation of State andLow-Temperature Opacities," Bull.Astron. Soc. India 24, 161 (1996).

Rogers, F.J., F.J. Swenson, and C.A.Iglesias, "OPAL Equation of StateTables for AstrophysicalApplications," Astrophys. J. 456, 902(1996).

Soukup, M. S., and A.N. Cox,"Theoretical Radial PulsationProperties of Massive YellowSupergiants," Bull. Am. Astron. Soc.28, 917 (1996).

The discrepancy between observed and calculated solaroscillation frequencies vs calculated frequency for the low-degree (0, 1, 2, and 3) acoustic waves that travel throughmost of the solar interior. The solar model includes diffusivesettling of helium and heavier elements relative to hydrogenand uses the latest opacity-library (OPAL) opacities and ananalytical EOS developed by F Swenson (Los Alamos), F.Rogers (Lawrence Livermore National Laboratory), and A.Irwin. We can eliminate the remaining small discrepancybetween observed and calculated frequencies by refining thesolar surface modeling.

This year we updated and are nowusing a nonlinear hydrodynamicscode to determine whether predictedradial "strange" modes can grow tolarge amplitude and trigger LBVoutbursts (see the second figure). Wecompared observed and calculatedoscillation frequencies to derivestellar parameters for two delta Scutistars, FG Vir and CD-24° 7599 (seethe third figure). We participated in avery successful multisite observingcampaign for the delta Scuti star 4CVn, which resulted in detection ofover 30 new frequencies.

In addition, we modified a two-dimensional stellar evolution code tohandle convective envelopes presentin lower-mass stars and benchmarkedthis code by calculating a rotating,two-dimensional solar evolutionmodel. We used the hydrodynamiccapabilities of this code to look forrotation-generated shear instabilities


oCD

1o

oo

iCO

'-a

1.0

0.5 -

0.0

-0.5 -

-1.0

I

I

/

L I

/

I

I

i

I

I

1/

0.0 1.0 2.0 3.0 4.0 5.0

Time (106 sec) Photosphere6.0

Growth in surface radial velocity from hydrodynamic calculation of the LBVenvelope model. This model represents a star of initial mass equal to 80 solarmasses that has lost nearly half its mass because of an intense stellar wind,exposing layers where 50% of the original hydrogen has been converted tohelium by nuclear fusion. Linear pulsation analysis shows that this model isunstable to radial "strange" mode pulsations. The model predicts that thekinetic energy of two modes, with periods of 7 and 15 days, more than doubleseach period. Nonlinear analysis shows that for this model, the pulsationamplitude grows to about 100 km/sec (only about 1/3 escape velocity) beforereaching a limiting amplitude.

1.50

1.45

1.40

1.35

© 1.30

o1.25 -

1.20

1.15

1.10

1.05

1

1 j

-

1 1

1 1 1

1 1

1

s/D-24

/

/

l '

FGVir

1

1 •

~ » .

Virf —»

s1

1

1

|

N\N.80 (

^2.0 Ms -

N . 9 M Q •

s1.82Mo~Z=0.018>-

t ,

3.95 3.90 3.85 3.80Log Teff

3.75 3.70

Location in the Hertzsprung-Russell diagram (the log of the luminosity vs thelog of the surface temperature) of best-fitting models for the delta Scuti starsFG Vir and CD-24° 7599, along with evolution tracks for 1.8, 1.9, and 2.0solar mass models. Models of 1.9-2.0 solar masses and effective temperature8200 K match most of the 13 reported oscillation frequencies ofCD-24° 7599.Models with effective temperature 7480 K, of either 1.8 or 2.0 solar masses,best match the 19 reported frequencies for FG Vir.


Magmatic Tritium

Fraser Goff

Tritium (3H) is one of the reactionproducts that should be producedduring "cold fusion" in condensedmatter. We are trying to determinewhether anomalous quantities oftritium are universally present inmagmatic waters from severalvolcanoes of different magma typesand tectonic settings. The presence ofsuch tritium could provide indepen-dent evidence for cold fusion as apotentially viable Earth process andwould require reevaluation ofaccepted concepts on primordial

helium, mantle heat flow, and platetectonics.

The object of our work is to collectsamples of high-temperature fumarolecondensates, thermal and nonthermalgroundwaters, precipitation, and freshvolcanic products from one additionalvolcano to determine the tritiumcontent of its magmatic water. Ourapproach is unique because weanalyze water with three isotopic

compositions (water containingdeuterium, oxygen-18, and tritium) toeliminate effects of meteoric contami-nation and contamination by near-surface groundwaters.

Targeted volcanoes for this pastyear were White Island and Ruapehu(New Zealand). We have not quitecompleted the data analysis for theNew Zealand samples, but we havecompleted the analyses of samplescollected last year from Vulcano(Italy), Kudriavy (Russia), andPanandayan (Indonesia) and foundthat their magmatic tritium is 0.0tritium units (T.U.). (1 T.U. = 3.193pCi per kilogram oi water) After\isitinj. 14 volcanoes from 1988through 1996, we conclude that

PLUG-DOME ANDESITE AND RELATEDHYPA8YSSAL INTRUSIVE ROCKS, KFBB-1993

ANDESITE FLOW, 1866

/ V A ? ^ SUBVOICANIC AND HYTABYSSAL\ £ v ! y INTRUSIVE ROCKS. PRE-1B66

VOLCANIC EDIFICE. PRE-1866 FLOWS.DOMES. PYROCLASTIC HOCKS. DEBRISFLOWS. EPICLASTIC HOCKS

PRECAMBRIAN-TERTIARY BASEMENT

SUAS AGRIAS SPRINGS

UCAMANCHA SPRINGS

|D| ALTERED PORPHYRITIC DACITE

|FB| FUENTE BLANCA SPRINGS

GOLD-BEARING DOLOMITE-OUARTZ-SULFIOE-SULFOSAU VEIN

MAGMATICFLUIDS

METEORICFLUIDS

..BOUNDARY OF POTENTIAL- PORPHYRY COPPER ZONE

Modified cut-away perspective drawing (viewed from the north) ofGaleras volcano, Colombia, showing the basicgeology and configuration of the shallow hydrothermal system. Magmatic volatiles mix with young, near-surfacegroundwaters to form acid springs. Magmatic fluids discharging inside the volcano create conditions favorable fordeposition of gold and copper. Magmatic fluids discharging at the summit mix with precipitation falling in the summitcrater and cone. The resulting mixtures contain measurable tritium from the meteoric end-member but no detectabletritium from a deep source.


magmatic tritium is in all cases0.0 T .U., subject to analytical andother errors. Thus, there are noidentifiable magmatic tritium anoma-lies and no evidence for cold fusion inthe deep Earth. The results of this

project also have application tostudies of natural cycling of meteorictritium and of metals transport inmagmatic fluids, as well as forhazards monitoring at volcanoes.

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

-120

-130

-140.

CO

• Cold springs, wells, rain

B Cold streams

x Warm springs

AA AguaAgrias

P Pandiaco

Fe Iron-rich

A Galeras fumaroles

V Galeras rocks, 7/92 explosion

• Other Galeras rocks

Rain<1/26/93)Q

MostGalerasStreams

Magmatic Water

Publications

Goff, R, "Vesicle Cylinders in Vapor-differentiated Basalt Flows," J.Volcanol. Geotherm. Res. 71,167(1996).

Goff, F., C. Werner, C. Seibe, et al.,"Geochemical Monitoring during1994-1995, Popocatepetl Volcano,Mexico" (American GeophysicalUnion Fall Meeting, San Francisco,Calif., December 15-19, 1996).

7(Xenolith)

O= +7.37 ± 0.56

Plot of deuterium versus oxygen-18 for waters from Galerasvolcano. The fumarolecondensates lie on a mixing linebetween magmatic and meteoricend-members. The extrapolateddeuterium of the magmatic wateris about -35%o.

-18 -16 -14 -12 -10 -8

(S18O<%c)

_ 65°CA—

LocalMeteoricWaters

Plot of deuterium versus oxygen-18forwaters from Galeras volcano. When thetritium data for the fumaroles areextrapolated to the oxygen-18 value formagma, the resulting magmatic tritium is0.0 T.U.

BOX Boiling

Rain (1/26/93)• g. Rain (1/13/93)

^ ^ Z ^ F e (Respirador)

DeformesMagmaticTritiumsO.O T.U.

l ^ r Besplima

-18 -16 -14 ^12^ 1̂0 -2


Minerals of Earth's Deep Interior

David Schiferl

The goal of this project is to gain afundamental understanding of theboundary between Earth's upper andlower mantle. The nature of thisboundary has been a major geophysi-cal issue for the past two decades.Specifically, we want to understandthe seismic velocity and densitydiscontinuity at the boundary, whichlies at a depth of 670 km and has atemperature of about 1900 K and apressure of about 23 GPa. A phasechange at this depth would represent arelatively small barrier to mantleconvection through the discontinuity,but a compositional change wouldinhibit thermal convection throughoutthe mantle.

In our project, we are measuringequation-of-state (EOS) parameters inmantle minerals as functions of highpressure and temperature usingsingle-crystal x-ray diffraction in aunique diamond-anvil cell (DAC).Measurements are made at up to25 GPa and 1200 K. Single-crystal

diffraction improves the absoluteaccuracy in lattice constants over thatobtained with powder diffraction by afactor of 5 to 10.

We modified the DAC to ensurestable high pressure at high tempera-tures and observed seven points on theEOS of silicate perovskite. We alsodetermined the pressure and tempera-ture derivatives of the bulk modulusand thermal expansion fororthoenstatite (MgSiO3) at up to1000 K at 1.5 GPa and at lowertemperatures with pressures up to4.5 GPa (see figure). These measure-ments break previous records forsingle-crystal diffraction at hightemperature and pressure and define anew state of the art.

In addition, we conducted large-volume pressure diffraction experi-ments at up to 10 GPa and 1300 Kusing a synchrotron x-ray radiationsource. Experimental data on twomaterials, MBN and NaAlSi2O6 jadeite,have improved our understanding of

the thermoelasticities of thesematerials and can be applied tomodeling pressure-temperaturesystematics and mantle mineralogy.

Publications

Schiferl, D., and Y. Zhao, "High-Pres sure/High-Temperature Diamond-Anvil Cell System for Single-CrystalX-Ray Diffraction" (to be publishedin Rev. Sci. Intrum.).

Zhao, Y., D. Schiferl, and J.M. Zaug,"RSCU-SOS: A Rapid IntensitySearching and Centering Routine forSingle Crystal Diffraction Studies atSimultaneous High Pressures andTemperatures," /. Appl. Cryst. 29, 71(1996).

Zhao, Y, R.B. Von Dreele, et al., "P-V-T Data of Hexagonal Boron-NitrideMBN and Determination of Pressureand Temperature using ThermoelasticEquation of State of Multiple Phases"(to be published in High Pressure Res.).

Zhao, Y, R.B. VonDreele, TJ.Shankland, et al., "ThermoelasticEquation of State of JadeiteNaAlSi2O6: Energy-Dispersive Studyof Low Symmetry and Multiple PhaseDiffraction" (to be published inGeophys. Res. Lettr.).

1U

850

840

830

820

810

800

—

1.01

9

- 3.73

2 --

i

1.22

0

3.96

i

1.35

8-4.22

i

1.49

4.52

i

1.23

_ i 5 Gfa 2

1.68

c3.28?

C5 2.48

>1

, ir ^ * -

LU-*-^—- ^ ^ PC=4-OG

i i i

0.69

oI

X -

^ - ^ • L 5 2

.95

,is

•

pa

-i

Pressure dependence of thethermal expansion ofMgSiO3.Open data points represent rawpressure-volume-temperaturedata, with their pressures labelednext to them. Solid points arecorrected data (using thethermoelastic equation of state)for two constant pressures: 1.5and 4.0 GPa. Data pointsbetween these two constantpressures are corrected twice toboth pressures; the dotted arrowsindicate the direction ofcorrection. Two straight lines arefit to obtain thermal expansionsatP= 1.5 and 4.0 GPa.

300 400 500 600 700 800 900 1000

Temperature, K


Striation-lmage Monitoring ofPlasmaspheric, L-ResolvedElectrodynamics (SIMPLE)

Abram Jacobson

The plasmasphere is a region ofrelatively dense ionized gas in Earth'satmosphere, located in near-spacewithin a few Earth radii in geo-altitude, that is confined by Earth'smagnetic field. Our project is aimed atdetecting irregularities in theplasmasphere using the electricalphase of radio signals transmitted bygeosynchronous satellites, whichrotate with Earth over a fixed positionnear the equator. The physics underly-ing this project is multiscale: the solarwind is the prime driver and energysource, the geomagnetic field is theintermediate store of energy from thesolar wind, and Earth's ionosphereand upper atmosphere are the electri-cal load at the base of the geomag-netic field.

One goal of this work is to developan entirely new approach to monitor-ing how Earth's near-space environ-ment is affected by geomagneticdisturbances, which are in turn relatedto solar flares. This new method ispotentially two orders of magnitudeless expensive than existing means ofmonitoring near-space electric fields(such as incoherent-scatter radar andpolar-orbiting satellites) duringgeomagnetic disturbances.

This past year has been one ofenormous accomplishment andencouragement. We succeeded intracking three satellite beaconssimultaneously, significantly increas-ing our ability to monitorplasmaspheric irregularities. Inaddition, we have better defined ourmeasurement error by examining a

subset of the data that provided a clearindicator of instrumental effects.

In addition, we firmly establishedthat the midnight sector is thepreferred site of plasmasphericirregularities, with more day/nightcontrast during northern winter thanduring northern summer. There is astriking correlation of the intensityand incidence of these irregularitieswith increased levels of geomagneticdisturbance as measured by the Kpindex. There is a prompt "turn-on" ofthe irregularities when the DST indexplunges negative.

Publications

Jacobson, A.R., R.C. Carlos, R.S.Massey, et al., "Total-Electron-Content Signatures of PlasmasphericMotions," Geophys. Res. Lett. 22,2461 (1995).

Jacobson, A.R., G. Hoogeveen, R.C.Carlos, et al., "Observations of InnerPlasmasphere Irregularities with aSatellite-Beacon Radio-InterferometerArray," /. Geophys. Res. 101,19665(1996).

Coupled Ocean-Atmosphere ModelSystem for Studies of Interannual-to-Decadal Climate Variability over theNorth Pacific Basin

Chung-Chieng Lai

This project will improve ourunderstanding of fluctuations inprecipitation (and, therefore, waterresources) in the southwestern UnitedStates. Only a coupled ocean-atmosphere model (COAM), likeours, can track the path of water fromoceans through the atmosphere toland. The objectives of our project areto construct a global COAM, use themodel to explore climate variabilityover the North Pacific basin within aperiod ranging from one year to

several decades, and then use theresults of this study to determine theeffects of climate variability in theNorth Pacific region on the precipita-tion over the Southwest.

This year, we completed threemajor tasks. First, we built a meso-scale COAM for the west coast bytaking advantage of an existingregional atmospheric model from theUniversity of California, Davis, and aregional ocean model from Missis-sippi State University. However, westill need to define a consistent set ofinterface boundary conditions and to

achieve temporal synchronizationbetween the two regional models.

In the area of global modeling, wecompleted coupling the global oceanmodel constructed at Los Alamoswith the global atmospheric modelfrom the National Center for Atmo-spheric Research (NCAR); we alsocompleted a one-year simulation withthe global COAM. To achievecoupling of the two models, we usedthe "flux coupler" package developedat NCAR as part of the ClimateSystem Modeling Project. However,we still need to improve the efficiencyof the coupling process.

Finally, we designed the boundaryinterface for the global nested-gridocean models in cooperation with theUniversity of California, Los Angeles,where the North Pacific circulationmodel was developed and withMississippi State, where the Gulf ofMexico model was developed.


Particle Acceleration fromReconnection in the Geomagnetic Tail

Joachim Birn

One of the major consequences ofthe reconfiguration of the geomag-netic field associated with magneto-spheric substorms and the underlyingmagnetic reconnection process is theacceleration of charged particles andtheir injection into the ionosphere andthe near-tail region of the magneto-sphere. The accelerated chargedparticles in Earth's magnetospherecause auroral brightening and mayaffect satellite safety and operations.We are investigating the mechanismsof particle acceleration and heatingusing self-consistent three-dimen-sional magnetohydrodynamic (MHD)simulations and by tracing testparticles in electromagnetic fieldsobtained from these simulations.

New MHD results indicate a muchstronger, more rapidly rising electricfield in the region earthward of thereconnection site, which has impor-tant consequences for the energy gainand the increase in particle fluxes.The energetic particle flux changesestimated from the test particle orbitsagree well with observations thatdemonstrate rapid ion-flux increasesat energies above -20 keV but littlechange at lower energies. The

accompanying figures show the ionflux changes and ion distributionfunctions during an observed particleinjection and in the test particlesimulation.

The "injection region" inferredfrom the test particles not only has asharp earthward boundary (the usualinjection boundary) but also a sharpbut ragged tailward boundary. Theearthward portion of the enhanced ionflux can be traced to the enhancedcross-tail electric field associated withthe collapse and dipolarization of theinner tail, whereas the tailward edge isclosely associated with a magneticneutral line, the site of reconnection.

Publications

Birn, J., and M. Hesse, "Details ofCurrent Disruption and Diversion inSimulations of MagnetotailDynamics," J. Geophys. Res. 101,15345 (1996).

Birn, J., M. Hesse, and S.P. Gary,"The Role of Microprocesses inMacroscale Magnetotail Dynamics,"in Cross-Scale Coupling in SpacePlasmas, Geophys. Monogr. Sen 93,275 (1995).

Birn, J., M. Hesse, and K. Schindler,"MHD Simulations of MagnetotailDynamics," / . Geophys. Res. 101,12939 (1996).

Birn, J., M. Hesse, M.F. Thomsen, etal., "Substorm Associated IonAcceleration in the DynamicMagnetotail" (to be published in Proc.Third Intl. Conf. on Substorms).

Birn, J., F. Iinoya, J.U. Brackbill, etal., "A Comparison of MHDSimulations of MagnetotailDynamics," Geophys. Res. Lett. 23,323 (1996).

Birn, J., M.F. Thomsen, J.E.Borovsky, et al., "CharacteristicPlasma Properties of DispersionlessSubstorm Injections atGeosynchronous Orbit" (to bepublished in J. Geophys. Res.).

Birn, J., M.F. Thomsen, J.E.Borovsky, et al., "Plasma andEnergetic Particle Properties ofDispersionless Substorm Injections atGeosynchronous Orbit" (to bepublished in Proc. Third Intl. Conf. onSubstorms).

Birn, J., M.F. Thomsen, J.E.Borovsky, et al., "Substorm IonInjections: GeosynchronousObservations and Test Particle Orbits"(to be published in J. Geophys. Res.).

ion injection 13 April 1990

IgJ

0.00

-1.00

-2.00

-3.00

-4.00

-5.00

-6.00

-7.00

Ion fluxes from test particle orbits

: i 5keV

j 20 keV

I 80 keV i ^_jS^,

i ! : \: 1 180 keVi _ _ ^ / '

: . . . : ; . . . . ! . . . . -

rv\'\IU

fl ^ In J 1:u ii|iy if

r '•] I? i :

. . , , i . , . , •

7:00:00 7:10:00 7:20:00 7:30:00 7:40:00 7:50:00 8:00:00UT

Ion flux increases observed during an injection at geosynchronous orbit (left panel) and obtained from test particle orbitsintegrated in the fields from an MHD simulation of the dynamic evolution of the magnetotail (right panel).


Hesse, M., J. Birn, M.M. Kuznetsova,et al., "A Simple Model of Core FieldGeneration during PlasmoidEvolution," /. Geophys. Res. 101,10797 (1996).

Hesse, M., D. Winske, and J. Birn,"Hybrid Modeling of the Formationand Structure of Thin Current Sheetsin the Magnetotail" (to be publishedin Proc. Third Intl. Conf. onSubs forms).

Hesse, M., D. Winske, M.Kuznetsova, et al., "Hybrid Modelingof the Formation of Thin CurrentSheets in MagnetotailConfigurations," /. Geomagn.Geoelec. 120,749 (1996).

ion distributions, 13 April 1990 ion distribution function from the simulation

105

103

102

10"

1 0-1

1020.1

e 0783 UT0729 UT

1000 10 100E (keV)

1000

Ion distribution functions for the previous figure; those observed during the injection (left panel) versus those calculatedon the basis of the simulation (right panel).

Fluxes of Water and Energy in PhysicallyHeterogeneous Environments

David D. Breshears

Fluxes of water and energy in thenear-surface environment are tightlyinterrelated with the heterogeneousvegetation pattern that is a mosaic ofcanopies of woody plants andintercanopy areas. Our objective wasto improve the predictability of theseinterrelationships, which are relevantto a variety of problems, includingglobal change, land management, andcontaminant transport. Using spatialautocorrelation, we demonstrated thatvegetation overstory determines thepatterns of soil moisture and near-ground solar radiation. The spatialpattern of soil moisture variestemporally—intercanopy patches areusually wetter than canopy patches,except after intense storms thatgenerate runoff. We developed a waterbalance model that predicted thetemporal shifts in soil moisturebetween canopy and intercanopypatches and conducted a suite of

spatial neighborhood analyses thatdemonstrated how trees exploitcanopy/intercanopy heterogeneity.The spatial relations of trees reflectspatial variability in fluxes of waterand energy; our study is the first torelate both of these fluxes with thespatial pattern of a plant community.

We developed a spatially explicitmodel for predicting near-groundsolar radiation and evaluated therelative roles of tree cover, height,and spatial pattern for sites along agrassland-forest continuum. Wedetermined that a site's mean solarradiation depended on the amount ofgroundcover and on tree height butwas independent of the spatial patternof canopy patches, whereas itsvariance depended on all three. Lastly,we used our acquired knowledge andour developed models collectively toassess large-scale ecosystem re-sponses to those climate variationsthat also lead to accelerated erosion.

Overall, this project demonstratedhow spatial and temporal variations influxes of water and energy determinetight interrelationships betweenvegetation, soils, and climate insemiarid environments.

Publications

Breshears, D.D., P.M. Rich, and F.J.Barnes, "Heterogeneity in SolarRadiation and Soil Moisture Imposedby Overstory with IntermediateClosure" (submitted to EcologicalApplications).

Davenport, D.W., D.D. Breshears, etal., "Viewpoint: Sustainability ofPiny on-Juniper Ecosystems: AUnifying Perspective of Soil ErosionThresholds" (submitted to J. RangeManagement).

Martens, S.N., D.D. Breshears, et al.,"Scales of Above- and Below-GroundCompetition as Detected from SpatialPattern" (submitted to J. VegetationScience).


Flare Star Monitoring with a NewSingle-Photon-Counting Imaging Detector

Donald E. Casperson

The objective of this project is tocharacterize optical transient phenom-ena in the nighttime sky, most notablyflares from red dwarf stars, using asingle-photon-counting imagingdetector presently under developmentin another project. In addition toproviding photon-counting sensitivity,this detector, a microchannel platewith crossed delay-line readout(MCP/CDL), provides high spatial aswell as high temporal resolution.

This year, we achieved majorimprovements in the detector readout,resulting in significantly higherphoton-counting rates; however,successive photocathode and vacuumfailures in the sealed MCP/CDL unitshave so far prevented the collection ofany extensive data sets for our project.As a result, we have shifted ouroptical transient measurement work totwo other directions.

First, we formed a collaborationwith a NASA orbital debris trackingteam that uses a charge-coupleddevice (CCD) camera at the 3-m-aperture Liquid Mirror Telescope(LMT) located in Cloudcroft, NewMexico. We have used a variant ofthis team's time-delay and integration(TDI) method for collecting stellaroptical data with 1-s temporalresolution. The first accompanyingfigure shows an example of a barredspiral galaxy. The second figureshows stellar time-history tracksgenerated for this project. Bothimages were recorded with the CCDcamera at the LMT.

In another effort related to all-skymonitoring of optical transients, wehave contributed to the ongoingdevelopment of a remotely operableobservatory that will be capable ofrecording visible images (in both TDIand standard framing format) withCCD cameras that are coupled totelescopes with programmablemounts.

Sample image of a barred spiral galaxy from the NASA 3-m-aperture LMT. ThisCCD camera image, courtesy of Mark Mulrooney (Lockheed-Martin/NASA/Johnson Space Center), was obtained with the TDI method and represents 96 sof total exposure. The V band stellar magnitude limit using this technique at theLMT is approximately m - 22.

Raw CCD image of stellar time-history tracks generated at the LMT using avariant of the TDI technique. For this image, the CCD sensor is rotated slightlyrelative to its position for the data of the previous figure. The 96-s integration ofeach stellar image is then uniformly distributed over a track of 100 CCD pixels,thus providing 1-s temporal resolution over each track. Lengthy TDI scansprovide a very large database with which one can search for optical transients.


Close Encounters of Asteroidsand Comets to Planets

Jack Hills

We are studying the physics of tidalencounters between comets, asteroids,and planets. In this study, we aremaking heavy use of an existing,robust few-body code to studyencounters between the sun, planets,and asteroids (including doubleasteroids), and we are writing a codeto study the breakup of an asteroid bythe tidal field of a planet.

We believe that our work willexplain a number of previouslymysterious properties of asteroidswhose orbits cross those of the innerplanets. We will also determine thenatural probability of capturingasteroids into orbits around Earth andthe other inner planets by the tidalinterplay between the sun and planets(and for Earth, that between the moonand Earth). In addition, we willdetermine the probability of asteroidcapture—if the asteroid is double—byan exchange collision. We believe thatthis mechanism allowed Mars tocapture its small moons. The perma-nent capture of asteroids around Earthwould reduce the number of poten-tially dangerous collisions with Earth,and it may allow us to utilize the

resources of these captured asteroidsfor construction in space.

We have studied the tidal deforma-tion of asteroids using an N-Bodycode. Most asteroids make severalclose approaches to Earth before theyimpact it. Many of the asteroids thatintersect the orbit of Earth haveextremely elongated shapes. We havefound that the tidal field of Earth canproduce elongations even larger thanthose yet observed if the asteroidshave made close approaches to Earth.If their shapes result from tidaldeformation, they are likely composedof loose blocks held together bygravity. This structure will have to beallowed for in any effort to mitigatetheir impact.

We have used an improved atmo-spheric model for asteroid collisionsto study the capture of these objectsinto bound orbits around Earth as theresult of grazing atmospheric colli-sions. The model uses a sphericalatmosphere with a curve fit to the realatmospheric density rather than aplane-parallel atmosphere withexponential falloff in density. We havefound that there is a narrow window

of atmospheric heights where an ironmeteoroid would be captured intoorbit by its energy dissipation in theatmosphere. However, stony meteor-oids within a certain range of sizescan never be captured into boundorbit around Earth because they breakapart easily in the atmosphere at theheights needed to cause enoughenergy dissipation to allow capture.Breakup greatly increases theirdissipation cross section and causesthem to plunge to Earth. We have alsocalculated the damage at ground levelcaused by such grazing colliders.

Publications

Hills, J.G., and R. Carlson, "Statisticsof Large Meteors Detected bySurveillance Satellites" (to bepublished in Bull. Am. Astron. Soc).

Hills, J.G., and M.P. Goda, "Damagefrom the Impact of Small Asteroidsand Comets" (submitted to Planet.Space Set).

Hills, J.G., and M.P. Goda,"Meteoroids Captured in Earth Orbitby Grazing Atmospheric Encounters"(submitted to Planet. Space ScL).

Solem, J.C., and J.G. Hills, "Shapingof Near-Earth Asteroids by TidalForces," Astron. J. I l l , 1382 (1996).

Isotopic Prediction of Eruption Volumeat Continental Volcanoes

Frank Perry

The goal of this project is toforecast eruption volume at stratovol-canoes using the neodymium isotopiccomposition of past eruptions. Thismodel is based on the premise that theisotopic composition and volume of amagma are both controlled by influxof new magma into the system.

We obtained samples for twostratovolcanoes, Pico de Orizaba insouthern Mexico and Daisen insouthwest Japan. We selected thesevolcanoes because their eruptivehistory and eruption volumes arereasonably well documented. In orderto assess the correlation between

eruption volume and isotopic compo-sition, we chose the samples torepresent a range of eruption volumes.Samples from both volcanoes wereanalyzed for neodymium, strontium,and lead isotopic compositions atUniversity of California, Berkeley,and for major- and trace-elementgeochemistry at Los Alamos. Inter-pretation of these data may lead to abetter understanding of what mecha-nisms control the magnitude ofvolcanic eruptions.


Experimental Cosmology:The Early Universe

Wojciech Zurek

We are using our N-body tree codeon massively parallel supercomputersto test the standard cold dark matter(CDM) universe by conductingnumerical studies of structure forma-tion on the largest scales accessible toobservations. These phenomena haverecently become accessible toobservations through both ground-based, very large telescope surveysand dedicated satellites.

Our simulations of the CDM modelon parallel supercomputers (see thefirst two figures) have shown that thegalaxy-galaxy velocity dispersion atsmall scales is consistent with resultsobtained from the sky survey done bythe Harvard-Smithsonian Center for

Astrophysics. This finding is signifi-cant since velocity dispersion limitshad been previously used to rule outthe model. Similarly, we have shownthat the redshift-space power spec-trum (also used to rule out CDM)does not provide an unambiguousconstraint at small scales and isconsistent with the power spectrummeasured in the Infrared Astronomi-cal Satellite galaxy catalog. Thecomparison between the numericalexperiments and the observations isnot as straightforward as was usuallyassumed because of radial velocityskewness (a significant scatter ofvelocity dispersions between differentobservation-sized samples) and theimportance of galaxy clusters.

Publications

Brainerd, T.G., B.C. Bromley, et al.,"Velocity Dispersion and theRedshift-Space Power Spectrum,"Astrophys. J. Lett. 464, 103 (1996).

Bromley, B.C., T.G. Brainerd, et al."On Cluster Cores and Redshift-Space Power Spectra," in Clusteringin the Universe: Proc. of the XXXRencontres de Moriond Meeting, S.Maurogordato, Ed. (EditionsFrontieres, Gif-sur-Yvette, France,1995).

Bromley, B.C., R. Laflamme, et al.,"The Distribution of Matter aroundLuminous Galaxies," in Dark Matterin Cosmology, Proc. of the XXXIRencontres de Moriond MeetingR. Ansari, Ed. (Editions Frontieres,Gif-sur-Yvette, France, 1996).

Bromley, B.C., M.S. Warren, andW.H. Zurek, "Estimating Omega fromGalaxy Redshifts: Linear FlowDistortions and NonlinearClustering," Astrophys. J. Lett. 475,414 (1997).

" •

• • » • • •

* - t* • .

*

• • ; . - "

• v

' . • * ,

•

•

• • • • • -

r . ••' .". .•• • ' • • .

/ ' • . • • •

• • * • *

• •

• •

• • i

* * •

1' *} . . -

* ^ y •*

• . . • • • " •

•

• • •

> • ,

- •

. * .

. . • • • .

« •

• *

• < *

^ • • • •

* - . *

" • .

. ; , ; • •

• • • * • « ' . * *

* • * • • . . ! ' * •

* • * • v "•

%i • " *

•

• ' * '

* . "

• ;

. • •

•

i •

••

'.» •

%.

• •

•

•

• • • • • ' • ' . '

' . ; • " • • • * • •

>• . i i -

. • :

• ' * • • • •

K •

' ' • ' ' • " *

> . * * • " •

1 .

. • . • *

t

..V *..•*. .y

• . •

• .

if, •

•

* *

C

•

•

r. ~M

• . . ' . , • . . - - . ; ^ V 4 . ^

• ' • . : • • ' . . . - • - • • • . " *

tf. • * ^ .

• , . • / - • * J ^ * ' . .

» j . . • i

^•^ ».*:•.t « ' -J»V.

I - ' . • • • & . • " • • ' •

i . - • ' • * ' . v - > *• ."-"V• • . * ' • •

• * * * ' . • . • *

. . . . * •

- • • * * ,

• • • * . ' - • '

• * • *• *

^ . : • • • " • • • * •

* * . •

A plot of the projected locations of"galactic halos" in one of the N-bodymodels. The size of the square isabout 180 Mpc across. Sizes of thedots are approximately proportionalto the masses of the halos. The smallsquare indicates the region that isshown in more detail in the nextfigure.


A high-resolution plot of everyparticle (about 250,000 of them) inl/50th of the total system (indicatedby the small square in the previousfigure), with the circles representingthe location of galaxy halos.

Distribution of the number of pairs asa function ofpairwise radial velocity.The triangular shape of this histo-gram over a large range of radialvelocity difference (8V) implies thatthe distribution is indeed exponential,and the fact that the diagram appearsisosceles allows us to infer thevelocity dispersion (av) from theslope.

<6v> = -280 km/s

-2000 0radial <5v (km/s)

2000


Cosmology with Massive Neutrinos

Wojciech Zurek

The goal of this project is tounderstand the implications forcosmology of massive neutrinos andis motivated by the recent evidencefor the neutrino mass obtained by theLiquid Scintillator Neutrino Detectorexperiment. We are conductingnumerical studies of cosmologicalmodels with a significant massfraction (20%-30%) attributable tolight (several electron volt) neutrinos.We are focusing on two aspects ofcosmic structure formation: (1) thepresent-day distribution and structureof galaxies and clusters; and (2) thenumber density of protogalacticobjects at early times (redshift z ofapproximately 2).

In this research, an objective is torun fast, parallel-supercomputersimulations of massive-neutrinocosmogonies with a resolution that isan order of magnitude better than hasbeen previously attempted. The speed(more than 10 Gflops) and accuracy(-10 kpc spatial force resolution) ofour code avoids problems of over-merging that have been reported byothers, enabling us to understand theimplications of massive neutrinos forcosmology, while setting cosmologi-cal constraints on neutrino mass.

The main accomplishment this firstyear is the development of a high-performance simulation code. Ourparallel treecode now evolvescosmological density fields withperiodic boundary conditions andhierarchical grids. Both are essentialto accurately model large-scaleneutrino free-streaming and formationof collapsed objects (galaxies andclusters) on small scales. In addition,we completed a battery of analysiscodes, including redshift-spacepower-spectrum estimators andgravitational lensing/ray tracers.

Publications

Brainerd, T.G., B.C. Bromley, et al.,"Velocity Dispersion and the RedshiftSpace Power Spectrum," Astrophys. J.Lett. 464, 103 (1996).

Bromley, B.C., M.S. Warren, andW.H. Zurek, "Estimating Omega fromGalaxy Redshifts: Linear FlowDistortions and Nonlinear Clustering"(to be published in Astrophys. J.).

Bromley, B.C., T.G. Brainerd, et al."On Cluster Cores and Redshift-Space Power Spectra," in Clusteringin the Universe: Proc. of the XXX

Rencontres de Moriond Meeting, S.Maurogordato, Ed. (EditionsFrontieres, Gif-sur-Yvette, France,1995).

Bromley, B.C., R. Laflamme, et al.,"The Distribution of Matter aroundLuminous Galaxies," in Dark Matterin Cosmology, Proc. of the XXXIRencontres de Moriond MeetingR. Ansari, Ed. (Editions Frontieres,Gif-sur-Yvette, France, 1996).

Warren, M.S., and J.K. Salmon,"Abstractions and Techniques forParallel N-Body Simulation," inParallel Object-Oriented Methodsand Applications '96 (published onthe Web, http://www.acl.lanl.gov/Pooma96/abstracts/warren.ps, 1996).

Global Climate Effects of the EmergingChinese Transportation System

Scott Elliott

Nonpolluting bicycles have longbeen the predominant means of localsurface transportation in the People'sRepublic of China. A major automo-bile manufacturing/importing efforthas begun in the country, and plan-ning documents indicate that theChinese are making plans to acquiremore than 100 million vehicles byearly in the next century. We expectboth regional- and global-scalepollution effects, judging from whatthe western world has experienced asa result of its large automotive fleets.

We are using the latest projectionsfor the manufacture of Chineseautomobiles to calculate potentialpollution generation. For this investi-gation we are focusing on the oxidant,ozone. We have constructed emissionsof the precursor species nitrogenoxides and volatile organics based ondata for the eastern United States. Wefirst estimated ozone production fromvalues that we measured for continen-tal/oceanic-scale yields relative to

precursor oxidation. We then corrobo-rated the estimates through two-dimensional modeling of photo-chemistry in springtime airflow offthe Asian land mass.

We expect the projected automobilefleet sizes to increase coastal andremote oceanic ozone by tens of partsper billion. We studied influences onthe tropospheric aerosol system andon the major greenhouse gas, carbondioxide, only peripherally. Nitrogenoxides created during the vehicularinternal combustion process willcontribute to nitrate pollution levelsthat will be measured in the Pacific. Itis also likely that soot and fugitivedust will increase and that a signifi-cant rise in global carbon dioxideinputs will ensue.

Publications

Elliott, S., et al., "Atmospheric Effectsof the Emerging Mainland ChineseTransportation System" (to bepublished in J. Atmos. Chem.).


Geometrodynamics in Supportof Gravity Wave Astronomy

Raymond Laflamme

The exciting feature of the emerg-ing field of gravity wave astronomy isthat these waves will allow us toprobe deeper into cosmic events thanwe can by any other known means.While it is true that the parameterizedpost-Newtonian calculations havebrought us far toward supporting sucha probe, nevertheless, any integratedeffect of cosmic coalescence will nodoubt require the numerical solutionof Einstein's equations.

We propose to solve Einstein'sequations by employing the innova-tive and beautifully geometricapproach known as Regge calculus(RC) in which the curved space-time

geometry is modeled by a lattice offour-dimensional triangles (simplices)in direct analogy with the two-dimensional triangulated nature of ageodesic dome. Recent developmentsin RC promise to make this trulyindependent tool numerically superioras compared with the finite-differenceapproaches. We are exploiting theunique geometric properties of RCand applying this numerical techniqueto the analysis of astrophysicallyrelevant gravity wave generation andits subsequent detection by the LaserInterferometry Gravitational Observa-tory (LIGO).

Remote Sensing of ThundercloudElectric-Field Airglow

Joseph Borovsky

We predict that strong electric fieldswill enhance the cosmic-ray-producedbackground of airglow. The objectivesof this project are to experimentallyconfirm the electric-field enhance-ment of the cosmic-ray-producedairglow near thunderclouds withphotometers, measure the magnitudeof the enhancement with photometersand compare the measurements withmodels, and spatially image theregions of enhanced airglow aroundthunderclouds. These images mightallow a simple, reliable prediction oflightning.

In Fort Collins, Colorado, we madea ground-based campaign in thesummer of 1996 and obtained imagesof sprites and sprite tendrils abovethunderclouds and photometric dataof the sprites. We used three intensi-fied television cameras and onefiltered photometer. Presently we areanalyzing this data and preparing amanuscript.

We investigated the signature of theLund-Regge metric on spaces ofsimplicial three-geometries, which areimportant in some formulations ofquantum gravity. Tetrahedra can bejoined together to make a three-dimensional, piecewise, linearmanifold. A metric on this manifold isspecified by assigning a flat metric tothe interior of the tetrahedra andvalues to their squared edge-lengths.The subset of the space of squarededge-lengths obeying triangle andanalogous inequalities is the simpli-cial configuration space. We havederived the Lund-Regge metric onthis space and showed how it providesthe shortest distance between simpli-cial three-geometries among allchoices of gauge inside the simplicesfor defining this metric (Regge gaugefreedom).

We showed analytically that there isalways at least one timelike directionin simplicial configuration space andprovided a lower bound on thenumber of spacelike directions. Wepropose to further evaluate thesignature numerically for the simpli-cial configuration spaces based onsome simple triangulations of thethree-dimensional sphere (S3) andtorus (T3). For the surface of a four-simplex triangulation of S3, we findone timelike direction and all the restspacelike over all of the simplicialconfiguration space. For the triangula-tion of T3 around flat space, we finddegeneracies in the simplicialsupermetric as well as a few gaugemodes corresponding to a positiveeigenvalue. We propose to extend thistriangulation to a 600-cell model of athree-dimensional sphere. At eachstage, we compared our results withthe known properties of continuumsuperspace.

Publications

Hartle, J.B., W.A. Miller, and R.M.Williams, "Signature of the SimplicialSupermetric" (submitted to Class.Quantum Grav.).


Accretion onto Black Holes:The Power-Generating Mechanism

Warner Miller

Most objects in the observableuniverse have a reasonable explana-tion in terms of physics, although thedetails in depth may be missing orinconsistent. The outstanding few forwhich the basic concept is still elusiveare gamma-ray bursts and thecombination of quasars, so-calledactive galactic nuclei (AGN), andtheir associated collimated radiosources or jets. Our project is directedtowards a consistent model of AGNand their jets. The most likely ex-planation of AGN is accretion onto ablack hole from a Keplerian accretiondisk, which is almost a uniqueexplanation of the frequently ob-served, double-peaked, ultravioletemission lines due to near-relativisticvelocities in the disk.

We emphasized the physicalrelationships among the variousphenomena: accretion disks, quasars,black holes, collimated radio sources,and galactic dynamos. Previously,these topics had been only weaklyrelated without explicit cause andeffect. We have constructed a modelof the physical evolution from large,primordial density perturbations to"damped" Lyman-alpha clouds, togalaxy formation, to black holes, jets,and the galactic dynamo. We havederived the general relativisticdistortions of radiation emitted fromclose to the black hole, therebyobtaining a new observational test ofthe central engine. See the accompa-nying two diagrams and the image forexemplary information about theAGN model.

The physics of accretion disks, theastrophysical dynamo, and magneticreconnection are the least understoodphysical phenomena in astrophysics.They are still less understood in thegeneral relativistic field close to theblack hole. This lack of physicalunderstanding frustrates a quantitativeevaluation of observations that define

the evolution from the early universeto star formation. We have madeprogress in this understanding.

Publications

Bromley, G.C., K. Chen, and W.A.Miller, "Line Emission from anAccretion Disk around a RotatingBlack Hole: Toward a Measurementof Frame Dragging," Astrophys. J.475, 57 (1997).

Bromley, B.C., K. Chen, and W.A.Miller, "Rotation of the SupermassiveBlack Hole in MCG-6-30-15"(submitted to Astrophys. J.).

a.-0.07Lyman a Cloud

i= 0.001 a/cm2

contraction =!

Bar Instability

=3/2

Faster rotationi contraction

Contractionand merger

X>QA

Tidal torquetransfers angularmomentum

Accretion Disc

= 107

GravitationalSeparation

Thickness = x =

lOtoioog/cm2Black Hole

KBI/2 / . ,1p O t e n t i a l

dJ/J = dM/MJ = M » vR.-. v = M/R =const J if Kep.-. M <* R

Thicknessx = M/R2 oc M't = 100,M=10

-1

The collapse of a Lyman-alpha cloud of about 1012 M@ (M@ = solar mass). Thecloud is subject to barlike instabilities that form the bars during collapse and causethe bars to break up into smaller bars. The smaller bars collapse further and rotatefaster. The mass of the arms of the smaller bars then torque the larger mass (m) atlarger radii of the larger bars, and an exchange of angular momentum takes place.The angular momenta (J) scales such that dJ/J - dm/m. Then, the Keplerianvelocity of the orbits of it is a constant. This constant velocity, independent ofradius, is what is observed for almost all galaxies and leads to what is called aflatrotation curve and the prediction of dark matter. This scaling also leads to the mass(10 8M&) at which an accretion disk forms at the center of the galaxy; M@ is whatis needed to make the massive black hole.


Stars that continuously collide(104 times) with the accretion disk(described in the previous figure)before disruption. These collisionsexplain the "broad emission lines"observed from quasars. Each collisionmakes a large plume of matter torn losefrom the disk that will rise far above thedisk. This plume will entrain anytoroidal magnetic flux embedded in thedisk. The expanding plume increases itsmoment of inertia and so will rotatemore slowly than the rotating frame ofthe disk. This relative rotation of theplume and the disk twists any entrainedmagnetic flux, giving rise to the"alpha" effect in the alpha-omegadynamo. The omega deformation is theshear in the rotation rate of matter as afunction of the radius of a Kepleriandisk. This dynamo should make enoughmagnetic flux in the age of the disk,10 8 years, to fill the galaxy with the

observed galactic field of 3 x lOr6 G.

Disk Dynamo

rotated trappedtoroidal flux

Expanding collision plume(Broad emission lines)

PoSloidal quadrapolebias fie

Black hole Inner radiusa t 6 M

Accretiondisk

Star in orbitaround Blackhole

Image of a geometrically thin andoptically thick accretion disk arounda maximally rotating black hole ofmass M. The inner radius and outerradius are at 1.25 M and 10 M,respectively. This accretion disk isviewed at a 75° inclination. Thefalse-gray-scale contour mapindicates the ratio of observedfrequency to emitted frequency; thedark, oval, shaded region at the toprepresents blue shift, and the bandsaround the radius indicate a redshift. The white (saturated) patchsuperimposed on the map containsthe zero-frequency-shift contour.


Thermal Rocketing and the LaserGeodynamic Satellite (LAGEOS-I)

Warner Miller

LAGEOS-1 is the most accuratelytracked satellite in orbit. It is a totallypassive, dense, spherical satellitecovered with 426 retroreflectors,which cause laser light to be reflectedand returned along paths parallel tothose of the corresponding incidentrays. Besides its great utility inmeasuring the length of Earth's dayand the polar wobble, this satellite canbe used to measure, for the first time,the general, relativistic frame-dragging effect of Earth. This frame-dragging effect causes the inertialframes surrounding Earth to precessand is the gravitational analogue of adipole magnetic field generated by arotating current of charges.

Of the five dominant sources forerror in measuring Earth's frame-dragging effect, the largest oneinvolves interaction of the thermalforces on the surface of the satellite(or thermal rocketing) and theinfluence of such interaction on thenodal precession. The objective of ourproject is to enhance an alreadyavailable code developed at LosAlamos to fit new optical-spin datarecently obtained at the University ofMaryland.

Enhancing our code involves threeimportant tasks: (1) creating a morerealistic model of Earth's magneticfield, (2) including the tidal preces-sion on the line of nodes of thesatellite, and (3) estimating the effectof the true geometry of LAGEOS-1

on our model predictions. Theresulting code will then be used tomodel the new optical-spin data. Bypredicting how thermal forces willcause the satellite's orbit to change,the code will predict the futureorientation of the satellite.

This year, we completed the firsttwo major tasks, and we used the codeto provide the first numerical modelof the spin dynamics of LAGEOS-1.The results were consistent with theobservations made at the Universityof Maryland. In particular, the drift ofthe spin axes of LAGEOS-1 towardthe North Pole was correctly modeledfor the first time. In addition, our codepredicts a spin-orbit resonance phasethat can dramatically affect theorientation of the satellite.

Our current code (including theenhancements completed this year) ismore advanced than any other in thefield. It will serve as the new spin-dynamics model for future LAGEOSsatellite missions.

Plasmasphere Refilling: New Numericaland Observational Tools

Dan Winske

The outflow of plasma from theionosphere and its interactions withinthe inner regions of the magneto-sphere remain important problems inspace physics. While outflow is acontinuous process, it becomes evenmore important after geomagneticsubstorms, when magnetic field linesthat have been vented of plasma arereconnected and the empty flux tubesare refilled with outflowing plasma.The purpose of this project is todevelop new computational, theoreti-cal, and observational tools to studythe dynamics and heating associatedwith the plasma outflow and refillingprocesses.

We developed new numerical toolsto model the transition from colli-sional plasma flow at low altitudes(-200 km) to collisionless behavior athigh altitudes (-4000 km) and

incorporated these tools in amultispecies kinetic model of theoutflow process. We also investigatedelectromagnetic instabilities in theouter magnetosphere to understandtheir contribution to the heating ofupflowing protons and minority ions(such as helium). In addition, we haveused new observational techniques toanalyze low-energy plasma data fromsatellites in geosynchronous orbit andto assess the effect of a spacecraft'selectric potential (typically a fewvolts) on these data.

Publications

Gary, S.P., M.F. Thomsen, et al.,"Electromagnetic Proton CyclotronInstability: Interactions with Protons,"J. Geophys. Res. 100, 21961 (1995).

Gary, S.P, V. Vasquez, and D.Winske, "Electromagnetic ProtonCyclotron Instability: Proton VelocityDistributions," /. Geophys. Res. 101,13327 (1996).

Gary, S.P., L. Yin, and D. Winske,"Electromagnetic Proton CyclotronInstability: Heating of CoolMagnetospheric Helium Ions," Ann.Geophys. 14, 1 (1996).

Jones, M.E., D.S. Lemons, RJ.Mason, et al., "A Grid BasedInterparticle Collision Model for PICCodes,"/ Comput. Phys. 123,169(1996).

Lemons, D.S., J. Lackman, et al.,"Noise-Induced Instability in Self-Consistent Monte CarloCalculations," Phys. Rev. E. 52, 6855(1995).

Miller, R.H., C.E. Rasmussen, M. R.Combi, et al., "PonderomotiveAcceleration in the Auroral Zone: AKinetic Simulation," /. Geophys. Res.100,23916(1995).


Time-Reversal Tests inPolarized Neutron Reactions

J. David Bowman

The goal of this project is todevelop cells of polarized 3He to useas polarizers and analyzers of neutronspin. The interaction of polarized 3Hewith neutrons is highly spin depen-dent. Neutrons that have their spinparallel to the 3He polarization areabsorbed. The 3He nuclei are polar-ized when cells containing rubidiumvapor are illuminated with circularlypolarized light from diode lasers. Thevalence electron in the rubidium atomabsorbs the laser light and becomespolarized. The atomic polarization istransferred to the 3He nuclei by

collisions. In order to use thesepolarizers and analyzers in tests oftime reversal, it is necessary toconstruct cells, polarize the 3He, andmeasure the polarization of theneutrons after passage through thecells.

We have built the apparatus neededto produce cells of polarized 3He. Thisapparatus incorporates diode lasers,optics, Helmholtz coils, nuclearmagnetic resonance pickup coils, andlock-in amplifiers. We are developingcells in which the natural boron in theglass is replaced by isotopically

Nuclear andParticle Physics

separated n B . These cells are neededfor work with cold neutrons becausethe absorption cross section of naturalboron for low-energy neutrons islarge. We have measured the polariza-tion of neutron beams polarized by3He with an accuracy of 1% by usingthe parametric relationship betweenthe transmission of neutrons throughthe cells and their polarization. Wehave developed the apparatus andtechniques needed to improve theaccuracy to 0.1%. The accompanyingfigure shows the measurementapparatus.

Publications

Bowman, J.D., and Y. Masuda, "TimeReversal Tests in Neutron-SpinOptics" (submitted to Phys. Rev.Lett.).

source beammonitor

backgroundwheel

He-3 cells:- polarized- unpolarized

neutrondetector

CZZ3

Tcollimator

Apparatus to measure precisely the polarization of a neutron beam prepared by a 3He polarizer. The Manuel Lujan Jr.Neutron Scattering Center neutron source produces a short, intense pulse of neutrons having a broad range of energies.The neutron energy is precisely measured by observations of the time it takes each neutron to reach the detector, located56 mfrom the source. The polarized 3He cell and a dummy cell are alternately placed in the beam. The ratio oftransmissions, R(0), is measured with the 3He cell unpolarized. The 3He cell is polarized, and the ratio R(p) is measured.The polarization of the neutron beam, P, is then obtained as P = [1+{R(O)/R(p)}2]1/2.

Individual Projects—Nuclear and Particle Physics 103

Exploring and Testing theStandard Model and Beyond

Geoffrey West

In this project we are primarilyworking to understand, and ultimatelyto explore, the limitations of theuniversally accepted Standard Modelof elementary particles, whichincorporates their strong andelectro weak interactions. As anoutgrowth of that, we are investigat-ing possibilities for unifying all of thefundamental forces of nature, includ-ing gravity. We anticipate that suchfrontier research will have phenom-enological implications for prospec-tive programs and experiments.

Last year we worked on theunification of the concepts of scalingand fractals with the renormalizationgroup. This year we extended ourwork to give a fractal description ofthe nucleon in a generalized quantumchromodynamics (QCD) partonmodel to biophysical systems such asthe cardiovascular and respiratorysystems.

We showed how duality insupersymmetric QCD follows fromnonpertubative instanton configura-tions. We estimated the masses oflight quarks using lattice QCD—ourestimates are considerably smallerthan the values commonly used andhave important implications for thecharge-parity-violating parameters.Also this year, we continued toexplore the interface of quantum andclassical chaos based on our discoveryof semiquantum chaos, and wecontinued work on the conformalanomaly, proving the effects of thetheory. We wrote several majorreviews, some in response to solicita-tions. We were also invited to givetalks on our work at many majorinstitutions worldwide as well as atinternational conferences and work-shops.

Publications

Anglin, J., and S. Habib, "ClassicalDynamics for Linear-Systems: TheCase of Quantum Brownian-Motion,"Modern Phys. Lett. A 11, 2655(1996).

Bender, CM., F. Cooper, and P.N.Meisinger, "Spherically SymmetricalRandom-Walks . 1. Representation inTerms of Orthogonal Polynomials"Phys. Rev. E 54 (1), 100 (1996).

Cooper, R, Y. Kluger, and E. Mottola,"Anomalous Transverse-Distributionof Pions as a Signal for theProduction of Disoriented Chiral,"Phys. Rev. C 54 (6), 3298 (1996).

Dorey, N., and M.P. Mattis,"Lagrangians, to Chiral Bags, toSkyrmions with the Large-N-CRenormalization-Group," Phys. Rev.D 52, 2891 (1995).

Dorey, N., V.V. Khoze, and M.P.Mattis, "Multiinstanton Calculus inN-2 Supersymmetric Gauge-Theory,"Phys. Rev. D 54, 2921 (1996).

Dorey, N., V.V. Khoze, and M.P.Mattis, "Multiinstanton Check of theRelation between the Prepotential-Fand the Modulus-U in N=2 SusyYang-Mills Theory," Phys. Lett. B390, 205 (1997).

Dorey, N., V.V. Khoze, and M.P.Mattis, "A 2-Instanton Test of theExact Solution of N=2 Super-symmetric QCD," Phys Lett. B 388,324 (1996).

Habib, S., E. Mottola, and P.Tinyakov, "Winding Transitions atFinite Energy and Temperature: An0(3) Model," Phys. Rev. D 54 (12),7774 (1996).

Lampert, M.A., J.F. Dawson, and F.Cooper, "Time Evolution of theChiral Phase-Transition during aSpherical Expansion," Phys. Rev. D54 (3), 2213 (1996).

L3 Physics at the Z Resonanceand a Search for the Higgs Particle

W. Kinnison

This project is a study of theStandard Model of electroweakinteractions using the L3 detector ofthe Large Electron-Positron Collider(LEP) at the European Center forNuclear Science. During the reportingperiod, we developed a new methodof vertex finding that is applicable formost colliding-beam, high-energyphysics experiments, and we used themethodology to analyze L3 data for apublished paper on Rb, which is ameasure of the amount of b-quarkproduction in hadronic decays ofthe Z°.

To carry out the analysis, weinvested a considerable amount ofeffort in improving the alignment

information and analysis techniquesfor several components of the L3detector including the "z chambers,"which had never before been usedsuccessfully to analyze L3 data.Additionally, we used the siliconmicrovertex detector—which LosAlamos had a major role in propos-ing, designing, building, and commis-sioning—for its first time in making acomplete physics analysis. Both theimprovements in the overall analysisof L3 data and the specific newvertex-finding algorithms that wedeveloped are now being used by theentire L3 collaboration in many newphysics analysis projects, includingb-meson tagging, which is requiredfor the Higgs meson search at LEP.

104 Los Alamos FY1996 LDR.D Progress Report

Neutrinos and Theory of WeakInteractions

Joseph Carlson

We are studying low-energymeasurements of parity violation innuclear systems, astrophysicalreactions involved in solar neutrinoproduction, neutrino interactions, andtime-reversal violation in extensionsto the Standard Model.

Parity Violation in Few-BodySystems. We are analyzing theprospects for measuring the parity-nonconserving asymmetry A inpolarized neutron-plus-protonradiative capture at the Los AlamosNeutron Science Center (LANSCE).The goal of the experiment is toextract a definitive value for the weakpion-nucleon coupling constant.Experimental work to date hasproduced only upper limits to thiscoupling.

We have calculated the parity-conserving contributions to A, whichhad been tacitly assumed to benegligible. We have shown thatexperimental "tricks" are required tosuppress this contribution to A belowthe 108 level sought in our experi-ments. We have also performed amicroscopic analysis of parityviolation in the transmission ofpolarized ultracold neutrons throughhelium. At these energies, the parity-violating neutron-neutron interactionresults in a spin rotation in thepolarized neutrons. We performedmicroscopic five-body calculations ofneutron-alpha scattering usingrealistic two- and three-nucleoninteractions. We continue to find thatthe pion-exchange term is dominant,but with the opposite sign to thatpredicted in simple models.

Time-Reversal Violation. The mosteconomical explanation of charge-conjugation parity (CP) violation inthe Standard Model is given by thephase delta of the Kobayashi-Maskawa model. One can search foradditional CP-violating interactions in

extensions of the Standard Model bydetermining observables where theeffects of delta are suppressed. In theKobayashi-Maskawa model, CP-violating effects in beta decay (and inother semileptonic processes) arisealso only in second order in the weakinteraction.

We have calculated the contributionof delta to the T-odd D- and R-correlations in beta decay. Thesecorreleations are time-reversal-oddscalar products of the momentum ofthe electron and neutrino and thenuclear spin. We find D = 10~12 andR = 10~14, compared with the bestpresent experimental limit of 10"3. Wehave calculated D and R also for thetheta-tenn in the quantum chromody-namics Lagrangian, a second sourceof CP violation in the StandardModel. With the present experimentallimit for theta, we obtain D =10~14 andR = 1012. The small values of D andR in the Standard Model leave a largewindow in which to search for newtypes of CP-violating interactions. Wehave also investigated scalar-type,CP-violating, muon-quark charged-current interactions in extensions ofthe Standard Model These interac-tions contribute to T-odd observablesin muon capture, which provideinformation complementary to thatprovided by nuclear beta decay.

Neutrino Properties and Interac-tions. We extended our theory of anadditional scalar interaction to formsinvolving three neutrinos. Theadditional coupling introduced doesnot alter the successful phenomenol-ogy of the Standard Model. We findthat there is a repulsive effect from thescalar field of a large vacuum-massneutrino on the local density of a lightvacuum-mass neutrino. The result isthat the neutrino clouds we foundpreviously may have a complexinternal structure, such as consistingof spherical annuli (with gaps)

surrounding a central cloud. Becausethe effective masses of the neutrinosmay become equal and opposite in theregions in which the scalar fieldstrength is rapidly varying, enhance-ment of neutrino-mixing oscillationsmay occur in such regions.

Publications

Goldman, T, "Source Dependence ofNeutrino Oscillations" (to bepublished in Phys. Lett. B; alsoavailable from the LANL E-Printarchive at http://xxx.lanl.gov asdocument hep-ph/9604357).

Herczeg, P. "Searches for T-OddInteractions in Nuclear Processes," inDark Matter in Cosmology, Clocks,and Tests of Fundamental Laws, Proc.of the XXX Rencontre de Moriond, B.Guiderdoni et al., Eds. (EditionsFrontieres, Gif-sur-Yvette, France,1995), p. 477.

Herczeg, P., "A Note on Limits onNew Interactions from the 7t—w(e)/jr—>(iv Branching Ratio," Phys. Rev.D 52, 3949(1995).

Herczeg, P., "Theoretical Aspects ofSearches for Time Reversal in NutronTransmission," in Parity and TimeReversal Violation in CompoundNuclear States and Related Topics,J.D. Bowman and N. Auerback, Eds.(World Scientific, Singapore, inpress).

Herczeg, P., "Time Reversal Violationin Nuclear Processes," in Symmetriesand Fundamental Interactions inNuclei, W.C. Haxton and E.M.Henley, Eds. (World Scientific,Singapore, 1995), p. 89.

Lowe, J., B. Bassalleck, H. Burkhardt,et al., "No Lambda Oscillations" (tobe published in Phys. Lett. B; alsoavailable from the LANL E-Printarchive as document hep-ph/9605234).

Stephenson, G.J., T. Goldman, andB.H.J. McKellar, "Neutrino Clouds"(to be published in Phys. Rev. D; alsoavailable from the LANL E-Printarchive as document hep-ph/9603392).

Individual Projects^Nuclear and Particle Physics 105

Weak Interaction Measurements withOptically Trapped Radioactive Atoms

David Vieira

The main objective of our project isto develop the technology that willultimately allow a high-precision testof electroweak interactions in atomicnuclei. To achieve this, we arefocusing our efforts on the beta-asymmetry measurements of polar-ized S2Rb (t1/2 = 75 s). The keytechnology needed to undertake thiswork is the efficient optical andmagnetic trapping of radioactive

atoms. A magneto-optical trap (MOT)consists of six circularly polarized,counterpropagating laser beams,which, in combination with a pair ofanti-Hehnholtz coils, enable thecooling and trapping of atoms. Ahigh-intensity MOT can easily trap1010 atoms out of the vapor state (seethe first figure); however, the trappingof radioactive atoms requires that thetrapping process also be efficient.

We have taken two steps to ensurehigh trapping efficiency. The first stepis to use a special nonstick octa-decyltrichlorosilane (OTS) dry-filmcoating on the glass trapping cell toprevent the "sticking" of alkalispecies to the walls. Using the OTS-coated glass cell shown in the secondfigure, we have measured a trappingefficiency of 20% (see the thirdfigure). This efficiency exceedscurrently published trapping efficien-cies by a factor of 3 and reflects theimproved trapping geometry of ourMOT. The second step involves gas-free sample loading using a mass-separator ion implantation and releasemethod. To this end, we have recentlycoupled a MOT to an existing, andnow upgraded, mass separator. We

An infrared picture of afluorescing cloud of~10w cesiumatoms trapped in a high-intensity,magneto-optical trap. Thepancake-shaped cloud isapproximately 15 mm in diam x10 mm thick.

A picture of a dry-film-coated glass cell (50-mm cube)with two remotely controlled glass valves used in theMOT measurements of trapping efficiency. The valve onthe left is connected to a cesium reservoir, and the valvein the background is connected to a 20-L/s ion pump.


have made good progress in implant-ing and releasing stable rubidiumspecies, and the high-efficiencytrapping of 82Rb is near at hand.

Publications

Vieira, D.J., R. Guckert, D.W.Preston, et al., "Parity Non-conservation Measurements inRadioactive Atoms: ExperimentalDevelopments," in Proc. 4th Int.Symp. on Weak & EM Interactions inNuclei, H. Ejiri, T. Kishimoto, and T.Sato, Eds. (World Scientific,Singapore, 1995), p. 97.

Guckert, R., E.P. Chamberlin, D.WPreston, et al., "Coupling an OpticalTrap to a Mass Separator" (to bepublished in Nucl. Instrum. Meth.Phys. Res. B).

7

6

5

8 4

§$ 3

2

1

0

close Cs reservoir

close valveto pump &drop £*toms

10

Results of fluorescence-derived efficiency measurements. The upper trace in theupper figure shows the trap filling as the valves to the cesium reservoir and ionpump are both open. At 5 s, the valve to the cesium reservoir is closed, and thefluorescence signal drops as atoms are slowly lost from the trap and untrappedcesium atoms are pumped out. At 7 s, the fluorescence signal is dominated bythe number of trapped atoms, and the height of this signal measures theirnumber. The trap is then turned off by shuttering the trapping laser light andturning off the magnetic field. At 7.5 s, the trap is turned back on and it refills.The relative height of the fluorescence signals measures the trapping efficiency.The bottom trace in the upper figure measures the background fluorescencesignal obtained when the magnetic field is reversed in the nontrappingdirection. The bottom figure shows the differences between the two traces givenin the upper figure. A 20% retrapping efficiency is determined.


Neutrino Physics at Fermilab

Fred Federspiel

The Los Alamos liquid scintillatorneutrino detector (LSND) has recentlyreported strong evidence for neutrinooscillations (and, hence, neutrinomass). If verified, this result will haveprofound consequences for nuclearand particle physics, cosmology, andastrophysics. We plan to carry out anexperiment at Fermilab to verify theLSND result and accurately determinethe parameters of the oscillations.

There has been considerable recentprogress in the development of high-speed, charge-coupled detector arrays

at Los Alamos. We are investigatingthe application of this new technologyto particle physics detectors. Thispromising new idea could potentiallyrevolutionize the field of neutrinophysics by enabling the constructionof massive, highly segmenteddetectors at a cost of -100 times lessthan a similar-sized, conventionallyinstrumented detector.

Our progress to date has been inthree areas: (1) design of a neutrinoproduction facility; (2) calculation of

expected signal and background rates;and (3) design and simulation of adetector. Our baseline design for theneutrino production facility has metits design goal of providing a puremuon-neutrino beam with contamina-tion less than 0.5% electron neutrinos.The calculation of background rateshas allowed us to establish thefollowing particle identificationrequirements for the detectors: fewerthan 0.1 % of muons along with fewerthan 1% of pions may surviveelectron selection criteria. Now thatwe have established these designgoals for the detector, we are pursuingthe development of capable detectortechnologies.

A Continuous Watch of the Northern Skyabove 40TeV with the CYGNUS Array

Cyrus Hoffman

We have been using the CYGNUSair-shower array to search for epi-sodes of ultra-high-energy (UHE,>40 TeV) gamma-ray emission fromastrophysical objects. Given that suchemissions are only sporadic, it isimportant to keep a continuous watchon the sky. The array operated wellduring most of FY 1996 to allow ourresearch, but in August 1996 a fatalhardware error occurred in theCYGNUS data-acquisition computer,shutting down the experiment.

We could not continue the CYG-NUS experiment after the repairbecause a more powerful detector,Milagrito (a prototype for the Milagrodetector), had been installed.Milagrito will be available for datataking later in the fall of 1996.Because of its lower energy threshold(-500 GeV), this new detector ismuch more sensitive than CYGNUSto gamma-ray emission from astro-physical objects; our sky watchexperiment for UHE gamma-ray

bursts will continue when Milagritocomes on-line. At this time, theanalysis of the CYGNUS data showsno evidence of UHE emission fromany source.

We have also used the pools atCYGNUS to experimentally test theconcept of searching for gamma-rayemissions from gamma-ray bursts bymonitoring the single rates of indi-vidual photomultiplier tubes in awater Cerenkov counter. The resultsof these tests are encouraging. Ifsuccessful, this method should beapplicable to both Milagrito andMilagro and should enhance thesensitivity of these detectors toemissions from gamma-ray bursts.

Neutron Measurements to OptimizeTreatment of Cancer Patients with FastNeutrons

John Ullmann and Robert Haight

Data for the interaction of neutronswith biological elements are impor-tant for radiation therapy and radia-tion protection dosimetry. Data forcarbon, and especially oxygen, aregreatly needed. We have set up asystem for detecting charged particles

produced by neutron interactions inthe energy range up to 150 MeV. Anew beam line and new electronicshave been developed at the WeaponsNeutron Research facility of the LosAlamos Neutron Science Center(LANSCE). We are beginning to

characterize the experimental appara-tus and approach and to take prelimi-nary data. This capability will put usin a good position for proposing alarger experimental program in FY1998. Some interest has been shownin our capabilities by the AcceleratorProduction of Tritium program.

Publications

Chadwick, M.B., P.M. DeLuca Jr.,and R.C. Haight, "Nuclear DataNeeds for Neutron Therapy andRadiation Protection" (to be publishedin Radiation Protection Dosimetry).


Antiquark Distributions in the Proton

Jen-Chieh Peng

The study of quark and antiquarkdistributions in the nucleon has been amajor endeavor in nuclear and particlephysics. Results from a recent deep-inelastic scattering experimentsuggest the surprising possibility thatthe up-and-down antiquark distribu-tions in the proton are not symmetric.We can directly determine theantiquark distributions in the protonby comparing the Drell-Yan crosssections on hydrogen versus deute-rium targets. A new experiment(E866) is in progress at Fermilab tocarry out such measurements.

We are performing E866 with an800-GeV proton beam, together with

a high-resolution, high-rate magneticspectrometer. Other experiments donot match the expected statisticalaccuracy and range of coverage in x(fraction of nucleon momentumcarried by the antiquark). E866 willhave sufficient accuracy to test alltheoretical models that predictasymmetric up-and-down antiquarkdistributions. We will also obtainadditional data on the production ofJ/\\f and v resonances (bound states ofheavy quarks) in E866.

The E866 has been taking datasince September 1996. Preliminaryresults show that the apparatus isworking very well. We anticipate

having at least six months of beam,which will allow us to achieve thesensitivities for a definitive measure-ment of flavor symmetry of seaquarks in the proton.

Publications

Melnitchouk, W, and J.C. Peng,"Large-x d/u Ratio in W-BosonProduction" (submitted to Phys.Lett).

Peng, J.C., and D.M. Jansen, "Probingd/u Asymmetry in the Proton Via Wand Z Production," Phys. Lett. B 354,460 (1995).

Peng, J.C., D.M. Jansen, and Y.C.Chen, "Probing the d/u Asymmetry inthe Proton Via QuarkoniumProduction," Phys. Lett. B 344,1(1995).

Nucleon-Nucleon Data Analysis

Michael W. McNaughton

The objective of this project wasto analyze and publish two sets ofnucleon-nucleon (NN) data. These arethe final sets of data to complete theset of NN measurements at the LosAlamos Meson Physics Facility(LAMPF) and determine the NN-scattering amplitudes from 485 to800 MeV.

These new data are the mostaccurate in the world, with precisionbetter than 1% and absolute accuracyabout 1%. With the inclusion of thesedata, all known ambiguities in thephase-shift analysis are resolved, andthe final phase-shift solutions areunique.

The measurements of the proton-proton (pp) elastic cross section are inexcellent agreement with previousresults from LAMPF. These data havestabilized the NN phase-shift analysisand determine the absolute normaliza-tion of both nucleon-nucleon and

nucleon nucleus data obtained atLAMPF over the past 20 years.

The analyzing power data resolvethe ambiguity in the absolute normal-ization of the LAMPF polarizedneutron beams. In addition, theystrengthen the conclusion that isospin-zero inelastic scattering is stronglycoupled to a pair of delta resonances,and is therefore very small at800 MeV, since 800 MeV is far belowthe mean energy of 1380 MeVrequired to create two deltas.

Publications

McNaughton, M.W., K.H.McNaughton, G. Glass, et al., "np-Elastic Analyzing Power AnO at 485and 788 MeV," Phys. Rev. C 53, 1092(1996).

Simon, A.J., G.Glass, M.W.McNaughton, et al., "Absolute pp-Elastic Cross Sections from 492 to793 MeV," Phys. Rev. C 53, 30(1996).


Solar Neutrino Physics

Andrew Hime

Our project focuses on extractingthe neutral-current signal from theSudbury Neutrino Observatory (SNO)using an array of ultralow-background3He proportional counters. In the pastyear, the neutral-current detector(NCD) project moved from the R&Dphase toward full-scale construction.Los Alamos has played the lead rolein defining the operating parametersand constraints for the NCDs,including requirements for gas fill andpurification and for optimizing thedetectors to collect the most signifi-cant data.

Much of our effort has focused ondesigning and constructing a largegas-handling system, which has beencombined with our main "NCDfactory." While the optimization ofoperating parameters is now essen-tially complete, in the coming year wewill continue our detector test-benchstudies to refine the front-endelectronics. This part of the project isrelated to our more general goal ofdeveloping data reduction andanalysis tools for detecting neutral-current signals.

Monitoring and controlling back-grounds are still significant aspects ofthe NCD program. Our radioassaysplayed an important role during thedesign phase and will be usedcontinuously during the productionphase to monitor detector compo-nents. Information on the radiopurityof detector construction materials isessential for extracting the neutral-current signal from SNO in thepresence of photodisintegrationbackgrounds.

We are continuing to study detec-tors at our low-background countingfacility at the Waste Isolation PilotPlant (WIPP). This work will help usestablish acceptable intrinsic back-grounds and contribute to the devel-opment of our signal extraction andpulse-shape discrimination techniques(see accompanying figure). Data fromour low-background experiments is

used in parallel with our detector test-bench studies to optimize our use ofdigitized waveforms to extract signalsand identify events. We are currentlyusing the information contained in thedigitized waveforms to extract in realtime the photodisintegration back-ground signals from the alphadistributions registered in the NCDs.In the upcoming year, we will extendthese activities to include more

sophisticated methods, such as event-by-event pulse-shape fitters, maxi-mum entropy techniques, and neuralnetworks, which promise to maximizeour ability to discriminate neutral-current events from backgroundsignals.

Publications

Hime, A., "The Sudbury NeutrinoObservatory" (Seventh InternationalWorkshop on Neutrino Telescopes,Venice, Italy, February 29-March 2,1996).

(sriCDCO3D.

'B

CO

rbit

-2-LU

4—

3 . 0 -

2 . 5 -

2 . 0 --

1.5--

1.0-

0 . 5 -

0 . 0 -

,

!]!i11

• 1 1 1 1 1 1 1

0

1.0-

-

0 . 8 --

0 . 6 ---

0 . 4 --

;

0 . 2 -

-

0-0 ~"(

1 1 1 1 1 1 1 1

1

i

-

TrTT|rrT)

, , , , i

jSjg|Gompton/Beta

* i^i£~——T~

i i i i i | i i i i 1

200 400Energy

, I I

Compton/Beta

I n [JL

• i i i I i i i i i i i i , 1 , , , , i , , , ,

^---~—~~~'~ToHe(n p)t'-'? -^

•-.••••,:Buik '}'••

'=y .''Alpha'"

• 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

•

\

-

' -

•

-

-

600 800 1000(keV). , . . i i , , i

1He(n,p)t 1

1111I1••1

•T Lf l Bulk Alpha •

• u

Ik.' • " i ' ' ' ' i ' ' ' niTi H200 400

Energy

n •

-

-

•

_

-

•

—

•

-

-

600 800 1000(keV)

Scatter plot demonstrating our pulse-shape discrimination capabilities usingevent topology from He(n,p)t events, bulk alpha activity, and gamma-inducedCompton electrons.


Chiral Symmetry in Finite Nuclei

David Madland

The goal of our project is tounderstand chiral symmetry in finitenuclei. As a first step, we havepublished the physical reasoning andprincipal evidence demonstrating therole of chiral symmetry in finitenuclei. To be able to continue thiswork, we have made the necessarychanges and additions to our twomain computer codes. We havemodified the generalized, nonlinear,least-squares, adjustment algorithmLACHI that determines the couplingconstants of the chiral Lagrangians.We have modified the algorithm by(1) introducing the covariance matrixin order to study the correlationsamong the various coupling constants;(2) redefining the chiral Lagrangiansso that their coupling constants form a

search vector whose elements are oforder unity if naturalness holds; and(3) deleting proton states that are onlyquasibound inside the Coulombbarrier. Given a set of couplingconstants, the predictive algorithmLANUC solving the Dirac-Hartreeequations self-consistently for eachtest nucleus has been made compat-ible with (2) and has the changespecified in (3).

We have also determined the mainelements (existing FORTRANroutines) that will be used to constructa new, nonlinear, least-squares,adjustment algorithm that will bemounted on an Ultra-SPARC worksta-tion. Finally, with the improved codes,we have found a new minimum chi-square for which seven of the nine

coupling constants are natural, asopposed to only six in our initialwork. In fact, the new value of chi-square is also lower, but the predictivepower is somewhat worse.

Publications

Friar, J.L., "Dimensional PowerCounting in Nuclei," (submitted toFew-Body Systems).

Friar, J.L., D.G. Madland, and B.W.Lynn, "QCD Scales in Finite Nuclei,"Phys. Rev. C 53, 3085 (1996).

Friar, J.L., G.A. Miller, and U.van Kolck, "The pp to pp.pi-zeroReaction near Threshold: A ChiralPower Continuing Approach," Phys.Rev.C 53, 2661 (1996).

Van Kolck, U., J.L. Friar, and T.Goldman, "PhenomenologicalAspects of Isospin Violation in theNuclear Force," Phys. Lett. B 371,169 (1996).

Simulating the Decays of Bottomand Charm Mesons

Tanmoy Bhattacharya

Our objective is to carry out adetailed study of the decay propertiesof bottom and charm mesons bysimulating the Standard Model ofstrong interactions on the lattice. Webelieve that the capabilities of themassively parallel machine, CM5, atthe Advanced Computing Laboratory(ACL) will allow us to producedefinitive predictions in this field, andput the standard model to stringenttests in present and proposed experi-ments. In addition, we shall work inclose collaboration with the staffscientists at the ACL to help develophardware and software optimizationtools and graphics, which willcontribute significantly to theLaboratory's growth as a forerunnerin advanced computing.

During the reporting period, wedeveloped the code required tosimulate the bottom quark on a latticewith a view to carrying out a detailedstudy of the decay properties of thebottom and charm mesons. The codewas developed in close collaborationwith the ACL on the CM5 there. Thecode uses the nonrelativistic formula-tion of quantum chromodynamics tosimulate the heavy quarks and the0(a) improved light fermions on a1 6 x 1 6 x 1 6 x 4 8 lattice. The physicsanalysis is done combining these twotypes of quarks together to study theproperties of hadrons made up ofheavy-heavy, heavy-light, and light-light quarks. We have so far analyzed75 lattices and have preliminary

results (based on this data set for themass spectrum and decay constants ofheavy-light mesons). We are now inthe process of adding in the physicsanalysis for the study of semileptonicform factors and matrix elements of4-fermion operators and increasingthe statistical sample size.

Publications

Ali Khan, A., and T. Bhattacharya,"B and Be Mesons with NRQCD andClover Actions" (to be published inInternational Symp. on Lattice FieldTheory Proc).

Individual Projects—Nuclear and Particle Physics 11 I

Nonequilibrium Dynamics of the Quark-Gluon Plasma in Heavy-Ion Collisions

Emil Mottola

We have developed field theory andnumerical methods for the generalproblem of quantum back reaction onclassical fields, with applications to awide variety of physical systems. Ourmain focus was on particle productionprocesses in the time evolution of thequark-gluon plasma following anultra-relativistic heavy-ion collision.In particular, we studied in somedetail the evolution of a disorientedchiral condensate (DCC) produced inthe chiral phase transition of nuclearmatter in heavy-ion collision experi-ments, as shown in both accompany-ing figures.

We have also studied dissipationand decoherence due to particleproduction in time-varying meanfields. We modified numerical codespreviously developed for particleproduction in strong electric fields inquantum electrodynamics for thequantum chromodynamics problem.We have made specific predictions forenergy-momentum flow and pionproduction in the central rapidityregion of experiments to be performedat the Relativistic High-IntensityCollider.

Publications

Cooper, R, Y. Kluger,"Nonequilibrium Dynamics ofSymmetry Breaking in Lambda Phi4

Field Theory" (to be published inPhys. Rev.).

Cooper, R, Y. Kluger, et al.,"Quantum Evolution of DisorientedChiral Condensates," Phys. Rev. D 51,2377 (1995).

Cooper, R, E. Mottola, et al.,"Anomalous Transverse Distribu-tion of Pions as a Signal for theProduction of DCCs," Phys. Rev. C54, 3298 (1996).

Habib, S., Y. Kluger, et al.,"Dissipation and Decoherence inMean Field Theory," Phys. Rev. Lett.76,4660 (1996).

•oUJ

&

150.0

100.0

50.0

n ft

/ /.//

mean

IA\>

/ /--/

field

v~—^\-v—

\V

dc/dx=-l initial

approximation

Tc=m

conditions

^ Jo=1.4m

0.0 2.0

kperp

4.0

Signature of the chiral phase transition in heavy-ion collisions. The curve labeled "mean field approximation" is theexpected distribution of pions as a function of momentum perpendicular to the collision axis if a region of DCC isproduced in the collision. For comparison, the other two curves are the pion distributions expected from strict adiabaticevolution from equilibrium at two different temperatures.


30

e

II

C 10

\ If =92.5 MeV

••• T=1.0— T=1.66

t=2.83- i=4.80

1=7.92-- -c=12.96

x=19.29

0.5

2 -

1 -

1.5

• v

-

\

. . • 1 • . . .

-

IIQ.

0.5 1.5

Particle number distributions as functions of transverse (p) and longitudinal (k^) momentum for initial conditionscorresponding to the formation of DCC (upper panels) compared with the locally thermal equilibrium number density nt

(lower panels). Notice the strong enhancements at lowp and low k^ in the case where DCC is formed in the collision event.

Determination and Study of Cosmic-RayComposition above lOOTeV

Constantine Sinnis

The origin of cosmic radiation haseluded researchers for nearly acentury. The composition of cosmicrays is perhaps the single mostimportant clue to their origin. Becauseof the low flux of the cosmic rays,measurements above -10 TeV mustbe done with ground-based detectors.

We are exploring the feasibility ofusing a new approach to ground-basedobservations. We have added anexperimental capability to theCYGNUS extensive air shower array

at Los Alamos to allow simultaneousground-based measurements of (1) theCerenkov radiation produced in acosmic-ray-induced air shower and(2) the electron and muon densities.The Cerenkov photon density -100 mfrom the air-shower core provides arelatively robust measurement of thecosmic-ray energy. The steepness ofthe lateral distribution of the Ceren-kov radiation and the muon content ofthe air shower depend on the compo-sition and energy.

In the past year, we successfullyacquired data from a second observa-tion period of an air shower. The new-event sample is a factor of six largerthan had previously been available.Since the end of the second observa-tion period, we have dismantled theexperimental setup, and we haveconcentrated our effort on performingthe final detailed analysis of the dataand improving the shower-reconstruc-tion algorithms. We have almostcompleted this work and will soonbegin the final analysis of cosmic-raycomposition using the combinedCerenkov, scintillator, and muon data.

At the 24th International CosmicRay Conference in Rome, Italy, wepresented preliminary results from thefirst year's data.

Individual Projects—Nuclear and Particle Physics I 13

Nonperturbative Estimates of theStandard Model Parameters

Rajan Gupta

Our project involves a comprehen-sive study of Standard Model physicsusing large-scale simulations of theunderlying quantum field theory. Withthe advent of massively parallelcomputers, lattice quantum chromo-dynamic (QCD) calculations arereaching a quantitative and predictivelevel. In the past year, we finished acomprehensive analysis of standard-model phenomenology-basedsimulations of lattice QCD on largelattices of size 32 x 32 x 32 x 64 andwith high statistical precision. Weobtained and published state-of-the-art results for the hadron spectrum,meson-decay constants, semileptonicform factors, form factors for the raredecay B —> K* g, and weak-matrixelements of 4-fermion operators. Allthese calculations were done usinghighly efficient computer codes on theThinking Machines ConnectionMachine 5.

Results of these calculations haveimpact on the 4 parameters thatdescribe the Cabibbo-Kobayashi-Maskawa mixing matrix and the 3light quarks, i.e., on 7 of the 19parameters of the Standard Model.Some of the highlights of our calcula-tions include the following results:

Hadron Spectrum. We obtained adetailed analysis of the chiralbehavior of meson and baryonmasses and the pattern of symme-try breaking for the octet anddecuplet baryon states.Quark Masses. We predicted themasses of light quarks by analyz-ing the behavior of the masses ofhadrons as a function of up, down,and strange quark masses. Ourresults show that these quarkmasses are almost a factor of 2smaller than conventionallyaccepted values.

Semileptonic form factors for thedecaysD —> KevandD —>K*ev. The data is cleanest forD —> K e v so it is used to test thepole-dominance hypothesis. Bycomparing the lattice result/+(0) = 0.66(4) with the presentexperimental values of 0.71(4) and0.77(4), we postulate that thediscretization and quenching errorsin these quantities are small. Forthe pseudoscalar to vector decayD —> K*ev, our result for thehard-to measure-ratio A2/A! = 0.63(0.10) is in good agreement withexperiments.

Bparameters. These parametersmeasure the QCD corrections toweak-interaction processesinvolving charge-conjugationparity (CP) violation. Our newresults for the electromagneticpenguin operators suggest anenhanced value for the direct CPviolation parameter e'/e.

Publications

Bhattacharya, T., et al., "DecayConstants with Wilson Fermions atBeta = 6.0," Phys. Rev. D 54,1155(1996).

Bhattacharya, T., et al., "HadronSpectrum with Wilson Fermions,"Phys. Rev. D 53, 6486 (1996).

Bhattacharya, T., et al., "LatticeAnalysis of Semi-Leptonic FormFactors," Nucl. Phys. B (Proc. Suppl.)47, 481 (1996).

Bhattacharya, T., et al, "Status Reporton Weak Matrix Element Calcula-tions," Nucl. Phys. B (Proc. Suppl.)47, 549 (1996).

Grandy, J., et al., "Topological Densityand Instantons on the Lattice," Nucl.Phys. B (Proc. Suppl.) 42, 246 (1995).

Gupta, R., "Chiral Limit of QCD,"Nucl. Phys. B (Proc. Suppl.) 42, 85(1995).

Gupta, R., et al., "Testing the ChiralBehavior of the Hadron Spectrum,"Nucl. Phys. B (Proc. Suppl.) 47, 549(1996).

I 14 Los Alamos FYI996 LDRD Progress Report

Biosciences

Biotechnology Approaches to Stable-Isotope Labeling for BiomolecularStructure/Function Studies

Jill Trewhella

A thorough understanding ofbiological function at the molecularlevel is essential for the developmentof new therapies to treat diseases andfor an increasing array of applicationsin biotechnology. Knowledge ofbiomolecular structure is a prerequi-site for understanding biomolecularfunction, and stable isotopes areplaying an increasingly important rolein the structural determination ofbiological macromolecules.

The application of stable isotopesis required for interpreting structuraldata from a variety of biophysicaltechniques (such as neutron scatter-ing, nuclear magnetic resonancespectroscopy, and vibrational spec-troscopies) that provide structuralinformation down to atomic resolu-tion. The application of these tech-niques to many importantbiochemical problems

AmpK

pET-32

is limited by the expense of labelingmacromolecules with stable isotopes.In this project we have developedbiotechnology approaches to labelingeukariotic proteins and peptides.

We have tested a large number ofcommercial bacterial expressionvectors for labeling peptide fragmentsof troponin I (an avian muscleprotein). Because peptides are subjectto nonspecific proteolysis and aredifficult to purify, expression ofrelatively small peptides in bacteriahas been difficult. These problemscan be circumvented by expressingpeptides as a fusion with proteinsthat are both stable and relativelyeasy to purify.

In our successful plasmid construc-tion (see accompanying figure), wecloned the DNA encoding for

troponin I peptides into amultiple-cloning site such

that the DNA wastranscribed as a

-_ fl origin

fusion with thioredoxin, a region thatencodes for polyhistidine (His-tag)and a specific protease cleavage site.Thioredoxin stabilizes the fusionprotein against proteolysis. Based onthe specific interaction of the His-tagregion with a nickel matrix, the fusionprotein is easy to purify. Finally, weliberated the troponin I peptide fromthe fusion protein by treating thefusion protein with enterokinase,which cleaves specifically the peptidebond to the C-terminal side of thesequence Asp-Asp-Asp-Asp-Lys.

Publications

Hernandez, G., S.E. Rokop, P.A.Springer, et al., "NMR Studies ofTroponin I (96-115): Free in Solutionand Bound to Troponin C," Biophys.J. 70, 384 (1996).

*'*// „„„. Plasmid for expressing our fusionproteins.

Start codon

lac operator 1 PolyhistidineEnterokinasecleavage site J

T7 promotor Thioredoxin His-tag(109 amino acids)

Asp-Asp-Asp-Asp-Lys Multiple-cloning site

Individual Projects—Biosciences I 15

Preparation and Utilization of I3C- and i5N-Labeled DNAs forthe Determination of Unusual DNA Structures Relevant to theHuman Genome Project by Nuclear Magnetic ResonanceSpectroscopy

Louis A. Silks

Recent reports have highlighted theinvolvement of DNA triplet repeats ina variety of human genetic diseases.The size and complexity of theseDNA motifs necessitate the use ofstable isotope labeling for structuraldetermination by nuclear magneticresonance (NMR) spectroscopy. Weare addressing this problem bydeveloping novel and efficient meansfor synthesizing these unusual DNAs,which will allow their subsequentstructural determination by NMRmethods. Our ultimate goal is tocorrelate the structure and functionof these DNA motifs.

We have begun to construct DNAmolecules containing triplet repeatsfrom easily accessible precursors suchas labeled methanol, carbon dioxide,and ammonia. The enzymatic syn-thesis of ribose (one of the compo-nents of DNA) requires carbon-labeled glycerol, so we developed a

method for synthesizing glycerol fromlabeled carbon dioxide and haveapplied for a patent on this newprocess. Our efforts to devise astraightforward procedure to construct2'-Deoxy[amino-15N]Adenosine, aswell as a new method for the synthe-sis of the unknown [9-15N]-2?-deoxyadenosine, have been reportedin the literature. In short, our proce-dures use water as the solvent, havebeen scaled to provide gram quantitiesin excellent yield, and do not requireany protection/deprotection steps.

Furthermore, we have constructedthe (C[6-15N]AG)5 repeat and opti-mized its purification using semi-preparative reverse-phase (C6)high-performance liquid chromatogra-phy techniques. We are currentlypurifying the labeled (C[6-15N]AG)5

repeat and expect subsequent solutionNMR studies to provide unambiguousevidence of the type and nature of the

hydrogen bonding to the 6-aminogroup on the adenines. We are alsocurrently constructing the(C[15N2]TG)5 and (G[15N3]C[15N3]C)5

repeats to explore the bondingenvironments around each of thelabeled nitrogens. Ultimately, theseexperiments will provide definitiveevidence for two- or three-centeredhydrogen bonding.

Publications

Orji, C , J. Kelly, D.A. Ashburn, et al.,"The First Synthesis of (3-2'-Deoxy-[9-15N]Adenosine," J. Chem. Soc,Perkin Trans. 1, 7, 595 (1996).

Orji, C, and L.A. Silks, "The FirstSynthesis of [9, amino-15N2]Adenineand (3-2'-Deoxy-[9, Amino-15N2]Adenosine," /. Labelled Compds.Radiopharm. 38, 852 (1996).

Applications of Strand-SpecificIn Situ Hybridization

Edwin Goodwin

Fluorescence in situ hybridization(FISH) is used to determine thelocation of specific DNA sequenceson chromosomes. A strand-specificversion of FISH, called chromosomalorientation (CO)-FISH, was devel-oped at Los Alamos. The procedurereveals not only the location but alsothe 5'-to-3' direction (or polarity) of atarget sequence (such as the sensestrand of a gene) and its orientationrelative to other sequences on thesame chromosome. This informationis not obtainable by any othercytogenetic method.

The goal of this project is to expandthe range of applications of CO-FISH.Specifically, we intend to developmethods to examine altered gene ex-pression associated with malignancy,investigate mechanisms of geneamplification, and facilitate genomicmapping.

Using CO-FISH, we have observedlong-range molecular order in therepetitive elements of tandemlyrepeated satellite DNAs. In addition,this year we completed our investiga-tion of the cytogenetic phenomenon

known as lateral asymmetry, contin-ued our investigation of aneuploidy-inducing agents, and successfullydetected isochromosomes andchromosomal inversions.

Publications

Bailey, S.M., E.H. Goodwin, J.Meyne, et al., "CO-FISH RevealsInversions Associated withIsochromosome Formation,"Mutagenesis 11, 139 (1996).

Goodwin, E.H., J. Meyne, S.M.Bailey, et al., "On the Origin ofLateral Asymmetry," Chromosoma104, 345 (1996).


Computer Simulation of Protein Solvation,Hydrophobic Mapping, and the OxygenEffect in Radiation Biology

Lawrence Pratt

Our work on the statistical mechan-ics of biomolecule solvation haswidespread applications in structuraland functional biology, includingunderstanding the stabilization offolded protein structures and thebinding of DNA, ligands, and otherbiomolecules to proteins. Our workwas motivated by the need to identifyhydrophobic and hydrophilic regionsof biomolecules in water. Thequestion that led to this work was,where would simple hydrophobicspecies such as an oxygen moleculestick to a hydrated protein? Wedeveloped theoretical molecularmodels of hydration (incorporatingboth hydrophobic and hydrophiliceffects) and validated our modelsthrough computer simulations.

These new models are now avail-able for use in structural biologystudies when computer simulationsare either not feasible or not insight-ful. They have recently been used tosolve a longstanding puzzle inmolecular biophysics, explaining thephenomenon of entropy convergence

in protein folding experiments. Acommentary in the Proceedings of theNational Academy of Sciences U.S.A.on our work notes that we "dramati-cally extend ideas" from previoustheories, that our Proc. Natl. Acad.Sci. U.S.A. paper is a "very interestingand important paper," and that ourresults are "remarkable." It is clearthat our work constitutes a break-through on these difficult problems ofsolvation of biological macromol-ecules.

Publications

B.J. Berne, "Inferring theHydrophobic Interaction from theProperties of Neat Water," Proc. Natl.Acad. Sci. U.S.A. 93, 8800 (1996).

Corcelli, S.A., J.D. Kress, L.R. Pratt,et al., "Mixed Direct-IterativeMethods for Boundary IntegralFormulations of Continuum DielectricSolvation Models," PacificSymposium on Biocomputing '96, L.Hunter and T. E. Klein, Eds. (WorldScientific, Singapore, 1995), p. 142.

Garde, S., G. Hummer, A.E. Garcia,et al., "Hydrophobic Hydration:Inhomogeneous Water Structure nearNonpolar Molecular Solutes," Phys.Rev. £53,4310(1996).

Garde, S., G. Hummer, A.E. Garcia,et al., "Origin of EntropyConvergence in HydrophobicHydration and Protein Folding,"Phys. Rev. Lett. 77, 4966 (1996).

Hummer, G., S. Garde, A.E. Garcia,et al., "An Information Theory Modelof Hydrophobic Interactions," Proc.Natl. Acad. Sci. U.S.A. 93, 8951(1996).

Hummer, G., L.R. Pratt, and A.E.Garcia, "Free Energy of IonicHydration," J. Phys. Chem. 100,1206(1996).

Hummer, G., L.R. Pratt, and A.E.Garcia, 'The Hydration Free Energyof Water,"/. Phys. Chem. 99, 14188(1995).

Pratt, L.R., "Molecular Theory ofHydrophoic Effects" (to be publishedin Encyclopedia of ComputationalChemistry, John Wiley and Sons, NewYork, 1997).

Pratt, L.R., GJ. Tawa, G. Hummer, etal., "Boundary Integral Methods forthe Poisson Equation of ContinuumDielectric Solvation Models"(submitted to Int. J. Quant. Chem.).

Electromagnetic Inverse Applications forFunctional Brain Imaging

Charles Wood

This project addresses an importantmathematical and computationalproblem in functional brain imaging,namely the electromagnetic "inverseproblem." Two electromagneticbrain-imaging techniques, magneto-and electroencephalography, are basedon measurements of magnetic fieldsand electrical potentials at hundreds oflocations outside the human head. Theinverse problem is the estimation ofthe locations, magnitudes, and time

sources of electrical currents in thebrain from surface measurements.Although this problem is ill-posed inits most general form, approximatesolutions are important for functionalbrain imaging used for diagnosing andtreating neurological disorders and forbasic research on the functionalorganization of the human brain.

We addressed the inverse problemusing two distinct approaches: (1) in-troducing constraints derived from

independent information (for example,from anatomical magnetic-resonanceimaging) and (2) developing newalgorithmic approaches to the problembased on recent developments in large-scale numerical methods. The resultssuggest that we can achieve significantimprovements in the accuracy androbustness of inverse solutions by thesetwo approaches.

Publications

George, J.S., et al., "Mapping Functionin the Human Brain with MEG, Ana-tomical MRI, and Functional MRI," J.Clin. Neurophysiol. 12, 406 (1995).


Gene Shuffling Using Flow Cytometry

L. Scott Cram

We are developing a technique toengineer protein molecules with novelproperties. Our technique combinesthe cell sorting capabilities of flowcytometry with the genetic diversitymade possible through gene shufflingtechniques.

Our technique is carried out inseveral steps. First, we create manydifferent versions of a protein through

in vitro recombination of genes, andthen we use flow cytometry toexamine individual bacteria express-ing the genes. Finally, we select andsort out those bacteria expressingproteins that are of particular interestusing the fluorescent properties of theproteins or of other proteins in the cellthat are affected by the proteins ofinterest. We have begun to apply this

approach to enhancing the fluores-cence of a naturally occurringfluorescent protein called fluorescentgreen protein.

Eventually, our technique may beused to isolate proteins that turn geneson and off in response to an externallyadministered stimulus. In this case,we would replace the gene of interestwith the gene for green fluorescentprotein and monitor the conditionsunder which the green fluorescentprotein is made.

Identification and Characterization of aHuman DNA Double-Strand BreakRepair Complex

David Chen

Mutations that affect the expressionor activity of the subunits of theheteromeric enzyme DNA-dependentprotein kinase (DNA-PK) result in

defective repair of double-strandedDNA breaks. This project studies thebiochemical properties of this enzymerelevant to the repair of DNA strandbreaks. This work will allow us tobegin to assemble DNA double-strandbreak repair complexes in vitro andbetter understand the role of DNA-PKin the repair process.

We have successfully designed anovel purification strategy that employs

Atomic force microscopy (top)and electron microscopy (middle)of the Ku70/80 associated with a2.6-kilobase-pair linear DNAfragment reveal the ability of KMto form DNA loops. End-to-endtethering by the DNA-PK com-plex is shown here in atomicforce micrographs of a 660-base-pair linear DNA circularized byinteractions between two DNA-bound DNA-PK complexes(bottom). These results suggestthat inside of the cell, DNA-PKholds broken DNA strandstogether until repair can occur.Micrographs provided by RobertGary.

a monoclonal antibody that bindsspecifically to the Ku80 subunit ofDNA-PK. The final product is approxi-mately 90% pure. We employed bothatomic force and electron microscopyto examine the behavior of the purifiedKu70/80 and DNA-PK catalyticsubunit. Direct observation of Ku/DNAcomplexes has shown that Ku will formnucleoprotein filaments in the presenceof linear DNA. Moreover, the studieshave revealed that Ku70/80 is capableof looping DNA, as the accompanyingfigure shows. We also used theimmunoaffinity purification protocol toscreen for proteins that associate withthe DNA-PK complex. The mostabundant protein found to associatewith DNA-PK was a 120-kD polypep-tide. This protein binds to DNA and isphosphorylated by purified DNA-PK.

We have used a yeast two-hybridsystem for three studies: (1) mappingthe domains of DNA-PK subunitsinvolved in enzyme assembly, (2)identifying novel proteins associatedwith DNA-PK, and (3) identifyingnovel proteins associated with XRCC4,another protein that functions in theDNA double-strand break repairpathway. We designed screens of two-hybrid cDNA libraries using fragmentsof the catalytic subunit of DNA-PK toidentify novel proteins associated withthe double-strand break repair complex.The recently cloned XRCC4 cDNA hasalso been used in yeast two-hybridlibrary screens.


Determining the Role of theTelomere onthe Severity of Birth Defects

Michael Altherr

The loss of genetic material nearthe ends, or termini, of chromosomesis associated with a variety of birthdefects. Terminal deletions can ariseby a variety of mechanisms, includingphysical breaking of chromosomes byionizing radiation and other clastogenicagents. At least one-third of humanchromosomes can have a terminaldeletion but still result in a live birth,though the baby will likely exhibitsignificant clinical abnormalities.

Our goal is to better understand therole that telomeric sequences play instabilizing chromosome breaks andhow they affect local gene expression.Specifically, we are working toprovide basic insight into the mecha-nism by which broken chromosomalends are healed; to determine whetherthe position of the telomere to knowngenes can affect gene expression andcontribute to the extreme variabilityof symptoms associated with terminaldeletions; and to determine whetherthe position of the telomere affectslocal chromatin structure and in turnaffects gene expression.

To meet these goals, we aremapping a chromosome regionassociated with a specific terminaldeletion syndrome. In the past year,we have reduced the physical regionthought to be involved in the Wolf-Hirschhorn syndrome to 10% of theprevious estimate, and we haveidentified a number of genes in themissing region common to all patientswith the disease.

In addition, we are using cell linesderived from patients with Wolf-Hirschhorn syndrome to examine thelevel of expression of cloned genes inthe vicinity of the novel termini. Andfinally, we are employing clonedgenomic material to analyze chroma-tin from these cell lines to identifystructural variations that may affectgene expression.

Publications

Altherr, M.R., K. Denison, T.J.Wright, et al., "Delimiting the WolfHirschhorn Syndrome Critical Regionto 750 kb" (to be published in Amer. J.Med. Genet).

Wright, T.J., K. Denison, V. Johnson,et al., "High Resolution Analysis ofthe Wolf Hirschhorn SyndromeRegion on Chromosome 4ql6.3" (tobe published in Cyto. Cell. Genet.).

Wright, T.J., K. Denison, D. Ricke, etal., "A Transcript Map of the 260 kbWolf Hirschhorn Syndrome CriticalRegion," Amer. J. Hum. Genet. 59,55(1996).

Wright, T.J., D. Ricke, K. Denison, etal., "A Transcript Map of the NewlyDefined 165 kb Wolf HirschhornSyndrome Critical Region" (to bepublished in Human MolecularGenetics).

Development of an Ultrasensitiveand Rapid DNA Repair Assay

Min S. Park

The main objective of this projectwas to develop a rapid, highlysensitive, and quantitative DNA repairassay. We expect such a kit to beuseful for large-scale epidemiologicalstudies for skin cancer risk assess-ment and for screening for newpotential environmental mutagens. Itmight also be used to prescreencancer patients who might be highlysensitive to radiation so that doctorscan choose lower risk therapies.

We recognized the need for such anassay after observing that the quantityof full-size, in vitro transcriptssynthesized from DNA templatesdecreases as a function of chemical-or radiation-induced damage to theDNA. By measuring the amount ofnew DNA produced after a templatehas been damaged, we can gauge theeffectiveness of the DNA repairmechanism and better estimate theultimate impact of the damage.

First, we studied the incorporationkinetics of nonisotopic ribonucleotideanalogs in the in vitro transcriptionreaction and worked to optimize theuse of these nonradioactive,chemilumiscent substrates. Then, we

tested the functionality of the purifiedDNA repair protein (XPG) using thenonradioactive substrates. Our nextgoal is to refine this assay so that itcan be readily converted into a user-friendly DNA repair assay kit.

Publications:

Cloud, K.G., B. Shen, G.F. Strniste, etal., "XPG Protein Has a Structure-Specific Endonuclease Activity,"Mutation Res. 347, 55 (1995).

Nolan, J.P., B. Shen, M.S. Park, et al.,"Kinetic Analysis of Human FlapEndonuclease-1 by Flow Cytometry,"Biochem. 35,11668(1996).

Park, M.S., J.A. Knauf, S.H.Pendergrass, et al., "UV-InducedMovement of the Human DNA RepairProtein XPG in the Nucleus," Proc.Natl. Acad. Sci. U.S.A. 93, 8368(1996).

Shen, B., J.P. Nolan, L.A. Sklar, et al.,"Essential Amino Acids for SubstrateBinding and Catalysis of Human FlapEndonuclease-1,"/. Biol. Chem. 271,9173 (1996).


Structure and Thermodynamicsof Surface Recognition

Goutam Gupta

We are combining protein engineer-ing, nuclear magnetic resonance(NMR) spectroscopy, and equilibriumand kinetic binding experiments tostudy the structural and thermody-namic features of HIV surfacerecognition—the features that enableHIV to bind to and enter susceptiblecells and the features that alert thebody's defenses to switch into highgear. Our goal is to identify thestructural characteristics required forenhanced antigenicity, or the ability toelicit a stronger immune response.

We have targeted two well-separatedsites on the HTV surface glycoproteingpl20 for our binding studies: theprincipal neutralizing determinant(PND) site and the CD4 receptor-binding site. For these studies weproduced a set of synthetic antigensand the mmiantibody/minireceptormolecules that mimic the bindingaffinity of the whole antibody/receptor.

Although we are primarily focusingon HIV, the methods we develop willalso apply to other pathogens.

First, we chemically synthesized aseries of polypeptides in which copiesof the V3 region of gpl20, whichcontains the PND site, were linkedwith mucin (a glycoprotein found inmucus) spacers. Using NMR andmolecular modeling programs, wefound that longer V3 sequences (withsix mucin/V3 repeats) more readilyadopted a native conformation andwere structurally more ordered thanthose with fewer (i.e., three) repeats.

Next, we tested the antigenicity ofour mucin/V3 polypeptides. However,the antisera produced by both the longand short mucin/V3 polypeptides inmice and monkeys showed no HIVneutralizing ability, which we inter-preted to mean that the V3 region innative gpl20 may not be as accessibleas the ones in the our synthesized

mucin/V3 polypeptides, a conclusionthat we have confirmed by two-dimensional (2-D) NMR structuralstudies on the V3 region of two strainsof HIV.

Furthermore, we observed that theconserved GPGR crest in the V3 loopcan be masked by the C-terminalsequence flanking the crest. In anattempt to unmask the conservedGPGR crest, we designed mini-V3loops that contained the central 15(out of 35) residues of the V3 loop inthe S-S bridged configuration. Wecarried out structural studies by 2-DNMR on two such mini-V3 loops.These two mini-V3 loops adopted arigid beta-hairpin structure in solutionand unmasked the conserved GPGRcrest.

Publications

Fontenot, D., J. Gatewood, S.V.Mariappan, et al., "HumanImmunodeficiency Virus (HIV)Antigens: Structure and Serology ofMultivalent Human Mucin MUC1-HIV Chimeric Proteins," Proc. Natl.Acad. Sci. U.S.A. 92, 315 (1995).

Neutron Structural Biology

Benno Schoenborn

This project investigated designconcepts of neutron-scatteringfacilities for structural biology atspallation sources at the Los AlamosNeutron Science Center. Our workincluded analyzing design parametersfor protein crystallography and formembrane-diffraction instruments.These instruments are designed forgeneral use by scientists fromindustry, universities, and othernational laboratories.

The use of large detectors will be amajor component of the planned newspectrometer. For the planned

crystallographic applications, we havedesigned a detector with a radius of70 cm, a height of 20 cm, and an arcof 120°. Such a detector will have anearly 10-fold increased active area ascompared with the presently useddetectors. In addition to such newdetectors, the new stations will usefocusing optics to increase flux. Theoptical systems will be based onsupermirror technology. We arestudying further increases in flux byemploying coupled moderatorsmatched to the energy resolutionrequired.

The completed design forms thebasis for a first neutron instrumentthat will strengthen the local struc-tural-biology effort and satisfy theDOE Office of Health and Environ-mental Research (OHER) goal tobring major diffraction tools to thescientific community. OHER hasindicated that it is interested infunding these efforts in neutronstructural science and supports anexternal-users program.

Publications

Schoenborn, B.P., "A ProteinCrystallography Station at LANSCE,'in Neutrons in Biology, B.P.Schoenborn and R. Rnott, Eds.(Plenum Press, New York, 1996).


Sum-Frequency Generation Studies ofMembrane Transport Phenomena

R. Brian Dyer

Vectorial pumping of ions, gener-ally carried out by membrane-boundproteins, is one of the most funda-mental processes in living organisms,critical for energy transduction inrespiration and photosynthesis and fora wide variety of cellular signal-transduction events. Because of thedifficulty of obtaining structural anddynamic information on membranesand membrane-bound proteins, amolecular-level understanding ofproton and ion pumping has remainedelusive.

Our objective is to develop andapply a new technique, sum-fre-quency generation (SFG), to the studyof proton and ion transport acrossbiological membranes. Our studies

have focused on cytochrome coxidase, a redox-driven transmem-brane proton pump.

We have developed a nonlinearspectroscopic technique that isuniquely sensitive to membraneinterfaces. Our approach uses afemtosecond titanium-sapphire laserto parametrically generate broad-bandIR pulses throughout the mid-IRusing the nonlinear optical materials[3-barium borate and silver thiogallate.The IR pulses are combined in anonlinear SFG process at the mem-brane/water interface and are detectedby a multichannel SFG instrument,which we developed, that uses aspectrograph and charge-coupleddevice detector to detect the broad-band, up-converted IR light.

Our initial studies have focused onthe water/phospholipid interface ofvesicles oriented randomly in solutionand on supported hybrid bilayers onfused silica. We have also worked outthe biochemistry to reconstitutecytochrome c oxidase in liposomevesicles. We expect the combinationof a carefully controlled membranecomposition and structure with thestructural sensitivity and interfacialspecificity of the SFG technique toprovide unique insight into thestructures and dynamics that effecttransmembrane ion transport.

Publications

Causgrove, T.P., and R.B. Dyer,"Picosecond Structural Dynamics ofMyoglobin Following Photolysis ofCO," J. Phys. Chem. 100,3273 (1996).

Williams, S., T. Causgrove,R.Gilmanshin, et al, "Fast Events inProtein Folding: Helix Melting andFormation in a Small Peptide,"Biochem. 35, 691 (1996).

Engineering Sequence-Specific RNA andSingle-Stranded-DNA Binding Proteins

Thomas Terwilliger

The technology to design a proteinthat binds to any given RNA orsingle-stranded DNA sequence hasmany potential applications. Forexample, viral diseases such as AIDScould be treated by transmitting asequence-specific engineered proteininto an infected cell, where it wouldbind to and inactivate a key messen-ger RNA. Our objective is to constructa group of protein modules, each ofwhich recognizes a specific four-nucleotide sequence of RNA or single-stranded DNA, and then to develop thetechnology to link four or more of thesemodules in any order to generateproteins that bind specifically to any 16(or more) nucleotide sequence of RNAor single-stranded DNA.

We have used the special propertiesof the gene 5 protein from bacterio-phage f 1 along with our experience inprotein engineering to set the frame-work for creating a set of proteins thatwill bind to any specific sequence ofRNA or single-stranded DNA. In thepast year, we constructed a four-domain modular protein consisting ofseveral tandem-linked gene 5 proteinsubunits that can be used as a tem-plate for generating a variety ofsequence-specific binding proteins.By genetically linking the gene 5protein subunits, we can designproteins in which each domain canbe modified individually.

Publications

Benevides, J.M., T.C. Terwiliger, S.Vhonik, et al., "Raman Spectroscopyof the Ff Gene V Protein andComplexes with poly(dA): Non-specific DNA Recognition andBinding," Biochem. 35, 9603 (1996).

Cheng, X., A.C. Harms, P.N.Goudreau, et al., "DirectMeasurement of OligonucleotideBinding Stoichiometry of Gene VProtein," Proc. Natl. Acad. Sci USA93, 7022 (1996).

Individual Projects-—Biosciences 121

Theoretical Studies of Allosteric Changesand DNA Binding of a cAMP-DependentTranscription Activation Protein

Angel Garcia

The E. coli cAMP receptor protein(CRP) plays an important role inmediating transcription activation ofseveral genes in enteric bacteria. CRPactivation is a complex processinvolving the binding of cAMP, DNA,and RNA polymerase. Although thecrystal structures of CRP with twocAMP molecules bound andcomplexed with DNA have beenreported in the literature, a detailedunderstanding of the mechanism bywhich cAMP affects allosteric controlover CRP activity remains unclear. Inthis project we model the structure,dynamics, and function of CRP bymeans of molecular dynamicssimulations in aqueous and crystalenvironments to determine structuresfor CRP in different binding states ofcAMP and DNA. This method willelucidate elements of the cAMP-mediated activation pathway of CRPand provide the rationale for futureexperimentation.

In the crystalline environment,CRP:(cAMP)2 subunits are asym-metrically related, with one subunit ina "closed" conformation and thesecond subunit in an "open" confor-mation. The CRP:(cAMP)2

complexed with DNA shows bothsubunits in a "closed" conformation.We performed molecular dynamicssimulation of CRP:(cAMP)2 in anoncrystalline environment for 625 psin vacuum and for 140 ps in solution.We used the crystal conformation inthe absence of DNA as the initialconfiguration. We sampled configura-tions during the course of the simula-tions and analyzed them throughMolecule Optimal Dynamic Coordi-nate trajectories. Two optimaldirections describe a transition of the"open" subunit to a "closed" subunitconformation during the first 125 psof simulation (a subunit conformationsimilar to the one observed in

CRP:(cAMP)2:DNA crystals). Thesimulation in solution showed that atransition from the "open" to "closed"state also occurs when water isexplicitly included in the calculations.These calculations suggest that theasymmetric conformation results fromlattice interactions, and that the solutionconformation is similar to the symmet-ric (closed-closed) conformation.

Publications

Garcia, A.E., and J.G. Harman,"Simulations of CRP:(cAMP)2 inNoncrystalline Environments Show aSubunit Transition from the Open tothe Closed Conformation," ProteinScience 5, 62-71 (1996).

Garcia, A.E., G. Hummer, and D.M.Soumpasis, "Hydration of an AlphaHelical Peptide: Comparison ofTheory and MD Simulations" (to bepublished in Proteins: Structure,Function and Genetics).

Engineering the Specificity of xylR:A Bacterial Protein that DetectsChemicals in the Environment

Thomas Terwilliger

Microorganisms have sensitivesystems that detect trace amounts oforganic compounds; these systemsare based on the ability of certainregulator proteins to bind thesecompounds. Binding of a compoundto a regulator protein initiates a cell'sresponse by activating the pathway todegrade that compound into nontoxicmetabolites useful to the cell. In thisproject we manipulate the specificityof such a detector protein to producemicroorganisms better able to detectand degrade organic pollutants suchas trichloroethylene (TCE). Ourapproach is to modify the xylRprotein, a regulatory protein thatnormally detects toluene, to detectTCE. We will determine the structureof the toluene-binding domain of thexylR protein bound to toluene usingx-ray crystallographic methods,identify the parts of the protein incontact with the bound toluene, createa large number of variant proteins inwhich the binding surfaces arealtered, and identify variants that bindTCE but not toluene using a sensitivemolecular bioassay.

During the first year of this project,we have developed a system formutagenesis and selection of xylRproteins. For efficient mutagenesisand selection of TCE-detectingvariants of the xylR protein, weconstructed a plasmid that containsthe natural xylR gene from P. putidaunder control of an inducible produc-tion promoter. Separately, but on thesame plasmid, we placed the xylRupper promoter region (which issubject to xylR control) upstream ofthe tetR gene, which controls theexpression of tetracycline resistance.The beta lactamase gene with itspromoter, which confers resistance toampicillin, is also present on thisplasmid to select for transformationinto E. coli. This arrangement of thenatural xylR gene, the xylR upperpromoter, and the tetR gene yieldstetracycline resistance in the presenceof toluene, as the xylR protein willactivate the expression of the tetRgene when toluene is present.


Optimization and Monitoring ofHollow-Fiber Bioreactors

James P. Freyer

Hollow-fiber bioreactors (HFB) area system for culturing cells at veryhigh densities that is currently usedfor the production of drugs andantibodies from mammalian cell lines.The original goals of this project wereto develop novel nuclear magneticresonance (NMR) methods forimaging transport and cellularphysiology within HFB, and to usethese techniques to optimize thedesign of HFB. To date we havedeveloped NMR methods to measurethe transport of protons (essentiallywater) in HFB and methods fornoninvasively assaying cell viabilityand proliferation in specific regions ofa three-dimensional culture. Unfortu-nately, limitations of signal strengthinherent in NMR microscopy havemade it impossible to measure eithercellular physiology or specific nutrientswithin different regions of HFB.

In response to these limitations wehave developed a completely novelthree-dimensional cell-culture systembased on essentially one-dimensionalnutrient supply through a flat, porousmembrane (see figure). We havenoninvasively measured nutrientconcentration gradients in this cell-culture system. Unlike HFB, this newsystem has the added advantage ofbeing able to recover intact, viablecells from precise locations. In thisway we are able to compare tradi-tional measures of cellular physiologywith noninvasive NMR measures ofnutrient concentrations and cellularphysiology. Thus, although thegeometry is different from thatemployed in current HFB, the newsystem embodies the same relation-ships between the environment andthe cells, but in a system that isamenable to noninvasive NMRmeasurement.

Publications

Freyer, J.P., "Mitochondrial Functionof Proliferating and Quiescent CellsIsolated from Multicellular TumorSpheroids" (to be published in /. Cell.Physiol).

Kunz-Schughart, L.A., and J.P.Freyer, "Adaptation of an AutomatedSelective Dissociation Procedure toMulticellular Spheroids of Oncogene-Transformed Fibroblasts" (to bepublished in In Vitro Cell. Dev. Biol).

mediumoutput

Kunz-Schughart, L.A., R.C.Habbersett, and J.P. Freyer,"Mitochondrial Distribution andActivity in Oncogene-Transfected RatFibroblast Isolated from MulticellularSpheroids" (to be published in Am. J.Physiol.:Cell. Physiol.).

Stegman, L.D., O. Ben-Yoseph, et al.,"Phosphorous MRS Evaluation ofCancer Gene Therapy Paradigm:Assessment of Ganciclovir Toxicity inGlioma Tumors Stably Expressing theHerpes Simplex Virus ThymidineKinase Gene" (to be published inMagn. Reson. Med.).

mediuminput

tnutrients

wastes

top cap

mediumreservoir

membrane

glasscylinder

cells inmatrix

bottomcap

A cutaway diagram along the axis of the cylinder of the new cell culture systemfor NMR analysis of microenvironment and physiology within three-dimensional cell-culture systems. Gradients in nutrients and waste products areestablished with a linear dependence on distance from the nutrient supply, asindicated on the left. The shading represents a gradient in cellular viabilitywithin the cell matrix, with viable cells (white) nearest the nutrient supply anddead cells (black) farthest from the supply.

Individual Projects—Biosciences 123

Optimal Screening Designs forBiomedical Technology

David Torney

Screening many types of moleculesto isolate a few types with desirableproperties is essential in biomedicaltechnology. Unfortunately, searchingfor a particular molecule is often likelooking for a needle in a haystack.

However, by testing groups or poolsof molecules, the desirable moleculescan be identified using a number ofexperiments that is proportional to thelogorithm of the total number of typesof molecules. The accompanying

YACs

t-design and panels illustrate theprinciples and practices of poolingmolecules.

We are investigating efficientnonadaptive pooling designs, such asoptimum random sets designs. Innonadaptive pooling designs, all poolsare assigned in one pass, and allclones occur in the same number ofrandomly selected pools. The resultsof optimizing the number of pools inwhich each clone occurs are shown inthe accompanying logarithmic plots.

CO_ lOoQ.

| l | 2 | 3 | 4 J 5 | 6 | 7 | s | 9|iOJii|i2|i3|i4|iS

i i BlB U wmim fclw H2 ̂ • i S I I H i • • • I H'?-3 S B I 11111111 miWm U mm4 H i l l H i l l I B i l l NT iHl Is6

8

910

jm • I

rrmm

• I mm l • lIS8ii H^ra I

M M I M M

16 17

;>}

B

18 19 20

r

21

'.

r ,

1Isif s

22

: •

23 24

,- \

'.

•'* i-

•

m

25

•

26r •

J

:

27 28

1[' 1-

\

Jr '

29

-••:

• ;'-

30

I

3i|32

T t

M

33 34

'a

• •

1

35 36

rV'

i

.,'"\V*

|

77iw t-design depicts 36 yeast artificial chromosome (YAC) clones that we have put into 10 pools. A dark square indicates thata clone occurs in a pool. Each clone occurs in 5 pools, and each pool contains 18 clones. Assume that one of these clones isour desired "positive " product. When we test for the presence of our desired clone, we will identify the five pools containingthe clone (the five positive pools). Using the information from the t-design for any four out of those five pools, we can identifyour desired clone. Thus, we could identify any single positive clone even if there were a false-negative pool assay (that is,even if one of the five pools did not give a positive result, for whatever reason). This design would, however, perform poorly inthe unusual circumstance that more than one of the clones is positive.

MINIMUM NUMBER OF POOLS: FRACTION OF DEFINITE POSITIVES-.951.2 =

OPTIMUM k; FRACTION OF DEFINITE POS1TIVES=.95

(a) (b)

Results are plotted for clone libraries with a number of clones, n, between 103 and 10s and the average number of positiveclones, c, between 0.25 and 16. It is required that the average number of definite positives (clones that must be positive) be95% of the average number of positives. Plot (a) shows the minimum number of pools necessary to achieve this result using arandom k-sets pooling design. Plot (b) shows the optimum values ofk, the number of pools in which each clone should occur.Our results show the minimum number of pools that would be required based on the optimum random k-sets design.


We have applied our ideas to pooland screen clone libraries that areused in the Human Genome Project.These pooling and screening experi-ments required us to use liquid-transferring robots, and for the largestclone libraries, we had to adaptsimpler, "row-column" poolingdesigns. Given the pool assay results,we developed an optimum techniquefor determining the probability thateach clone contains the sequence of

interest. This technique works welleven if there are substantial rates oferrors in the pool assay data.

Publications

Balding, D.J., WJ. Bruno, et al., "AComparative Survey of Non-AdaptivePooling Designs," in Genetic Map-ping and DNA Sequencing, IMAVolumes in Mathematics 81,133(1996).

Balding, D.J., and D.C. Torney,"Optimal Pooling Designs with ErrorDetection," /. Comb. Theory A 74,131(1996).

Bruno, W.J., F. Sun, and D.C. Torney,"Optimizing Non-Adaptive GroupTests for Objects with HeterogeneousPriors" (to be published in SI AM J.Appl. Math.).

Knil, E., A. Schliep, and D.C. Torney,"Interpretation of Pooling ExperimentsUsing the Markov Chain Monte CarloMethod," J. Comp. Biol. 3,396 (1996).

(a) Primary YAC Pool

V "H d2 d3 04 d5 do d7 diOdii di2 d13 ". • • O> Z

123

(b) Secondary YAC Pool of d14

M PI P2 P3 W P5 P8 P7tragmenl

Sengtli{basepairs)

1107 —881 -615 —492 -3S9 -

246 -

P8

E!c

P9 P10 HO> z

(c) Single YAC

Y664 Mfragmentlength(basepairs)

123

These panels show the results of implementing the t-designfor batches of 36 clones from a 550-clone YAC library ofhuman chromosome 16. In panel (a), the results of polymerase chain reaction (PCR) assays are shown for 15 batches of36 clones, denoted dl through dl5. We determined the size of the PCR products by gel electrophoresis; the desired PCRproduct has a size of approximately 150 base pairs. The batch denoted dl4 is the only batch yielding the product. Inpanel (b) are the results of PCR assays of the ten pools created from the 36 clones in batch dl4. These pools are denotedPI through P10. The five pools that are positive (contain the desired PCR product) are PI, P2, P4, P5, and P8. Referringto our t-design (top figure, p. 124), we deduced that the positive clone should be clone 5. Panel (c) verifies that clone 5 isour desired clone. Note that the negative pools in panel (b) contain a pair of spurious bands, a frequent PCR artifact.Also, there is a trace of putative desired product in P9.


Nuclear Magnetic Resonance (NMR)Spectroscopy of Unusual DNA Structuresand Functions Associated with HumanDisease

E. Morton Bradbury

This work focuses on the structuralbiology of the insulin minisatellite,which contains a region known as theinsulin-linked polymorphic region(ILPR) that is associated with insulin-dependent diabetes mellitus. Thehuman insulin minisatellite is locatedupstream of the insulin gene and itslength is highly polymorphic.

We have performed two-dimen-sional NMR spectroscopy, gelelectrophoresis, digestion by single-strand-specific PI nuclease, and invitro replication to determine the

structure of the human insulin mini-satellite. Our efforts have focused ona region of the ILPR in which onestrand is rich in guanine (G) and theother in cytosine (C).

We have shown that the G-richstrand adopts a hairpin G-quartetstructure, whereas the C-rich strandadopts an intercalated C+»C paired i-motif structure (see accompanyingfigure). Formation of these structurescauses slippage during replication,which might contribute to theobserved length polymorphism.

Formation of these structures alsocauses unwinding (and negativesupercoiling) upstream of the tran-scription start site, which mayfacilitate transcription. We also foundthat single-site mutations that disruptthe stem or loop structure of thehairpin G-quartet or the C+«C pairedi-motif reduce the transcriptionalactivity of the insulin gene and thattwo or more site mutations block alltranscriptional activity. These resultssupport our hypothesis that thestructures of the hairpin G-quartet andthe C+*C paired i-motif regulatetranscription of the insulin gene.

Publications

Catasti, P., X. Chen, R.K. Moyzis, etal., "Structure-Function Correlationsof the Insulin-Linked PolymorphicRegion," / Mol. Biol. 264,534(1996).

y 5*

hairpin(•quartet

hairpin with( «C paired

i-motif

A schematic representation of the structure of the multiple hairpin G-quartets and the C+*C paired i-motif.


Emerging Pathogens: Dynamics, Mutation,and Drug Resistance

Alan Perelson, Los Alamos National LaboratoryFrederick G. Hay den, University of Virginia

Pathogens that can grow rapidlyand mutate into drug-resistant formspose a serious health threat. One suchpathogen, influenza, is one of theworld's greatest killers. In a normal"flu" season, between 20,000 and40,000 deaths in the United States areattributable to influenza infection, andin the 1918-1919 pandemic, over 21million people died worldwide. Twoantiviral drugs, amantadine andrimantadine, are currently availableand in limited use against influenzainfection; their use should preventsuch large numbers of deaths ifanother pandemic strikes.

However, before large-scaletreatment programs are begun, asmight occur with a major outbreak orpandemic, the health significance ofpotential drug-resistant viruses mustbe addressed. Furthermore, treatmentstrategies must keep emergence ofdrug-resistant strains at reasonablylow levels and still permit treatmentof infected individuals. (Researchersdesigning countermeasures tobiological agents released duringwarfare or by terrorist activitiesaddress similar public health issues.)

The goal of this project is toconsider strategies to reduce theseverity of an ongoing biological

threat without compromising ourfuture ability to respond to the samethreat because of the emergence ofdrug-resistant pathogens. To this end,we have developed a quantitativemodel that describes the spread of oneinfectious pathogen, influenza. Wehave fitted our model to data on oneoutbreak of influenza and foundexcellent agreement.

Our model suggests that large-scaletreatment of individuals once theybecome sick readily generates drug-resistant variants. Prophylaxis, astrategy in which individuals aregiven drug treatment before theybecome sick, leads to lower levels ofinfection and, hence, lower emergenceof drug-resistant variants. Because ourmodel's predictions depend on howwe assessed various parameters,extending our results to other patho-gens will require detailed knowledgeon the spread of the disease and theeffects of treatment.

Optical Measurement of DrugConcentrations in Tissue

Irving Bigio

The goal of this project is todevelop noninvasive fiber-opticmethods for measuring drug concen-trations (specifically, chemotherapeu-tic drugs) in tissue. Such a capabilitywould greatly benefit the study ofchemotherapy drug kinetics (i.e., thetime dependence of drug concentra-tions) at specific targeted locations inthe body after a drug has beenadministered. Our specific objectiveis to develop a general method formeasuring the concentrations ofoptically absorbing compounds inturbid media by circumventing theproblems caused by scattering.

We performed Monte Carlosimulations of photon transport todetermine optimal fiber spacings andfiber sizes for measuring absorbancein highly scattering media such astissue. Based on the results of theMonte Carlo simulations, we de-signed and constructed fiber-opticprobes and used them to take mea-surements on a variety of tissuephantoms (materials with opticalproperties similar to those of tissue).We also developed a technique formeasuring changes in absorption in amedium with unknown scatteringproperties, and we tested our newtechnique on media with scattering

properties similar to those of tissue.We were able to measure concentra-tion changes of an added absorbersimilar to what might be expected fordrugs at typical therapeutic doses. Theresults of this work have beensubmitted to Applied Optics forpublication.

Finally, we measured the absor-bance of some chemotherapeuticdrugs to determine whether they haveabsorption bands in a wavelengthrange feasible for absorbance mea-surements in tissue.

Publications

J.R. Mourant, I.J. Bigio, D.A. Jack,et al., "Measuring AbsorptionCoefficients in Small Volumes ofHighly Scattering Media: Source-Detector Separations for which PathLengths Do Not Depend on ScatteringProperties" (submitted to AppliedOptics).


Stable-Isotope Labeling of OligosaccharideCell-Surface Antigens for StructuralStudies

We are presently collaborating withthe Danishefsky group on the synthe-sis of the Lewis oligosaccharides andthe NMR analysis of their solutionconformation.

Clifford Unkefer

The cellular envelopes of manytypes of animal cells are coated witholigosaccharides that are involved inimportant processes such as cell-cellrecognition and adhesion. In addition,oligosaccharides are capable ofeliciting immune responses anddifferentiating, for example, the bloodgroups (A, B, AB, and O). Cell-surface oligosaccharides are alsorecognized by and serve as receptorsfor many infectious agents, includingviruses and bacterial toxins.

All of these functions of oligosac-charides involve the specific bindingof the cell-surface oligosaccharide bya protein molecule. The design ofpharmaceutic agents that can specifi-cally inhibit the binding of a bacterialtoxin to an oligosaccharide receptorwould be greatly facilitated byknowledge of the conformation ofboth the free and bound forms of theoligosaccharide. Advancing ourunderstanding of the conformation ofoligosaccharides is dependent on theapplication of methods such asnuclear magnetic resonance (NMR)for determining their structures. Ashas been demonstrated in the NMRanalysis of protein structures, stable-isotope labeling is required forincreasing spectral resolution andassigning the resonances. At present itis not possible to label most oligosac-charides with 13C.

Because most of the interestingoligosaccharide structures derive frommammalian sources, biochemicalapproaches to labeling them areimpossible. Recently, Danishefskyand coworkers at Slone KetteringCancer Center developed a methodfor the solid-phase chemical synthesisof oligosaccharides. The goal of ourLDRD project was to prepareuniformly 13C-labeled aldohexoseprecursors required for the solid-phase synthesis of the Lewis blood-group antigenic determinants.

The solid-phase synthesis of theLewis oligosaccharides required threeprecursors: a D-glucose or N-acetyl-D-glucosamine precursor (1), a D-galactose precursor (2), and anL-fucose precursor (3). These precur-sors are shown in the accompanyingfigure. Compounds 1 and 2 containthree asymmetric centers (C3-C5);compound 3 contains four asymmetriccenters (C2-C5). Using uniformly13C-enriched D-glucose as a chiralprecursor, we have prepared 1, 2, and3 in good yield. In two steps weconverted D-[U-13C6]glucose to 1; thestereochemistry at C3, C4, and C5 isretained. Synthesis of 2 required theinversion of the center at C4. Theconversion of D-glucose to L-fucoserequired the inversion of threeasymmetric centers (C2, C3, and C5).

Publications

Lodwig, S.N., and C.J. Unkefer,"Stereoselective Synthesis of StableIsotope-Labeled L-a-Amino Acids:Electrophilic Amination of Oppolzer'sAcyl Sultams in the Synthesis of L-[15N]Alanine, L-[15N]Valine, L-[15N]Leucine, L-[15N]Phenylalanineand L-[1-13C,

15N]Valine," J. LabelledCompounds and Radiopharma-ceuticals 38, 239 (1996).

Lodwig, S.N., L.A. Silks III, and C.J.Unkefer, "Synthesis of 1-Chloro-l-[15N]Nitrosocyclohexane: anElectrophilic Aminating Reagent," J.Labelled Compounds and Radio-Pharmaceuticals 38, 161 (1996).

Oppenheimer, J., and L.A. Silks III,"Synthesis of 2-Phenyl-l,2-benziso [77Se] selenazol-3 (2H)-one;'Ebselen,'" J. Labelled Compoundsand Radiopharmaceuticals 38, 281(1996).

Orji, C.C., J. Kelly, et al., "TheFirst Synthesis of [9-15N]-2'-Deoxyadenosine," J. Chem. Soc,Perkin Trans. 1 7, 595 (1996).

Wu, R., and L.A. Silks III, "Synthesisof D- t l^^^^^-^CJGluca l and D-[l,2,3,4,5,6-13C6]Galactal Using D-[U-I3C6]Glucose as the Sole CarbonSource" (submitted to Carbohydr.Res.).

OAc

AcOAcO

H3C OBn

OBnBnO 3

The precursors that we used in our solid-phase synthesis of the Lewis oligosaccharides (Ac is an acetyl group, andBn is a benzyl group). Compound (1) is the precursor of D-glucose and N-acetyl-D-glucosamine, (2) is the precursorof D-galactose, and (3) is the precursor of L-fucose.


Protein Motions that Determine theEfficiency of Photosynthesis

Joel R. Berendzen

In this project our goal is tounderstand the quantum efficiency ofbiomolecular photocells. Achievingthis goal requires that we combinex-ray crystallography at cryogenictemperatures with theoretical calcula-tions to determine the structure ofreaction centers under illuminationand understand the changes in proteinstructure that occur upon chargetransfer. These structural changes arethought to be responsible for theremarkable quantum efficiency(greater than 98%) of these cells.Understanding them could help toanswer fundamental questions about

energy transduction in the reactioncenter, including the role that thevarious pigments and protein domainsplay in preventing the unwanted"back" reaction.

We have made substantial progresstoward our goal. We have attracted thecollaboration of Nobel Prize winnerHartmut Michel's group at the Max-Planck Institute for Biophysics,Frankfurt, Germany, in carrying outthe crystallography. We constructed anovel instrument, an ultraviolet-visible (UV-VIS) absorption spectrummicrospectrophotometer, designed foron-line operation at a synchrotron to

measure the absorbance spectra ofreaction center crystals and carry outphotoactivation. We have obtained thefirst-ever data set for a reaction centercrystal at cryogenic temperatures, andit diffracts well. In collaboration withthe National Institutes of Health, wehave developed methods that allowaccurate and efficient calculations offree-energy differences from simula-tions of equilibrium states. Thesemethods will enable examination ofelectron-transfer mechanisms. Wehave also developed an electron-transfer pathway analysis programbased on a tree search that can findthe 100 best electron-transfer path-ways in a small protein (such ascytochrome c with 1700 atoms) in justa few seconds on a desktop worksta-tion. We will use this tool to analyzedifferences in pathways before andafter illumination.

Studying Properties of Cell Suspensionswith Elastic Scattering

Irving Bigio

Cancer diagnosis is commonlyverified with surgical biopsiesfollowed by pathology assessment, aninvasive and time-consuming proce-dure. Optical techniques for non-invasive tissue diagnosis are nowbeing developed, offering significantadvantages over standard biopsy andcytology techniques, both in terms ofpatient care and medical costs.

In previous work using elastic-scattering spectroscopy to detectcancer, we obtained sensitivities andspecificities in the upper-90thpercentile range for some forms of

cancer of the bladder and colon.These results were obtained empiri-cally without a detailed understandingof the sources of the spectral differ-ences. The purpose of this project wasto study suspensions of cancerous andnoncancerous cells in order todetermine the cause of the spectralchanges.

We have made measurements onMl, MR1, RAT1, and RAT1-T1 cells,which are derived from the same lineof normal rat fibroblast cells. TheMR1 and RAT1-T1 cells are capableof forming a tumor while the others

are not. We found repeatable differ-ences in light scattering properties ofthe Ml and MR1 cells; however, thedata on the RAT1 and RAT1-T1 cellsis still inconclusive. Our preliminaryevidence suggests that the growthstage of the cells affects the scatter-ing. We also developed two newmethods for estimating the size of thescatterers in highly scattering mediaand have determined that the pre-dominant scattering centers averageonly 0.3 microns in diameter.

Publications

J.R. Mourant, J.P. Freyer, and T.M.Johnson, "Measurements ofScattering and Absorption inMammalian Cell Suspensions," SPIEProc. 2679, 79-84 (1996).


Numerical Simulations of BiochemicalSelf-Organization: Calcium WavePropagation and Microtubule Growth

John Pearson

We are investigating the calciumfertilization wave in xenopus eggs andmicrotubule dynamics. These issuesare treated separately, although weintend ultimately to couple thecalcium dynamics with the microtu-bule dynamics to create a plausiblenumerical model of mitosis. We arealso working to elucidate the differ-ences between the mature andimmature oocytes.

We have developed both particleand mean-field models of microtubuledynamics that reinforce our prelimi-nary result that the generic behaviorof tubelike objects is to form clumpsof growing tubes separated by emptyregions. The separation betweenclumps is apparently determined bythe rate of tubulin diffusion and of thebinding constants.

We have developed computer codesfor simulating the nonlinear dynamicsof the calcium wave propagation.These codes are in one, two, and threedimensions. We have performed adetailed analysis of the traveling wavesolutions in one dimension of thenonlinear dynamical. This analysiswill be used as a guide in performingnumerical simulations in the morerealistic two- and three-dimensionalmodels. This involves the numericalcontinuation of the traveling wavesolutions of the de Young-Keizermodel as parameters are varied. Itturns out that there are over a dozenparameters that are not well known inthe case of the mature oocyte. Wehave extended our numerical modelsto account for a nonuniform distribu-tion of the endoplasmic reticulum,and we have begun the exploration ofthe effects of the endoplasmicreticulum distribution in the sphericaloocyte.

We have developed both mean-fieldmodels and a particle model for thedynamics of microtubulelike objectsin two space dimensions. To performensemble averages of the particledynamics, we have ported our code tothe massively parallel Cray T3D, thusgenerating several hundred realiza-tions. The clumping phenomenonobserved in the particle simulationswas also observed in the mean-fieldmodel. We performed a crudeanalytical calculation on the mean-field model that indicates suchclumping should be expected. Wehave also developed mean-fieldmodels for the dynamics of tubes withtail dynamics but these remain to beexplored.

Publications

Reynolds, W., S. Ponce-Dawson, andJ. Pearson, "Self-Replicating Spots"(to be published in Phys. Rev. E).

Baras, R, M. Mansour, and J.Pearson, "Microscopic Simulation ofChemical Bistability of HomogenousSystems," J. Chem. Phys. 105 (18),8257 (1996).


i^S=»^=?-

r^^"^?j2=?:i

Materials Science

Actinide Crystal Structures with anEmphasis on Plutonium Alloys

Joyce Roberts

Complexity of crystal structure isthe outstanding scientific problem ofactinide crystal chemistry. We do notknow why the idiosyncratic structuresof plutonium metal occur, and we donot know how they transform amongthemselves. The electronic instabilityof the 5f electronic shell that is justbeginning to be filled in the lightactinides causes "self-intermetallic"compounds (in which the sameelement is in more than one valencestate or crystallographic site) to beformed in both plutonium metal andits alloys, and the formation of thesecompounds is responsible for theobserved complexity of structure andphase behavior.

The goal of this project is tocontribute to an understanding of thiscomplexity by determining the crystalstructures of several actinide alloys:Np-U, Pu-Th, and Pu-Zr. It is ourintention that this additional structuraldata will eventually lead to a solutionof the plutonium structure problem.The ultimate goal of this research is tounderstand the complex phases ofplutonium and the interrelationsbetween them.

During the past year we madeprogress in the following areas: (1) Weare establishing new sample-prepara-tion facilities, and these facilities arenearly complete. (2) We spent severalweeks on an unsuccessful attempt toindex our neutron data from the eta-phase in the Pu-Np and Pu-U systems.Although we have not yet indexed thisstructure, this attempt has eliminatedseveral blind alleys and will contributeto the eventual success of this effort.(3) We performed low-temperaturecharacterization of zeta-phase Pu-U

using neutron diffraction. We ob-served that the rhombohedral angleapproaches 90° more closely than itdid in our previous high-temperatureexperiments, but that no furthertransformations take place (see plotof lattice constants vs temperature).Completing the low-temperaturemeasurements allowed us to extendour analysis of the Debye-Wallertemperature (a characteristic parameter

Rhombohedral latticeconstants vs temperaturefor the zeta-phase Pu-U(a is the rhombohedralangle, and a is the latticeconstant). During thisstudy we added data takenbelow room temperatureto our previous data takenabove room temperature.Error bars are smallerthan the plotted points.

10.80

10,76

10.72 -

10.68 -

10.64

of a solid that measures the soundvelocity). An anharmonic model thatallows the Debye-Waller temperature tovary with temperature provided a betterfit to the data than a simple Debye-Waller model (see plot of averagemean-square displacements vs tem-perature). This outcome is consistentwith our results from the lightactinides.

Publications

Lawson, A.C., J.A. Goldstone, B.Cort, et al., "Structure of Zeta-PhasePlutonium-Uranium," ActaCrystallogr. B 52, 32 (1996).

90.0

- 89.8 £:

to

1

- 89.6

89.4

200 400Temperature (K)

600

7vo8

30

20

10

Obw=132(2)K

- 0 B W = ( 1 5 3 - 0.042 * T ) K

200 400Temperature (K)

600

Mean-square thermaldisplacements of the atomsisotropically averaged overall crystallographicdirections for the zeta-phasePu-U vs temperature. Thesolid line is the anharmonicmode (in which the Debye-Waller temperature varieswith temperature) fit to thesedata. The simple Debye-Waller model is given by thedashed line.

Competency Development Projects—Materials Science 135

The Implications of Diffraction In SituLoading Macro strain Measurements inComposites and Finite-ElementInterpretations

Ning Shi

The morphology of the evolution ofelastic macrostrain can be affected bydifferent physical processes, such asmatrix plastic and creep flow andreinforcement fracture. The onset ofthese processes sometimes cannot bereadily detected by conventionalmethods. We are using neutron-diffraction, in situ loading measure-ments, and finite-element analysis tounderstand the evolution of the elasticmacrostrain in composites with theobjective of enabling nondestructiveassessment of internal damage. Inaddition, we are studying the effectof in situ creep on the load sharingbetween phases during isostressloading.

We have measured the dislocationdensity and thermal residual elasticstrains in NiAl reinforced by 20 vol %A12O3 particulates. As the size of thereinforcement increases, the averagedislocation density increases and thecorresponding thermal residual elasticstrain decreases, as shown in the firstfigure. The changes with respect toparticle size in the dislocation density

and residual strain can be explainedneither by continuum theory nor bycontinuum-based dislocation mechan-ics. This disagreement can be ex-plained by the fact that insufficientindependent slip systems in NiAlhinder plastic relaxation in individualgrains when embedded into a crystalaggregate because of the constraintsby neighboring grains. As the particlesize increases, a greater number ofgrains participate in the relaxationprocess, and a collaborative slipamong grains eases the constraints.That is, as the neighboring grains slip,each individual grain does not have"rigid" surroundings. This model issupported by the polycrystallineplasticity calculations.

The second figure is from a two-dimensional (2-D) crystal-plasticitycalculation and shows that the totalamount of slip stays almost un-changed relative to the particle sizewhen the matrix possesses a sufficientnumber of slip systems (threeindependent slip systems are suffi-cient for 2-D). As the number of

Matrix Strain for Equi-Axed Particle Composites

§, 200 "

^sj 1 1

: — J . j..J\i —

' . . . . i i... i

— - -j - — j - :

. . . . i . . . . i . . . .

II

<z

0 50 100 150 200 250 300 350 400

Particle Size (|im)

Measured NiAl thermal residual strain as a functionof reinforcement size.

0.006

0.00S9

0.0058

0.0057

0.0056

0.0086

0.0054

0.0053

0.0052

independent slip systems reduces toone, the amount of slip increases withthe particle size, in line with theexperiment and the model.

Publications

Shi, N., R.J. Arsenault, et al.,"Relaxation of Thermal Mismatch inDiscontinuously ReinforcedMaterials," in Micromechanics ofAdvanced Composites, S.N.G. Chu,P.K. Liaw, et al., Eds. (The Minerals,Metals & Materials Society,Pittsburgh, Pa., 1995), p. 471.

Shi, N., M.A.M. Bourke, and J.A.Roberts, "A Study of Internal Damageof Metal Matrix Composites byNeutron Diffraction," in NeutronScattering in Materials Science II376, 441 (1995).

Shi, N., M.A.M. Bourke, et al., "LoadSharing during Loading in CeramicReinforced Al Composites"(submitted to Metall. Trans. A).

Shi, N., K. Xu, et al., "ThermalMismatch Dislocation Generation inPolycrystalline Metal" (submitted toMetall. Trans. A).

Song, S.G., N.Shi, etal.,"Reinforcement Shape Effects on theFracture Behavior and Ductility ofParticulate-Reinforced 6061-A1Matrix Composites," Metall. Trans. A27A, 3739-3746 (1996).

Single Slip SystemThree Slip Systems

Normalized Particle Volume (V/v )

Calculated average accumulated slip vs normalizedindividual particle volume. A comparison of single- andthree-slip systems.


Chemical and Physicochemical Propertiesof Submicron Aerosol Agglomerates

Ronald Scripsick

Nanometer-sized aerosol particlesare a by-product of high-thermal-energy processes including wasteincineration and explosions. Theymay also be intentionally generatedfor use as superconducting powdersand ultraviolet screening films. Thisresearch focuses on the chemicalproperties of nanometer particles andtheir agglomerates.

In previous experiments wegenerated binary aerosol mixtures ofzinc oxide with magnesium oxide andof copper oxide with magnesiumoxide from aqueous solutions of metalsalts. We atomized, dried, and passedthem through a flat flame burner. Wefound the agglomerate-particle massdistribution with respect to aerody-namic diameter to be bimodal for thezinc and magnesium in the ZnO/MgOsystem. In the CuO/MgO system, themagnesium distribution was bimodaland the copper was concentrated inthe smallest size ranges (particlediameter < 0.5 micron). The bimodalsize-distribution of the aerosol

suggests that two simultaneouspathways exist to metal-oxide aerosolformation from solid-phase, metal-saltprecursors: (1) vaporization andchemical reaction followed by gas-to-particle conversion, and (2) solid-phase reaction to the oxide.

Recent focus has been on the gas-to-particle pathway to aerosol formation.In order to study the effect of precur-sor chemistry on particle-compositionheterogeneity, we generated mixedSiO2/TiO2 aerosol in a flat flameburner from three sets of gas-phaseprecursors: SiBr4/TiCl4, SiCL4/TiCl4,and hexamethyldisiloxane (HMDS)/TiCl4. We found SiO2/TiO2 an interest-ing system because no mixed phaseexists, nor is there any mermodynami-cally stable solubility of SiO2in TiO2

in the solid phase.We developed techniques to deter-

mine the scale of mixing using trans-mission electron microscopy/energy-dispersive spectroscopy (TEM/EDS)and scanning transmission electron

microscopy/energy electron lossspectroscopy (STEM/EELS). For allcombinations of precursors, TEM/EDSrevealed little variation in compositionfrom particle to particle. The homoge-neity from particle to particle suggeststhat chemical reactions of the precur-sors to form the condensable speciesare occurring simultaneously, and anydifferences in chemical reactionbehavior of the precursors are insig-nificant. The segregation within theparticles is probably occurring by solid-state diffusion during particle formationas a result of the immiscibility of thetwo oxide species.

Publications

Ehrman, S.H., and S.K. Friedlander,"Formation of a Binary Aerosol in aHigh Temperature Process: FactorsInfluencing the Segregation ofSpecies" (Fifth World Cong, of Chem.Engineers, San Diego, Calif.,July 14-18, 1996).

Ehrman, S.H., and S.K. Friedlander,"Formation of Binary Aerosols in aHigh Temperature Process," (Am.Assoc. for Aerosol Res. Ann. Mtg.,Pittsburgh, Pa., October 9-13, 1995).

Characterization of BioactiveMaterials Using Neutron Reflectivityand Atomic Force Microscopy

Gregory Smith

The objective of this project is toapply neutron reflectivity and atomicforce microscopy to characterize thestructure and phase behavior, theinterlayer and intermacromolecularinteractions, and the protein shapestability of a fundamentally new classof bioactive molecular systems. Thissystem is composed of reconstitutedand native self-assembled membraneproteins complexed with associatingand surfactant polymers.

This year we have prepared ori-ented films of the lipid DMPC onsilicon substrates. However, thesefilms have not proved to be ideal forthese studies. Although the filmsinitially form well-oriented samples,they delaminate from the substratesupon hydration.

Our major accomplishment thisyear was to design and construct acontrolled-humidity oven that can beused for producing oriented, freely

suspended films of lipid multilayers.Because these films are 5 cm x 5 cmin area, they are appropriate for ourneutron-reflectivity studies. We alsobegan testing of the oven, and wehave designed and are currentlyconstructing a new constant-humiditycontrol system for use with the oven.We expect to begin a series of experi-ments with simple lipid multi-membranes first and then lipids withDNA, polyethylene glycol lipid, orlipoproteins.


Bulk Amorphous Materials

Ricardo B. Schwarz

Bulk amorphous metallic alloys(also know as "bulk metallic glasses")are strong, corrosion-resistantmaterials that can be cast in near-net-shape form by techniques such asinjection molding. Because of thesecharacteristics, bulk metallic glassesare used to make such equipment asgears (especially complicated shapesthat are difficult to machine), surgicaltools, corrosion-resistant parts such asvalves, and seamless tubes.

The broad goal of our project is todevelop novel materials with potentialfor industrial or defense applications.We are developing methods to synthe-size and characterize bulk metallicglasses and multiphase metastablealloys formed by mechanical alloying.We are researching the conditions forforming these alloys and the basicproperties of the alloys, includingthermal stability, mechanical proper-ties, and hydrogen storage character-istics. Another goal of our research isto develop bulk magnetic glassymaterials. Currently, no such materi-als exist, but the discovery of bulkmagnetic metallic glasses would leadto a tremendous energy savingsnationwide.

This year we have achieved thefollowing:

1. Improvement in the SynthesisTechniques. We improved a melt-fluxing technique that we haddeveloped last year. This techniqueenables us to produce l-in.-diamrods of amorphous Pd4ONi4<)P2o, thelargest rod of this material everproduced (see accompanyingfigure). A patent application forthis method is being processed bythe Laboratory.

2. New Alloy Compositions. Previ-ously, bulk amorphous Pd-Ni-Palloys were only known at thecomposition of Pd40Ni40P20. Thisyear, we were able to cast amor-phous alloys containing only25 at. % of palladium in the form

of 10-mm-diam rods. Being able touse less palladium represents asignificant reduction in the cost ofthese alloys. We have also discov-ered the formation of bulk amor-phous alloys in Pd-Cu-P andPd-Ni-Fe-P systems.

3. Collaborations with OtherNational Laboratories. We havesupplied samples of our alloys toother national laboratories anduniversities to establish collabora-tive work using their uniquefacilities and expertise (corrosionstudies at Brookhaven NationalLaboratory; structure determina-tion at the National SynchrotronLight Source, Brookhaven; andatom probe microscopy at OakRidge).

4. Metal-Ceramic CompositePowders. In another phase of ourresearch, we are using mechanicalalloying—a high-energy ball-milling technique—to preparemetal-ceramic composite powdersfrom vanadium oxide, magnesium,and aluminum powders. The fine-grained powders that we produceby this method are quite resistantto mechanical degradation inhostile radiation environments anddo not crack as easily as thecorresponding large-grain powders

produced by other preparationmethods.

Publications

Desch, P.B., R.B. Schwarz, and P.Nash, "Formation and Phase Stabilityof Ll2 Phases in the Al-Ti and Al-ZrSystems Produced by MechanicalAlloying" in Applications ofThermodynamics in the Synthesis andProcessing of Materials, P. Nash andB. Sundman, Eds. (The MaterialsSociety, Warrendale, Pa., 1995), pp.75-89.

Desch, P.B., R.B. Schwarz, and P.Nash, "Mechanical Alloying toProduce Ll2 Phases in the Al-ZrSystem," Scripta Materialia 34, 37(1996).

He, Y., R.B. Schwarz, and J.I.Archuleta, "Bulk Glass Formation inthe Pd-Ni-P System," Appl. Phys.Lett. 69, 1861 (1996).

He, Y., R.B. Schwarz, and D.G.Mandrus, "Thermal Expansion ofBulk Amorphous Zr412TiJ3 gCu12 5," / .Mater. Res. 11, 1836 (1996).

He, Y, R.B. Schwarz, et. al, "ElasticModuli, Density, and StructuralRelaxation in Bulk Amorphous Zr-Ti-Cu-Ni," (to be published in J. Non-Crystalline Solids).

Schwarz, R.B., "Introduction to theViewpoint Set on MechanicalAlloying," Scripta Metallurgica etMaterialiaM, 1(1996).

A l-in.-diam rod of amorphous Pd40Ni40P20 alloy prepared by our melt-fluxingtechnique.


Schwarz, R.B., and Y. He, "Formationand Properties of Bulk Amorphous Pd-Ni-P Alloys" (International Symposiumon Metastable, Mechanically Alloyed,and Nanocrystalline Materials, Rome,Italy, May 20-24,1996).

Schwarz, R.B., and A.G.Khachaturyan, "Thermodynamics ofOpen Two-Phase Systems withCoherent Interfaces," Phys. Rev. Lett.74, 2523 (1995).

Shi, N., R.B. Schwarz, and P.B. Desch,"Formation of MoS^ ThroughAnnealing of Ball-Milled Mo and SiElemental Powders," in Applications ofThermodynamics in the Synthesis andProcessing of Materials, P. Nash and B.Sundman, Eds. (The Materials Society,Warrendale, Pa., 1995), pp. 63-74.

Solovioff, G., D. Eliezer, et al.,"Hydrogen-Induced Cracking in anAl- Al3Ti- A14C3 Alloy," ScriptaMetallurgica et Materialia 33, 1315(1995).

Thakur, A.M., N.N. Thadhani, andR.B. Schwarz, "Shock-InducedMartensitic Transformations in Near-Equiatomic NiTi Alloys" (to bepublished in Metallurgical Trans.).

Ustiindag, E., K.E. Sickafus, Y. He, etal., "Metal-Ceramic Composites forHostile Environment Application," inAdvances in Ceramic MatrixComposites HI, N.P. Bansal, Ed.(American Ceramic Society,Westerville, Ohio, in press).

Wasz, M.L., and R.B. Schwarz,"Structure and Properties of MetalHydrides Prepared by MechanicalAlloying," Mater. Set Forum 225-227, 859 (1996).

Wasz, M.L., P.B. Desch, and R.B.Schwarz, "The Effect of Tin Alloyingon the Structure of LaNi5," Philos.Mag. A. 74,15 (1996).

Wasz, M.L., R.B. Schwarz, et al.,"Sn-Substituted LaNi5 Alloys forMetal Hydride Electrodes," Mater.Res. Soc. Symp. Proc. 393, 237(1995).

Yvon, P.J., R.B. Schwarz, et al.,"Covalent and Liquid-LikeAmorphous Phases in Al-Ge Alloys,"Philos. Mag. 72,167 (1995).

Characterization of Advanced ElectronicMaterials

Joe D. Thompson

The ability to characterize (measureand interpret) properties of advancedelectronic materials bridges the gapbetween materials synthesis andtheoretical modeling. This projectbuilds on and extends theLaboratory's competency in nuclearand advanced materials by character-izing the ground states of materials inwhich electronic correlations domi-nate the materials' properties. Ourgoal is to discover new physics byunderstanding the complex interplayamong microscopic interactions thatproduce these ground states.

This year we have discoveredevidence for an unexpected form ofmagnetism that develops in thesuperconducting state of B-dopedUBe13. We also used a broad range ofexperimental techniques to study theevolution of a first-order, isostructuralvalence transition with silver substitu-tion in YbIn!_xAgxCu4 and found thatinteractions driving this transition areplayed out on the unit-cell scale.Scaling analysis of thermodynamicdata established that gaps in the spin-

and charge-excitation spectra of acorrelation-driven semiconductor obeydifferent functional dependences.Analysis of the competition betweenmagnetic and electronic interactions forthe ground states of several rare-earthand actinide intermetallic compoundshas been made.

Publications

Heffner, R.H. and M.R. Norman,"Heavy Fermion Superconductivity,"Comments Condensed Matter Phys.17, 361 (1996).

Heffner, R.H., L.P. Le, G.J.Nieuwenhuys, et al., "PossibleEvidence for Spin or OrbitalMagnetism Below theSuperconducting TransitionTemperature in UBe1291B009"(submitted to Physica B).

Hundley, M.F., J.J. Neumeier, J.D.Thompson, et al., "Magnetostrictionand Thermal Expansion of the KondoSemiconductor Ce3Bi4Pt3," PhysicalPhenomena at High Magnetic Fields-7/2,203(1996).

Kwei, G.H., J.M. Lawrence, J.L.Sarrao, et al., "Structure and Disorderin YbInCu4," Phys. Rev. B 54, 6011(1996).

Mentink, S.A.M., H. Amitsuka, A.deVisser, et al., "ThermodynamicStudy of the Magnetic PhaseTransition in UNi4B" (submitted toPhysica B).

Movshovich, R., T. Graf, D. Mandrus,et al., "Response of CeRh2Si2 toPressure," Physica B 223 & 224, 126(1996).

Movshovich, R., T. Graf, D. Mandrus,et al., "Superconductivity in HeavyFermion CeRh2Si2," Phys. Rev. B 53,8241 (1996).

Movshovich, R., M.F. Hundley, J.J.Neumeier, et al., "Magnetism inCePtPb," Phys. Rev. B 53, 5465(1996).

Sarrao, J.L., CD. Immer, C.L.Benton, et al., "YbInlxAgxCu4:Evolution from First-Order ValenceTransition to Heavy FermionBehavior," Phys. Rev. B 54, 12014(1996).


Neutron Scattering Studies onShear-Induced Structure in Polymers

Rex Hjelm

Our objective is to study polymer-surface interactions and shear-induced, polymer orientation in thebulk. These aspects include self-lubrication effects in polymers underflow- and shear-induced phasetransitions in liquid crystal polymers.Shear is introduced in industrialprocessing when a polymer melt orconcentrated solution is passedthough an orifice, such as a spinnerused in fiber formation, or by injec-tion into the mold used in injection

molding. Thus the production offibers and molded parts in industrialapplications naturally introduces flowshear, which affects the conformationand orientation of polymer chains,making the effects of shear on poly-mer conformation and orientation ofconsiderable industrial interest. Adetailed understanding of the physicsof polymers under shear that could beused to connect the structure ofpolymers with their unique rheologi-cal properties has yet to emerge. Thus

there is little basis for predicting theeffect of an industrial processingstrategy on material properties.

The task for this year was to designand construct the apparatus neededfor this project. This work includedcompletion of an improved Couilette-geometry shear-cell rig with betterthermal isolation and control andbetter shear-cell alignment character-istics as well as fabrication ofaluminum, Couilette-geometry shearcells for high-temperature shear work.We also designed a cone and platerheometer for neutron reflectometryexperiments. We prepared materials tostudy shear flow characteristics ofliquid crystal polymers for measure-ments planned for early next year.

Structural and Magnetic Characterizationof Actinide Materials

Barbara Cort

The focus of this project is toextend our fundamental researchcapability and to answer questions ofpractical importance to stockpileintegrity and long-term storage ofnuclear material. We have success-fully used neutron scattering tech-niques to investigate physicochemicalproperties of elements, compounds,and alloys of the light actinides forthe last ten years. We now addressnew issues vital to the Laboratory'smission such as long-term storage ofnuclear materials and aging ofplutonium in primaries in the nuclearstockpile.

We made significant progress indevelopment of encapsulationtechniques for milligram quantitiesof actinides for neutron scatteringstudies. These techniques are impor-tant for studies of rare isotopesavailable only in small quantities orisotopes that are difficult to handle inlarger quantities because of theirradiological properties. We performeda successful test on a nonradioactivesample using the encapsulationassembly shown in the first figure. We

observed clear diffraction peaks, asshown in the second figure, for 15 mgof CaF2 counting for two hours on theManuel Lujan Jr. Neutron ScatteringCenter's high-intensity powderdiffractometer (HIPD). We used theseresults to calculate patterns for twoactinides of interest, AmD2 and PuO2,each counted for 24 hours (see secondfigure). We predict well-defineddiffraction peaks.

Based on these results, we plan touse neutron diffraction to investigatethe nature of intriguing changes in thetemperature dependence of theresistivity of AmD2 5. We will alsoperform neutron diffraction experi-ments to determine the structures ofsuperstoichiometric oxides ofplutonium produced from the reactionof plutonium oxides with water understorage conditions.

Publications

Threaded end attachesto HIPD

inner capsule

Haschke, J.M., T.H. Allen, and J.L.Stakebake, "Reaction Kinetics ofPlutonium with Oxygen, Water, andHumid Air," J. Alloys Compounds243, 23-35 (1996).

outer capsule

neutron flight path

actinide sample

support

welded caps

Assembly drawing of the small sampleencapsulation; scale is 2:1, in inches.


test of small cans - 4132 Hist 3Bank 3, 2-Theta 9 0.0, L-S cycle 22 Obsd. and Calc. Profiles

o

X

o

'musec.

3.0

count

2.0

Norm.

1.0

I

-

-1

i

I1

i

1

1.0D-spacing, A

15 mg. CaF2 - 2 hours - measured

test of small cans Hist 5Bank 3, 2-Theta 90.0, L-S cycle 13 Obsd. and Calc. Profiles

1.0D-spacing, A

100 mg. AmD2 - 24 hours - calculated

500 mg PuO2Bank 3, 2-Theta 90.0, L-S cycle

Hist 25 Obsd. and Calc. Profiles

1.0>-spacing, A

500 mg. PuO2 - 24 hours - calculated

Neutron diffraction data for CaF2 (top) and calculated patterns for AmD2 and PuO2.


Equation-of-State, Thermodynamic,and Structural-Mechanical Propertiesof Intermetallic Compounds

John Wills

Intermetallic compounds haveimportant applications as high-temperature structural materials.Their elastic, mechanical, andstructural properties as a function oftemperature, pressure, and composi-tion are key measures of theirusefulness. The goal of this projectwas to develop the theory andresources to perform ab initiocalculations of (1) the elastic proper-ties of high-temperature structuralmaterials, (2) the structural propertiesof ordered alloys, and (3) the equationof state of materials.

For our first goal, calculation of theelastic constants of C15 NbCr2 wascompleted during this fiscal year, aswell as calculations of the relativestructural stability of C15, C14, andC36 NbCr2 and HfV2. (C14, C15, andC36 designate various crystal struc-tures.) We calculated the isotropicshear modulus from Reuss/Voigtaverages and compared them with

experimental data; theory and exper-iment appear to be in significantdisagreement. These calculationswere done on the related structuralmaterials NbCr2 and HfV2 instead ofthe originally proposed Ti-Al and Ni-Al systems because of the timelyavailability of new experimental datawith which to compare.

Toward our second goal, wedeveloped and tested a method forperforming ab initio electronicstructure calculations on orderedalloys. This method improves on thevirtual crystal approximation for fullpotential calculations of inter-rowalloys. We applied this method to thecalculation of structural stability of(Ti, Zr)-(V,Ta) alloys for comparisonwith experimental results; experimen-tal results are thus far disappointing,and we are applying the method toelasticity in Nb-Cr alloys.

Finally, because of recent develop-ments in ab initio calculations oflinear response functions, we putaside our third goal of using fittedpotentials to generate a full-zonephonon spectrum in favor of thedevelopment of the resources toperform ab initio calculations of full-zone phonon spectra using linearresponse theory. We completed thedevelopment of the theory of thiscapability for the electronic structuremethod that we use. We also testedthe calculation of forces for a varietyof materials. The capability tocalculate phonons with linear re-sponse is currently being written intoour electronic structure codes.

Publications

Asta, M., R.C. Albers, et al., "First-Principles Study of IntermetallicPhase Stability in the Ternary Ti-Al-Nb" (proceedings of the fall meetingof the Materials Research Society,Boston, Mass., 1995).

Ormeci, A., F. Chu, J.M. Wills, et al.,"Total-Energy Study of ElectronicStructure and Mechanical Behavior ofC15 Laves" (to be published in Phys.Rev. E).

Neutron Scattering fromCorrelated-Electron Systems

Robert Robinson

The purpose of this project is toexploit the neutron scattering facilitiesat the Los Alamos Neutron ScienceCenter in the studies of correlated-electron behavior in both f-electronsystems (e.g., heavy fermions) andtransition-metal oxides (like the high-temperature superconductingcuprates). There are two main thrusts:(1) the use of pair-distribution-function (PDF) structural methods tostudy local disorder, particularly inthe cuprates, and (2) the use ofinelastic neutron scattering for thestudy of magnetic excitations in such

systems. The PDF method consists ofanalyzing the data in real (rather thanreciprocal) space, much as one does inmeasuring pair distribution functions inglasses or liquids; it complements moreconventional crystallographic methodslike Rietveld refinement. Inelasticneutron scattering is the technique ofchoice for measuring the magneticexcitation spectra in such systems.

We performed a number of highlysuccessful inelastic scattering studieson the PHAROS high-resolutionchopper spectrometer. These includeda study of the temperature depen-

dence of the 40-meV crystal-fieldlevel in UPdSn, a search for crystal-field excitations in UPd2Pb, and adefinitive experiment on the crystal-field level in PuO2. The PuO2 experi-ment showed, in contrast to a previouslower-resolution experiment atArgonne National Laboratory, thatthere is no quadrupolar splitting ofthis level, but that there is someresidual broadening.

On the diffraction side, we studiedthe Li-doped version of La2Cu04, theparent compound for the high-temperature superconductors, bymeans of conventional neutrondiffraction. Both the structural andthermal parameters are unusual andindicate that the local and averagestructures are not identical.


Advanced Deformation Process Modeling

U.FredKocks

The general aim of this project wasto improve the understanding of theconstitutive behavior of metals for usein deformation processing applica-tions. This project has had two majorcomponents: the description (on thebasis of dislocation mechanisms) of thekinetics of flow and strain hardeningand the description (on the basis ofpolycrystal plasticity models andmeasured textures) of the anisotropyof macroscopic strength properties.Progress was made on both fronts,with the following highlights.

The overall status of our strainhardening theory was reviewed andcompared with some new proposals(which were found wanting). Inparticular, the processes of dynamicrecovery seem well understood, butthis knowledge is not always appliedto best advantage. Some inroads havebeen made into improving the generalappreciation of this part of plasticitytheory.

For a long time, and according toall investigators, the prediction ofdeformation textures has sufferedfrom yielding textures that are toosharp, compared with experiments.A systematic investigation of theinfluence of texture sharpness (real orperceived) on macroscopic propertieshas demonstrated that this effect isnegligible in most cases. On the otherhand, slight shifts in the location oftexture peaks, whether as a result ofexperimental errors or of faulty modelpredictions, can have significanteffects on strain anisotropies, such asthose causing the so-called earing indeep-drawn metal sheets.

Continued cooperation withArmand Beaudoin of ReynoldsMetals Corporation and with HeinzMecking of the Technical UniversityHamburg-Harburg (Germany) hasbeen very effective, both from themodeling and from the applicationspoint of view.

Publications

Beaudoin, A.J., H. Mecking, and U.F.Kocks, "Development of Local ShearBands and Orientation Gradients inFCC Polycrystals," in Simulation ofMaterials Processing (NUMIFORM-5) (Balkema, Rotterdam, theNetherlands, 1995), pp. 225-230.

Beaudoin, A.J., H. Mecking, and U.F.Kocks, "Development of LocalizedOrientation Gradients in FCCPolycrystals," Philos. Mag. A 73,1503-1517(1996).

Beaudoin, A.J., P.R. Dawson, et al.,"A Hybrid Finite Formulation forPolycrystal Plasticity with Considera-tion of Macroscopic/MicroscopicLinking," Int. J. Plasticity 11,501-521(1995).

Beaudoin, A.J., T. Kota, H. Uto, et al.,"Simulation of Sheet Metal FormingUsing Polycrystal Plasticity," inDynamic Plasticity and StructuralBehaviors (Gordon & Breach, Boston,Mass., 1995), p. 221.

Kocks, U.F., S.I. Wright, and A.J.Beaudoin, "The Sensitivity of YieldSurface Predictions to the Details of aTexture," in Textures of Materials(ICOTOM-11) (InternationalAcademic Publishers, Beijing, China,1996), pp. 763-768.

MacEwen, S.R., A. Langille, J.Savoie, et al., "Characterization,Validation, and Finite ElementModelling of Extrusion," inSimulation of Materials Processing(NUMIFORM-5) S.F. Shen and P.R.Dawson, Eds. (Balkema, Rotterdam,the Netherlands, 1995), pp. 95-100.

Maudlin, P.J., S.I. Wright, et al., "AnApplication of Multisurface PlasticityTheory: Yield Surfaces of TexturedTa," in High Pressure Science &Technology (Warsaw Polish Academyof Sciences, Warsaw, Poland, 1995),pp. 138-140.

Mecking, H., C. Hartig, and U.F.Kocks, "Deformation Modes inGamma-TiAl as Derived from theSingle Crystal Yield Surface," AdaMater. 44, 1309-1321(1996).

Mecking, H., U.F. Kocks, and C.Hartig, "Taylor Factors in Materialswith Many Deformation Modes," Scr.Mater. 35, 465^71 (1996).

Poole, W.J., S. MacEwen, et al.,"Deformation Texture Developmentin a Model Composite System," TenthInt. Conf. Compo. Mat. II, 59-67(1995).

Wright, S.I., and U.F. Kocks, "AComparison of Different TextureAnalysis Techniques," in Textures ofMaterials (ICOTOM-llj(International Academic Publishers,Beijing, China, 1996), pp. 53-62.


Scanning Probe Microscopy CompetencyDevelopment

Marilyn Hawley

Our goal is to develop the ultra-high-vacuum (UHV) scanningtunneling microscope system toinclude in situ film fabrication andcomplementary analytical capabili-ties. We plan to integrate this systemwith existing scanning probe andsurface technologies. A broad rangeof applications will be enhanced fromthe existence of a range of scanningprobe instruments and the associatedstate-of-the-art expertise, particularlyat the nanoscale level. Of particularvalue is an extension of the presentcapabilities for examining surfaces inair to include the measurement ofsurfaces prepared under clean(vacuum) conditions.

We have now modified the systemto include a new vacuum chamber, anew load-lock system for sampleinsertion, and sample positioning andsample heating capabilities for both

( J

metal and semiconductor materials. Inaddition, we have added magnetic andelectric force capabilities to the airscanning probe and have used thesecapabilities to perform growth andcharacterization studies of magneto-resistive films. We have obtainedsome preliminary data on magneticstructure of thin films and stressedmagnetic ribbons, as shown in theaccompanying figure.

The combined capabilities nowenable us to respond to a wide varietyof problems requiring localizedimaging of conducting and noncon-ducting surfaces in liquids, air, UHV,and at low or elevated temperatures.We will further expand these capabili-ties to include imaging during or afterin situ mechanical stressing ofmaterials. Work has begun on addingnanoindenting, scratching, and in situtensile stress capabilities.

u. vv«r. '- »• <v

Topograph Magnetic Image

Tapping-mode atomic force microscope images, shown in profile, of the surfaceof a stressed Fe-Si-B magnetic melt-spun amorphous ribbon. The left-handimage shows the surface structure of the slip bands, while the right-hand imageshows the corresponding magnetic structure due to magnetoelastic effects thatcan be associated with residual stress in the ribbon. The magnetic image wasmade possible through the employment ofnoncontact and field gradienttechniques and the use of a CoCr- or permalloy-coated silicon tip. In thistechnique, the images are collected simultaneously. Topographic and magneticinformation is collected during alternate line scans.

Publications

Hawley, M.E., R.J. Houlton, et al.,"The Effect of Temperature, GrowthKinetics, and Substrate on theMicrostructure of RF Off-AxisSputter Deposited YBa2Cu3O7 ThinFilms," in Extended Abstracts of the1995 International Workshop onSuperconductivity (ISTEC &Materials Research Society, Pittsburg,Pa., 1995), p. 113.

Hawley, M.E., CD. Adams, P.N.Arendt, et al., "CMR Films' Structureas a Function of Growth andProcessing" (to be published in /.Crystal Growth).

Hawley, M.E., X.D. Wu, P.N. Arendt,et al., "Microstructural Study of CMRFilms as a Function of GrowthTemperature, As-Deposited andAnnealed," Mat. Res. Soc. Symp.Proc. 401, 531 (1996).

Hundley, M., J J . Neumeier, X.D.Wu, et al., "Transport-MagnetismCorrelations in the FerromagneticOxide La0 7Ca0 3Mn03," Appl. Phys.Lett. 67, 860 (1995).

Jia, Q. X., F. Chu, X. D. Wu, et al.,"Characteristics of ConductiveSrRuO3 Thin Films with DifferentMicrostructures," J. Mat. Sci. 11,2263 (1996).

Kistenmacher, T.J., D.K. Wickenden,et al., "Effect of Carrier Gas on theSurface Morphology and MosaicDispersion for GaN Films by Low-Pressure MOCVD," Mat. Res. Soc.Symp. Proc. 395, 261 (1996).

Kistenmacher, T.J., D.K. Wickenden,et al., "Real and Reciprocal SpaceMapping of the Mosaic Dispersion inSelf-Nucleated AlxGalxN Thin-Filmson (001) Sapphire," Appl. Phys. Lett.67, 3771 (1995).

Kodali, P., M. Hawley, K.C. Walter, etal., "Tribological Properties ofCarbon and Nitrogen ImplantedSi(100)" (to be published in Wear).


Design and Implementation of an X-RayStrain Measurement Capability Using aRotating Anode Machine

Joyce Roberts

Residual stresses close to thesurface of materials can improve thereliability and lifetime of parts such asgears, spindles, and axles for techno-logical applications. An exactknowledge of the stresses at thesurface and their depth distribution isimportant. X-ray diffraction plays asignificant role in measuring surfaceresidual stresses. Our project isfocused on developing an x-raycapability as a key to measuring andinterpreting strain effects.

We used finite-element models topredict the thermomechanicalprocessing effects on the residualstresses in a unidirectionally rein-forced SCS-6/Ti-6-2-4-2 [0]6material, and we used x-ray andneutron diffraction to measure theeffects. Both x-ray and neutrondiffraction recorded a reduction instresses in the processed materialcompared with the as-fabricatedmaterial. The decrease correlated withimprovement in fatigue lifetime.

A novel approach developed atCornell University employs thevolume shrinkage thataccompanies reductionreactions to inducecompressive residualstresses in thesurfaces of ceram-ics. In this ap-proach, alumina isbonded to a nickel-spinel oxide sampleduring hot pressing.When the spinel isreduced, it shrinks,inducing compressiveresidual stresses in thealumina. Our prelimi-nary x-ray measure-ments indicate that the

residual stresses present in thealumina fall below the predictedvalues.

Reduction reactions can also beapplied to magnetic metal-ceramicthin films. Nickel-spinel is reduced toobtain thin films containing nanoscalenickel. The nickel particles possessinteresting magnetic properties,including perpendicular magnetiza-tion. Anisotropic residual stressespresent in the nickel because of thevolume shrinkage and the coefficientof thermal expansion mismatch arebelieved to be the cause of theperpendicular magnetization. Ourpreliminary x-ray stress measure-ments have yielded tensile stresses ofseveral hundred megapascals; thesemeasurements correlate well withmagnetic anisotropy data obtained atCornell.

Another method for measuringstress, the crack-compliance method,offers a unique capability for measur-ing stress variation with depth. A slotincrementally introduced into a partcontaining residual stress causes localrelaxation. The resulting surface

Gear Blank

Slot

XP5120PFMBCO 8H19M

strains are measured at each incre-ment of slot depth and are used tosolve for the original residual stresses.Using this technique, we comparedthe results of the crack compliancemethod with x-ray and neutrondiffraction measurements. Thesecomparisons are shown in theaccompanying figure.

Publications

Bourke, M.A.M., P. Rangaswamy, etal., "Complementary Neutron andX-Ray Measurements in an Attemptto Obtain a Strain Profile through aCarburized Layer" (to be published inMater. Sci. Eng. A).

Jayaraman, N., and P. Rangaswamy,"Oxide Scale Stresses in Poly-crystalline Cu/Cu2O System" (to bepublished in Adv. X-Ray Anal).

Rangaswamy, P., M.A.M. Bourke,A.C. Lawson, et al., "Residual Stressand Microstructural CharacterizationUsing Rietveld Refinement of aCarburized Layer in a 5120 Steel" (tobe published in Adv. X-Ray Anal).

Rangaswamy, P., M.A.M. Bourke,P.K. Wright, et al., "Influence ofResidual Stresses on Thermo-mechanical Processing of SCS-6/T1-6-2-4 Titanium Metal MatrixComposites" (to be published inMater. Sci. Eng. A).

Tension

StressMeasurementLocations

0.0 0.2 0.4

Depth from0.6 0.8 1.0

Surface (mm)

Front View Side View

Comparison of stress measurements on a carburized gear blank (also shown) thatwere determined using x-ray and neutron diffraction and the crack-compliancemethod. The results from analysis are also shown for comparison.


Computational Modeling of MaterialsProcessing and Processes

Terry C. Lowe

The objective of this research wasto create a computational model todescribe the processing of porous,anisotropic materials. The initial focuswas on deformation processing ofbulk, high-temperature, superconduct-ing oxides. The anisotropic mechani-cal properties of densified powderscomposed of Bi-Sr-Ca-Cu-O(BSCCO) are of paramount impor-tance during thermomechanicalprocessing of superconducting tapesand wires. Maximum current trans-port requires high relative densitiesand high degrees of alignment of thesingle-crystal superconducting planesparallel to the plane of the tape. Thisconfiguration causes high stressesduring compressive processing modesand can lead to cracking and thusdegrade the density and conductiveproperties of the tape.

Early in the project we developed amodel to describe the mechanicalbehavior of BSCCO during deforma-tion processing. The model combinestheories of deformation for porous,elastic-viscoplastic, polycrystalmaterials. We conducted compactionexperiments on 2223 BSCCO powderin a confined channel-die environmentto obtain data for calibrating themodel. We then compared the modelwith other experimental results andused them to resolve the effects ofinitial texture and confinementpressure on the densification andultimate formability of the BSCCOpowder.

We performed a detailed, finite-element analysis of the tape-rollingenvironment and calculated bothpressures and shear strains in the coreof oxide powder-in-tube (OPIT)processed tapes. In addition, we

investigated rod-in-tube processingand rolling with extra packingmaterial. The calculated deformationswere then applied as boundaryconditions to the model we devel-oped. We used the calculated resultsto interpret a set of prototypicalrolling experiments designed toinvestigate core morphologiesresulting from various rolling environ-ments. Our goal was to understand thedeformations in the core of the OPITworkpiece and the resulting micro-structural evolution of the BSCCOpowder. We were able to simulate theeffects of multiple processingparameters on the texture and densityof the superconducting material. Oneof the most significant results was theprediction of the important role ofshear deformation on the evolution oftextural anisotropy.

Publications

Schoenfeld, S.E., S. Ahzi, et al., "TheBulk Processing of 2223 BSCCOPowders; Part I: Densification,"Philos. Mag. A 73,1565 (1996).

Nanometer-Scale Materials

David Devlin

Our focus is the science andtechnology needed for molecular-levelcontrol of materials on a nanometerscale—from advanced computingarchitectures to microelectronics andcatalysis. Molecular-level control thatrelies on artificial structures andnanometer-scale materials will help usdevelop entirely new devices andchemistries.

Using the metal amideMo2(N(CH3)2)6 as a molecular precur-sor, we prepared highly selective,alumina-supported, molybdenumcarbonitrides by solution impregnation.On the basis of relative weight per-cents, these materials demonstrate a 5-to 8-fold increase in catalytic activityover similar materials prepared bytraditional, solid-state approaches.

The catalytic activities of thesematerials depend on the type of

alumina support used. Impregnationof MomCxNy into preformed aluminapellets resulted in a material thatspecifically isomerized n-heptaneinto equal amounts of 2- and 3-methylhexanes and iso-butane. Wesaw no evidence of aromatic productsat operating temperatures below420°C. The product selectivity of theisomers was 56% at an n-heptaneconversion efficiency of 57%.Impregnation of MomCxNy into analumina powder resulted in anextremely selective aromatizationand dehydrogenation material. Theproducts from this material consistonly of aromatics and n-hepteneswith less than 2% isomerization orcracking products.

We developed scanning forcemicroscopies (atomic force and lateralforce) to probe the microscopic

structures of self-assembled, mono-layer systems (SAMs). Lateral forcemicroscopy proved especially usefulin imaging patterned SAMs formedusing microcontact printing tech-niques. We were surprised to observedifferences between SAMs ofalkanethiols on gold in stampedversus filled-in regions of u-contact,even when the molecules wereidentical. We studied these patternedSAMs, using Fourier transforminfrared and other spectroscopicmethods, and now attribute thedifference between stamped andfilled-in areas to density differences inthe SAMs.

Publications

Barrera, J., and D.C. Smith, "AluminaSupported MolybdenumCarbonitrides: An ExtremelySelective Material" (submitted to J.Catalysis).


Science and Technology of Reduced-Dimensional Magnetic Materials

Robert Heffher

Our research objective is to developa clear microscopic understanding ofthe physical mechanisms responsiblefor the unusual electronic transportproperties exhibited by the transition-metal oxides La1.xMxMnO3 (where Mcan be calcium, barium, or strontium).These materials typically undergo avery large reduction in resistance inmodest magnetic fields near theirferromagnetic transition temperatures,making them strong candidates forimportant technological applications.Our efforts combine the three keytools of advanced materials research:

(1) materials synthesis (single-crystaland poly crystal growth techniques);(2) physical characterization (x-raydiffraction, electronic transport,magnetization, thermopower, thermalexpansion, and magnetostriction); and(3) theoretical modeling.

We have grown large single crystals(7 mm in diameter and 1 to 2 cm long)of the ferromagnet Lai_xMxMnO3

(where M can be calcium or stron-tium) at the Los Alamos single-crystalfacility in the Materials ScienceLaboratory. Thermopower measure-ments on materials where M iscalcium and x = 0.0-0.45 indicate thatconventional transport models withnominal valence cannot account forthe small (doping-independent)magnitude of the high-temperature-carrier contribution to the Seebeckcoefficient. Because the number ofactive carrier sites is less thanexpected from the doping x (x = Mn3+

concentration), charge disproportion-ation (2Mn3+ goes to Mn2+ + Mn4+)may be important in these systems.

In the theoretical realm, we havecarefully analyzed the double-exchange model and found that theground state and the low-lyingmagnetic excitations are far richerthan often assumed in approximateand mean-field treatments. This result

is consistent with a variety of experi-mental data (e.g., neutron pair-distribution function analysis, x-rayabsorption fine-structure analysis,thermopower) and with the fact thatreal materials involve orbital interac-tions, disorder, and Jahn-Tellerelectron-lattice coupling.

Publications

Heffner, R.H., L.P. Le, M.F. Hundley,et al., "Ferromagnetic Ordering andUnusual Magnetic Ion Dynamics inLa67Ca33MnO3," Phys. Rev. Lett. 77,1869 (1996).

Hundley, M.F., and J J. Neumeier,"Thermoelectric Power of

Laj xCaxMnO3: Inadequacy of theNominal Mn(3+/4+) ValenceApproach" (submitted to Phys. Rev. B).

Neumeier, J.J., A.L. Cornelius, andM.F. Hundley, "Volume-BasedThermodynamic Considerations forthe Magnetoresistance Effect andMetal-Insulator Transition of CMRManganese-Oxide Perovskites"(submitted to Phys. Rev. Lett.).

Roder, H., J. Zang, and A.R. Bishop,"Lattice Effects in the ColossalMagnetoresistance Manganites,"Phys. Rev. Lett. 76,1356 (1996).

Tyson, T.A., et al., "Evidence for aLocal Lattice Distortion in Ca-DopedLaMnO3" (to be published in Phys.Rev. B).

Zang, J., A.R. Bishop, and H. Roder,"Double Degeneracy and Jahn-TellerEffects in ColossalMagnetoresistance," Phys. Rev. B 53,8840 (1996).

Complementary Neutron Diffraction andComputational Micromechanics Studies ofPolycrystalline Deformation in AdvancedMaterials

Mark A. M. Bourke

The objectives of our project are touse neutron diffraction to improve theunderstanding of polycrystal deforma-tion and to relate the results tomicromechanical models. The scopeincludes measuring residual and in situloading strains, as well as thermalrelaxation effects. We have selectedseveral materials for study and, to date,have performed measurements on NiAl-A1N-A12O3 composites, CuMo,austenitic steel, and NiTi composites.

Our effort in computational modelinghas focused on validating a self-consistent elastic-plastic model used topredict the response of a face-centeredcubic stainless steel. The model predictselastic lattice strains (that developwithin subsets of grains in predeter-mined orientations) which are thencompared with the measured values

averaged over the bulk using neutrondiffraction. To date, we have observedgood agreement between the predictedand measured values for strains parallelto the load, whereas we found signifi-cant differences between the two valuesfor strains perpendicular to the load.

In developing the experimentalcapabilities, we purchased a 1200°Ccontrolled-atmosphere furnace andadapted it for operation on the neutronpowder diffractometer at the LosAlamos Neutron Science Center.During the next year, we will use thisfurnace to determine relaxationtemperatures of NiAl-based compos-ites. In a separate development, weimplemented two infrared lampheaters on an existing stress rig andare presently performing creep studieson a model CuMo system.


Characterization of Active Sites inZeolite Catalysts

Juergen Eckert

Atomic- or molecular-level detailsof the interaction of adsorbed mole-cules with active sites in catalysts areurgently needed to facilitate develop-ment of more effective and/orenvironmentally benign catalysts. Tothis end we are carrying out inelasticneutron scattering (INS) studiescombined with theoretical calcula-tions of the dynamics of smallmolecules inside the cavities ofzeolite catalysts.

Our principal approach has been toutilize molecular hydrogen (H2) as aprobe of active sites in the zeolite.The interaction of H2 with adsorptionsites gives rise to a barrier to rotationfor the molecule, which is readilyobtained by INS techniques. Wefound that this barrier differedsubstantially for different sites.

The unit cell of zeolite A is shownin the accompanying figure. Eachvertex is occupied by either a siliconor an aluminum atom, and thesevertices are bonded to one another viaan oxygen atom. Cations, such as Na+,are located on extraframework sites.Three of these cations are shown: Na Iapproximately in the plane of a six-ring (a ring of six vertices), Na II inthe plane of the large eight-ring (theopening to the large cavity called thesupercage), and Na III above the four-ring. With the aid of Quantum MonteCarlo simulations, we were able toshow that an area near the four-ring isthe most likely adsorption site for H2

in zeolite A, and we established atrend for adsorption near a variety ofdivalent cations (located near the six-rings) exchanged for Na+. Coadsorp-tion of N2 and H2 displaced H2 from

the preferred adsorption sites andenabled us to identify secondaryadsorption sites.

Our INS studies of the adsorptionof other small molecules (water,ethylene, and cyclopropane) serve asa benchmark for theoretical calcula-tions of the dynamics of adsorbates incatalysts. We experimentally deter-mined the modes of adsorbed ethyl-ene in zeolite NaX and found thesemodes to be in excellent agreementwith the results of ab initio calcula-tions. We also demonstrated the utilityof INS spectroscopy to monitor slowreactions in zeolites by observingisomerization of cyclopropane inpartially Cu2+-exchanged zeolite A.

Publications

Eckert, J., J.M. Nicol, et al.,"Adsorption of Hydrogen in Ca-Exchanged Na-A Zeolites Probed byInelastic Neutron ScatteringSpectroscopy," J. Phys. Chem. 100,10646 (1996).

Eckert, J., R. Varma, et al., "Effects ofCycling Conditions of Active Materialfrom Discharged Ni Positive PlatesStudied by Inelastic NeutronScattering Spectroscopy" (submittedto J. Electrochem. Soc).

Na !M

Unit cell of zeolite A with three cationic sites. Adsorption ofH2 is strongest near Na III.


New Initiatives in MaterialsCharacterization, Modeling, and Synthesis

Don Parkin

This project is a collaborationbetween Laboratory and externalmaterials science researchers to explorenew techniques in a variety of areasrelated to the characterization, constitu-tive modeling, and synthesis ofmaterials. Specifically, in the area ofcharacterization, the focus is onexpanding strengths in electron,scanning-probe, and atomic forcemicroscopy and x-ray and neutroncharacterization of matter, and to dothis in collaboration with outsideacademic institutions. In modeling, thefocus is on improving our ability tomodel both the fundamental electronicstructure of materials and theirmechanical behavior. Another goal isan improved ability to synthesizedifferent kinds of materials rangingfrom electronic to structural materials.

As part of the collaboration, weheld three major workshops on thefollowing topics to explore the stateof the art and potential scientific

advances: "Ion Interactions andRadiation Damage," "MaterialsSolidification," and "FundamentalElectronic Structure of Plutonium."The radiation damage workshopfocused on fundamental aspects ofradiation effects on ceramic materialsand nuclear material waste forms. Theworkshop on solidification focused oncasting processes, including pluto-nium casting issues. The electronicstructure workshop addressedfundamental issues in modeling theelectronic structure of f-electronmaterials (actinides).

In related activities, we developedan alternative to the standard molecu-lar dynamics approach for atomisticsimulation of dislocation crossing,annihilation, and short-range forces.We also developed a high-temperatureprobe for operation in the NationalHigh Magnetic Field Laboratory's20-T magnet and measured the high-temperature Hall constants.

Publications

Becker, J.D., J.M. Wills, et al.,"Electronic Structure of PuCompounds with Group IIIB Metals:Two Regimes of Behavior," Phys. Rev.B 54, 17265 (1996).

Griffin, A. Jr., J. Embury, M. Hundley,et al., "Residual Stress, MechanicalBehavior and Electrical Properties ofCu/Nb Thin Film Multilayers," Mater.Res. Soc. Proc. 382, 309 (1995).

Sickafus, K., R. Raj, and P. Prakash,"Vanadium Metal-MGA1204 SpinelComposites for Structural Applicantsin Neutron and Other HostileEnvironments" (to be published in J.Nucl. Mater.).

Ustundag, E., K. Sickafus, Y. He,et al., "Metal-Ceramic Composites forHostile Environment Applications," inCeramic Matrix Composites Sym-posium Proceedings, Vol. 74, N.P.Bansil, Ed. (American CeramicsSociety, Westerville, Ohio, in press).

Walter, K., K. Kern, J. Tesmer, et al.,"Nitrogen and Boron Ion Implantationinto Electrodeposited Hard Chrome,"in Surface and Coatings Technology(Elsevier, Oxford, U.K., in press).

Dynamics of Polymers at Interfaces

Gregory Smith

This project addresses fundamentalquestions concerning the behavior ofpolymers at interfaces and poses thefollowing questions: What processescontrol the formation of an adsorbedlayer on a clean surface? Can weaccurately predict the structure of non-equilibrium layers? What processescontrol the desorption or displacementof preadsorbed polymers?

Last year we performed the firstexperiments to study the nonequi-librium architecture of polymer layersstrongly adsorbed from the polymermelt. We constructed a sample holderfor our film-spinner that supported theweight of the quartz crystals for theexperiment (the crystal dimensionswere 1.5 x 3 x 0.5 in.). Hydrogenated

(poly)methyl methacrylate (H-PMMA)was spin-coated onto the quartz crystalsurfaces and subsequently annealed atmelt conditions. After cooling, un-bound material was leached away in asolvent bath.

Using neutron reflection (NR), weinvestigated the architecture of theresidual bound layer swollen in goodsolvent (benzene) or collapsed against anonsolvent (D2O). The quartz crystalswere mounted in a specially designedcell, which placed the coated surfacesin contact with a solvent and at thesame time permitted the NR studies.We measured the reflectivity ofneutrons, R(q) vs q (q is the neutron'smomentum transfer) at the ManuelLujan Jr. Neutron Scattering Center for

both swollen and collapsed layers forseveral molecular weights. Collapsedlayer thicknesses generally increasedwith molecular weight. Data for swollenlayers suggest diffuse segment-densityprofiles. A detailed analysis will allowus to verify the Guiselin theory ofadsorbed polymers, which in turn willallow us to predict the structure ofnonequilibrium layers

In a separate experiment, the residuallayer was overcoated with a layer ofdeuterated PMMA (D-PMMA) and thesystem annealed at the melt conditions.Subsequent leaching and interrogationby NR indicated substantial replacementof the strongly adsorbed H-PMMA byD-PMMA in the overcoating, suggest-ing that the residual H-PMMA layersstudied were formed by suddenimmobilization at the surface of anequilibrated melt. These studies give usclues into the process of displacement ofadsorbed polymers.


Understanding and ControllingSelf-Assembly

Basil Swanson

The fields of self-assembly and self-organizing mesoscale structures havegrown rapidly over the past decade. Inaddition to fundamental research thatspans simple self-assembled monolayers(SAMs) to complex, biologicallyinspired self-organizing structures,there has been increased interest inapplying self-assembly to produceuseful, functionalized materials. Inorder to enhance useful materialsproperties, we must first understandthe relationships between structure andfunction in SAMs and in more com-plex self-assembled structures thatincorporate specific functional groups(for example, donor-acceptor com-plexes, molecules with high opticalnonlmearity, and reagents for molecu-lar recognition).

The overall objectives of this projectare to develop an in-depth understand-ing of how complex molecular struc-tures form by self-assembly and how theindividual molecular components andbulk functionality are interrelated. Ourapproach is to (1) experimentallycharacterize and theoretically modelintra- and interplanar ordering of modelSAMs in an effort to understand andcontrol the self-assembly process, (2)develop new experimental probes ofmesoscale structure and use them toaugment more traditional characteriza-tion methods, (3) prepare well-orderedmodel SAMs and characterize theirmesoscale structures using the experi-mental probes, and (4) couple theoryand experiment to develop models thatwill allow us to predict mesoscalestructures and, thus, to synthesize SAMswith optimal physical properties.

During this year we used scanningforce microscopies to image patterned,alkanethiol SAMs that we formed ongold using microcontact printing, andwe correlated the results from theimaging with spectroscopic studies. Wediscovered that the different densities ofstamped and solution-grown SAMs ofhexadecanethiolate on gold caused the

frictional and compressional forcedifferences that we observed withscanning force microscopies. Usingspectroscopic techniques, we probedthe structures of different end-functionalized, alkanethiol SAMs andfound the results to be consistent withnanoscale cluster formation. We alsobegan studying new techniques (sum-frequency generation and surface-enhanced Raman spectroscopy) forcharacterizing the organic-inorganicinterface.

To simulate the behavior of theSAMs of alkanethiols adsorbed ongold, we wrote a new, large-scale,massively parallel molecular dynamics(MD) code. In addition, we performedab initio, quantum-chemistry calcula-tions of the sulfur-gold potential-energysurface and used these calculations todevelop a detailed model of theorganic-inorganic (specifically, thesulfur-gold) surface. From this modelwe developed an empirical functiondescribing the sulfur-gold interactionand used in it in MD calculations. Wealso further developed a three-dimensional analog of alkanethiolSAMs and studied it using a variety ofstructural and spectroscopic probes.

Publications

Bar, G., S. Rubin, A.N. Parikh, et al.,"AFM-Studien zum Materialkontrastan Diinnen Organischen Filmen"(Mikrosymposium Elektronenmi-kroskopie in der Materialforschung,Merseburg, 1996).

Bar, G., S. Rubin, A.N. Parikh, et al.,"Compositional Imaging of PatternedSelf-Assembled Monolayers UsingScanning Probe Microscopies: Effectsof Chain Length, Packing, andDensity" (43rd National Symposiumof the American Vacuum Society,Philadelphia, Pa., October 1996).

Bar, G., S. Rubin, A.N. Parikh, et al.,"Scanning Force Microscopy Study of

Patterned Monolayers of Alkanethiols onGold. Importance of Tip-Sample ContactArea in Interpreting Force Modulationand Friction Force Microscopy Images"(to be published in Langmuir).

Bar, G., S. Rubin, A.N. Parikh, et al.,"Tribology Studies of Organic ThinFilms by Scanning Force Microscopy"(Materials Research Society 1996 SpringMeeting, San Francisco, Calif., April1996).

Bar, G., S. Rubin, T.N. Taylor, et al.,"The Influence of Contamination onthe Compositional Imaging of Self-Assembled Monolayers by ScanningForce Microscopy" (to be published inSupramol. ScL).

Bar, G., S. Rubin, T.N. Taylor, et al.,"Self-Assembled Monolayer ofFerrocene and Methyl TerminatedAlkanethiols on Gold: A CombinedElectrochemical, Scanning ProbeMicroscopy, and X-Ray PhotoelectronStudy," J. Vac. Sci. Technol. A14 (3),1794 (1996).

Beardmore, K.M., N. Gr0nbech-Jensen,and J.D. Kress, "Dynamical Simulationof Perturbed Systems of Alkanethiols onGold Surfaces" (American VacuumSociety Symposium, Philadelphia, Pa.,October 1996).

Beardmore, K.M., J.D. Kress, et al.,"Ab Initio Calculations of the Gold-Sulfur Interaction for AlkanethiolMonolayers" (International Conferenceon Synthetic Metals, Snowbird, Utah,July 1996).

Li, D., J.-X. Shi, et al., "Cyclodextrin-Based Surface Acoustic WaveChemical Microsensors" (Spectrum'96, Seattle, Wash., July 1996).

Parikh, A.N., G. Bar, et al., "LateralForce Microscopy Characterization ofMicro-Contact Printed PatternedMolecular Films" (Materials ResearchSociety 1996 Fall Meeting, Boston,Mass., November 1996).

Yang, X., D. McBranch, et al., "Design,Construction, and Architecture ofCovalently Bound, Polar Self-Assembled Molecular Pyramids onOxide Surfaces," Angew. Chem., Int. Ed.Engl. 35 (5), 538 (1996).

150 Los Alamos PC 1996 LDRD Progress Report

Role of Charge Localization in the BasicHigh-Temperature SuperconductivityMechanism

P. Chris Hammel

Local structure profoundly affectsthe superconducting, normal elec-tronic, mechanical (for example,elastic), and other response functionsof materials. By emphasizingcuprates, our project examines thisdifficult, important, and as yet barelystudied problem of structure. We havebeen focusing on oxide superconduc-tors, and related nonsuperconductingcompounds, by using an array ofexperimental and theoretical tech-niques to characterize the localstructure and its correlations, measurethe effects of the local structure onsuperconducting and other macro-scopic properties, and create a newtheoretical understanding of high-temperature superconductors.

This year, we have used nuclearmagnetic resonance to study thedoped-hole state in La2Cu5Li5O4(LiLCO) and found a surprisinglylow-lying excitation. We have usedelectron, x-ray, and neutron diffrac-tion to investigate the structure ofLiLCO and its magnetometry, whichwill then enable us to characterize thematerial's magnetic properties. Wehave found that the temperature andnickel-content dependencies of thethermal conductivity of severalnickel-doped bismuth cuprates(BSCCO) between 0.05 and 2 K arecontrary to theoretical predictions.

We have developed a self-consistenttreatment of magnetic and nonmag-netic impurity states in d-wavesuperconductors, which result instrongly anisotropic quasi-particlestates; formulated a three-dimensionalmodel for layered superconductorsthat couples structural buckling andstrong electron-electron interactionsin the a-b plane to antiferroelectricpolarizability fluctuations in the

c-direction; begun a systematic studyof spin-charge-lattice coupling inPeierls-Hubbard models in the contextof charge (polaron) ordering inLiLCO and in the context of stripedsuperlattice phases in hole-dopedCuO2 planes; understood the broken-symmetry solutions observed in abinitio cluster calculations on theCu2On dimer in terms of anoccupation-dependent hoppingintegral and showed that this rehy-bridization produces an attractiveinteraction; and proposed a strongcoupling explanation for why pairingshould have d-wave symmetry in thepresence of antiferromagneticcorrelations.

Publications

Balatsky, A.V., and M. Salkola,"Impurity States and the Absence ofQuasi-Particle Localization inDisordered d-Wave Superconductors,"Phys. Rev. Lett. 76, 2386 (1996).

Bishop, A.R., J.T. Gammel, andM. Salkola, "Local Polarizability,Structure, and Charge-Transfer inHigh-Temperature Superconductors,"J. Superconductivity 8, 1 (1996).

Bussmann-Holder, A., andA.R. Bishop, "Time-DependentEvolution of Double-Well Potentialsto Model Structural Anomalies," Phil.Mag. 73, 657 (1996).

Bussmann-Holder, A., A.R. Bishop,et al., "3-Dimensional Gap Structurein Layered High-TemperatureSuperconductors," Phys. Rev. B R53,11968(1996).

Hammel, P C , and D.J. Scalapino,"Local Microstructure and theCuprate Spin Gap Puzzle," Phil. Mag.B 74 (5), 523 (1996).

Martin, R.L., "Electronic Localizationin the Cuprates," Phys. Rev. B 53,15501 (1996).

Martin, R.L., "Rehybridization andPairing in the Cuprates," Phys. Rev. BR54, 9647 (1996).

Salkola, M., A.V. Balatsky, andD. Scalapino, "Theory of Scanning-Tunneling-Microscopy Probe ofImpurity States in a d-WaveSuperconductor," Phys. Rev. Lett. 77,1841 (1996).

Salkola, M., A.V. Balatsky, andJ.R. Schrieffer, "Spectral Properties ofQuasi-Particle Excitations Induced byMagnetic Moments in Super-conductors" (to be published in Phys.Rev. B).

Sarrao, J.L., D.P Young, Z. Fisk,et al., "Structural, Magnetic andTransport Properties ofLa2CUj xLixO4," Phys. Rev. B 54,12014 (1996).

Scalapino, D.J., and S.A. Trugman,"Local AntiferromagneticCorrelations and dx2 _yi Pairing,"

Phil. Mag. B 74 (5), 607 (1996).

Schmeltzer, D., and A.R. Bishop,"Bosonization of the 2-Dimensionalt-J Model in the Continuum-Limit,"Phys. Rev. B 54 (6), 4293 (1996).

Shenoy, S., V. Subrahmanyan, andA.R. Bishop, "Quantum ParaelectricModel for Layered Superconductors"(submitted to Phys. Rev. Lett.).

Yoshinari, Y, PC. Hammel,J.A. Martindale, et al., "MagneticExcitations of the Doped-Hole Statein Diamagnetic LajCuQ 5Li0 5O4,"Phys. Rev. Lett. 77, 2069 (1996).


Measurement by Neutron Diffractionof Strains in Advanced EngineeringStructural Materials including AlSiCand AITiC

Mark A. M. Bourke, Los Alamos National LaboratoryDavid C. Dunand, Massachusetts Institute of Technology

Drawing on our earlier work withAITiC and given the similarity inmechanical properties, we chose toexamine a shape-memory alloycomposite (NiTiTiC). Initially weconcentrated on the composite'smatrix (NiTi). Using neutron diffrac-tion, we studied the formation ofstress-induced martensite insuperelastic NiTi during uniaxialcompressive loading and unloading.Using a Rietveld refinement with aMarch-Dollase texture formulation,we determined the martensitic andaustenitic phase fractions as afunction of the applied stress. Beforeloading, the specimen was fullyaustenitic. At the highest appliedstress (-625 MPa), about 90% of theaustenitic phase had transformed tomartensite, with a concomitantmacroscopic strain of -2.8%. Uponunloading, all of the stress-inducedmartensite reverted to austenite, andthe totality of the macroscopic strainwas recovered. We determined thepropensity for various austeniticcrystallographic orientations totransform at different stresses.

After yield at a stress of about-350 MPa, plastic deformationresulted from the austenite-to-martensite transformation. Thedifference in structure between theunstressed and stressed states wasvisible in the broad martensitic peaksthat were clearly discernible from thesharp austenite peaks. The progres-sion and reversibility of the transfor-mation are illustrated in the firstfigure, which shows a short section ofthe spectra for each stress level. Uponloading, the shift to shorter d-spacings

resulted from increasing elasticcompressive strains, while thedecrease in intensity of the austeniticpeak and simultaneous increase in themartensitic peak were due to transfor-mation. The stress-dependence of thephase volume fractions determined bythese refinements are shown in thesecond figure. One unexpected resultwas that about 90% of the austenitewas trans-formed to martensite at amacro-scopic strain of only -2.8%.

0.002

| 0.0015 -

Publications

Bourke, M.A.M., R. Vaidyanathan,and D.C. Dunand, "NeutronDiffraction Measurement of StressInduced Transformation inSuperelastic NiTi," Appl. Phys.Lett.69 (17), 2477-2479 (1996).

Dunand, D.C., D. Man, et al."Neutron Diffraction Study of NiTiduring Compressive Deformation andafter Shape Memory Recovery," J.Physique IV 5,653(1995).

o

CO

0.001 -

0.0005 I-

-7 MPa (Final)

-130 MPa

-210 MPa

-268 MPa

-317 MPa

-439 MPa

-625 MPa

-580 MPa

-540 MPa

-490 MPa

-390 MPa

-261 MPa

-132 MPa

-5 MPa (Initial)

2.8 2.85 2.9 2.95 3.05 3.1

d spacing (A)

Displaced spectra showing a short section of the diffraction patterns obtainedwith the scattering vector parallel to the loading direction. The austenitic [100]at 3.0 A r educes in intensity to 0 at -625 MPa. Conversely the martensitic[100] at 2.86 A becomes visible at -490 MPa and reaches a maximum inintensity at -625 MPa (bold line). The shift to shorter d-spacings is due to theincreasing elastic compressive strain. The data has been smoothed anddisplaced vertically for clarity.


100

The relative intensities of theaustenitic and martensitic diffractionpatterns can be converted to volumefractions of the two phases.Martensite starts to form atcompressive loads greater than-400 MPa; upon unloading, however,it remains present until below-280 MPa.

1CD

CL 20 -

0 - -

-700 -600 -500 -400 -300 -200 -100

Applied compressive stress (MPA)

Chemistry and Microstructure of High-Temperature Superconductor Interfaces

Quanxi Jia

The research objectives of thisproject are to investigate the interfacechemistry, physics, and microstructureof superconductor and normal-metalcomposites and to use these compos-ites to develop high-performancesuperconducting quantum interferencedevices (SQUIDs) with controllableand reproducible properties. SQUIDsare state-of-the-art ultrasensitivedevices that detect very low magneticfields. Among other applications, theyare used to nondestructively evaluatematerials, measure the biomagnetismof human living organs, measuregravity in mineral surveying, anddetect underground bunkers andsubmarine communication.

At the core of this project, we aredeveloping composites and investigat-ing the mechanisms that control theelectrical properties of the materials.This year, through processing controland material engineering, we investi-gated the interface chemistry andmicrostructure between superconduc-tor and normal-metal layers of thedevices. We fabricated superconduct-ing Josephson junctions (two super-conductor electrodes separated by athin barrier, across which currentflows without a voltage drop) and dc

SQUIDs using an edge-geometrysuperconductor/normal-metal/super-conductor (SNS) configuration. Weused Ag-doped YBa2Cu3O7_-t: aselectrodes and PrBa2Cu3O7_J. as thenormal-metal barrier. The IcRn value(the product of the critical current andthe junction resistance) was in therange of 120-140 uV; we determinedthis value from the current-vs-voltagecharacteristic of the devices. The dcSQUIDs showed a differential-fluxmodulation depth, dV/d<S> (whereV is voltage and <J> is flux), ofgreater than 150 uV/<&0 at 75 K(<D0 = 2.07 x 10"15 Wb). More than90% of the SQUIDs on a chip (14 dcSQUIDs on a 1-cm2 LaAlO3 sub-strate) showed well-behaved voltage -vs-flux characteristics. Three typicalmeasures of performance are theSQUID modulation depth, the SQUIDnoise, and the process control. Weobtained devices at 75 K with amodulation depth of 49 uV, a noisevalue of 5 UOQ/HZ05 at 1 kHz, and astandard deviation in SQUID resis-tance of 11%. All these values aresuperior to the best results for SNS-configured device structures fromother research groups.

Publications

Jia, Q.X., X.D. Wu, and D. Reagor,"Material and Device Engineering inHTS Josephson Junctions," in Studies ofHigh Temperature Superconductors, A.Narlikar, Ed. (Nova Science Publishers,Inc., New York, 1996), p. 217.

Jia, Q.X., D. Reagor, H. Kung, et al.,"HTS Edge-Geometry SNS Junctionswith Engineered Normal-MetalLayers," Supercond. Sci. Technol. 9,985 (1996).

Jia, Q.X., D. Reagor, X.D. Wu, et al.,"Characterization of Ramp Edge-Geometry SNS Junctions and dcSQUIDs" (to be published in IEEETrans. Appl. Supercond.).

Jia, Q.X., X.D. Wu, D. Reagor, et al.,"Edge-Geometry SNS dc SQUIDsUsing Ag-Doped YBCO Electrodes,"Electron. Lett. 32, 499 (1996).

Jia, Q.X., X.D. Wu, D. Reagor, et al.,"Properties of Edge-Geometry HTSSNS Junctions and SQUIDs" (1996Applied Superconductivity Conference,Pittsburgh, Pa., August 25-30,1996).

Jia, Q.X., X.D. Wu, D. Reagor et al.,"Superconducting GaBaCuO EdgeJunctions with Lattice MatchedBarriers," /. Appl. Phys. 78,2871(1995).

Wu, X.D., Q.X. Jia, D. Reagor et al.,"High Performance YBCO Edge SNSJunctions and SQUIDs" (8thInternational Symposium onSuperconductivity, Hamamatsu, Japan,October 30-November 2,1995).


Texture Science and Technology

Michael Stevens

The objectives of this project are to(1) perform basic research on theeffects of texture on material proper-ties, (2) increase the utilization oftexture and anisotropy informationthrough texture analysis, and (3) im-prove our texture measurement andmodeling capabilities. Texture refersto studying the orientation, shape, andsize of the individual crystals inpolycrystalline materials.

We have made significant progresson advanced texture analysis algo-rithms that use many pole figures(diffraction peaks) and a few sampleorientations. Our new algorithmgreatly reduces the data collectiontime needed at a time-of-flightneutron diffraction facility. It com-bines crystallographic Rietveldanalysis of diffraction spectra withcalculations of orientation distributionfunctions. The algorithm is particu-larly useful for monochromatic

radiation with position-sensitivedetectors or for polychromatic radia-tion. Full diffraction spectra may nowbe used in the analysis, resulting inmaximum use of data. We applied ouradvanced texture algorithm to a sampleof experimentally deformed limestoneand produced excellent simultaneousresults on the sample's texture, crystalstructure, microstructure, and residualstress. It appears that the algorithm'smethodology is applicable to low-symmetry and polyphase materials withcomplicated diffraction spectra; suchmaterials presently elude quantitativetexture analysis.

Through our collaboration with theGeology Department at the Universityof California, Berkeley, we refinedour BEARTEX software to allowsimultaneous goniometer control anddata acquisition on both of our x-raytexture diffractometers. The improve-ments allow operation with a common

WINDOWS desk-top computer andbetter coverage of orientation space.

After comprehensively reviewingorientation-imaging microscopes anddata collection and analysis hardwareand software, we ordered a Philipsfield-emission-gun scanning electronmicroscope (SEM). This SEM willallow us to map orientations on asubgrain scale and determine mis-orientations between grains inpolycrystalline aggregates. Mis-orientation data are essential forunderstanding the process of recrys-tallization, which is of interest in avariety of structural materials.

Publications

Von Dreele, R., "Quantitative TextureAnalysis by Rietveld Refinement" (tobe published in /. Appl. Crystallogr.).

Wright, S., and U. Kocks, "AComparison of Different TextureAnalysis Techniques," in Textures ofMaterials (ICOTOM-II), Z. Liang, L.Zuo, and Y. Chu, Eds. (InternationalAcademic Publishers, Beijing, China,1996), pp. 53-62.

Microstructures of Transition MetalOxides Characterized by Neutron andX-Ray Scattering

Michael Fitzsimmons

The La-Mn perovskites of the typeLa1_JVI;tMnO3 (where M can becalcium, strontium, or barium, and xvaries from 0 to 0.5) are materialswhich become ferromagnetic at lowtemperatures. The transition tempera-ture, magnetoresistance, and atomicand magnetic structures of thematerials are believed to be deter-mined in part by the valence ofmanganese, which can be changedthrough the doping of the M species.Our studies of these materials areconcerned with using x-ray andneutron scattering to characterize the

atomic and magnetic structures andvibrational modes of the perovskites.

During the past year, we measuredthe neutron diffraction patterns of twosintered polycrystalline LaMnO3

samples. The samples were dopedwith 20 and 33 at. % calcium. Themost interesting and challengingexperiment involved measuring theeffect of a 1-T magnetic field on theatomic structure of the sample dopedwith 33 at. % calcium. We took themeasurements with field on and offand at a variety of temperatures

within two degrees of the transitiontemperature of the sample. Ouranalysis of the data is not yet com-plete. However, we can report thatstartling changes in the atomicstructures of the samples were notobserved at any time.

We also examined the atomicstructure of a single crystal ofLaMnO3 doped with 20 at. % cal-cium. We found the structure of thismaterial to be monoclinic withmonoclinic symmetry. This result isvery surprising in light of the fact thatearlier studies of polycrystallinesamples, including ours, suggestedthat the structure of this perovskitewas orthorhombic with orthorhombicsymmetry.


AThermodynamically Consistent,Damage-Dependent, Interface DebondingModel for Composites

Bradford E. Clements

The ability to design compositematerials and analyze processingprocedures relies on the availability ofconstitutive models that describe thecomposites' dynamic responseaccurately. The strength, damageevolution, and failure of interfaceswithin composites often dominatetheir macroscopic performance butare not well characterized. The designof such composites for particularapplications requires adequateknowledge of interfacial characteris-tics. Given the large number ofpotential loading scenarios that anengineering composite can be sub-jected to, it is extremely beneficial tohave reliable and accurate theoreticalmethods for their quantitativetreatment in numerical calculation.

We have developed a method foranalyzing interfacial debonding basedon the highly successful method ofcells (MOC) homogenization tech-nique for composite structures. Whenperfect interfacial bonding applies,displacement and traction continuityare conditions that are enforced by theMOC analysis. On the other hand, forimperfect interfacial bonding, thedisplacement becomes discontinuousat the interface. Imperfect bonding ismodeled by an interfacial constitutiveequation (ICE).

Our specific accomplishments inthe past year include quantifying theICE model for tensile and shearloading in plastic bonded explosives.Furthermore, we have used slightlydifferent ICE formulations to modelbrittle and ductile interfaces. We have

also implemented the imperfect-bonding MOC model into our three-dimensional finite-difference codes.These models are sufficiently generalto allow for laminated systems, long-fiber-reinforced composites, andparticulate (discontinuous reinforce-ment) composite systems. Further-more, the constituents of the com-posites are not restricted to elasticcrystalline or amorphous solids; thecomposites can also have viscoelasticproperties (i.e., polymeric materials).

Publications

Addessio, F.L., and J.B. Aidun,"Analysis of Shock-Induced Damagein Fiber-Reinforced Composites" (tobe published in High-Pressure ShockCompression of Solids).

Aidun, J.B., and F.L. Addessio, "AnEnhanced Cell Model with NonlinearElasticity," J. Composite Mater. 30,248 (1996).

Clements, B.E., J.N. Johnson, andR.S. Hixson, "Stress Waves inComposite Materials," Phys. Rev. E54, 6876 (1996).

Zircon as a Host Phase for PlutoniumDisposition

John Huang

To address problems involving theminimization and long-term storage ofnuclear waste, we have proposed zircon(ZrSiO4) as a host medium for pluto-nium and other actinides recoveredfrom dismantled nuclear weapons. Theobjective of this project is to investigatethe feasibility of large-scale fabricationof plutonium-bearing zircon. BecausePuO2 is thermodynamically less stablethan ZrO2, process parameters deter-mined for zircon can be safely applied

to plutonium-zircon. The emphasis ofour work, therefore, has been to developprocessing parameters that alleviatepotential problems in containing nuclearmaterials during processing.

We have subjected stoichiometricmixtures of ZrO2 and SiO2, in 100-gbatches, to hot isostatic pressing attemperatures near 1500°C and pres-sures of 10,000 psi. Analysis of theproduct materials by x-ray powderdiffraction has shown that after

approximately two hours of reactiontime, the materials consist of zircon,although the reaction is not com-pleted. Therefore, fabricating largequantities of plutonium-zircon isfeasible. The most significant resultof our work is the evidence thatcontainer problems exist, which inturn has suggested potential solutionsto these problems. Experiments witha quartz inner container, a glasssealant, and a secondary metal outercontainer are under way in order tofind ways of confining contaminationduring processing.


Many-Body Theory Research

Alexander Balatsky

The foundations of the theory ofmetals and superconductors have beenshaken by a number of discoveriesover the last 15 years, including high-temperature superconductors, organicsuperconductors, and fullerenes. Newclasses of materials, such as colossalmagnetoresistive materials, cuprates,and organic polymers, have a numberof properties that favor a much richerspectrum of ground and excited states.These properties include strongelectronic and lattice correlations,reduced dimensionality, restrictedgeometry, disorder, and nonlinearity.The interplay of different effects andthe complexity of these materialsmake the materials suitable forelectronic applications.

In this project we are taking on oneof the biggest challenges in con-densed-matter theory today: we areattempting to understand the behaviorof these materials by developingmicroscopic theories to describethem. This year we focused on heavy-electron physics, including propertiesof plutonium, and we are workingclosely with collaborators at a numberof universities. One of our collabora-tors is developing a new model ofvolume collapse in alpha-delta phaseplutonium. This model takes intoaccount the electron-phonon interac-tion as well as f-d hybridization.Another research group is investigat-ing the charge ordering in Cu-0ladder materials; they found thatdomain walls tend to form in theseCu-O systems. They also carried outnumerical calculations of the opticalproperties of the two-leg t-J ladder.

A third collaborator has developedthe theory that the spin gap in cupratesresults from the precursor pairing incuprates. Other collaborators investi-gated the role of lithium impurities inLa2CuO4 and found a novel insulatingphase (at 50% lithium doping) with aspin gap of approximately 1500 K.Work on the transport properties ofKondo insulators continues as well.

Another researcher is working on bothelectronic-structure and many-bodycomputational schemes that haveyielded insight into how magneticstates are formed in quasi-one-dimensional systems.

All these described developments arerelated to the core of our project: a self-consistent treatment of the magneticand nonmagnetic impurity states in d-wave superconductors. We developedthis self-consistent treatment and foundthat the impurity states have a stronglyanisotropic nature.

Publications

Abrahams, E., A. Balatsky, et al.,"Property of Odd Gap Super-conductors," Phys. Rev. B 52,1271(1995).

Alverenga, A.D., D. Rao, J.A.Sanjurjo, et al., "Raman and WeakFerromagnetism in Eu2Cu04,"Physica B 223-224, 522 (1996).

Alvarenga, A.D., D. Rao, J.A.Sanjurjo, et al., "Raman-Scattering andWeak-Ferromagnetism Studies inEu2Cu04," Phys. Rev. B 53, 837 (1996).

Amann, A., P. Visani, K. Aupke, et al.,"Unconventional Vortex Dynamics inthe Low-Field SuperconductingEu2CuO4," Europhys. Lett. 33, 303(1996).

Andrews, A.B., J.J. Joyce, A.J. Arko,et al., "Momentum-Dependent Effectsin 4f Photoemission Spectra fromActinides," Phys. Rev. B 53, 3317(1996).

Balatsky, A.V., and M. Salkola,"Absence of QuasiparticleLocalization in Disordered d-WaveSuperconductors," Phys. Rev. Lett. 76,2386 (1996).

Bucher,B., Z. Schlesinger, D.Mandrus, et al., "Charge Dynamics ofCe-Based Compounds," Phys. Rev. B53, 2948 (1996).

Butero, A., A. Fainstein, M. Tovar, etal., "Gd Concentration Dependence ofthe Spin Reorientation Critical FieldYBaCuO7," J. Appl. Phys. 79,6577(1996).

Fisk, Z., J.D. Thompson, and J.L.Sarrao, "Heavy Fermions," Curr.Opin. Solid State Mater. Sci. 1, 42(1996).

Hammel, P.C., and D.J. Scalapino,"Local Microstructure and theCuprate Spin Gap Puzzle" (submittedto Phil. Mag. B).

Hayden, S.M., G. Aeppli, H.A. Mook,et al., "Comparison of the High-Frequency Magnetic Fluctuations inLaSrCuO4," Phys. Rev. Lett. 76,1344(1996).

Hayward, C.A., D. Poilblanc, and D.J.Scalapino, "Optical Conductivity of a t-J Ladder" (submitted to Phys. Rev. B).

Lawrence, J.M., T. Graf, M.F.Hundley, et al., "Kondo HoleBehavior in Ce0 97La9 O3Pd3," Phys.Rev. B 53, 12559 (1996).

Movshovich, R., T. Graf, D. Mandrus,et al., "Superconductivity in Heavy-Fermion CeRh2/Si2," Phys. Rev. B 53,8241 (1996).

Movshovich, R., J.M. Lawrence, M.E.Hundley, et al., "Magnetism inCePtPb," Phys. Rev. B 53, 5465(1996).

Noack, R.M., S.R. White, and D.J.Scalapino, "The Doped Two ChainHubbard Model," Europhys. Lett. 30,163 (1995).

Park, C.-H., Z.-X. Shen, A.G. Loeser,et al., "Direct Observation of aNarrow Band Near the Gap Edge ofFeSi," Phys. Rev. B 52,16981 (1995).

Rettori, C , S.B. Oseroff, D. Rao, etal., "ESR of Gd in MagneticallyOrdered Eu2Cu04," Phys. Rev. B 54,1123(1996).

Salkola, M., A.V. Balatsky, and D.Scalapino, "Theory of ScanningTunneling Microscopy Probe ofImpurity States in d-Wave Super-conductors," Phys. Rev. Lett. 11, 1841(1996).


Salkola, M , A.V. Balatsky, and J.R.Schrieffer, "Spectroscopy ofSuperconducting QuasiparticleInduced by Magnetic Impurity" (tobe published in Phys. Rev. B).

Scalapino, D.J., and S.A. Trugman,"Local AntiferromagneticCorrelations and d-WaveSuperconductivity," Phil. Mag. B 74,607 (1996).

Schrieffer, J.R., "ARPES: NovelEffects in Energy and MomentumDistributions," J. Phys. Chem. Solids56,1673 (1995).

Schrieffer, J.R., "ARPES: NovelEffects in the Energy and MomentumDistributions" (Physical Phenomenaat High Magnetic Fields-II,Tallahassee, Fla., April 1995).

Schrieffer, J.R., "Ward Identities andthe Suppression of Spin FluctuationSuperconductors," J. Low Temp. Phys.99, 397 (1995).

Seaman, C.L., N.R. Dilley, M.C. deAndrade, et al., "Superconductivity andMagnetism in the Heusler Alloys,"Phys. Rev. B 53,2651 (1996).

Statt, B.W., PC. Hammel, Z. Fisk, etal., "Oxygen Ordering and PhaseSeparation in La2CuO4+d," Phys. Rev.B 52,15575 (1995).

Uwatoko, Y., T. Ishii, G. Oomi, et al.,"Pressure Collapse of Kondo Gap inKondo Compound CeRhSb," J. Phys.Soc. Jpn. 65, 27 (1996).

White, S.R., and D.J. Scalapino,"Ground State Phases of the Doped 4-Leg t-J Ladder" (submitted to Phys.Rev. B).

Yoshinari, Y, P.D. Hammel, J.A.Martindale, et al., "MagneticExcitations of the Doped-Hole Statein Diamagnetic LaCu0 5LiQ 5O4," Phys.Rev. Lett. 11, 2069 (1996).

Alloy Design and Phase Stability ofthe Ternary Alloy Ti-AI-Nb

Robert Alters

Several classes of binary intermetal-lic compounds, such as Ti-Al, haveimportant potential application as high-temperature structural materialsbecause of their high melting tempera-ture, low density, and high strength.The use of these binary alloys islimited, however, by their poor low-temperature ductility and fracturetoughness. Adding a third element (e.g..niobium) to these binary alloys is onepossibility for improving their low-temperature properties withoutsacrificing, for example, the desirablehigh-temperature ductility.

We are using high-precisionelectronic-structure calculations andmolecular dynamics simulations tostudy the electronic and structuralproperties of selected ternary interme-tallic alloy systems. The goal of ourresearch is to understand and predictthe structural stability of these ternary

intermetallics and to understand thecorrelation between the changes inelectronic properties and the improvedlow-temperature properties in thesematerials.

During the past year, we focused onthe effects of alloying on the energeticsof the continuous structural pathwaythat links the body-centered cubicphase of Ti-Al with the omega phase.Omega phase precipitates modify themechanical properties of the quenchedmartensitic alloys by acting as astrengthening element. Our calculationsshow that under constant volume, pureTi-Al has an energy barrier to thisphase transition. In contrast, ourcalculations also show that the additionof niobium (substituted on one of thealuminum sites) removes this barrier.The calculations show that the niobiumalloy has a clearly different density ofstates than the pure Ti-Al alloy.

Moreover, the stability of the omegaphase (and the presence or absence ofan energy barrier) seems to track withd-electron occupation. We are veryclose to finishing some additionalcalculations that should show whetherthese differences can be correlated andexplained by directional d-bondingforces due to the extra niobiumd-electrons.

Publications

Asta, M., A.H. Ormeci, et al., "FirstPrinciples Study of IntermetallicPhase Stability in the Ternary," Mat.Res. Soc. Symp. Proc. 364, 157(1995).

Chu, F., A.H. Ormeci, T.E. Mitchell,et al., "Stacking Fault Energy of theNbCr2 Laves Phase," Phil. Mag. Lett.72, 147 (1995).

Ormeci, A.H., F. Chu, J.M. Wills, etal., "Total-Energy Study of theElectronic Structure and MechanicalBehavior of C15 Laves PhaseCompounds: NbCr2 and HfV2," Phys.Rev. B 54, 12753 (1996).


Synthesis and Characterization ofCorrelated-Electron Materials

Joe D. Thompson

With discoveries—heavy fermions,conducting polymers, fullerenes, andcolossal magnetoresistive materials—beyond traditional solid-state physics,we are at the beginning of a goldenage for complex electronic materials.These new materials are characterizedby strong electronic correlations thatarise from competitions betweenmicroscopic electronic, magnetic, andstructural degrees of freedom. Tuningthese competitions by performingchemical substitutions and by varyingthe pressure, magnetic field, andtemperature ultimately controlsmacroscopic functionalities that willenable next-generation technologiesranging from magnetic sensors andthermoelectric coolers to plutoniumapplications.

Our objective is to understand andcontrol the coupling and competitionamong spin, charge, and latticedegrees of freedom in these corre-lated-electron materials throughcoordinated efforts in synthesis,characterization, and modeling. Ourresearch focuses on understanding(1) the role of electron-electron andelectron-lattice interactions inproducing metal-insulator/magnetic-nonmagnetic transitions in transition-metal perovskites (compounds with acubic structure and chemical formABO3), (2) the consequences ofmesoscale structure on spin-charge-lattice coupling, and (3) the origin ofnon-Fermi-liquid behavior inf-electron materials.

We used pair-distribution-functionand Debye-Waller analyses of neutrondiffraction data to discover evidencefor polaron formation (mesoscalestructure) and Jahn-Teller distortionsin manganite perovskites. We estab-lished that the polaron-binding energyreflects strong coupling betweenlattice and spin degrees of freedom,and we discovered that a volumechange is required for a metal-insulatortransition in these materials. Inaddition, we showed that the spindynamics and electronic structure areunusual for a ferromagnetic metal, andwe tested prevailing theories (multi-channel Kondo, proximity to a T = 0phase transition, and disordered Kondolattice) for the origin of non-Fermi-liquid behavior in f-electron materialswith extensive measurements oncerium-, praseodynium-, and uranium-based correlated-electron systems. Thisexperimental effort was closelycoordinated with a companion theoreti-cal project, 'Theory and Modeling ofCorrelated-Electron Materials."

Publications

Billinge, S.J.J., R.G. DiFrancesco,G.H. Kwei, et al., "Direct Observationof Lattice Polaron Formation in theLocal Structure of La^Ca^MnO^"Phys. Rev. Lett. 77, 715* (1996).

Heffner, R.H., L.P. Le, M.F. Hundley,et al., "Ferromagnetic Ordering and

Unusual Magnetic Ion Dynamics inLa67Ca33MnO3,"/)/zyi'. Rev. Lett. 77,1869 (1996).

Heffner, R.H., L.P. Le, M.F. Hundley,et al., "Zero-Field uSR Study of theColossal Magnetoresistance MaterialLa67Ca33MnO3" (submitted toHyperfine Interactions).

Heffner, R.H., D.E. MacLaughlin,G.M. Luke, et al., "UnusualRelaxational Dynamics inLaj^Ca^MnOj" (submitted toPhysica B).

Hundley, M.F., and J J. Neumeier,"Thermoelectric Power ofLaj^Ca^MnOj^: Inadequacy of theNominal Mn3+/Mn4+ ValenceApproach" (submitted to Phys. Rev.Lett.).

Maple, M.B., M.C. deAndrade, J.Hermann, et al., "Non-Fermi-LiquidBehavior in Chemically Substituted f-Electron Compounds" (submitted toPhysica Q.

Maple, M.B., D.A. Gajewski, R.Chau, et al., "Fermi- and Non-Fermi-Liquid Groundstates in Mj^UJPdj(M = Sc, Y, La, Pr, Zr, Th) Systems"(submitted to Physica B).

Neumeier, J.J., A.L. Cornelius, andM.F. Hundley, "Volume-BasedThermodynamic Considerations forthe Magnetoresistance Effect andMetal-Insulator Transition in CMRManganese-Oxide Perovskites"(submitted to Phys. Rev. Lett.).

Yatskar, A., W.P. Beyermann, et al.,"Possible Correlated-ElectronBehavior from QuadrupolarFluctuations in PrInAg2" (to bepublished in Phys. Rev. Lett.).


Tailoring the Interfacial ElectronicStructure of Organic Electronic Materialsand Devices

Ian Campbell

In this project, we are using self-assembled molecular coupling layers totailor the electronic structure of metal/organic interfaces and organic/organicheterojunctions in order to control theelectrical transport properties of theseinterfaces. Metal/organic interfaces are theessential active element in every organicelectronic device, and organic/organicheterojunctions are the key element inefficient, organic light-emitting diodes.Because of their processing advantages,the tunability of their electronic properties,and their flexibility in both materials anddevice design, organic electronic materialsand devices are poised to revolutionizesuch technological areas as informationdisplay and optical communication.Learning to manipulate the electricaltransport properties of these interfaces isthe key to realizing the potential of organicelectronics.

This past year, we used self-assemblytechniques to insert a controlled andcharacterized molecular coupling layerat metal/polymer interfaces. Molecularcoupling layers with electric dipoleshave been used to manipulate theSchottky energy barrier at these inter-faces. We used internal photoemissionand electroabsorption techniques todetermine these Schottky energybarriers and also to measure basicexcitation energies in conjugatedpolymers. We also developed a theoreti-cal model that describes the current-voltage characteristics of polymerlight-emitting diodes.

Publications

Campbell, I.H., T.W. Hagler, et al.,"Direct Measurement of ConjugatedPolymer Electronic Excitation EnergiesUsing Metal/Polymer/Metal Structures,"Phys. Rev. Lett. 76,1900 (1996).

Campbell, I.H., S. Rubin, T.A.Zawodzinski, et al., "ControllingSchottky Energy Barriers in Organic

Electronic Devices Using Self-Assembled Monolayers" (submitted toPhys. Rev. B).

Davids, P.S., Sh.M. Kogan, et al.,"Charge Injection in Organic Light-Emitting Diodes: Tunneling into Low

Mobility Insulators" (to be published inAppl. Phys. Lett.).

Heller, CM., I.H. Campbell, D.L.Smith, et al., "Equilibrium ElectronTransfer at Metal/C60 Doped PolymerInterfaces" (submitted to Phys. Rev. B).

Joswick, M.D., I.H. Campbell, et al.,"Systematic Investigation of the Effectsof Organic Film Structure on Light-Emitting Diode Performance," /. Appl.Phys. 80,2883 (1996).

Smith, D.L., "Steady State Model forPolymer Light-Emitting ElectrochemicalCells" (submitted to J. Appl. Phys).

Controlling Function of PolarOrganic Multilayers

Duncan McBranch

Charge separation on a molecular scale,combined with the large polarizabilities oforganic molecules, can be used to designnovel, nonlinear optical materials withgreatly enhanced performance. Our projectinvolves research in two areas: (1) thedesign and measurement of new molecularsystems that exhibit charge separation andtransfer following photoexcitation and (2)the design of approaches for synthesizingmultilayers for solid-state electron-transferdevices.

Our strategy for synthesizingmultilayers involves self-assembly usingalternating positively and negativelycharged layers held together by multipleionic bonds. We have recently synthe-sized 100 bilayers of nickel phthalocyaninewith poly(diallyldimethylammoniumchloride). This technique can begeneralized to other interesting photo-synthetic systems such as conductingpolymers. When these conductingpolymers (donors) are mixed in blendswith fullerenes or other polymers(acceptors), electrons undergo chargetransfer in less than 300 fs. We haverecently shown that this photo-inducedcharge transfer provides a recordingmechanism for ultrafast photochromicgratings and allows the tailoring of thedecay dynamics of recorded holographicgratings. This type of composite charge-

transfer blend constitutes an entirely newclass of nonlinear optical material.

A closely related problem involves thedesign of biomimetic light-harvestingsystems that use either photo-inducedcharge or energy transfer. We havestudied model systems that incorporatecovalently linked porphyrins to mimicnatural photosynthetic pigments. Ourresults demonstrate the feasibility ofdesigning biomimetic energy-transferpigments to produce efficient energytransfer with controlled rates. Further-more, high transfer efficiency can berealized without extensive perturbationof the photophysical properties of theindividual "building blocks."

Publications

Maniloff, E.S., D. Vacar, et al., "ChargeTransfer Polymers: A New Class ofNonlinear Optical Material" (to bepublished in SPIE Proc).

Maniloff, E.S., D. Vacar, et al.,"Femtosecond Charge TransferHolography in Conducting Polymer/Cg0

Blends" (to be published in Synth.Metals).

Maniloff, E.S., D. Vacar, et al.,"Ultrafast Holography Using ChargeTransfer Polymers" (submitted to Opt.Lett).


Pinning Vortices and EnhancingHigh-Temperature Superconductor(HTS) Critical Currents

Martin Maley

We are investigating flux-pinningmechanisms in high-temperaturesuperconductors to discover means ofenhancing HTS critical currentdensity (Jc)—a key performanceparameter for superconductingmaterials. We have achieved largeenhancements in Jc at 75 K in barium-strontium-calcium-copper oxide/silver(BSCCO/Ag) conductors by introduc-ing columnar defects, using fissiontracks induced by high-energyprotons. We have worked to determinethe optimum density of columnardefects to maximize Jc and to gainunderstanding of the mechanisms.

We also carried out two successfulstudies: enhancing Jc through lower-energy-proton irradiation (500 MeV)and irradiating stacked conductors.We were particularly interested in thecommercial feasibility of theseprocesses. We discovered that, at highdoses, the intergrain connections arebroken, but we found an annealingprocedure that heals grain-boundarydamage while retaining the enhancedpinning.

The new yttrium-barium-copperoxide (YBCO) conductors preparedby the ion-beam-assisted depositionprocess contain strong pinning defectsof unknown origin that allow them tomaintain high Jc at 75 K in highfields. We determined the defectsresponsible and introduced additionalcolumnar defects by heavy-ionirradiation to seek further enhance-ments. Patterned bridges in thesefilms show a strong dependence of Jc

on the orientation between currentand the twin structure. This and otherevidence demonstrate that twinboundaries play a major role in theflux pinning. Heavy-ion irradiationproduced further substantial enhance-ments when the magnetic field wasaligned with the defects.

Our theoretical investigationsdiscovered a new collective "plasmaresonance" mode in layered HTSconductors that is a measure of Jc

normal to the superconducting layers.

Publications

Bulaevskii, L.N., "Interaction ofPancake Vortices with C-AxisPlasmons in Josephson Currents" (tobe published in Journale dePhysique).

Bulaevskii, L.N., "Intrinsic JosephsonEffects in Layered Superconductors,"Turkish J. Phys. 20, 594 (1996).

Bulaevskii, L.N., D. Dominguez, etal., "Collective Mode and the C-AxisCritical Current of a Josephson-Coupled Superconductor at HighParallel Magnetic Fields," Phys. Rev.5 53,14601(1996).

Bulaevskii, L.N., D. Dominguez, M.P. Maley, et al., "Linewidth of C-AxisPlasma Resonance in Josephson-Coupled Superconductors," Phys. Rev.B 54, 7521 (1996).

Bulaevskii, L.N., M. Maley, et al.,"Angular Dependence of C-AxisPlasma Frequency and CriticalCurrent in Josephson-CoupledSuperconductors at High MagneticFields," Phys. Rev. B 53, 6634 (1996).

Bulaevskii, L.N., V.L. Prokovsky, andM.P. Maley, "Field Dependence of C-Axis Plasma Resonance in Josephson-Coupled Superconductors," Phys. Rev.Lett. 76, 1719(1996).

Bulaevskii, L.N., V.M. Vinokur, andM. P. Maley, "ReversibleMagnetization of Irradiated High-TcSuperconductors," Phys. Rev. Lett.11, 936 (1996).

Cho, J.H., M.P. Maley, et al., "Role ofSuperconducting Fluctuations in C-Axis Transport of Bi-2212 Super-conductors in High Magnetic Fields,"Physica C 265, 277 (1996).

Dominguez, D., L.N. Bulaevskii, etal., "Interaction of Vortices withUltrasound and the Acoustic FaradayEffect in Type-II Superconductors,"Phys. Rev. B 53, 6682 (1996).

Maley, M.P., J.O. Willis, et al.,"Effects of Splayed Columnar DefectsProduced by Heavy FissionFragments on Vortex Dynamics inBSCCO Conductors," in PhysicalPhenomena at High Magnetic Fields-II (World Scientific, Singapore,1996), pp. 467-483.

Safar, H., J.Y. Coulter, et al.,"Anisotropy and Lorentz-ForceDependence of the Critical Currentsin YBa2Cu3O7 d Thick FilmsDeposited on Nickel AlloySubstrates," Phys. Rev. B (RapidCommunications) 52, 9875 (1995).

Safar, H., S.R. Foltyn, et al., "AB-Plane Anisotropy of the CriticalCurrents in Twinned YBa2Cu307 d

Superconductors," App. Phys. Lett.68, 1853 (1996).

Safar, H., S.R. Foltyn, et al., "BoseGlass Vortex Phase Transition inTwinned YBa2Cu307 d Super-conductors," Philos. Mag. B 74, 647(1996).

Willis, J.O., H. Safar, et al., "HighEnergy Proton Irradiation InducedPinning Centers in Bi-2212 and Bi-2223 Superconductors," in Advancesin Superconductivity VIII (Springer-Verlag, Tokyo, 1996), p. 509.


Nonlinearity in Structural andElectronic Materials

Alan Bishop

This project has developed andapplied a technology base of nonlin-ear techniques that are relevant to avariety of nonlinear, nonequilibriumproblems in condensed matter andmaterials science. Our controlledsynthesis of, and experiments on,novel electronic and structuralmaterials help motivate nonlinearscience at Los Alamos, which in turnadvances our understanding of theprocesses that govern the structureand dynamics of today's complexmaterials. Important concepts fromnonlinear science include (1) theprevalence of coherent space-timestructures in strongly nonlinearclassical and quantum systems, (2) thepossibility of deterministic chaos evenin low-dimensional dynamicalsystems, and (3) the coexistence ofboth coherence and chaos, leading toa rich variety of phenomena connotedby the term complexity. Our projectstudies these concepts and appliesthem to significant problems incondensed-matter physics andmaterials science.

Achievements this year include thefollowing:• large-scale simulations and

microscopic modeling of nonlin-ear, coherent energy storage at thecrack tips and sliding interfaces oflattice models (see figure);

• large-scale simulation and micro-scopic elasticity theory forprecursor microstructure anddynamics at solid-solid diffu-sionless phase transformations;

• large-scale simulation of self-assembling, organic thin films oninorganic substrates;

• analysis and simulation of thesmoothing of rough atomicsurfaces; and

• modeling and analysis of flux-pattern formation in equilibriumand nonequilibrium Josephson

junction arrays and layeredsuperconductors.

In addition to this work and as partof our communication with others inthe field, we organized a seminarseries on nonlinear materials andthree international conferences on"Fracture, Friction, and Deformation,""Nonequilibrium Phase Transitions,"and "Landscape Paradigms in Physicsand Biology." We also gave severalinvited talks, including talks at theinternational conferences on "Syn-thetic Metals" and on "QuantumPhase Transitions," at the 1996CECAM Euroconference, and at the1995 Fall Meeting of the MaterialsResearch Society.

Publications

Beardmore, K.M., et al., "Ab-InitioCalculations of the Gold-SulfurInteraction for Alkanethiol Mono-layers" (1996ICSM Conference,Snowbird, Utah, July 29-August 2,1996).

Beardmore, K.M., et al., "MolecularDynamics Simulation of Low-EnergyBoron and Arsenic Implant intoSilicon" (1996 IEEE Ion/ImplantTechnology Conference, Austin, Tex.,June 16-21, 1996).

Bishop, A.R., et al, "Disorder-InducedBreakdown of Soliton and PolaronParticles," in Noise, Nonlinearity andFluctuation Phenomena, A.R. Bishopet al., Eds. (World Scientific,Singapore, in press).

Bishop, A.R., et al., "NonlinearEquations and Structural PhaseTransitions," in NonlinearSchrb'dinger and Klein-GordonEquations (World Scientific,Singapore, in press).

A 35-million-atom simulation of crack blunting by dislocation emission incopper under tensile loading. An elliptical crack (center of figure) in a 0.1-mm-thick copper sheet is placed under tension in the vertical direction. As the crackattempts to propagate horizontally, it emits clouds of dislocations (white dots),some of which collide directly above the crack. Only atoms at the surface of thecrack, or within the cores of dislocations, are depicted. The visualizationtechnique used in the simulation suppresses atoms that are not displaced.


Bishop, A.R., et al., "Simulations ofCurrent-Driven 3-DimensionalJosephson Junction Arrays," PhysicaB 222, 396 (1996).

Bronold, F.X., et al., "NonlinearOptics of Conjugated Polymers: ACoupled Exciton-Phonon Approach,"Phys. Rev. B 53,13456 (1996).

Bussmann-Holder, A., et al.,"Quasiharmonic Periodic TravelingWave Solutions in AnharmonicPotentials," Phys. Rev. B 53, 11521(1996).

Bussmann-Holder, A., et al., "Time-Dependent Evolution of Double-WellPotentials to Model StructuralAnomalies," Philos. Mag. 73,657(1996).

Cai, D., et al., "Electric-Field-DrivenNonlinear Bloch Oscillations andDynamic Localization," Phys. Rev.Lett. 74, 1186(1995).

Cruz-Pacheco, G., et al., "TheRelationship of Periodic Wavetrainsand Solitary Waves in Optical FiberAmplifiers Modeled by ComplexGinzburg-Landau Type Equations"(submitted to Phys. Lett. A).

Dandoloff, R., et al., "Violation ofSelf-Duality for Topological Solitonsdue to Soliton-Soliton Interaction on aCylindrical Geometry," Phys. Rev.Lett. 74, 813 (1995).

Diez, E., et al., "DynamicalPhenomena in FibonacciSemiconductor Superlattices" (to bepublished in Phys. Rev. B).

Dominguez, D., et al., "ResistiveHysteresis and Nonlinear I-VCharacteristics at the First OrderMelting of the Abrikosov VortexLattice," Phys. Rev. Lett. 75, 4670(1995).

Dominguez, D., et al., "TransformerConfigurations in 3-DimensionalJosephson Lattices," Phys. Rev. Lett.75, 717 (1995).

Farkas, D., et al., "Embedded AtomCalculations of Unstable StackingFault Energies and Surface Energiesin Intermetallics" (to be published inJ. Mater. Res).

Gumbsch, P., et al., "MolecularDynamics Investigation of DynamicCrack Stability" (submitted to Phys.Rev. B).

Hammerberg, J.E., et al., "Studies ofSliding Friction in CompressedCopper," in Proc. APS Topical Conf.on Shock Compression in CondensedMatter (North Holland, Amsterdam,in press).

Holian, B.L., et al., "MolecularDynamics Simulations of Fracture:An Overview of System Size andOther Effects," Mat. Res. Soc. Symp.Proc. 409, 3 (1995).

Jensen, N.G., et al., "MetastableFilamentary Vortex Flow in Thin FilmSuperconductors," Phys. Rev. Lett. 76,2985 (1996).

Kenkre, V.M., et al., "MemoryFunction Approach to InteractingQuasiparticle-Boson Systems," Phys.Rev. 5 53,5407(1996).

Mertens, EG., et al., "Hierarchy ofEquations of Motion for NonlinearCoherent Excitations Applied toMagnetic Vortices" (submitted toPhys. Rev. B).

Raghavan, S., et al., "Validity of theDiscrete Nonlinear SchrodingerEquation in the Context of theFluorescence Depolarization of aSpin-Boson System," Phys. Rev. B 53,8457 (1996).

Salkola, M., et al., "CoupledQuasiparticle-Boson Systems: TheSemiclassical Approximation andDiscrete Nonlinear SchrodingerEquations," Phys. Rev. B 52, 3824(1995).

Sanchez, A., et al., "RougheningTransition of Driven Surface Growth,"Phys. Rev. B 51, 14644 (1995).

Sanchez, A., et al., "Smoothing ofRough Surfaces," Phys. Rev. B 52,5433 (1995).

Saxena, A., et al., "HierarchicalTwinning: Martensites as Pattern-Forming Systems" (submitted toPhys. Rev. Lett:).

Shenoy, S., et al., "QuantumParaelectric Model for LayeredSuperconductors" (submitted to Phys.Rev. Lett.).

Villain-Guillot, S., et al., "TopologicalSolitons and Geometric Frustration,"Phys. Rev. A 52, 6712 (1995).

Wang, L., et al., "Charge DensityWave of a Multiband Fermi Liquid,"Phys. Rev. B 51, 7407 (1995).

Zang, J., et al., "Lattice Effects in theColossal MagnetoresistanceManganites," Phys. Rev. Lett. 76,1356(1996).

Zharnitsky, V., "Resonances in aContinuously Forced AnharmonicOscillator" (to be published in Phys.Lett. A).

Zhou, S.J., et al., "DislocationEmission from a Three-DimensionalCrack—A Large-Scale MolecularDynamics Study" (to be published inProc. Ninth Int. Conf. Fracture).

Zhou, S.J., et al., "Dynamic CrackProcesses via Molecular Dynamics,"Phys. Rev. Lett. 76, 2318 (1996).

Zhou, S.J., et al., "Large-ScaleMolecular Dynamics Simulations ofThree-Dimensional Fracture" (to bepublished in Phys. Rev. Lett.).

Zhou, S.J., et al., "Large-ScaleMolecular Dynamics Simulations ofFracture and Deformation" (to bepublished in /. Computer-AidedMater.).

Zhou, S.J., et al., "Study of FiberComposite Failure Criterion," Mater.Res. Soc. Symp. Proc. 409, 267(1995).


High-Resolution Electron Microscopy ofAdvanced Materials

Terence Mitchell

Our objective has been to improvethe key performance of a full range ofspectroscopy instruments and soincrease our ability to analyzeadvanced materials significantly. Theinstruments include a field-emissionscanning electron microscope (FE-SEM), a 100-kV field-emissionscanning transmission electronmicroscope (FE-STEM), a 300-kVfield-emission, high-resolutiontransmission electron microscope(FE-HRTEM), and a 300-kV analyti-cal transmission electron microscope.We are presently adding a neworientation-imaging microscope.

X-ray energy dispersive spectrom-eters for chemical analysis areavailable on all four microscopes, andparallel electron energy loss spec-trometers (PEELS) are operational onthe FE-STEM and FE-HRTEM. ThePEELS systems enable evaluation oflocal atomic bonding as well aschemical composition in nanometer-scale regions. We have successfullydemonstrated the FE-HRTEM point-to-point resolution of 1.6 A. Inaddition, because of the high bright-ness and coherency of the FE source,we have been able to push themicrocsope's resolution to its infor-mation limit of 1 A by computerreconstruction of a focal series ofimages.

We have used HRTEM to image theatomic structure of defects such asdislocations, grain boundaries, andinterfaces in a wide variety ofmaterials from superconductors tostructural ceramics. We have used thenew HRTEM to image such defectswith much greater accuracy at theatomic level, making it possible tocompare them with modeling predic-tions and improve interatomicpotentials.

Recent examples of applicationsinclude the characterization of defectsand interfaces in thin films ofYBa2Cu307 deposited on varioussubstrates and buffer layers, HRTEManalysis of interfaces in variousceramic composites, analysis of thecore structures of dislocationsproduced in ceramics and intermetal-lics by high-temperature deformation,and analysis of nanolayered materials.Future applications will involve elec-tron holography by the incorporationof a biprism in the column of the FE-HRTEM.

Publications

Albert, D.E., and A.W. Thompson,"Effect of Stress-TemperatureRegimes on Creep Mechanisms in Ti-24 Al-llNb," Mater. Set Engin. A.210, 48-56 (1996).

Ablen, S.P., R.D. Field, and M.Mataya, "Elevated TemperatureStress-Strain Behavior of BerylliumPowder Product," (Second IEAInternational Workshop on BerylliumTechnology for Fusion, Jackson Hole,Wyo., September 6-8, 1995).

Butt, D.P., D.A. Korzekwa, S.A.Maloy, et al., "Impression CreepBehavior of SiC Particle-MoSL,Composites," J. Mater. Res. 11, No. 6(1996).

Butt, D.P., K.S. Lackner, C.H. Wendt,et al., "Kinetics of Thermal Dehy-droxylation and Carbonation ofMagnesium Hydroxide," /. Am.Ceram. Soc. 78, 1892 (1996).

Chen, C.L., T.T. Tsong, et al.,"Surface Diffusion and SurfaceAtomic Roughness on Ir (001)Surface and Terraces," Appl. Surf. Sci.94/95, 224-230 (1996).

Chen, C.L., D. Zhou, et al., "DirectObservation of TaH Precipitation inTantalum-Hydrogen Solution," /. Vac.Sci. Tech. 14, 2551-2553 (1996).

Chu, F., Y. He, et al., "ElasticConstants of the C15 Laves PhaseCompound NbCr2," Scripta Met.Metall. 33, 1295-1300 (1995).

Chu, F , Q.X. Jia, et al.,"Microstructures and ElectricalProperties of SrRuO3 Thin Films onLaA103 Substrates," J. Electron.Mater. 25,1754-1759 (1996).

Chu, F , M. Lei, et al., "Single CrystalElastic Constants of C40 NbSi2" Phil.Mag. B 71, 373-382 (1995).

Chu, F, M. Lei, S.A. Maloy, et al.,"Elastic Properties of C40 TransitionMetal Disilicides," Acta Metall.Mater. 44, 3035-3048 (1996).

Chu, F, A.H. Ormeci, T.E. Mitchell,et al., "Stacking Fault Energy of theNbCr2 Laves Phase," Phil. Mag. Lett.72, 147-153 (1995).

Chu, F , D.P. Pope, and T.E. Mitchell,"Phase Stability and Elastic Propertiesof C15 Compounds HfV2+Nb," inMechanical Properties and PhaseTransformations of Multi-PhaseIntermetallic Alloys, A.F. Giamei, K.Inoue, and Y. Mishima, Eds. (TheMetals, Materials, and MineralsSociety, Warrendale, Pa., 1996),pp. 17-24.

Cooper, E.A., H. Kung, and M.Nastasi, "Systematic Study of the IonBeam Mixing of Oxide Markers intoAlumina," Nucl. Instrum. Methods B106, 9-16 (1995).

Devanathan, R., N. Yu, et al.,"Electron Diffraction Analysis of aMetastable State in Ion-IrradiatedMgAl2O4 Spinel," Microscopy andMicroanalysis Proc. 53, 160 (1995).

Devanathan, R., N. Yu, et al.,"Relationship between Structure andMechanical Properties of Ion-Irradiated MgAl2O4 Spinel,"Microscopy and Microanalysis Proc.53, 358 (1995).


Devanathan, R., N. Yu, et al.,"Structure of the Metastable State inIon-Irradiated Magnesio-AluminateSpinel," Phil. Mag. Lett. 72,155-161(1995).

Griffin, A.J., M.F. Hundley, T.R.Jervis, et al., "Residual Stress,Mechanical Behavior and ElectricalProperties of Cu/Nb Thin FilmMultilayers," Mater. Res. Soc. Symp.Proc. 382, 309-314 (1995).

Hirvonen, J-R, I. Suni, H. Kattelus, etal., "Crystallization and OxidationBehavior of Mo-Si-N Coatings,"Surface Coatings Technol. 74/75,981(1995).

Hirvonen, J-R, P. Torri, R.Lappalainen, et al., "TribologicalCharacteristics of MoSi2/SiCNanocomposites," Nanostruct. Mater.6, 881 (1995).

Jervis, T.R., J-R Hirvonen, et al.,"Tribology and Mechanical Propertiesof Excimer Laser Processed Ti-Si3N4

Surfaces," /. Mater. Res. 10,1857(1995).

Jia, Q., F. Chu, CD. Adams, et al.,"Characteristics of ConductiveSrRuO3 Thin Films with DifferentMicrostructures," /. Mater. Res. 11,2263-2268 (1996).

Jia, Q., S.G. Song, X.D. Wu, et al.,"Epitaxial Growth of HighlyConductive Oxide RuO2 Thin Filmson (001) Si," Appl. Phys. Lett. 68,1069 (1996).

Jia, Q.X., X.D. Wu, et al., "Depositionof Epitaxial YSZ on Single-Crystal Siand Subsequent Growth of anAmorphpous SiO2 Interlayer," Phil.Mag. Lett. 72, 385-391 (1995).

Jia, Q.X., X.D. Wu, S.R. Foltyn, et al.,"Fabrication and Characterization ofHigh Temperature SuperconductorJosephson Junctions with A NovelDesign," IEEE Trans. Appl.Supercond. 5, 2103-2106 (1995).

Jia, Q.X., D.S. Zhou, et al.,"Characterization of Ba0 5Sr0 5TiO3

Thin Film Capacitors Produced byPulsed Laser Deposition," IntegratedFerroelectrics 10, 73-79 (1995).

Kotula, P.G., I.M. Anderson, F. Chu,et al., "ALCHEMI of NbCr/V CIS-Structured Laves Phase," Microscopyand Microanalysis Proc. 54, 554-555(1996).

Kung, H., R.G. Castro, et al., "TheStructure of Plasma Sprayed MoSi2-A12O3 Microlaminate Tubes," Scr.Metall. Mater. 32, 179 (1995).

Kung, H., J. Griffin, et al., "TheStabilization of B.C.C. Cu in Cu/NbNanolayered Composites,"Microscopy and Microanalysis Proc.54, 228-229 (1996).

Kung, H., T.R. Jervis, et al., "HighTemperature Structural Stability ofMoSi2-Based Nanolayer Composites,"J. Vac. Sci. Tech. A13, 1126-1129(1995).

Kung, H., T.R. Jervis, et al.,"Structure and Mechanical Propertiesof MoSi2-SiC NanolayerComposites," Phil. Mag. A. 71,759-779 (1995).

Kung, H., T.R. Jervis, et al.,"Synthesis, Structure and MechanicalProperties of NanostructuredMoSi2Nx," Nanostruct. Mater. 7,81-88 (1996).

Mitchell, T.E., M. Nastasi, et al.,"Synthesis, Structure and MechanicalProperties of NanolayeredComposites of Mo, MoSi2, MoSi2Nx

and SiC," in Novel Techniques inSynthesis and Processing of AdvancedMaterials, J. Singh and S. Copley,Eds. (The Metals, Materials, andMinerals Society, Warrendale, Pa.,1995) p. 271-281.

Maloy, S.A., and T.E. Mitchell,"Dislocation Decomposition,Dissociation, and Deformation inMoSi2 and a-Al2O3 Single Crystals,"in Plastic Deformation of Ceramics,R.C. Bradt, and C.A. Brookes, Eds.(Plenum Press, New York, 1996),pp. 53-62.

Ormeci, A., F. Chu, et al., "A Total-Energy Study of Electronic Structureand Mechanical Behavior of C15Laves Phase Compounds: NbCr2 andHfV2," Phys. Rev. B 54,12753 (1996).

Reimanis, I.E., M.E. Hawley, et al.,"The Fracture Characteristics ofCzochralski-grown Y3A15O12," /.Amer. Ceram. Soc, 78, 2282-2286(1995).

Reimanis, I.E., JJ. Petrovic, et al., "ACrystalline Si3N4 /Amorphous Si3N4

Composite," J. Amer. Ceram. Soc. 79,395_400 (1996).

Reimanis, I.E., J J. Petrovic, et al.,"The Fracture Behavior of a CVDCrystalline Si3N4/Amorphous Si3N4

Composite," Ceram. Trans. 42, 277-283 (1995).

Reimanis, I.E., J.J. Petrovic, et al.,"The Mechanical Properties of SingleCrystal a-Si3N4" Ceram. Trans. 42,229-236 (1995).

Reimanis, I.E., H. Suematsu, et al.,"The Properties of Single CrystalSi3N4," /. Amer. Ceram. Soc. 79,2065-2073 (1996).

Safar, H., S. Foltyn, H. Kung, et al.,"ab-Plane Aniostropy of the CriticalCurrents in Twinned YBa2Cu3O7 d

Superconductors," Appl. Phys. Lett.68, 25 (1996).

Sickafus, K.E., N. Yu, and M. Nastasi,"Radiation Resistance of the OxideSpinel: The Role of Stoichiometry onDamage Response," Nucl. Instr. Meth.B 116, 85 (1996).

Sickafus, K.E., N. Yu, et al., "TheIrradiation Damage Response ofMgO-3Al2O3 Spinel Single CrystalsUnder High-Fluence Ion-Irradiation,"Nucl. Instr. Meth. B 106, 573-578(1995).

Song, S.G., C.L. Chen, et al.,"Observation of Nano-scale EpitaxialGrowth of Diamond on the Si (100)Surface," /. Appl. Phys. 79,1813(1996).

Song, S.G., R. Vaidya, et al.,"Stacking Faults in SiC Particles andTheir Effect on the Fracture Behaviorof a 15 Vol % SiC/6061-Al MatrixComposite," Met. Mater. Trans. 27A,459 (1996).


Suematsu, H., JJ. Petrovic, and T.E.Mitchell, "Plastic Deformation ofSilicon Nitride Single Crystals,"Mater. Sci. Eng. A 209, 97-102(1996).

Thoma, D.J., E.M. Schwartz, S.R.Bingert, et al., "MicrosegregationDuring Melt-Spinning of DilutePalladium Alloys," Melt Spinning,Strip Casting and Slab Casting, E.F.Matthys and W.G. Truckner, Eds.(The Metals, Materials, and MineralsSociety, Warrendale, Pa., 1996).

Tiwari, P., X.D. Wu, et al., "High-quality Epitaxial YBCO Thin FilmsDirectly on LiNbO3" Phil. Mag. B 71,903-912 (1995).

Tiwari, P., X.D. Wu, et al., "Study ofHigh Quality YBCO Thin FilmsGrown Directly on Y-cut LiNbO3," J.Electron. Mater. 25, 131-135 (1996).

Tiwari, P., X.D. Wu, et al., "Synthesisof Low Resistivity Complex Oxideson MgO Using Pt as Buffer Layer," J.Electronic Mater. 25, 51-55 (1966).

Vaidya, R.U., D.P. Butt, et al., "Effectof Microbial Corrosion on the TensileStress-Strain Response of Aluminumand A12O3 Particle ReinforcedAluminum Composite" (to bepublished in Corrosion Preventionand Control).

Vaidya, R.U., L.E. Hersman, et al.,"Microbiologically InfluencedCorrosion of Aluminum 6061 andA12O3 Particle Reinforced Aluminum6061 Composite under AnaerobicConditions and Elevated Temper-atures: Effect on the UTS and Strainto Failure" (to be published inCorrosion Prevention and Control).

Vaidya, R.U., S.G. Song, et al., "TheEffect of Structural Defects in SiCParticles on the Static and DynamicResponse of a 15 Percent SiC/6061-Al Matrix Composite" (APS TopicalConference, Seattle, Wash., August1995).

Vaidya, R.U., and A.K. Zurek, "Effectof Aging Treatment on the Com-pression Behavior of a B4C/A16061Composite," / . Mater. Sci. Lett. 15,385-387 (1996).

Vaidya, R.U., A.K. Zurek, and A.Wolfenden, "Effect of PlasmaSprayed A12O3 Coating on theStrength, Elastic Modulus andDamping of Ti-25 Al-lONbIntermetalric," /. Mater. Eng. Perf. 4,3 (1995).

Walter, K.C., H. Kung, J.T. Tesmer,et al., "Characterization andPerformance of DLC FilmsSynthesized by Plasma and Ion BeamTechniques," Surface and CoatingsTechnol. 74/75, 734-738 (1995).

Walter, K.C., M. Nastasi, H. Kung,et al., "Diamond-Like CarbonDeposition for TribologicalApplications at Los Alamos NationalLaboratory," Mater. Res. Soc. Symp.Proc. 383,411(1995).

Yan, M., S.P. Chen, et al., "AtomisticStudy of Energy and Structure ofSurfaces in NiO," Phil. Mag. A 72,121-138 (1995).

Yan, M., S.P. Chen, et al., "AtomisticStudy of Energy and Structure ofSurfaces in NiO," in Structure andProperties of Interfaces in Ceramics,D. Bonnell, M. Ruhle and U.Chowdhry, Eds. (Materials ResearchSociety, Pittsburgh, Pa., 1995)pp. 441^46.

Yano, T., M. Ikari, et al., "Effect ofNeutron Irradiation on KnoopHardness Anisotropy in MgO-3Al2O3

Single Crystal," /. Amer. Ceram. Soc.78 (6), 1469-74 (1995).

Yu, N., P.C. Mclntyre, et al., "High-Quality Epitaxial Growth of Gamma-Alumina Films on Sapphire Inducedby Ion Beam Bombardment," Phys.Rev. 5 52,17518(1995).

Yu, N., K.E. Sickafus, and M. Nastasi,"Temperature Effects on IonIrradiation Damage in MgAl2O4

Spinel Single Crystals," Mater. Res.Soc. Symp. Proc. 373, 401 (1995).

Yu, N., Q. Wen, D.R. Clarke, et al.,"Formation of Fe or Cr DopedEpitaxial Sapphire Thin Films onSapphire Substrates," / . Appl. Phys.78,5412 (1995).

Zhou, D.S., C.L. Chen, T.E. Mitchell,et al., "Thin Films of Cubic BoronNitride on Silicon," Phil. Mag. Lett.72, 163-166 (1995).

Zhou, D.S., and T.E. Mitchell,"Atomic Structures of a StackingFault and a Domain Boundary in a-Silicon Nitride," /. Microsc. Soc.Amer. 1,263-266 (1995).

Zhou, D.S., and T.E. Mitchell,"Dislocations in as-Grown CVD a-Silicon Nitride," J. Amer. Ceram. Soc.78,3133-3136(1995).

Zhou, D.S., and T. E. Mitchell,"Rotation Domains in a-SiliconNitride," Phil. Mag. A 72, 1131-1140(1995).

Zurek, A.K., W.R. Thissell, and D.L.Tonks, "Spall Behavior and DamageEvolution in Tantalum" (Assoc. forthe Advancement of High PressureScience and Technology International.Conf., Warsaw, Poland, Sept. 10-15,1995).



Molten Salt and Molten LeadSystems Studies

Gary Doolen

Accelerator-driven transmutation ofnuclear waste (ATW) is a technologythat can essentially eliminate theplutonium, higher actinides, andenvironmentally hazardous fissionproducts in the spent fuel fromnuclear reactors. This project ad-dresses key systems and programmaticissues related to ATW—specifically,how molten salt and liquid leadtechnologies developed for ATW fitinto the waste management infrastruc-ture. We have focused our efforts onmodeling and analyzing the physicsof the ATW target and blanket tooptimize transmutation performance.

First, we defined the active part ofthe system as consisting of a graphite-reflected, molten salt subcritical blanketassembly coupled to an appropriateliquid lead/bismuth neutron productiontarget. Our system does not have aninternal graphite moderator.

Then, we performed preliminarycalculations that coupled the neutrontransport codes LAHET and MCNPwith the depletion codes ORIGENand DYNA. These calculationsshowed that our system maintains lowactinide inventories while efficientlyburning fuel (by fission), two impor-tant features. We have also introducedsignificant passive safety featuressuch as a massive heat sink of liquidsalt around the exterior of the reactorvessel.

In addition, we initiated a study tocompare our new ATW system withthe 8-MW molten salt reactoroperated at Oak Ridge NationalLaboratory during the 1970s to

develop a thorium-uranium breederreactor. We believe that key featuresof our system—the accelerator drive,the robust fuel cycle, the low powerdensity, the absence of breedingrequirements, and the use of trivalentactinides—should make our ATWsystem considerably simpler than theOak Ridge reactor.

Finally, development of effectivetools for neutronics calculations,including the coupling of neutrontransport, depletion, and kineticcodes, has enabled us to developinnovative designs involving liquidfuels in previously unexploredneutron flux and spectrum regimes.These designs are now feasiblethrough the use of our acceleratordrive, which enables us to usesubcritical fuel levels for improvedcontrol and efficiency. We arecontinuing to explore the use of a fastneutron spectrum to enhance theefficiency of transmutation.

Publications

Bowman, CD., "Accelerator-DrivenTransmutation Technologies forResolution of Long-Term NuclearWaste Concerns," in Proceedings ofthe International Workshop on NuclearMethods for Transmutation of NuclearWaste, M.K. Khankhasayev, H.S.Plendl, and Z.B. Kurmanov, Eds.(World Scientific, Singapore, 1997),pp. 257-270.

Bowman, CD., "Current Status andRecommended Future Studies ofUnderground Supercriticality"(ICENES '96, Eighth InternationalConference on Emerging NuclearEnergy Systems, Obninsk, Russia,June 24-28,1996).

Bowman, CD., "Optimization ofAccelerator-Driven Technology forLight-Water Reactor WasteTransmutation" (Second InternationalConference on Accelerator-DrivenTransmutation Technologies andApplications, Kalmar, Sweden, June3-7,1996).

Bowman, CD., and F. Venneri,"Underground Supercriticality fromPlutonium and Other FissileMaterial," Science and GlobalSecurity 5, 279 (1996).

Doolen, G., F. Venneri, M.A.Williamson, et al., "The Los AlamosAccelerator-Driven Transmutation ofNuclear Waste Concept (ATW)," inProceedings of the InternationalWorkshop on Nuclear Methods forTransmutation of Nuclear Waste,M.K. Khankhasayev, H.S. Plendl, andZ.B. Kurmanov, Eds. (WorldScientific, Singapore, 1997),pp. 26-28.

Venneri, F., N. Li, and M.A.Williamson, "Physics and Chemistryof Accelerator-Driven TransmutationSystems" (Second InternationalConference on Accelerator-DrivenTransmutation Technologies andApplications, Kalmar, Sweden, June3-7, 1996).

Competency Development Projects—Engineering and Base Technologies 167

Advanced Measurements and Techniquesin High Magnetic Fields

Laurence Campbell

The objective of our project was touse advanced measurement technol-ogy in order to better understand thefundamental properties of materialssubjected to high magnetic fields.Properties of interest included thematerials' electrical conductivity,microscopic structure, and thermalcharacteristics. We had two maintasks: a study of correlated electronsand optical measurements on semi-conductors.

In our correlated-electron study, welooked at ground-state properties ofheavy fermion compounds in highmagnetic fields, with a focus oncompounds that exhibit magnetic-field-induced transitions. In particular,we looked at YbNi2B2C, a new heavyfermion compound presentingextremely high magnetic anisotropy,

which suggested the possibility ofhaving metamagnetic transitions inmagnetic fields to 100 T. We alsolooked at unconventional semicon-ductors in high magnetic fields,examining the energy-gap formationsof Kondo insulator compounds. Inparticular, we studied the effect thatvery high magnetic fields have on theenergy-gap formation in SmB6

compounds. Magnetoresistanceexperiments were performed inmagnetic fields to 50 T and attemperatures down to 40 mK. For thefirst time, we observed that the lowexcitation gap closes in a magneticfield of 35 T at 40 mK. Studies werealso carried out to verify that theobserved effects were not sample-dependent and to obtain a theoreticalunderstanding of the phenomena.

In our study of semiconductors, avariety of optical measurementsrevealed the behavior of semiconduc-tor heterostructures in high magneticfields. These included measurementsof magneto-photoluminescence(MPL) intensity, energy oscillations,and optical Shubnikov-de Haas(OSdH) oscillations in a modulation-doped, GaAs/AlGaAs singleheterojunction. The MPL and OSdHmeasurements showed energy andintensity oscillations caused by theinteraction (crossing) between thesecond sub-band Landau levels(occupied by photo-generatedelectrons) and the Fermi level. Wealso looked at MPL measurement ofGaAs/AlGaAs double-well structuresthat included (1) a modulation-doped,coupled double quantum well and(2) an asymmetric, coupled doublequantum well. We further looked atundoped GaAs/AlGaAs multiplequantum wells and CdTe single-crystal thin films.

Dynamic High-Strain Deformation ofMaterials: Experiments, AdvancedConstitutive Modeling, and ComputationalImplementation

Dean Preston

Science-based stockpile steward-ship requires the capability to predictthe implosion dynamics of primariesand the subsequent expansion ofwarhead components, for which theproperties of material under extremeconditions (large strain, high strainrates, and high temperatures) arecritically important. The thrust of thisproject is directed at providing theLaboratory with the ability to performpredictive numerical simulations oflarge-strain dynamical behavior bysynthesizing material strength andtexture data with condensed mattertheory and mesoscale physics toconstruct advanced constitutivemodels. For this project we have

selected a set of coordinated experi-mental, mathematical-modeling, andcode-implementation tasks that we areusing to (1) improve the calibration ofthe mechanical threshold stress (MTS)and Preston-Tonks-Wallace (PTW)strength models with new Hopkinsonbar data at elevated temperatures andat very large strains; (2) extend themodels to include texture evolution;(3) employ the methods of moleculardynamics (MD) to improve themodels at intermediate strain rates;(4) develop an advanced model ofductile damage growth and spall; and(5) analyze and model solid-solidphase transformations.

Our major accomplishments reflectthe coordinated nature of this project.We performed MD simulations ofextended-dislocation intersection inface-centered-cubic metals to improveour understanding of plastic deforma-tion at strain rates of 10V1 to 10V1.We successfully applied the Tonksductile damage model to spallationdata of ultrapure tantalum. Wemeasured and analyzed the textureand plastic constitutive propertiesinduced by upset forging high-puritybar stock. By reloading prestrainedsamples over a wide range of tem-peratures and strain rates to about10V1, we obtained data required foraccurate determination of PTW andMTS model parameters. We modeledthe nonequilibrium, shock-inducedtransformation from the body-centered cubic phase to the hexagonalclose-packed phase of iron. To datewe have focused the texture evolutionmodeling on implementating ananalytical anisotropic elastoplasticstrength model into the CHAD code.


Publications

Boettger, J., and D. Wallace,"Metastability and Dynamics of theShock-Induced Phase Transtion in1ion,"Phys. Rev. B 55, 2840 (1997).

Johnson, J.N., R.S. Hixson, D.L.Tonks, et al., "Rate-DependentSpallation of Tantalum," in ShockCompression of Condensed Matter,S.C. Schmidt and W.C. Tao, Eds.(American Institute of Physics, NewYork, 1995) p. 523.

Tonks, D.L., "Application of theTonks Ductile Damage Model toSpallation in High-Purity Tantalum,"Los Alamos National Laboratoryreport LACP-95-416 (1995).

Zurek, A.K., W. Richards Thissell,D.L. Tonks, et al., "Micromechanicsof Spall and Damage in Tantalum," J.Mater. Process. Technol. 60, 261(1996).

Zurek, A.K., W. Richards Thissell, D.L.Tonks, et al., "Spall Behavior andDamage Evolution in Tantalum," inProceedings of AIRAPT InternationalConference, W.A. Trzeciakowski, Ed.(World Science Publishing, Singapore,1995) pp. 941-3.

Ultrasensitive Sensors for WeakElectromagnetic Fields Using HTSSQUIDs for Biomagnetism, NDE, andCorrosion Currents

Edward Flynn

This project centers on developingultrasensitive sensors for detection ofweak magnetic fields and has threetask areas: (1) a new concept insuperconducting weak-field sensorarrays, (2) introduction of digitalsignal processors (DSPs) into thesuperconducting quantum interferencedevice (SQUID) circuit, and (3) im-proved high-temperature supercon-ducting (HTS) Josephson junctionsfor HTS SQUIDs.

We have focused on developingHTS (superconducting at liquidnitrogen temperature, 77 K) SQUIDsensors and systems, and on back-ground noise rejection using a DSP-controlled flux-locked loop to enabledirect cancellation of the noisemagnetic field at the SQUID sensor.These efforts have yielded SQUIDsensors for applications that requireunshielded environments.

We have developed and publishedthe results of a low-performance,prototype electronics system thateliminates 99.5% of a simulatedbackground field in a system inte-grated with a Los Alamos HTSSQUID. Thus we have improved thebackground rejection and developed aSQUID sensor system for unshieldedapplications. We also successfullytested a similar low-Tc system(superconducting at liquid heliumtemperatures, 4 K).

In addition, we developed bettersuperconducting-normal-supercon-ducting (SNS) junctions to improveboth SQUID performance and themechanics of wire bonding andSQUID circuit layout. A silver-dopingtechnique has significantly improvedthe performance of the SQUID

devices and increased the productionyield. We fabricated and testedSQUIDs with both large-area (1 mm2)pickup loops for magnetometerapplications and those with small-area(100 urn2) pickup loops for SQUIDmicroscope applications.

Publications

Flynn, E.R., R. Bracht, R.H. Kraus Jr.,et al., "A Digital-Signal-Processor(DSP) Flux-Locked Loop for Bio-magnetic Applications of SQUIDs"(to be published in the 1996 Inter.Biomagnetics Conf. Proc).

Jia, Q.X., X.D. Wu, D.W. Reagor,et al., "Edge-Geometry SNS DCSQUIDs Using Ag-dopedYba2Cy3O? x Electrodes," Electron.Lett. 32, 499 (1996).

Kraus, R.H. Jr., R. Bracht, E.R. Flynn,et al., "High Temperature SQUIDMagnetometer and GradiometerSystems with Digital-Signal-Processor (DSP) Flux-Locked Loopfor Biomagnetic Applications" (to bepublished in the 1996 Inter. Biomag-netics Conf. Proc).


Short-Pulsed Electric-DischargeDegradation of Toxic and Sludge Wastes

Louis A. Rosocha, Los Alamos National LaboratoryFrank J. Wessel and Vitaly M. Bystritskii, University of California, Irvine

To overcome the drawbacks ofconventional pollutant-degradationtechnologies, we are developing ashort-pulsed electric-dischargechemical reactor (see accompanyingdiagram) to ionize and degradeaqueous-based pollutants, particularlyorganic compounds such as chlori-nated solvents and biphenyls. Suchcompounds are hazardous air andwater pollutants that are harmful tohuman health. They are not decom-posed by natural microorganisms andare, therefore, persistent in theenvironment. An ideal degradationmethod would convert these pollut-ants into harmless or easily handled"mineralized compounds" such ascarbon dioxide and simple acids.

Our reactor offers several advan-tages over current degradationtechnologies: it has the potential toproduce higher levels of degradationand less secondary waste, and it canhandle aqueous-based wastes that aredifficult to incinerate. Our degrada-tion process could have widespreaduse for the treatment of industrialwastes such as those from chemicalplants, the petrochemical and pharma-ceutical industries, painting opera-tions, and manufacturing.

During the first year of the project,we commissioned the reactor,established its operating parameters(such as voltage and current), andassessed its ability to decompose anaqueous solution of a model organicpollutant, paranitrophenol (pNP).During this second year, we opti-mized the operating parameters forvoltage, pulse duration, pulse-repetition frequency, flow density, anddroplet dimension. In addition, weextended the reactor studies to includechlorinated compounds and as-sembled a new reactor incorporatingbeneficial design modifications in thechamber-material construction,

aerosol-injection geometry, electrodegeometry, and pulse-dischargecircuitry.

We have successfully demonstratedan innovative technique for degradingan aerosol mixture of variousorganics—pNP, dichlorophenol(DCP), and perchloroethylene—using

atomizer

a medium-voltage, repetitive, short-pulsed discharge. The accompanyingplot shows the data for DCP. Thetechnique provides relatively highelectrical efficiency for applicationsinvolving waterborne pollutants. Thespecific energy input for the degrada-tion of one pollutant molecule is inthe range of 40-100 eV and dependson both the operational parameters ofthe discharge and the concentration.We plan to conduct future studies toidentify intermediate by-products andto optimize the operating parametersthat lead to a higher degree ofmineralization.

Cross section of the cell of theshort-pulsed electric-dischargechemical reactor.

I Pyrex tube

T3

9o

o

6

t \J

60 -

5 0 -

40 -

30 -

20 -

10 -

0 -

; ^

i

_

Number of treatment cycles

Plot of the amount of chlorine that the pulsed-discharge reactor removed froma 1000-ppm aqueous solution of dichlorophenol over repeated treatments.


Laser-Sheet Imaging of HE-DrivenInterfaces

Robert Benjamin

Interfacial instability of a thin,high-density fluid layer that liesbetween two less-dense fluids is afundamental research problem inweapons and inertial confinementfusion (ICF). Experimental observa-tions of highly distorted, preturbulent,shock-accelerated gas flows motivatethe study of such flows in liquids.

Our project studies thin liquidlayers driven by a high explosive(HE). We are using multiple imagingof laser-sheet illumination (MILSI) todiagnose the transient flow patterns.The objective of our work is to

incorporate MILSI at a Laboratoryfiring site, enhancing diagnosticcapability. This work is supported inboth design and data analysis by flowsimulations with computer codes usedin weapons and ICF work.

Several HE-driven experiments thispast year demonstrated the feasibilityof producing a useful laser sheet witha 10-W, air-cooled argon laser. Thelaser beam becomes in effect a thinsheet that illuminates a two-dimen-sional slice through the liquidinterfaces. The resulting image is thendetected with a high-speed camera.

For our experiments, we used afluorescein-loaded layer embedded inwater as the test object, and wesuccessfully observed the opticalsignal from the fluorescein dye. A10-gal. aquarium contained theexperiments.

Other experiments compared twoframing methods: pulsed laser versuspulsed camera. The pulsed cameramethod, which puts an image intensi-fier on the front end of a charge-coupled-device camera, proved better.We intend to use this method forfuture HE experiments. Finally, two-dimensional design calculationsindicate that diagnostic time willprobably be limited by lateralrarefaction waves and that the denser,thin fluid layer should be only 1-2 cmfrom the HE.

A Neural-Network-Based System forDamage Identification and Location inStructural and Mechanical Systems

Charles R. Farrar

There are many large structures andmechanical systems for which itwould be desirable to monitor their"health" and to identify damage asearly as possible. The objective of thisproject is to develop a computer-based system that can remotelymonitor and detect damage instructural and mechanical systems.Clearly, such development would beof high value and wide application.We have begun to integrate newdamage identification algorithms (thatmonitor the vibration response of aphysical structure or system) withadaptive computing strategies. Ourresearch will couple expertise in

structural dynamics, neural networks,and pattern recognition to develop acomprehensive, self-diagnosing,structural-monitoring and damage-detection system.

Our primary technical achievementthis year is the development ofnonlinear time-frequency-analysisalgorithms that can be applied tomeasured vibration data for globaldamage detection in structures andmechanical systems. We have verifiedthese algorithms by applying them tosimple test specimens in which thedamage produces a nonlinear vibra-tion response not present in undam-aged specimens. We are beginning to

adapt these algorithms into a general-purpose computer code that will beused to detect damage in structuraland mechanical systems. We havecompleted a comprehensive literaturesurvey of the damage identificationfield, and we sponsored a workshopon damage identification fromchanges in vibration characteristics.Researchers from the United Statesand many foreign countries attendedthe workshop and helped to define thestate of the art.

Publications

Doebling, S.W., "Minimum-RankOptimal Update of ElementalStiffness Parameters for StructuralDamage Identification," AIAA J. 34,2615-2621 (1996).


Development of Inexpensive Continuous-EnnissionMonitors for Feedback Control of CombustionDevices to Minimize Greenhouse Gases, Toxic Emissions,and Ozone-Damaging Products

David J. Funk

There is little doubt that combus-tion is the major cause of poor urbanair quality and depletion of the ozonelayer and a major source of thegreenhouse gas carbon dioxide.Furthermore, there is little doubt thatglobal combustion activity is increas-ing. We are addressing these concernsthrough research and development ofsensitive, inexpensive, continuous-emission monitors (CEMs) based onthe optical properties of expected,gas-phase, hazardous materials. Todate we have begun work on threespecific tasks: (1) proof-of-principleexperiments for an inexpensive, solid-state NOX detector; (2) proof-of-principle experiments of a solid-state,Fourier transform (FT) spectrometer(see the first figure), which has led toa disclosure and pursuit of a patent;and (3) infrared HeNe detection ofhydrocarbons. Our preliminaryexperiments indicate high sensitivityfor absorption of the infrared HeNewavelengths by hydrocarbons foundcommonly in fuels. We are presentlyquantifying these results.

We have conducted studies of thesolid-state FT spectrometer using abroad-band light source, dispersingthe radiation, modulating four bandsof light at four different frequencies,recombining the light, and recordingthe time output in single-shot mode,as shown in the second figure. Weapplied a Fourier transform to the dataand observed the four frequencypeaks corresponding to the fourbands, as shown in the third figure.

We expect that these inexpensiveoptical sensors will assist in providingdirect feedback of turbine powersystems and assure the public andoperators of facilities that facilityemissions lie within accepted bounds.

IRSource

Polarizer

000^7Dispersing/Combining

Prisms

Sample/ReferenceChamber

Lens

Detectors

FrequencyGenerator Computer DSP Board

Schematic of the solid-state Fourier transform spectrometer.

•8c8

COco

0.5 0.6Time (s)

0.8

Raw output of the phototubes (light detectors) as a function of time. The toptrace is the time-dependent signal transmitted through a red filter; only one ofthe stripes in the mask (the focal plane of an optical system) is transmittinglight and only a signal frequency is detected. The bottom trace is the time-dependent signal of the full output from the mask (no filters); the four carriersexhibit the expected beating behavior.


3.5

3.0

2.5

2.0

1.5

1.0

0.5

nn

-

\ / !

/ v/ \l \ \/ v N 'V V 1/ ' X ^ A A \

/ • • / \ ' A - A \

y;(iitii(1

ii

700

(A)

650 600 550

Wavelength (nm)

500 450

Data from studies of the solid-stateFT spectrometer. (A) Solid lines areGaussian fits to the transmission ofeach of the striped elements. Thedashed and dotted-dashed lines arethe absorption of each of the filtersstudied. (B) Transmission spectra ofthe filters. The solid line is with nofilter in place.

(B)

55 60 65 70 75 80

Frequency85 90Hz

Distortion, Residual Stress, and ThermalGradient Issues for Plutonium GravityCasting in Ambient-Temperature Molds

S. Dale Soderquist

The goal of this one-year projectwas to begin development of theprocess of casting plutonium alloys inthin-walled, ambient-temperaturemolds and to develop the methodsnecessary to numerically simulate theprocess. The new casting techniquedecreases equipment complexity andincreases cooling rates after casting.These effects simplify heat-treatingrequirements for the plutonium alloys.An additional benefit of the new

process is that it will minimize theamount of waste generated during thecasting operation. The numericalmethods that were developed tomodel the process increased under-standing and could lead to optimiza-tion of the process. Numericalprediction of fluid flow, heat transfer,thermal gradients, stresses, anddistortion aids in process design andwill eventually allow fabrication of ahigher quality product.

During the year we developed acomputational model that predicts thedistortion and residual stresses in afinal cast plutonium part. By numeri-cally tracking the temperature historyat different locations in the part, wecan estimate the final metallurgicalcondition of the part. We made severalcastings to develop information forthe model and to develop the molddesign. Five of the castings were ofsurrogate material (four depleteduranium and one bismuth). We madeone casting of a plutonium alloy andperformed metallurgy on the final partto determine the as-cast material state.Use of a thin-walled mold greatlysimplified the casting process, and weexpect the metallurgy of the as-castpart to be superior to that of castingsmade by traditional methods.


Radiation Resistance Measurements ofRare-Earth Permanent Magnet Materialfor High-Intensity Linac Applications

David Barlow

The objective of this project is tocharacterize the radiation resistance ofrare-earth permanent magnet materi-als in an accelerator environment byirradiating samples with neutrons.High-strength, rare-earth permanentmagnet materials can be used invarious compact magnets for steeringand focusing high-energy particlebeams. Such permanent magnetassemblies take considerably lessspace than comparable electromag-nets and are extremely attractive ifspace is at a premium. In addition,permanent magnets offer a level ofreliability that far surpasses that ofelectromagnets—an important ad-vantage for applications that requirehigh reliability.

During this reporting period, weexposed samples of samarium cobalt,a rare-earth permanent magnetmaterial, to neutron radiation at theLos Alamos Neutron Science CenterA-6 target facility. A total of 20samples from 4 different sources wereexposed to 5 different dose levelsranging from 1.0 x 1017 to 1.0 x1019 n/cm2. We then retrieved thesamples from the neutron source andstored them to allow the short-livedactivation products to decay. Tenmonths later, we took the samples outof storage just long enough tomeasure their relative magneticmoment before returning them tostorage.

After exposure, the relative mag-netic moment of each sample wasfound to be within one standarddeviation (0.5%) of its preirradiationvalue. These results indicate nomeasurable change in the strength ofeach sample's magnetization. Wedetermined the neutron dose for eachexposure by integrating the protonbeam on the target and the neutronenergy spectrum by analyzing theresults of a set of activation foils froma companion experiment at the samefacility.

These results indicate that perma-nent magnet assemblies can survivedoses of 1.0 x 1019 n/cm2 or morewith little or no degradation in theirmagnetic-field strength. However, inan actual assembly, the permanentmagnet material will be exposed toexternal demagnetizing fields, whichhave been shown to greatly increasethe rate of radiation damage. The realtest of a permanent magnet's radiationresistance will require exposing theassembly to the expected radiationfield.

Molten Salt and Separations TechnologiesEvaluation

Francesco Venneri

Accelerator-driven transmutation ofnuclear waste (ATW) offers greatpromise as a method to essentiallyeliminate plutonium, higher actinides,and environmentally hazardous fissionproducts in the spent fuel waste fromnuclear reactors. The goal of thisproject has been to evaluate thepotential of existing technologies andadapt them for use in ATW, focusing onheat generation, fluid motion, andchemical separations for molten saltand lead-based systems.

We have identified significant newmethods for preparing spent fuel forATW treatment and post-transmutationseparations and have submitted anapplication for an international patent

for these processes. Building on theIntegral Fast Reactor (IFR) fueltechnology processes developed atArgonne National Laboratory and theplutonium pyrotechnology developedat Los Alamos, we have refined themolten salt/liquid metal pyrochemicalprocesses and identified the individualprocess steps for particular applica-tion for ATW. Moreover, we haveestablished a universal process fortreating pyrochemical fuel that isapplicable to many different types ofspent fuel elements and other nuclearwaste products.

In addition to molten salt fuels, wehave worked on liquid metal fuels,revisiting the bismuth-based fuels

considered by Brookhaven NationalLaboratory in the past and extendingour analysis to lead-based fuels.Molten salt and bismuth-based fuelsare especially well suited for thepyrochemical processes underinvestigation, and these solvents arereusable. Finally, we have modeledand analyzed the thermodynamics ofthese fuels in state-of-the-art three-dimensional simulations.

This project steadily continues toattract increasing interest from otherU.S. national laboratories, industry,and universities.

Publications

Li, N., "Performance Estimates forWaste Treatment Pyroprocesses inATW" (Second InternationalConference on Accelerator-DrivenTransmutation Technologies andApplications, Kalmar, Sweden, June3-7,1996).


Neutron Metrology for StockpileStewardship at LANSCE

Chris Morris

The goal of this project is todevelop neutron-detector technologyto advance research in support of theLaboratory's stockpile stewardshipmission. In particular, the emphasis ison higher-resolution imaging detec-tors for both high-energy and coldneutrons. An additional task is toevaluate new technology for position-sensitive detection of thermal, cold,and ultracold neutrons.

We have made progress in severalareas. For example, we have devel-oped and implemented new technol-ogy for imaging with high-energyneutrons. We designed and are puttingtogether a detector with an active areaof 20 x 20 cm2 and a pixel size of1.8 x 1.8 mm2 for neutron radiogra-phy. We have coupled converters toimage plates and have begun investi-gating these for fast-neutron imaging.We have designed and are building a

fast, two-dimensional, delay-line-readout, position-sensitive detector forthermal and cold neutrons. Becausereadout speed is important forultimate performance, we built a PC-based system aimed at 20 Mbytes/s.We have built two 3He-doped, wire-chamber systems and have success-fully used them for detecting the firstultracold neutrons produced at LosAlamos. We also developed a newconcept of a velocity-matcheddetector for epithermal neutrons andwill test it next year.

Publications

Morris, C , V. Armijo, L.G. Atencio,"An Integrating Image Detector forEnergy Neutron Radiography" (FifthInternational Conf. on Applications ofNuclear Techniques: "Neutrons inResearch and Industry," Crete,Greece, June 1996).



High-Energy Test of ProtonRadiography Concepts

Chris Morris

Proton radiography offers thepromise of outstanding performancein terms of position-resolution andsensitivity to density variations.Proton radiography is also very wellsuited to provide a complete historyof explosive-driven compressions ofheavy-metal systems. In addition,through the use of multiple beams anddetector systems, we may be able toreconstruct tomographic images of theobject under test. We can alsoimplement proton radiography usingestablished accelerator technology for

beam generation and available test-recording technology for dataacquisition. Proton radiography offerspotential advantages over current andproposed x-ray radiography technolo-gies and could be an alternative orcombined technology for the Ad-vanced Hydrotest Facility (AHF)initiative.

We completed a proof-of-principleexperiment for proton radiographyusing 3- to 9-GeV proton beamsavailable at Brookhaven NationalLaboratory's Alternating GradientSynchrotron (AGS). The experiment

produced proton radiographs of asuitably dense, unclassified testobject. The experiment tested capa-bilities in data collection, imagereconstruction, and hydro-codesimulation and validated models ofhigh-energy proton radiography.

We designed a lens using existingquadrupole magnets, constructed it onthe Al beam line of the AGS, andused it to image 10-GeV protons. Theresults include (1) images made withan integrating detector, (2) measure-ments of the background and mea-surements of the resolution functions,and (3) forward-model fits to thetransmission data. In all cases theresults agree with initial estimates andprovide strong support for the utilityof proton radiography as a newhydrotest diagnostic.

Comparison of Cyclotrons and Linacs forHigh-Intensity-Beam Applications

Tarlochan S. Bhatia

Two types of high-intensity sub-GeV ion accelerators are in use asdrivers for neutron sources. The firstof these is the linear accelerator,which accelerates up to ~1 mA of800-MeV protons as operated at LosAlamos. The second class of driver isa cyclotron such as the one at the PaulScherer Institute in Switzerland,where a beam of ~1 mA of 600-MeVprotons is available. The aim of thisproject is to develop a better under-standing of the capabilities andlimitations of circular machines incomparison with linear accelerators.

We have conducted a preliminaryinvestigation of the cost benefits of

cyclotrons versus linacs. We find thatfor applications requiring beam powerin the range of 10-20 MW, a cyclo-tron of high efficiency is probablycheaper than a similar linac of highefficiency because of both the distri-buted nature of the power feeds inlinacs and the significantly lowerradio frequency at which a cyclotronoperates. In addition, the pulse formatof the cyclotron (continuous wave) isnaturally better suited to targetrequirements than a room-temperaturelinac of high efficiency, which wouldhave to be pulsed to achieve highbeam loading. We plan a detailed costcomparison.

We have been looking at thefundamental limits that might restrictthe operation of cylcotrons. Inparticular, we have begun to formu-late a halo-formation model analo-gous to that used by Gluckstern forthe treatment of halo in linacs butwith the addition of larger externalnonlinear terms introduced by theedge focusing in the cyclotron sectormagnets. The model formulation isvery similar to that in Gluckstern'slinac model. The beam-dynamicsmodel of Ryne and Wangler shouldallow us to simulate halo formationfor a high-intensity beam thatcompares favorably with the linacmodel.

Finally, we have started to set updetailed simulations for cyclic-ionaccelerators with a view towardestimating beam losses not only atextraction but also during acceleration.

Competency Development Projects—Plasmas, Fluids, and Particle Beams 177

A I -kW-Power Demonstration from theAdvanced Free-Electron Laser

Richard Sheffield

Free-electron lasers (FELs) are notwidely used because of two principaldrawbacks: (1) they tend to be large,complex, and thus costly, and (2) theaverage power they can deliver in theoptical beam is generally low com-pared with that of other laser sources.As a result, credible use of FELs forhigh-power applications still requiresa demonstration that they can deliversuch power. In fact, the highestaverage power achieved to date withany FEL is only 10 W.

This project was initiated to addressthe issue of FEL size, which wasanswered by building the AdvancedFEL, a table-top device that demon-strated reliable operation at modestbut significant power levels (a fewwatts). During its operation, wedeveloped a new idea in FEL designthat, based on computer simulations,showed would generate as much as

1-kW optical beam power and thatwould require only minor modifica-tions to the Advanced FEL.

The additional objectives of thisproject then became to engineer andprocure an electron beam line com-patible with the proposed operation ofa 1-kW optical beam. An associatedmajor task was the physics design ofthe electron beam line from the end ofthe wiggler to the electron beamdump. This task was made especiallydifficult because the beam wasexpected to have 20 kW of averagepower and a 25% energy spread.

We accomplished all projectgoals—the high-power electron beamdesign was completed (see figure),and the hardware necessary for high-power operation was designed andprocured. The next step is to test theAdvanced FEL at the full 1-kWoptical beam power.

Publications

Goldstein, J.C., et al., "TheoreticalStudy of the Design and Performanceof a High-Gain, High-Extraction-Efficiency FEL" (submitted Nucl.Instrum. Methods Phys. Res.).

Nguyen, D.C., "SynchronouslyInjected Amplifiers, a NovelApproach to High-Average PowerFELs" (submitted to Nucl. Instrum.Methods Phys. Res.).

Sheffield, R.L., et al., "ElectronBeamline Design for LANL 1 kWFEL" (submitted to Nucl. Instrum.Methods Phys. Res.).

Engineering layout of the high-power FEL beam line at the Advanced Free-Electron Laser facility. The 1.3-GHz linearaccelerator is on the left. The optical table is actually a 6-ft-high x 10-ft-long "wall" on which beam line components,such as the 6-ft-long wiggler, are mounted. The beam line is now fully installed and operational.


Advanced Techniques for Producing,Polarizing, and Storing Ultracold Neutrons

Susan Seestrom

Project objectives are modelingultracold neutron (UCN) productionin cryogenic materials and develop-ment of techniques for storing andpolarizing ultra-cold neutrons. Thisactivity is centered around developingtechniques and experimental appara-tus to make use of an UCN source atLos Alamos as well as to study thedesign and performance of a second-generation UCN source. Such asource is the planned long-pulsespallation source that would provideUCNs of parameters unmatchedanywhere else. The techniques beingdeveloped will open up a range offundamental physics studies as wellas novel experiments in materialsscience. Fundamental physicsexperiments include improvedmeasurement of the neutron lifetimeand decay parameters; such measure-ments provide a sensitive and uniquetest of the Standard Model forelementary particle interactions.

We have designed and are assem-bling a UCN transport system and anexperimental storage bottle for UCNs.This bottle incorporates a novelshutter design that will allow us tostudy the spectrum of UCNs producedby the source at the Manuel Lujan Jr.Neutron Scattering Center. The bottlewill allow us to study the UCNstorage time as a function of differentneutron velocity. We have identifiedand obtained a superconductingmagnet suitable for initial attempts topolarize UCNs.

We have designed and are assem-bling two separate experimental UCNdetectors; one is a helium-3 gasscintillator and the other is a helium-3proportional counter. We have alsodesigned and acquired the compo-nents for a data acquisition systemthat will be used to take and analyzedata from these detectors to determinethe UCN production rate and thebottle-storage lifetime.

We have written a computer code tocalculate the UCN production rate fora solid deuterium superthermal sourceand compared the results with datataken at the Petersburg NuclearPhysics Institute reactor in Gathchina,Russia. We identified uncertainties inthe cross-section databases availableas well as the need for better normal-ization of benchmark data.

Publications

Bowles, T.J., R. Hill, et al., "UltraCold Neutrons at a Spallation Source"(Int. Symp. on Neutrons Optics andRelated Research, Kumatori, Japan,March 1996).

Seestrom, S.J., TJ. Bowles, et al.,"Plans for an Ultra Cold NeutronSource at Los Alamos" (Japan HadronProject Workshop, Tskuba, Japan,March 1996).

Seestrom, S.J., T.J. Bowles, R. Hill,et al., "Development of an Ultra Coldneutron Source at MLNSC" (Int.Conf. on Applications of NuclearTechniques, Crete, Greece,June 1996).

Development of Ion-Beam Techniques forthe Study of Special-Nuclear-Materials-Related Problems

Carl Maggiore

The objective of this project is todevelop ion-beam techniques forcharacterizing actinides and theireffects on other materials. The projectis designed to enhance our abilitymeasure the oxidation, corrosion,diffusion, and stability of actinidesand the materials with which theymay come in contact.

Using ion beams at the Los AlamosIon Beam Materials Laboratory(IBML) to simulate alpha particles,we have accelerated the aging ofpolymeric materials in contact with

actinides in engineered systems andunder conditions of temperature,pressure, and residual gas compositionthat correspond to those in the field. Wehave measured the radiolytic break-down products of the polymers bymounting a quadrupole mass spectrom-eter to the scattering chamber at theIBML. We have also determined thedepth distribution of hydrogen andhelium isotopes in actinides and insurrogates such as the gold/silver alloysused to simulate actinides.

We also evaluated the detectionmethods required to distinguishbetween the ions used to probeactinides from the alpha particlesproduced by natural decay. We havemeasured the limitations of solid-statedetectors for analyzing alpha-activematerials and have identified alternativeresonance and nuclear reactionmethods with time-of-flight detectionas preferable when extreme sensitivityis needed for such problems assubmonolayer surface contamination.When masking and the use of absorberfoils cannot be used to minimize theinherent alpha activity from actinidematerials, we have identified particleidentification methods for near-surfaceanalysis. We have also measured thesensitivity, spatial and depth resolution,and precision of elastic recoil detectionand nuclear reaction analysis instudying actinides.


Generation and Compression of a TargetPlasma for Magnetized Target Fusion

Ronald Kirkpatrick

The goal of this project is todevelop a computational capabilityfor the design and interpretation of anexperiment on magnetized targetfusion (MTF). MTF relies onmagnetoinsulation to allow slow,near-adiabatic compression of a hottarget plasma to fusion conditions.

This year we employed ourcomputational tools to assess theimpact of experimental compromisessuch as a necessary design change inthe region near one electrode. Wedeveloped a capability to simulate theemission from a hot, magnetizedplasma in order to be prepared tointerpret pending experimental data interms of density and temperature, andwe tested its effectiveness on the datafrom related MAGO experiments. ForMTF we need to achieve temperaturesabove 50 eV and magnetic fieldsabove 5 T. In addition, it is necessaryto keep impurities at a sufficiently lowlevel to avoid significant radiationlosses during the compression phase.

We made significant progress on anew transport method for the compu-tation of alpha-particle energydeposition in the magnetized deute-rium-tritium (DT) fusion targetplasma. This method will allowefficient computation for the dynamicproblems that we must handle forMTF target design. We establishedinformal interactions with the FrenchCEA laboratory, Limeil; AdvancedLaser and Fusion Technology, aCanadian company; and GeneralAtomics in La Jolla, California. Weare also developing the potentialapplications of this research toscience-based stockpile stewardship.

The first accompanying graphshows a computed Kadomtsev stableprofile for a plasma produced by adischarge through a cryogenicdeuterium fiber in a 2-cm-high by 2-cm-radius cylindrical container. Thecalculations indicate that a plasmasuitable for MTF can be produced.

The second graph shows the three-dimensional trajectory of a single DTfusion alpha particle through amagnetized target plasma. We aredeveloping a charged particle trans-port method intended to efficientlyand accurately treat energy depositionby the DT alphas in an MTF plasmaduring fusion ignition and burn.

The third graph represents thetemperature history inferred by analysisof filtered silicon diode data from theMAGO II experiment conducted at LosAlamos in October 1994. It suggeststhat the magnetized plasma reachedover 300 eV and remained above100 eV from 2.5 to 7.5 us, after whichthe diagnostic failed.

Publications

Idzorek, G., and R. Kirkpatrick,"Analysis of Filtered Silicon DiodeData from the MAGO 2 and MAGO 3Experiments" (to be published in theProc. 7th Int. Conf. Megagauss FieldGeneration, MegaGauss VII).

Kirkpatrick, R., and D. Smifherman,"Energetic Alpha Transport in aMagnetized Fusion Target" (to bepublished in Fusion Technol).

Kirkpatrick, R., P. Sheehey, et al.,"Proposed Generation and Com-pression of a Target Plasma for MTF"(to be published in Proc. Tenth IEEEInt. Pulsed Power Conf.).

Lindemuth, I., R. Reinovsky, V.K.Chernychev, et al., "Target PlasmaFormation for MagneticCompression/Magnetized TargetFusion," Phys. Rev. Lett. 75,1953(1995).

Sheehey, P., R. Faehl, et al.,"Computational Modeling ofMagnetically Driven Liner-on-PlasmaFusion Experiments" (to be publishedin the Proc. 7th Int. Conf. MegagaussMagn. Fields).

Sheehey P., J. Guzik, et al.,"Calculations of Proposed Mag-netized Target Fusion Experiments"(to be published in Proc. I Oth Bienn.Nucl. Explos. Des. Phys. Conf. 1995).

Sheehey, P., J. Guzik, R. Kirkpatrick,et al., "Computational andExperimental Investigation ofMagnetized Target Fusion" (to bepublished in Fusion Technol.).

Temperature and Density Profiles

100000

0.02

Computed Kadomtsev stable profile for a plasma produced by a dischargethrough a cryogenic deuterium fiber in a 2-cm high by 2-cm radius cylindricalcontainer.


The trajectory of a single DTfusion alpha particlethrough a magnetized target plasma.

3

0.0

Effective Plasma Temperature

1.E+3 -

1.E+2 -

1.E+1 -

1.E+0 -

1.E-1 -

V1t11

I

» noise level%

*

I1\ .

1

I\

» »

2.0 4.0 6.0

time (us)8.0 10.0

The temperature history inferred by analysis of filtered silicon diode datafrom the MAGO II experiment conducted at Los Alamos in October 1994.


Advanced Modeling of High-IntensityAccelerators

Robert Ryne

The goal of this project is todevelop an advanced modelingcapability for the design of futurehigh-intensity accelerators that can beused for waste transmutation, pluto-nium conversion, spallation-neutronproduction, tritium production, etc.Our goal is to develop a suite of codesthat can model the beam throughkilometers of complex acceleratingstructures, including radio-frequencyquadrupoles, drift-tube linacs,coupled-cavity drift-tube linacs,coupled-cavity linacs, and high-energy, beam-transport sections.

In prior years' work, we developeda family of codes to perform simula-tions of simple test systems. Now ouremphasis has been placed on model-ing realistic accelerator systems.Realistic linacs are usually designedand optimized using complex simula-tion codes. The most widely usedlinac simulation code in the UnitedStates is called PARMILA (for phase

and radial motion in ion linearaccelerators). A major accomplish-ment in our project has been todevelop a version of PARMILA thatruns on parallel computers, currentlythe most powerful computers avail-able. The parallel version ofPARMILA has significantly improvedperformance over the original (scalar)version and has been run with up to30 million particles. In addition, it ismore accurate than the scalar versionbecause of the development of athree-dimensional (3-D), as opposedto two-dimensional, parallel space-charge routine.

In another area, we applied split-operator, symplectic techniques toefficiently compute the dynamics ofintense beams in radio-frequencyaccelerating gaps, including compli-cated z-dependent fields in the gaps.

A third area in which we havemade significant progress is ineffectively dealing with very largeamounts of data. For example, thememory required to store 100 millionparticles in a 3-D simulation is nearly10 Gbytes. To handle this volume, weperform "data pruning" inside a codebefore the data is written to disk. Insome cases this process has enabledus to visualize the beam halo whileconcurrently reducing the size of thedata set by more than three orders ofmagnitude.


Chemistry

Binding Carbon Dioxide in Mineral Form:A Critical Step toward a Zero-EmissionCoal Power Plant

Klaus Lackner

Fossil fuels are a large and estab-lished energy resource, and coalreserves will last for centuries. How-ever, for fossil fuels to remain animportant energy source, the environ-mental impact of their carbon dioxideemissions must be eliminated. To thatend, we are working to developdisposal processes that permanentlybind carbon dioxide into environmen-tally safe, solid waste products, suchas carbonate rock. The reason theseprocesses are potentially economi-cally viable is that the underlyingchemical reactions are energeticallyand thermodynamically favored. Lastyear we published a paper thatoutlined the basic concepts andsketched out several approaches basedon different readily available calcium-or magnesium-bearing minerals anddifferent chemical reaction paths. Weare continuing to refine our process-ing schemes. We are focusing some ofour attention on the basic chemistryin an effort to speed up the chemicalreaction, thereby making it more cost-effective.

This year we developed severalviable processes, selected the mostpromising candidate processingscheme, and experimentally verifiedall of the steps in the laboratory. Forour candidate process we haveimproved the reaction rate of thecentral solid-gas reaction, the carbon-ation of magnesium hydroxide. Wecan now achieve rates of carbonationten times faster than our first experi-ment appeared to indicate. Withregard to alternative processes, we

have tested a wide variety of commonminerals for the direct gas-solidreaction with carbon dioxide. Wefound that either pretreatment or somesort of elevated pressures are neces-sary to obtain sufficient reaction rates.

By developing this technology, wewill provide the fossil power industrywith the means to remain competitive,even if greenhouse gases need to beeliminated. Fossil fuels could satisfy agrowing world energy demand formany more centuries.

Publications

Butt, D.P., K.S. Lackner, C.H. Wendt,et al., "Kinetics of Thermal Dehy-droxylation & Carbonation ofMagnesium Hydroxide," /. Am.Ceram. Soc. 19, 1892-1898 (1996).

Lackner, K.S., D.P. Butt, and C.H.Wendt, "Progress on Binding CO2 inMineral Substrates" (Third Inter-national Conference on CarbonDioxide Removal, Cambridge, Mass.,September 9-11, 1996).

Lackner, K.S., D.P. Butt, et al.,"Carbon Dioxide Disposal in SolidForm," Proc. of 21st Int. Tech. Conf.on Coal Utilization & Fuel Sys. 21,133-134 (1996).

Lackner, K.S., C.H. Wendt, D.P. Butt,et al. "Carbon Dioxide Disposal inCarbonate Minerals," Energy, Int. J.20, 1153-1170(1995).

Foreign Nuclear Test RadiochemicalDiagnostics

Michael Macinnes

For this project, one of our goals isto develop a capability to interpretradiochemical data from foreignnuclear tests. This ability would bean obvious benefit in non- andcounterproliferation and wouldsupport the draft language of theComprehensive Test Ban Treaty. Weare also working to develop methodsto enhance our ability to extractinformation from the early nuclearweapons tests of other countries. Weare evaluating alternative weaponstechnologies and improvements tointerpretation techniques becausethese capabilities will be useful inassessing potential proliferantdesigns.

We can best gain expertise in theevaluation of atmospheric nuclear test

data through manipulating actualradiochemical data. Last year wefocused our efforts on a survey ofearly tests of nuclear weapons states,concentrating on the technology usedby most states in their initial nucleardevices. We revived two computercodes that evaluate nuclear test debrison-line, and we trained three analyststo use these and other evaluationtools. This year we used theseanalysts and tools to evaluate alterna-tive technologies that weapons statesmight be employing as they expandtheir technology base and as theyincorporate elements of thermo-nuclear technology. To date, we havereevaluated 10 nuclear events,including those that we selected asbenchmarks.

Competency Development Projects—Chemistry 183

The Characterization of AtmosphericAerosols: Applications to HeterogeneousGas-Particle Reactions

Jeanne M. Robinson, Los Alamos National LaboratoryKimberly A. Prather, University of California, Riverside

We have continued the developmentof aerosol time-of-flight massspectrometry for the analysis of thesize and chemical composition ofindividual aerosol particles in realtime. We characterized the particlesproduced directly from variouscombustion sources such as woodsmoke and diesel and gasolineexhaust. The goal of these source-characterization studies is to establishunique size and composition profilesfor particles from various sources,which will allow for more-accuratesource allocation. Information atthis level of detail is necessary forestablishing more-directed controls ofparticulate emissions.

We also built two field-portableinstruments for establishing regionalvariations in aerosol particles, whichwill add to our understanding ofatmospheric processes by probing

different environments in whichdifferent chemical processes areexpected. We will also use theseinstruments as on-line probes formonitoring controlled, heterogeneous,chemistry processes important in thestratosphere and troposphere at thesingle-particle level.

In addition, we have investigatedthe thermodynamics of model polarstratospheric aerosols. Using secondharmonic generation, we monitoredthe adsorption and phase behavior ofHCl on water ice films. We identifiedthe quasi-liquid/solid transitionpostulated by theorists. We arepresently using mass spectrometry tomeasure vapor pressures over thehydrate ice films in conjunction withoptical measurements, as shown in thefigure. Our goal is to map out thephase diagram of the HC1/H2O system

as a function of temperature, pressure,and surface coverage.

Publications

Henson, B.F., K.R. Wilson, and J.M.Robinson, "Quantitative Measure-ments of Multilayer PhysicalAdsorption on Ice from NonlinearLight Scattering" (1996 InternationalSymposium on Physics andChemistry of Ice, Hanover, N.H.,August 1996).

Noble, C.A., and K.A. Prather, "Real-Time Measurement of Correlated Sizeand Composition Profiles ofIndividual Atmospheric Aerosols,"Env. Sci. Tech. 30, 2667 (1996).

Wilson, K.R., B.F. Henson, and J.M.Robinson, "Physical AdsorptionMeasurements of HCl on Water Ice,"EOS Trans., Am. Geophys. Union 76(1995).

Wilson, K.R., B.F. Henson, et al.,"Equilibrium Thermodynamics ofHCl Adsorption on Water Ice" (211thAmerican Chemical Society NationalMeeting, New Orleans, La., March1996).

Rate= 4.22 x 10"7

moles/sec

Rate= 4.76 x 10~8

moles/sec

2 3

Coverage (monolayers)

Adsorption spectra for HCl on water ice at 180 K. The HCl vapor was introduced at two different rates. Our preliminarydata analysis using classical physical adsorption suggests that different hydrates are formed in these experiments.


Kinetic Studies of Competitive AdsorptionProcesses Related to Automobile CatalyticConverters

Mark Paffett, Los Alamos National LaboratoryFrancisco Zaera, Unversity of California, Riverside

This project focuses on the studyof the reaction kinetics in catalyticconversion processes for exhaustgases by using the method devised byKing and Wells. We have investigatedboth the oxidation of CO and thereaction between NO and propene onPt(ffl) surfaces.

We found that in the first case, thepresence of preadsorbed atomicoxygen does not significantly affectthe initial sticking coefficient of CO,but preferentially blocks the bridgesites. No reaction takes place below300 K, and above 400 K, CO2

production is controlled by theimpinging frequency of the incomingCO. However, between 300 and 400K, the rate of surface recombinationof CO with oxygen competes withthat of CO adsorption, and not all ofthe surface oxygen is reactive.

The behavior observed in that latterregime suggests that the reactivity ofthe adsorbed oxygen depends on thelocal coverage of neighboring sites.Beams with CO + O2 mixtures werealso used to better mimic realisticcatalytic conditions. We found that athigh temperatures, the rate of COoxidation is equally determined by theCO incoming flux as long as theCO:O2 ratio is kept low. For highCO:O2 ratios, however, the COsteady-state coverage increases,poisoning the adsorption of oxygenand slowing down the overall CO2

production.Finally, preliminary data has now

been acquired for the second system(NO and propene) and is beinganalyzed.

Publications

Liu, J., M. Xu, and F. Zaera,"Determination of the Rate LimitingStep in the Oxidation of CO on Pt(III)Surfaces," Catal. Lett. 37,9-13(1996).

Liu, J., M. Xu, et al., "StickingProbabilities for CO Adsorption ofPt(III) Surfaces Revisited," J. Phys.Chem. 99, 6167-6175 (1995).

Xu, M., J. Liu, and F. Zaera, "KineticEvidence for the Dependence ofSurface Reaction Rates on theDistribution of Reactants on theSurface," /. Chem. Phys. 104, 8825-8828 (1996).

Zaera, F., J. Liu, and M. Zu,"Isothermal Study of the Kinetics ofCarbon Monoxide Oxidation onPt(III): Rate Dependence on SurfaceCoverage" (submitted to J. Chem.Phys.).

Investigations of BiomimeticLight-Energy-Harvesting Pigments

Robert Donohoe

The design of materials for con-trolled photophysical response, suchas energy conversion or destruction ofpollutants, can be approached from amolecular level. The goal of thisproject is construction of extendedarrays of molecular pigments withpredictable and controllable light-initiated responses.

We have approached the investiga-tion of the excited-state dynamics inporphyrin oligomeric arrays byacquiring transient absorption andtime-resolved fluorescence measure-ments. The present effort serves as acomplement to these excited-statemethods by using resonance Raman,electron paramagnetic resonance, and

absorption spectroscopies to charac-terize the ground-state structures ofthe neutral and oxidized porphyrinarrays. The electrochemical andspectral properties of the arraysindicate that the electronic communi-cation between the macrocycles isrelatively weak in the ground andexcited electronic states. This commu-nication is through-bond, rather thanthrough-space, and is mediated by thediarylethyne linker.

In the case of the torsionallyunconstrained dimers, we observedextremely large resonance Ramanintensity enhancements for aryl ringand ethyne-bridge stretching modes.These intensity enhancements are

attributed to an excited-state confor-mational change that enhances theconjugation between the p-electronsystems of the porphyrin ring andbridging diarylethyne group. Theintensity of the aryl and ethyne-bridgevibrations monotonically decreases asthe degree of steric constraintincrease. This trend parallels thatobserved for the rates of energytransfer in these arrays and indicatesthat the excited-state electroniccommunication can be tuned viastructural modification of thediarylethyne linker.

We are about to begin the investiga-tion of new arrays that incorporateredox switches to mediate energytransfer. These switches may includepigments capable of selective oxida-tion or, possibly, chromophores thatcan be photo-oxidized, therebyproviding a light switch of theexcited-state energy transfer.

Competency Development Projects—Chemistry 185

Mathmatics andComputational Sciences

Nuclear Futures Analysis andScenario Building

Edward D. Arthur

In this project we have begunexamination of future nuclear-energyscenarios and assessed the size of theresulting inventories of plutonium andother nuclear materials. We alsomodeled various technologicalapproaches and their impacts on themanagement of such inventories. Theeffort emphasizes establishing quantita-tive metrics to assess proliferation riskfrom projected material accumulationsduring civilian nuclear-power use.Principal focuses of these analyses areidentification and testing of technolo-gies and materials managementstrategies that contribute positively tofuture security, nonproliferation, androbust-energy scenarios.

We accomplished the followingobjectives in FY 1996. (1) A robustnuclear-fuel-cycle model was addedto a major global energy, economics,energy-projection model (i.e., thePacific Northwest National Laborato-ries' Edmunds, Reilley, and Barnesmodel) and the results tested. Theseresults provide unique capabilities forassessing and testing nuclear materi-als-management strategies for ninemajor world regions. The accompany-ing figure provides an example ofprojected growth in global plutoniuminventories (arising from spent nuclearreactor fuel) along with regionalcontributions to the total. We alsodeveloped a more detailed nuclear-fuel-cycle model to be used separately thatprovides a platform for testing theenergy model results and for technol-ogy impact assessment (see item 3).(2) We developed a model to determineproliferation-risk metrics associated

with the civilian nuclear-fuel cycle andbegan testing plutonium managementstrategies. (3) We modeled threetechnologies for management of globalplutonium inventories—mixed-oxide-fueled light-water reactors, liquid-metalreactors, and accelerator systems—viathe code system of item 1 and assessedthe impacts in terms of residual-plutonium inventories, time period toachieve results, and the systemdeployments required.

Publications

Arthur, E.D., "Impact of ADTTConcepts on the Management ofGlobal Plutonium Inventories" (SecondInt. Conf. on Accelerator-DrivenTransmutation Technologies andApplications, Kalmar, Sweden, June 3 -7,1996).

Arthur, E.D., and R.L. Wagner, "TheLos Alamos National LaboratoryNuclear Vision Project" (GlobalFoundation Energy Conf.; Technologyfor the Global Economic andEnvironmental Survival and Prosperity,Miami Beach, Ha., Nov. 8-10,1996).

Krakowski, R.A., "Global NuclearEnergy/Materials Modeling in Supportof Los Alamos Nuclear Vision Project"(Global Foundation Energy Conf.Technology for the Global Economicand Environmental Survival andProsperity, Miami Beach, Fla., Nov. 8-10,1996).

Krakowski, R.A., "Long-TermTradeoffs between Nuclear-Fossil-FuelBurning" (Global Foundation EnergyConf.; Technology for the GlobalEconomic, Environmental and Survivaland Prosperity, Miami Beach, Ha.,Nov. 8-10,1996).

Results for projectedplutonium inven-tories in spentreactor fuel arisingfrom use of theenergy-projectionand nuclear-fuel-cycle modeldiscussed in the text.

2070

Competency Development Projects—Mathematics and Computational Sciences 187

New Numerical Models forGlobal Ocean Modeling

Len Margolin

We have developed new numericalmethods that improve the accuracyand efficiency of models of geophysi-cal flows, especially models of theglobal circulations of the ocean overclimate time scales. We adaptedanalytical techniques from nonlineardynamics and nonequilibriumstatistical mechanics to develop thesemethods. We developed new algo-rithms based on these methods in aformat compatible with the currentgeneration of ocean models, and weimplemented these algorithms on avariety of platforms, includingworkstations and the massivelyparallel Connection Machine, CM-5.

Specifically, we constructed anapproximate inertial manifoldmethodology for finite-difference andfinite-volume approximations, andgeneralized the underlying theory toinclude both dissipative and quasi-geostrophic flows; we developed a

method of averaging for multiple-time-scale problems; and we implementeda semi-Lagrangian formulation of thedispersive shallow-water equations.We constructed numerical models forBurgers' equations in one and twodimensions and for a 1.5-layer modelof shallow and dispersive shallowwater (to simulate ocean basincirculations).

After formulating and implement-ing our new algorithms, we testedthem on problems representative oflarge-scale ocean dynamics. Weapplied singular spectrum analysis(SSA) to compare the time spectra ofthe numerical solutions of the two1.5-layer models. Similarly, we usedthe principal orthogonal decomposi-tion (POD) to compare the spatialaccuracy of these different approxi-mations. We demonstrated that thenew models would reproduce theaccuracy (in space and time) of morefinely resolved simulations, but at a

reduced cost of computer time andmemory. We believe this is the firstapplication of SSA and POD, whichwere designed for experimental dataanalysis, to compare the accuracy ofdifferent numerical realizations ofstochastic flows.

We have presented our results atprofessional meetings in the fields ofapplied mathematics, computationalphysics, and meteorology and havepublished these results in appropriatepeer-reviewed journals.

Publications

Nadiga, B.T., L.G. Margolin, and P.K.Smolarkiewicz, "Different Approxi-mations of Shallow Fluid Flow overan Obstacle," Phys. Fluids 8, 2066(1996).

Nadiga, B.T., M.W. Hecht, et al., "OnSimulating Flows with Multiple TimeScales" (submitted to Theor. andComput. Fluid Dyn.).

Poje, A.C., D.A. Jones, and L.G.Margolin, "Enslaved Finite DifferenceApproximations for Quasi-Geostrophic Flow," Physica D 98, 559(1996).

Lie Group Applications to theSolution of Differential Equations

Charles W. Cranfill

This project applies Lie Grouptechniques to the solution of partialdifferential equations (PDEs) describ-ing physical systems important to LosAlamos National Laboratory'sscientific mission. There are two mainobjectives: (1) to construct analytic orquasi-analytic solutions for use asbenchmark test problems and (2) todevelop improved numerical solutionalgorithms that possess the samesymmetries (e.g., rotational, transla-tional, and scaling invariance) as thePDEs.

This year we developed a generalprocedure for finding analyticsolutions to the hydrodynamicequations for fluids having morerealistic equations of state than that ofan ideal gas. The procedure was usedto construct analytic solutions to theone-dimensional Noh test problem,which describes an imploding fluidwhose stagnation against a symmetrysurface produces an outward-movingshock, for both the stiff-gas and Mie-Gruneisen equations of state.

We also constructed an analyticsolution to the Sedov test problem,

which describes the spherical blastwave produced by a point explosion,for the case in which the ambient gashas an initial density gradient in agiven direction. This provides a two-dimensional generalization of theusual one-dimensional solution.

Publications

Axford, R.A., "Group Theory ofInvariant Flux and Slope Limiters"(Ninth Nuclear Explosives CodeDevelopers Conf., San Diego, Calif.,Oct. 22-25, 1996).

Axford, R.A., "Lie Group SymmetryProperties of the Besnard-Harlow-Rauenzahn-Zemach SpectralTurbulence Transport Model"(JOWOG-32M Mtg. on MixResearch, Los Alamos, N.Mex., July22-26, 1996).


Lithospheric Processes

W. Scott Baldridge

Our objective was to improve ourunderstanding of the origin and evo-lution of the lithosphere by studyingselected processes such as deformationand magmatic intrusion during crustalextension, formation and extraction ofmantle melts, fluid transport of heatand mass, and surface processes thatrespond to deep-seated events. Addi-tional objectives were to promote anddevelop innovative techniques andsupport relevant educational endeavors.

Our seismic studies suggest threecentral points: (1) that underplating ofcrust by mantle melts is an importantcrustal-growth mechanism, (2) thatlow-angle faults can be seismogenic,and (3) that shear deformation createsmantle anisotropy near plate bound-aries. Results of geochemical workdetermined that magmas from oceanicintraplate islands derive from auniform depth in the upper mantle,whereas melts erupted at mid-oceanridges are mixed from a range of

depths. We determined the extent andstyle of fluid infiltration and trace-element distribution in naturalmagmatic systems, and we investi-gated neon-21 as a tool for datingsurficial materials.

Publications

Ferguson, J.F., W.S. Baldridge, L.Braile, et al., "Structure of theEspanola Basin, Rio Grande Rift,New Mexico, from SAGE Seismicand Gravity Data," New Mex. Geol.Soc. Guidebook 46, 105-110 (1995).

Jiracek, G.R., C.L. Kinn, C.L. Scott,et al., "Tracing Crustal Isothermsunder the Western Margin of theJemez Mountains Using SAGE andIndustry Magnetotelluric Data," NewMex. Geol. Soc. Guidebook 47', 129-133 (1996).

Olsen, K.H., "Continental Rifts:Evolution, Structure, and Tectonics,"in Developments in Geotectonics(Elsevier, Amsterdam, 1995), vol. 25,pp. 453^60.

Sims, K.W., W, DePaolo, DJ.Murrell, et al., "Mechanisms ofMagma Generation beneath Hawaiiand Mid-Ocean Ridges: U-Th andSm-Nd Isotopic Evidence," Science267,508-512(1995).

Slack, P.D., P.M. Davis, W.S.Baldridge, et al., "The Upper-MantleStructure of the Central Rio-GrandeRift Region from Teleseismic P-Waveand S-Wave Travel-Time Delays andAttenuation," /. Geophys. Res., SolidEarth 101,16003-16023 (1996).

Wendlandt, E., D.J. DePaolo, andW.S. Baldridge, "Thermal History ofColorado Plateau Lower Crust fromSm-Nd Mineral Geochronology ofXenoliths," Geol. Soc. Am. Bull. 108,757-767 (1996).

White, T.D., G. Suwa, and B. Asfaw,"Australopithecus Ramidus, a NewSpecies of Early Hominid fromAramis, Ethiopia," Nature 375, 88(1995).

WoldeGabriel, G., et al., in "ScientificCorrespondence," reply to "Age ofEarly Hominids," Nature 376, 559(1995).

Geometrically Compatible 3-D MonteCarlo and Discrete-Ordinates Methods

Jim Morel

The first objective of this projectwas to develop a discrete-ordinates(Sn) radiation transport code forcalculating three-dimensional (3-D),unstructured, tetrahedral meshes. Thesecond objective was to developvariance reduction techniques for thegeneral-geometry Monte CarloNeutron and Photon (MCNP)transport code that would utilizeadjoint solutions from the unstruc-tured-mesh Sn code. Our Sn code wasthe first 3-D unstructured-mesh Sn

code ever developed. As such, it

provides us with a unique capabilityfor efficiently and accurately perform-ing calculations in complex 3-Dgeometries. In addition, this Sn codecan generate adjoint solutions whichcan be used by the MCNP code todramatically reduce the statisticalvariance obtained in difficultcalculations.

In the past year, we investigatednew iterative acceleration techniquesfor our Sn code; investigated auto-matic mesh refinement techniques forour Sn code; tested the accuracy and

cost of the code by modeling neutron-based oil-well logging tools; andgenerated adjoint solutions used in thetesting of a new Monte Carlo variancereduction technique called the localimportance function transform. Thelatter technique was developed by ourcollaborators at the University ofMichigan.


Adaptive Monte Carlo Methods forRadiation Transport

Thomas E. Booth

For discrete-transport problems,exponential convergence can beobtained either by learning the zerovariance biasing (adaptive MonteCarlo) or by repeatedly solving for thedifference between the true solutionand the current estimate of the solution(reduced-source Monte Carlo). Thisproject seeks to generalize these knownexponential-convergence methods fromdiscrete-transport problems to continu-ous-transport problems. The ultimategoal is to apply these methods toproblems that currently cannot besolved.

The project sought to produce thefirst exponential-convergence resultsfor continuous Monte Carlo problems,either by adaptive or reduced-sourceMonte Carlo. Additionally, we soughtto understand and protect against falseconvergence. We successfully showedadaptive Monte Carlo to produceexponential convergence (withcomputer time) on a bidirectional,continuous-transport problem witharbitrary scattering, as shown in thefirst figure. We extended the results toK-directional problems and tested forK=10.

The solution method used thedifferential transport equation toconstrain the possible solutions to a2K-parameter family. Statisticianshave proved exponential convergencefor such families on discrete prob-lems. The false convergence problemwas ameliorated by enforcing localconstraints on the biasing. That is,although the global solution is not

Publications

Booth, T.E., "Adaptive Monte CarloAttempts on a Continuous TransportProblem" (The Adaptive Monte CarloWorkshop, August 14-16, 1996, LosAlamos, N.Mex.).

Booth, T.E., "Exponential Conver-gence on a Continuous Monte CarloTransport Problem" (submitted toNucl. Sci. Engin.).

Kong, R., and G. McKinney, "ErrorReduction Using Adaptive MonteCarlo: The Reduced Source Method"(The Adaptive Monte CarloWorkshop, August 14-16, 1996, LosAlamos, N.Mex.).

Lichtenstein, H., "Investigation ofFalse Learning in Adaptive MonteCarlo Transport" (The AdaptiveMonte Carlo Workshop, August 14—16,1996, Los Alamos, N.Mex.).

Exponential Convergence by Taylor Expansion1mfp (expansion order 50)

known, the local characteristics of thesolution are known, and the globalsolution must be locally consistent.

The reduced-source methodproduced exponential convergence fora unidirectional problem with pureabsorption, as shown in the secondfigure. Expressing the reduced sourceas an expansion of continuous-basisfunctions seems to offer the best hopefor extending the exponential conver-gence to multidimensional problemswith scattering.

erderl .fsigt=1 sigs-5 f=.5 b=.5 thick=1 delta=.12 surfaces1000 particles per iteration

4 5 6iteration number

10

Plot of the relative error of the penetration probability through aslab with bidirectional scattering as a function of iteration number(1000 particles per iteration).


Plot of the relative errorversus iteration number forpenetration through a5-mean-free-path, purelyabsorbing slab, using thereduced-source method.Different values of theparticles per iteration (W)and number of slab zones(K) are shown.

1.00E+QQ

1.00E-Q1

l.OQE-02

1.00E-03

1.00E-04

1.DOE-05

1.00E-06

I.OOE-07

I.OQE-08

1.00E-09

LOOE-tO

i

:

;

^ 1

i

k^vS

K=50CW-1O

zones,GO0mer.

K=| 000 zones ||yNiQQ,OQP/iter.[

1 2 3 4 5 6 7 B 9 10 11 12 13 14 15 16

Namber of Iterations

High-Performance Computing ofElectron Microstructures

Alan Bishop

The purpose of this project, acollaboration with scientists at theUniversity of California at SantaBarbara (UCSB), is to model novelquantum properties of opticallydriven, electronic nanostructures(quantum wells). These structures arefabricated and measured at UCSBusing dedicated molecular-beamepitaxy and free-electron laserfacilities. We have developed a newtime-dependent density-functionalmodel that is being implemented inlarge-scale parallel computations andthat can systematically handle all therelevant physical interactions innonequilibrium properties. Thismodel is helping us understand thenanostructures' response to opticalexcitation.

We extended our model with adensity matrix formalism thatincorporates dephasing and energyrelaxation processes. We also general-ized the formalism and numericalimplementation to include multiplequantum-level processes. We thenused this robust model to simulate a

bifurcation sequence in a quantumwell. Our simulation agrees withpreliminary experimental measure-ments and points the way to designingoptical devices with technologicallyimportant frequency-mixing andsubharmonic responses. Finally, wedeveloped a theory of nonequilibriumtransport in a double quantum-dotsystem.

Our project draws on theLaboratory's core competency intheory, modeling, and high-perfor-mance computing. It is relevant toprograms in nanotechnology, semi-conductor modeling, information andsensor technology, and multiscalenonlinear and nonequilibriumprocesses.

Publications

Bewley, W.W., C.L. Felix, J.J.Plombon, et al., "Far-Infrared Second-Harmonic Generation in GaAs/AlGaAs Heterostructures:Perturbative and Nonperturbative

Response" (to be published in Phys.Rev. B).

Birnir, B., V. Gudmundsson, and K.Johnson, "Floquet States and ElectronInteractions for Laser-DrivenQuantum Wells" (submitted to Phys.Lett. A).

Galdrikian, B., and B. Birnir, "PeriodDoubling and Strange Attractors inQuantum Wells," Phys. Rev. Lett. 76,3308 (1996).

Kenkre, V.M., S. Raghavan, et al.,"Memory Function Approach toInteracting Quasiparticle BosonSystems," Phys. Rev. B 53, 5407(1996).

Wang, L., W.Z. Wang, and A.R.Bishop, "Theory of QuantizedDynamic Capacitance ChargingSpectroscopy in Nanostructures,"Phys. Rev. Lett. 74, 4710 (1995).

Zang, J., A.R. Bishop, et al.,"Nonequilibrium Transport andPopulation Inversion in DoubleQuantum Dot Systems" (to bepublished in Int. J. Mod. Phys.).


Modeling Complex Phenomena:Multiple Length and Time Scales inExtended Dynamical Systems

Peter Lomdahl

This research combines competen-cies in high-performance computing,theory of complex systems, andmaterials science in a new way thathas great potential for applications tomultiple length- and time-scalephenomena in condensed matter andmaterials science. We are developing(1) analytical techniques in non-equilibrium and nonlinear science and(2) numerical algorithm and simula-tion techniques using massivelyparallel computation and advancedvisualization. We then apply thedeveloped techniques to the study ofmesoscopic textures and theirassociated dynamics for a number of

topical problems in materials scienceand condensed matter. The meso-scopic scale provides a fundamentalbridge between microscopic andmacroscopic modeling approachesand, ultimately, is the link between(1) synthesis and processing and(2) functionality.

Using nonlinear techniques andlarge-scale simulations, we havesystematically studied mesoscalepattern formation and dynamics innonlinear, nonequilibrium systemsexhibiting topological excitations(i.e., dislocations, vortices, vortexlines, and domain walls). Specifically,we have focused our research effortson the following:

Continuing Benchmarking ofOcean-Circulation Models

David Poling

Our objectives in this project wereto (1) become proficient at runningocean- and climate-related simulationcodes and analyzing their outputs,(2) use this proficiency to follow themigration of simulation to massivelyparallel computers, and (3) communi-cate the lessons we learn to ourcolleagues and coworkers.

This year we completed a series ofensemble runs using two computercodes: one that simulates the atmo-sphere, the other the ocean (ECHO).These runs of the ECHO-coupled,ocean-atmosphere model shouldprovide insight into using computermodels to predict climate changes.The resulting amount of data will beimmense and take some time toanalyze.

The 100-year run will provide abaseline for comparisons of ocean and

atmosphere simulations for years tocome. Analysis of this run willprovide insight into the strengths andweaknesses of such simulations andbetter understanding of the subgridprocesses that will always be neces-sary in such calculations. Theensemble runs should provide one ofthe first attempts to study the variabil-ity of this kind of simulation and thusa means of evaluating the predictivecapability of any such simulation.

Publications

"Preliminary Results from EnsembleRuns of the ECHO-Coupled, Ocean-Atmosphere Model" (CooperativeAntarctic Research Center, Universityof Tasmania, Hobart, Australia,July 29, 1996).

• dislocation generation from crackfronts in ductile materials;

• the smoothing of rough surfaces insolid-on-solid models;

• ordering and melting of movingflux lattices in three-dimensionalJosephson junction arrays withdisorder and external magneticfield and current;

• filamentary and plastic vortex flowin disordered thin-film supercon-ductors;

• magnetic vortices in Heisenbergspin layers; and

• hierarchical twinning and tweedtexture in elastic models.

Publications

Cirillo, M., A.R. Bishop, et al., "High-Frequency Pumping of JosephsonSoliton Oscillators," Phys. Rev. B 52,506 (1995).

Dominguez, D., N.G. Jensen, andA.R. Bishop, "Resistive Hysteresisand Nonlinear J-V Characteristics,"Phys. Rev. Lett. 75,4670 (1995).

Dominguez, D., N.G. Jensen, et al.,"Transformer Configuration in 3-Dimensional Josephson Lattices,"Phys. Rev. Lett. 75, 717 (1995).

Jensen, N.G., A.R. Bishop, and D.Dominguez, "Metastable Filamen-tary Vortex Flow in Thin FilmSuperconductors," Phys. Rev. Lett. 76,2985 (1996).

Sanchez, A., A.R. Bishop, and N.G.Jensen, "Smoothing of RoughSurfaces," Phys. Rev. B 52, 5433(1995).

Zhou, S.J., B.M. Beazley, et al.,"Large-Scale Molecular DynamicsSimulations of Three-DimensionalFracture" (submitted to Phys. Rev-Lett).

Zhou, S.J., D.M. Beazley, P.S.Lomdahl, et al., "DislocationEmission from a Three-DimensionalCrack" (submitted to Proc. 9th Int.Conf. Fracture).

Zhou, S.J., P.S. Lomdahl, et al.,"Dynamic Crack Processes viaMolecular Dynamics," Phys. Rev.Lett. 76,2318 (1996).


Simulation Methods forAdvanced Scientific Computing

James Gubernatis

The rapid increase in raw computa-tional power has created excitingopportunities for scientific computa-tion. The complexity and realism ofthe problems that can be simulatedpromise to greatly advance manyscientific and technological fields.Accordingly, scientific computing isenjoying considerable worldwidepopularity. Yet many challengingscientific problems remain unsolvedbecause of inadequate algorithms,especially algorithms that are suitablefor massively parallel architectures.

In this project, our objective is tocreate effective new algorithms forsolving these problems, giving theLaboratory the initiative in keytechnical areas by combining thetalents and efforts of our physicalscientists and applied mathematicians.We concentrate on developingadvanced N-body simulation tech-niques, including classical andquantum Monte Carlo techniques,molecular dynamics techniques, and

Langevin methods for stochasticdifferential equations. We also try toimprove current algorithms used tosimulate problems with disparate timeand/or space scales.

This year we developed and applieda different algorithmic approach to theproblem of quantum-mechanicalsimulations of hydrogen diffusing onand into the surface of a metal.Instead of performing a real-timesimulation, we performed the simula-tion in imaginary time and then usedBayesian statistical inference methodsto analytically continue the simulationdata into real time. This methodresulted in improved accuracy ofpredicted spectral properties of thediffusing hydrogen. Our mostdramatic finding was a significantshift in vibrational frequencies fromthose predicted by normal-modetheory, underscoring both the quan-tum and the anharmonic nature of thehydrogen diffusion.

In addition, we developed astochastic model of the bacterialflagellar molecular motor and appliedour numerical methods to the directsimulation of stochastic differentialequations.

Publications

Brandow, B., "The ExoticSuperconductors: CharacteristicFeatures and a Possible Explanation"(submitted to Adv. Phys.).

Castillo, J., et al., "A GeneralizedLength Strategy for DirectOptimization in Planar Grid-Generation" (submitted to /. Comput.Phys.).

Castillo, J., et al., "A Practical Guideto Direct Optimization for PlanarGrid-Generation" (submitted to SIAMRev).

Davis, K., "PERs from Projections forBinding-Time Analysis," J. LispSymbolic Comput. 8, 249 (1995).

Zhang, S., et al., "A Constrained PathMonte Carlo Method for FermionGround States" (submitted to Phys.Rev. B).

Adaptive Mesh Refinement AlgorithmDevelopment and Dissemination

Jeffrey S. Saltzman

Our objective is to develop anddisseminate adaptive mesh refinement(AMR) algorithms for structuredmeshes. Areas of development includealgorithms for parallel architectures,techniques for the solution of partialdifferential equations on adaptivemeshes, mesh generation, andalgorithms for nontraditional orgeneric applications of AMR. AMRalgorithms are perceived as difficult tomeld to current algorithms. Therefore,we are developing tools that diminishthis perception and will allow morecomputational scientists to use AMRwithin their own work.

During this fiscal year, we haveconcentrated on developing algo-rithms that are conservative foradaptive overset grids. We have alsosupported some development work foran AMR library written in C++ calledAMR++. This library is a collectionof routines that facilitate the manipu-lation and generation of adaptive gridsand data. Efforts for conservationinclude using both algebraic andCartesian techniques to solve ellipticequations on overset adaptive meshes.Algebraic and Cartesian methods canpossibly be extended to hyperbolic

and parabolic systems because theoperator is cast in divergence gradientform. We have begun designing C++sparse data structures that can be usednot only for our methods but for anywork that needs to be performed ondata of codimension one.

Publications

Brislawn, K., D. Brown, et al.,"Adaptively-Refined OverlappingGrids for the Numerical Solution ofHyperbolic Systems," Proc. ICASE/LaRC Workshop Adaptive GridMethods 3316, 95 (1995).


Neutron Transport Methods for3-D Cartesian Adaptive Meshes

Raymond E. Alcouffe

The mesh representation of complexthree-dimensional (3-D) geometries iscurrently accomplished using Cartesiangrids that are very regular or arbitrarymeshes that are accurate but do nothave any regular connectivity. Methodsthat use regular grids are computa-tionally efficient because the con-nectivity of the mesh is regular andwell characterized. Arbitrary grids canaccurately represent complex geom-etries, but the complex structure of theresulting matrices makes them difficultto solve efficiently. An efficientcompromise is the adaptive Cartesian

mesh, which allows internal meshrefinement in areas where gradients inphysical quantities (such as pressure,density, temperature, and neutron flux)are large. We are developing efficientnumerical methods for the solution ofthe discrete-ordinates transportequation on such meshes.

Building upon the two-dimensional,adaptive-mesh solver that we devel-oped last year, we have investigated3-D solvers this year. The thrust of thisdevelopment is to use parallel architec-ture in our 3-D calculations, and so we

have changed the focus of the effort inthis direction. To formulate a 3-D,adaptive-mesh-refinement solver forthe transport equation, we have gone toa more object-oriented paradigm,which is being done through FOR-TRAN^. Using the features of thislanguage, we have explored the conceptof solving the equations for theinversion of the transport operator cellby cell and in a block-of-cells method.Our results show that the cell-by-cellmethod as implemented on the CrayT3D is about a factor of 3 slower thanour regular parallel sweeper. In goingto the block sweeper, we hope torecoup much of the inefficiency of thecell-by-cell method in the parallelenvironment. We do not yet haveresults for the block-parallel sweeper.

Applications of Nonlinear andStochastic Dynamics

Charles Doering

This project supported research inapplications of nonlinear and stochas-tic dynamics systems with the aim ofexploiting the last decade's progressin understanding the dynamics ofnonlinear, or noisy, systems related toproblems in theoretical physics,chemistry, and biology. The commondenominator is the fundamental rolesthat nonlinearity, noise, and disorderplay in the dynamics of both simpleand complex systems. We also studiedthe underlying theoretical problemsthat have much in common within theparadigms of nonlinear science. Themajor areas of research included(1) stochastic models of molecularmotors; (2) turbulent diffusion andconvective heat transport; (3) self-

organized, spatial structures innonequilibrium models; and (4) nonlin-ear wave and soliton applications inoptics and ocean modeling.

Last year's accomplishmentsincluded (1) development of new,nonlinear, evolution equations forweakly nonlinear internal waves in atwo-fluid system; (2) establishment ofa framework for comparison ofcentury-long simulations of the wind-driven double-gyre; (3) asymptoticsolution of a model problem explain-ing the deflection of laser beams inplasma flows; (4) development of ascheme for stable pulse transmissionsin optical fibers and investigation ofthe nonadiabatic dynamics of darksolitons; (5) demonstration of a

method for controlling front dynamicsin reaction-diffusion systems withnonuniform external fields; and(6) derivation of rigorous bounds onheat transport by turbulent convection.

Publications

Cai, D., A.R. Bishop, and N. Gronbech-Jensen, "Discrete Lattice Effects onBreathers in a Spatially LinearPotential," Phys. Rev. £53,1202-1205(1996).

Cai, D., A.R. Bishop, and N. Gronbech-Jensen, "Perturbation Theories of aDiscreet Integrable NonlinearSchrodinger Equation," Phys. Rev. E 53,4131^136(1996).

Cai, D., A.R. Bishop, and N. Gronbech-Jensen, "Spatially Localized TemporallyQuasi-Periodic, Discrete NonlinearExcitations," Phys. Rev. E52, R5784-R5787 (1995).


Choi, W., and R. Camassa, "LongInternal Waves of Finite-Amplitude,"Phys. Rev. Lett. 77,1759-1762 (1996).

Constantin, P., and C. Doering, "Heat-Transfer in Convective Turbulence,"Nonlinearity 9,1049-1060 (1996).

Doering, C , et al., "Random Walks,Resonance, and Ratchets," in Non-equilibrium Statistical Mechanics inOne Dimension, V. Privman, Ed.(Cambridge University Press, NewYork, 1996).

Konotop, V.V., D. Cai, et al.,"Interaction of a Soliton with PointImpurities in an Inhomogeneous,Discrete, Nonlinear, SchrodingerSystem," Phys. Rev. E 53, 6476-6485(1996).

Reimann, P., and T.C. Elston,"Karmer's Rate for Thermal PlusDichotomous Noise Applied toRatchets," Phys. Rev. Lett. 11, 5328-5331 (1996).

Salkola, M.I., A.R. Bishop, et al.,"Coupled Spin-Boson Systems Farfrom Equilibrium," Phys. Rev. B 54(18), 12645 (1996).

Wang, W.Z., J.T. Gammel, et al.,"Quantum Breathers in a NonlinearLattice," Phys. Rev. Lett. 76, 3598(1996).

Theoretical Foundation forAdaptive Monte Carlo

Richard Picard

The Monte Carlo method is a keytool for analysis of many complexproblems, especially in the nuclearfields. This project is one of severalthat are aimed at significantlyextending the effectiveness of themethod.

The standard central limit theorem,applicable to Monte Carlo workwhere N simulation runs are statisti-cally independent, provides for thestandard deviation to converge to zeroat the rate of the square root of N.Under restrictive conditions, thereplacement of independent samplingwith adaptive learning algorithms hasrecently been shown to provideexponential convergence. The goal ofthis project is to obtain exponentialconvergence under less restrictiveconditions.

In the first year of the effort, wesuccessfully generalized the existingtheory, which required the simulationto visit all process states—a burden-some requirement for large problems.

We overcame this requirementthrough the use of interpolatingsmoothing functions. When theexpected score conforms to a modellinear in its parameters (such as apolynomial in several variables, forexample), use of results from a fullrank experimental design is sufficientto obtain exponential convergence.We discussed this work as part of anextensive workshop involvingparticipants from across the interna-tional Monte Carlo community.

We also obtained simulationevidence of exponential convergencefor Halton's sequential Monte Carlomethod when applied to large, sparsematrices. Use of path information andsplitting/roulette techniques acceler-ated this convergence.

In addition, our efforts in statisticalmechanics focused on improvingconvergence properties of multi-canonical recursion algorithms, whichovercome the long correlation timesof the standard Metropolis algorithm.

Publications

Baggerly, K., "Part III: InterfacingTheory and Practice" (AdaptiveMonte Carlo Methods, Los Alamos,N.Mex., August 14-16, 1996).

Cox, D., "Part II: Continuous StateSpaces" (Adaptive Monte CarloMethods, Los Alamos, N.Mex.,August 14-16, 1996).

Kollman, C , K. Baggerly, D. Cox,and R. Picard, "Adaptive ImportanceSampling on Discrete MarkovChains" (submitted to Ann. Appl.Probability).

Picard, R., "Part I: Discrete StateProblems and InterpolatedSmoothing" (Adaptive Monte CarloMethods, Los Alamos, N.Mex.,August 14-16, 1996).


Advanced Three-Dimensional EulerianHydrodynamic Algorithm Development

William Rider

The purpose of this project is toinvestigate, implement, and evaluatealgorithms that have high potential forimproving the fidelity and efficiencyof large-scale, three-dimensional,Eulerian hydrodynamic simulations.This project combines core strengthsof several Laboratory divisions. Theproject is of high potential institu-tional benefit given the renewedemphasis on numerical simulations inscience-based stockpile stewardshipand the Accelerated Strategic Com-puting Initiative.

We used data generated in otherprojects, such as Telluride (a moldingand casting simulation tool), as activeplatforms for testing our algorithms.Examples of algorithms we imple-mented are interface-tracking meth-ods, multidimensional advectionmethods, interfacial physics, andparallel communication libraries.

Chief among the improvements wemade is the application of fullymultidimensional methods foradvection in the form of both inter-face-tracking and shock-capturingtechniques. The first figure provides agraphical depiction of both standardand modified multidimensionalinterface-tracking methods. We foundthat these methods reduce themagnitude of grid-dependent effectsand improve solution accuracy. Thesegrid dependencies are most acute forconverging coordinate frames.

Our implementation of interfacetracking uses systematic techniquesfrom computational geometry. Thesecond and third figures show severalfundamental aspects of this algorith-mic approach.

We achieved another importantadvance in interfacial closure ofmultifluid equations in both com-pressible and incompressible regimesby including relevant physicalphenomena in a physical manner (thefourth figure shows two potentialtypes of interface topologies).

y/////////W3/

\

\(a) A v-direction pass of the operator

split method.

volumes fluxed twice

(c) The naive unsplit method.

Publications

Rider, W.J., "Filtering NonsolenoidalModes in Numerical Solutions ofIncompressible Flows" (submitted toInt. J. Numer. Methods Fluids).

Rider, W.J., "Robust Formulation ofApproximate Projection Methods forIncompressible Flows" (submitted to/. Comput. Phys.).

Rider, W.J., and D.B. Kothe,"Reconstructing Volume Tracking"(submitted to J. Comput. Phys.).

(b) An x-direction pass of theoperator split method.

(d) The unsplit method.

A comparison of three multidimensional advection schemes we investigated.For the operator split integration (a and b), the x-pass follows the y-pass. Wedo not recommend the naive unsplit method (c) because of its inability toadvect volumes in a conservative, monotonic manner. We obtained the bestresults with the corner-coupled geometrically unsplit method (d).


The method we implemented forcomputing the flux volume involvesfundamental geometric steps(represented here as polygons). Weformed these polygons by sweepingout areas with a positive velocity field. (a) Edge volume flux polygon. (b) Comer volume flux polygon.

1II• -

:

*

X(a) The initial normal and interface (b) A new guess at the normal,

in the local stencil.

[

\

_

(c) The method applied to a curvedinterface.

The interface reconstruction step is the function of several fundamental geometric steps.

(a) A simple unmixed cell. (b) A complex well-mixed cell.

The algorithm for the interfacial physics treats unmixed or well-mixed cells self-consistently. This includes processessuch as surface tension or solidification for low-speed casting applications or pressure and volume relaxation for high-speed hydrodynamics.


Phase Transitions, NonequilibriumDynamics, and Critical Behavior ofStrongly Interacting Systems

Emil Mottola

In this project, we performed large-scale simulations of strongly interactingsystems and investigated a variety ofapproaches to the nonequilibriumdynamics of phase transitions andcritical behavior. Focus areas included(1) the finite-temperature, quantumchromodynamics (QCD) phase-transition and nonequilibrium dynam-ics of a new phase of matter (thequark-gluon plasma) above the criticaltemperature, (2) nonequilibriumdynamics of quantum fields usingmean-field theory and, (3) stochasticclassical field theoretic models with

applications to spinodal decompositionand structural phase transitions in avariety of systems such as spin chainsand shape-memory alloys.

In FY 1996 we extended non-equilibrium field theory beyondmean-field techniques and studiedrare B particle decays. We alsoperformed a kink calculation for asixth-order-polynomial strain-fieldtheory that describes shape-memoryalloys. Finally, we computed correla-tion functions, structure factors, andthermodynamic quantities like thespecific heat for the alloys.

Publications

Cooper, F , S. Habib, et al.,"Nonequilibrium Dynamics ofSymmetry Breaking in Lambda Phi4

Field Theory" (submitted to Phys.Rev D).

Cooper, F., Y. Kluger, E. Mottola,"Anomalous Transverse Distributionof Pions as a Signal for the Pro-duction of DCCs," Phys. Rev C 54,3298 (1996).

Cooper, R, Y. Kluger, et al.,"Nonequilibrium Quantum Dynamicsof Disoriented Chiral Condensates,"Phys. Rev. D 51, 2377 (1995).

Gupta, R., and T. Bhattacharya,"Light Quark Masses from LatticeQCD" (submitted to Phys Rev. D).

Gupta, R., and P. Tamayo, "CriticalExponents of the 3-D Ising Model,"Int. J. Mod. Phys. C. 7, 305 (1996).

Habib, S., E. Mottola, and P.G.Tinyakov, "Winding Transitions atFinite Energy and Temperature: An0(3) Model" (to be published in Phys.Rev.).

Numerical Simulations ofDisordered Superconductors

James Gubernatis

The objectives of this projectincluded studying (1) the interplay ofdisorder and interactions in quantumsystems with applications to mobilityproblems, the onset of superfluidity,disordered superconductors, andquantum phase transitions, (2) theproblem of flux-line motion insuperconducting materials with highcritical currents, and (3) the develop-ment of software and computationalalgorithms for these classes ofproblems. Specifically, we carried outMonte Carlo studies of the criticalbehavior of superfluid 4He in aerogel.We found that the superfluid densityexponent increases in the presence offractal disorder with a value roughlyconsistent with experimental results.

We also addressed the localizationof flux lines caused by splayedcolumnar pins. Using a Sine-Gordontype of renormalization-group study,we obtained an analytic form for thecritical temperature. We also deter-mined the critical temperature fromcurrent-voltage characteristicsobtained from a molecular dynamicssimulation. The combined studiesenabled us to construct the phasediagram as a function of interactionstrength, temperature, and disorder.

Finally, we employed the recentlydeveloped mapping between bosonworld-lines and the flux motion inquantum Monte Carlo simulations toanalyze localization in the presence ofdisorder. From measurements of the

transverse flux-line wandering, wedetermined the critical ratio ofcolumnar-to-point disorder strengthneeded to localize the bosons.

Publications

Devereaux, T.P., R.T. Scalettar, G.T.Zimanyi, et al., "Phase Diagram forSplay Glass Superconductivity," Phys.Rev. Lett 75, 4768 (1995).

Moon, K., and S. Girvin, "CriticalBehaviour of Superfluid 4He inAerogel," Phys. Rev. Lett. 75, 1328(1995).

Moon, K., R.T. Scalettar, andG.T. Zimanyi, "Dynamical Phases ofDriven Vortex Systems," Phys. Rev.Lett. 11,2778 (1996).

Sandvik, A.W., and M. Vekic,"Quantum Phase Transitions in 2DAntiferromagnets," J. Low Temp.Phys. 99, 367 (1995).


Transactional Memories: A NewAbstraction for Parallel Programming

Joseph Fasel

Current distributed-memorymultiprocessor computers make thedevelopment of parallel programsdifficult. From a programmer'sperspective, it would be most desir-able if the underlying hardware andsoftware could provide the program-ming abstraction commonly referredto as sequential consistency—a singleaddress space and multiple threads.But enforcement of sequentialconsistency limits opportunities tooptimize architectural and operatingsystem performance and leads to poorperformance. A new abstraction called"transactional memories" mayprovide a solution to this problem.The programming model is sharedmemory with multiple threads.However, we obtain data consistencythrough the use of transactions ratherthan mutual exclusion based on

locking. This transaction approachpermits the underlying system toexploit the potential parallelism intransaction processing. We are explor-ing the feasibility of designing parallelprograms using the transactionparadigm for data consistency and abarrier type of thread synchronization.

We experimented with alternativeimplementations of transactionalmemories, specifically a pessimisticapproach, appropriate for lowcommunication latency, and anoptimistic approach for higherlatency. The optimistic approachminimizes communication butincreases the probability of a conflictbeing detected at transaction commit-ment. When such a conflict occurs,low-priority transactions may need toabort in favor of high-prioritytransactions. We improved on one

conflict-resolution scheme byestablishing an order on conflictingtransactions when a conflict isdetected (called the "required commitorder"). So long as this order isacyclic, no transaction need beaborted.

Unfortunately, our parallel virtualmachine (PVM) implementation oftransactional memory was not able todemonstrate a performance improve-ment over traditional approaches toparallel programming. As thissituation probably results from PVM'shigh overhead and latency, wedirected our efforts toward imple-menting a low-latency implementa-tion of the message-passing interface(MPI is another standard parallel-programming library) on the MeikoCS/2 massively parallel super-computer and a cluster of work-stations on a high-speed switch. Wecompleted this implementation in thesummer of 1996. At the end of FY1996, we had not yet ported thetransactional memory implementationto this new framework.

Development of an Integrated System forEstimating Human Error Probabilities andModeling Their Effects

Heidi Hahn

This project is aimed at developingan expert system that will allow in-tegrated error estimation using inputfrom many different sources withdiffering quantitative bases. Theresulting knowledge-based systemwill allow analysts to find appropriatehuman error probabilities (HEPs) foruse in probabilistic risk assessmentand human reliability analysis (HRA).Our system will (1) allow analysts toinput relevant information; (2) com-pare the analyst's situation withdifferent approaches and identify oneor more "matches"; (3) provide validestimates based on selected matches;and (4) provide an estimate drawn

from a weighted average across thematches, with weights being deter-mined by the "goodness of fit" foreach match.

So far, we have completed twotasks: we built a prototype systemwith limited data incorporated, andwe validated system design with HRApractitioners. The prototype systemnow contains all but one of the majorHRA methodologies used to generateHEPs. We will incorporate theremaining method, along with datafrom several minor sources, into thefinal system during the next projectyear.

We validated the initial system at aprofessional society meeting inSeptember 1996. We guided HRApractitioners through a hands-ondemonstration and had them completea survey on system utility. We will usethe data gathered at the meeting toguide further system development.Final validation will occur in the nextphase of the project.

Publications

Hahn, H.A., J.L. Auflick, and J.A.Morzinski, "Demonstration of aPrototype Knowledge-Based Systemfor Estimating Human ErrorProbabilities," Proc. Human FactorsErgonom. Soc. 40th Annual Meet. 2,869(1996).


Novel Monte Carlo Algorithms forStatistical Mechanics

James Gubernatis

The Monte Carlo method is a keytool for analysis of many complexproblems. This project is aimed atsignificantly extending the effective-ness of the method and specificallylooks at novel methods applicable tostatistical mechanics.

We made progress on three problemareas. In the first, we successfullyimplemented the Gibbs ensemblemethod for a mixture of hard disks ofvastly different radii. This implemen-tation required devising special rulesfor moving large disks into regions ofpredominantly small disks, produceda much more efficient algorithm thanthe standard implementation, andpermitted an extensive study of phaseseparation in mixtures.

In the second problem area, wedeveloped a novel algorithm tosimulate micelle formation in ternaryfluid mixtures involving surfactants.The base system being simulated is anIsing model, and the new algorithmmakes a special use of the Swendsen-Wang cluster algorithm to producestatistically independent configura-tions at each Monte Carlo step. Witheach new configuration, we used theinversely restricted sampling tech-nique to grow the micelles. Wecomputed micelle density and sizedistributions as a function of surfac-tant concentration.

For the third problem area, westudied in detail a collection of newalgorithms to simulate first-orderphase transitions, spin-glass prob-lems, protein-folding problems, etc.,that adaptively construct an impor-tance sampling function. We identi-fied three areas in which existingmethods can be improved: the mannerin which certain density functions areestimated, the manner in which thelearning process is executed, and themanner in which the Monte Carlosamples the importance function. Forthe first area, we developed codes topermit the use of kernel estimationmethods to improve the densityfunction estimation. For the second,we identified several other learningprocesses that might be more effectiveand have started to test them. Work onthe third area will occur in the comingyear.

Advanced Computational Science

Andrew White

For this project we used advancedmodeling and simulation techniques(both classical and learning-based) totry to predict the occurrence andcourse of various kinds of crisisevents. Because of their complex,time-critical nature, these applicationsclearly emphasize the need for high-performance computing and commu-nication technology.

Accurately predicting the course ofwildfires (for example, in YellowstoneNational Park and in Glenwood

Springs, Colorado) requires theintegration of sophisticated turbulentburn models and adaptive mesoscaleweather models. We have used a self-predicting transport description of therelevant combustion and transportphenomena to successfully character-ize the bulk evolution of a wildfire.We then implemented this descriptionin a computer code and validated itusing data provided by the U.S. ForestService.

Influenza is a prime example of areemergent viral health threat, and itis a prototype for threats from naturaland artificial biological agents. Weare working with the Center forDisease Control (CDC) to define and

implement a unique database that willprovide researchers with validatedinfluenza sequence data. We havedeveloped a model of influenzaepidemiology that includes theimplementation of antiviral drugtreatment and the possibility that thevirus will be drug resistant.

Unusual periods of excessive heatcan lead to increased mortality. Forexample, from July 11 to July 27,1996, Chicago, Illinois, recorded 465heat-related deaths. We are studyingimprovements to the "effectivetemperature" index (comprisingtemperature and humidity) that iscommonly used. To that end, we arestudying historical weather data(1973-1993) from the NationalOceanographic and AtmosphericAdministration (NOAA) and mortal-ity data from the CDC through the useof Expert Network modeling toolsthat combine the best features of rule-based systems and neural networks.


Development of an AutomatedCore Model for Nuclear Reactors

Russell Mosteller

This project is aimed at developingan automated package of codes thatcan model the steady-state behavior ofnuclear-reactor cores of variousdesigns. As an added benefit, the dataproduced by the steady-state analysiscan also be used as input to the TRACtransient-analysis code for subsequentsafety analysis of the reactor at anypoint in its operating lifetime.

The basic capability to performsteady-state reactor-core analysisalready exists in the combination ofthe HELIOS lattice-physics code andthe NESTLE core-simulation code.Our purpose is to complete theautomated package by obtainingcross-section libraries for HELIOS,

developing a linkage code to trans-form HELIOS output into NESTLEinput, developing additional steady-state thermal-hydraulics modules forNESTLE, and benchmarkingHELIOS and NESTLE both individu-ally and in combination.

During this reporting period, wehave completed the standalonebenchmarking of NESTLE andperformed extensive benchmarking ofHELIOS. We have also obtained anew version of HELIOS, along withseveral new cross-section libraries forit. These new libraries are based onENDF/B-VI Release 3, whereas theold libraries were based on ENDF/B-VI Release 2. Currently, we are

benchmarking HELIOS with the newlibraries, a task we previouslyperformed with the old libraries.Finally, we also began writing thelinkage code that will transformHELIOS output into NESTLE input.Completing that linkage code will bethe next step in our project.

Publications

Mosteller, R.D., "Benchmarking ofNESTLE against Measured PWRData at Beginning of Life," Trans.Am. Nucl. Soc. 73, 369 (1995).

Mosteller, R.D., "Comparison ofDoppler Coefficients from ENDF/B-V and ENDF/B-VI," Trans. Am. Nucl.Soc. 74, 331 (1996).

Mosteller, R.D., "Validation ofNESTLE against Static ReactorBenchmark Problems," Trans. Am.Nucl. Soc. 74, 310(1996).

Density Function Estimation forMonte Carlo Simulations

James Gubernatis

Applying modern statisticalmethods to experimental data candramatically enhance the informationextracted, effectively increasing theefficiency of data collection. Mostmodern statistical methods forestimating density functions beginwith histograms as a crude estimateand then move on to a wide variety ofmore sophisticated and powerfulmethods such as kernel estimators,orthogonal series, and maximumpenalized likelihood methods.

The goal of this project is to usemodern statistical methods, such asadvanced density function techniques,to analyze Monte Carlo data. Specifi-cally, we are adapting such methodsto determine the configurational

densities of states in order to evaluatethe free energies in phase equilibria.This is a long-standing problem in theapplication of the Monte Carlomethod.

Presently, density function estima-tion is a key step in the Swendsen-Ferrenberg histogram method forpostsimulation data analysis and inadaptively improving the importancesampling in recently proposedmethods such as multicanonical andsimulated tempering algorithms. Ineach case, a simple histogram methodis used to estimate the density

function. For the postsimulationanalysis, we showed that althoughadvanced kernel estimation methodscan improve the representation of thedensity function, there is littleadvantage to using an estimator otherthan a histogram because the estimateis subsequently used to computeaverage quantities. We are presentlyinvestigating the use of these ad-vanced methods to adaptivelyconstruct the importance samplingfunction used in simulations. Here weexpect these new methods to offer asignificant advantage.


Self-Organization and Pattern Formation

Robert Ecke

The formation of regular structures isimportant in science and technology,and recently there has been muchattention focused on self-organizingand self-assembling systems. Instead ofbuilding structures by hand, as inmicroelectronic lithography, one woulddesign or search for systems that putthemselves together. If successfullydeveloped, self-organizing and self-assembling systems could have a majorimpact on a wide range of technologi-cally useful applications.

One variety of such systems ispattern-forming systems that canproduce simple regular and irregularstructures. Two examples of patternformation are thermal convection andreaction-diffusion systems, in whichtwo-dimensional patterns of stripes,spirals, targets, hexagons, squares, and"self-replicating" spots have beenobserved and modeled. The elucidationof types of patterns, their dynamics,and the possible application of suchmechanisms to problems of technologi-cal interest is a large part of our work.Specific systems we have studied arespatio-temporal patterns in cellularautomata, defects in rotating thermalconvection (shown in accompanyingfigure), replicating spot dynam-ics in reaction-diffusionsystems, and spatio-temporal dynamics of

Opticalshadowgraphimage of spiraldefect chaos inthermal con-vection. Thisstate was totallyunexpected, andits discovery andsubsequentexploration havechanged dramaticallythe way researchers thinkabout the system of thermalconvection.

calcium waves (as models of biologicalself-organization).

Our successes include demonstratingthe nucleation mechanism for disloca-tions with rotation and measuring thelong-wavelength distortion angle. Wehave also extended the study ofmultivalued front speeds to thederivation of dynamical equations forfront transitions and correctly predictedspontaneous transitions betweencounterpropagating fronts. We havefurther suggested a way to controldomain patterns using a spatiallynonuniform, external advective field. Inthe simulation area, we have written athree-dimensional simulation code formessage-passing machines such as theT3D machine to elucidate the role ofvarious cell processes for Ca2+ dynam-ics. We also demonstrated numericallyand analytically that a self-organizationprocess is intrinsic to the dynamics ofmicrotubules.

Publications

Baras, R, et al., "MicroscopicSimulation of Chemical Bistability inHomogenous Systems," J. Chem. Phys.105, 8257 (1996).

Camassa, R., et al., "Layer-MeanQuantities, Local Conservation Laws"(submitted to Phys. Rev. Lett).

Camassa, R., et al., "Long InternalWaves of Finite Amplitude," Phys. Rev.Lett. 11,1759 (1996).

Camassa, R., et al., "Long TimeEvolution Equations for Shallow Waterwith a Varying Bottom" (to bepublished in Physica D).

Camassa, R., et al., "A MelnikovMethod for Homoclinic Orbits withMany Pulses" (to be published inArchive F, Archive for RationalMechanics and Analysis).

Camassa, R., et al., "Nonlinear InternalWaves in a Two-Layer Fluid," J. FluidMech. 313, 83 (1996).

Choi, W, "On the Fission of AlgebraicSolitons" (submitted to Proc. R. Soc.London).

Ecke, R., et al., "Spiral Defect Chaos inRayleigh-Benard Convection: DefectPopulation Statistic" (to be published inPhysica A).

Hagberg, A., et al., "ControllingDomain Patterns Far from Equili-brium," Phys. Rev. Lett. 76,427 (1996).

Hagberg, A., et al., "Order ParameterEquations for Front Transitions: Planarand Circular Fronts" (to be published inPhys. Rev. E).

Haim D., et al., "Breathing Spots in aReaction-Diffusion System," Phys. Rev.Lett. 11,190 (1996).

Hu, Y., et al., "Convection UnderRotation for Prandtl Numbers nearOne: Part I. Linear Stability"(submitted to Phys. Rev. E).

Liu, Y, et al., "Dynamics of SurfacePatterning in Salt Crystal Dissolution,"Phys. Rev. E 53,5572 (1996).

Oron, A., et al., "Evolution and Forma-tion of Dispersive-Dissipative Patterns"(to be published in Phys. Rev. E).

Reynolds, W.N., et al., "Self-Replicating Spots" (to be published inPhys. Rev E).


Sullivan, T., et al., "Turbulent SolutalConvection and Surface Patterning inSolid Dissolution," Phys. Rev. £54,486 (1996).

Zharnitsky, V., "Breakdown of Stabilityof Motion in Superquadratic Potentials"(submitted to Phys. Rev. E).

Application of Discrete Mathematics

Vance Faber

This project in combinatorialanalysis is aimed at studying andquantifying the properties of discreteobjects and their operations. Theknowledge gained is applicable to allareas of science and engineering. Ourgoal is to extend the combinatorialmethod as a viable and useful tool tohelp in solving Laboratory problems.Since this project was conceived, wehave used the methods of combinato-rics to solve problems in numericalanalysis, computer networks, clusteranalysis, learning theory, DNAmapping, group testing for biology,evolutionary trees, quantum physics,and wavelet analysis. The basicapproach of the researchers participat-ing in this project is to gain a deepunderstanding of problems arising inlaboratory research and to use theirskills in combinatorial methods tosolve them.

In the field of quantum computing,we have designed several new andefficient algorithms for quantum errorcorrection and fault-tolerant comput-ing. As a result of this and other work,quantum computing has been provento be physically realizable. Incommunication networks we havedeveloped new approximationalgorithms for several basic problemsthat arise in network design andanalysis. These algorithms willpotentially be useful in upgradingnetwork performance and especiallyin finding efficient routing methods.

In computational finance we haveapplied innovative computationalmethods to pricing various derivativesand options. In computationalgeometry we have found efficientmethods for point location andDelaunay triangulations as well asefficient computational methods forgeometric problems arising in patternmatching and cartography. Wecontinue to develop methods forefficient cluster analysis. The algo-rithms, some of which have beenpatented, are now being extensivelyused at the Laboratory.

Publications

Arikati, S.R., A. Dessmark, et al.,"Approximation Algorithms forMaximum Two-Dimensional PatternMatching," in 7th Annual Symposiumon Combinatorial Pattern Matching(Springer Verlag, Berlin, 1996), Vol.1075, pp. 348-360.

Chalasani, P., and S. Jha, "ATopological Study of ConcurrentProcesses" (submitted to Science ofProgramming).

Chalasani, P., A. Blum, and S.Vempala, "A Constant FactorApproximation for the k-MSTProblem in the Plane" (AnnualSymposium on Theory ofComputation, Las Vegas, Nev., 1995).

Chalasani, P., S. Jha, and I. Saias,"Approximate Option Pricing"(Conference on Foundations ofComputer Science, Burlington, Vt,1996).

Chalasani, P., R. Motwani, and A.S.Rao, "Algorithms for Robot Graspand Delivery" (submitted to SIAM J.Computing).

Krumke, S.O., H. Noltemeier, et al.,"Compact Location Problems withBudget and CommunicationConstraints," in 1st Intl. Conf. onComputing and Combinatorics(Springer Verlag, Berlin, 1995), Vol.959, pp. 510-519.

Krumke, S.O., H.-Noltemeier, et al.,"Complexity and Approximability ofCertain Bicriteria Location Prob-lems," in 21st Workshop in GraphTheoretic Concepts in ComputerScience 1017, 73 (1995).

Krumke, S.O., H. Noltemeier, H.U.Drangmeister, et al., "NetworkImprovement Problems," in 22ndWorkshop in Graph Theoretic Conceptsin Computer Science (in press).

Marathe, M.V., and S.S. Ravi,"Approximation Algorithms for theMinimum Satisfiability Problem,"Information Processing Letters 58 (1),23 (1996).

Marathe, M.V., R. Ravi, and R.Sundaram, "Service ConstrainedNetwork Design Problems," in 5thScandinavian Workshop on AlgorithmTheory (SWAT) (Springer Verlag,Berlin, 1996), Vol. 1097, pp. 28-30.

Marathe, M.V., H.B. Hunt III, et al.,"Approximation Schemes forPSPACE-Complete Problems forSuccinct Specifications" (to bepublished in SIAM J. Computing).

Marathe, M.V., H.B. Hunt III, et al.,"Complexity of Hierarchically and 1-Dimensional Periodically SpecifiedProblems" (to be published in AMSProc).

Marathe, M.V., R. Ravi, R. Sundaram,et al., "Bicriteria Network DesignProblems," in Proc. 22nd Int'l.Colloquium on Automata, Languagesand Programming (Springer Verlag,Berlin, 1995), Vol. 944, pp. 487-498.


Theory and Modeling of Correlated-Electron Materials

Alan Bishop

There is today a significant oppor-tunity for exploiting complex elec-tronic materials based on propertiestotally beyond those of traditionalsolid-state materials. The newmaterials are characterized by strongcompetitions between coupledelectronic, structural, and magneticdegrees of freedom and by sensitivi-ties to dimensionality and geometry.This project provides theory andmodeling of correlated electronicmaterials for three major tasks:

(1) isolation of novel phenomena;(2) integration of synthesis andcharacterization with theoreticalmodeling of phenomena in specificclasses of materials; and (3) develop-ment of scientific control of synthesis-microstructure-property relationships.These tasks in turn address threecritical science issues at the cuttingedge of research in correlatedelectronic materials: What are theroles of electron-electron and elec-tron-lattice interactions, disorder,chemical doping, magnetic field,pressure, and temperature in control-ling metal-insulator transitions? Whatconditions induce non-Fermi-liquidmetallic behavior and what are theirexperimental signatures? How can thelocal structure of these materials beprobed?

We have worked closely withexperimentalists to study the originand detection of intrinsic fine-scalestructure in strongly correlatedelectronic materials, includingdouble-exchange and Jahn-Tellereffects in perovskite oxides, that leadsto the polaronic and elastic short-range textures recently observedthrough neutron, x-ray, and resonantultrasound probes. We have begunpair-distribution function analysis ofmodels with local and long-rangeorder. We have developed newnonperturbative methods for, andincreased our understanding of,

nonadiabatic and inelastic quantumtransport, including multiple spatial-and temporal-scale effects. We havemodeled the origins of non-Fermi-liquid and pseudogap behavior inperovskites and heavy-fermioncompounds, including intrinsic andextrinsic disorder, d-wave symme-tries, and multiphonon bound states.Finally, we have established regulardiscussion and seminar sessions forcommunication between and amongexperimentalists and theorists.

Publications

Abrahams, E., A.V. Balatsky, et al.,"Properties of Odd Gap Super-conductors," Phys. Rev. B 52, 1271(1995).

Balatsky, A.V., and E. Abrahams,"Odd Time Magnetic Correlations andChiral Spin Nematic," Phys. Rev. Lett.74, 1004 (1995.)

Balatsky, A.V., and M. Salkola,"Impurity Induced States and theAbsence of Quasiparticle Localizationin Disordered D-Wave Super-conductors," Phys. Rev. Lett. 76, 23(1996).

Bishop, A.R., "Tuning Ground Statesand Excitation in Complex ElectronicMaterials" (to be published inSynthetic Metals).

Bonca, J., and S.A. Trugman, "TheEffect of Inelastic Processes onTunneling," Phys. Rev. Lett. 75, 2566(1995).

Engelbrecht, J.R., M. Randeria, andC.A.R.S. de Melo, "BCS-BoseCrossover: Broken Symmetry State"(to be published in Phys. Rev. B:Rapid Communication).

Kenkre. V., S. Raghavan, et al.,"Memory-Function Approach toInteracting Quasiparticle-Boson

Systems," Phys. Rev. B 53,5407(1996).

Louca, D., T. Egami, et al., "LocalJahn-Teller Distortion inLa j xSrMnO3 Observed by PulsedNeutron Diffraction" (submitted toPhys. Rev. Lett.).

Matveenko, S., A. Bishop, and A.V.Balatsky, "SuperconductivityFluctuations in 1-D 2-Band Electron-Phonon Model with Strong RepulsiveElectron-Electron Interactions" (to bepublished in Phys. Rev. B).

Rabson, D.A., and S.A. Trugman, "ASpin Model for InvestigatingChirality," /. Phys. Condensed Matter7,9005 (1995).

Roder, H., A.F. Voter, et al.,"Chebyshev Moment Problems:Maximum Entropy and KernalPolynomial" in Maximum Entropyand Bayesian Methods, K.M. Hansonand R.N. Silver, Eds. (KluwerAcademic Press, New York, 1996),pp. 187-194.

Roder, H., J. Zang, and A.R. Bishop,"Lattice Effects in the CMRManganites," Phys. Rev. Lett. 76,1456 (1996).

Salkola, M., A.R. Bishop, and V.Kenkre, "Coupled Quasiparticle-Boson Systems: The SemiclassicalApproximation and NonlinearSchrodinger Equation," Phys. Rev. B52 (R), 3824 (1995).

Salkola, M., A.R. Bishop, and V.Kenkre, "Quantum Complexity inCoupled Spin-Boson Systems" (to bepublished in Phys Rev B: RapidCommunication).

Salkola, M.I., A.R. Bishop, et al.,"Correlation-Function Analysis ofNonadiabatic and Nonlinear Systems:Polaron Tunneling," Phys. Rev. B 51,8878 (1995).

Scalapino, D.J., and S.A. Trugman,"Local Antiferromagnetic Correlationand D-Wave Pairing" (to be publishedin Philos. Mag. B).


Schmeltzer, D., and A.R. Bishop,"Bosonization of the ContinuumVersion of t-J Model Coupled to aDissipative Guage Field in 2-Dimensions," Phys. Rev. B 54, 4293(1996).

Silver, R.N., A.F. Voter, and J.D.Kress, "Linear-Scaling TightBinding from a Truncated MomentsApproach," Phys. Rev. B 53,12733(1996).

Silver, R.N., B. Bauml, et al ,"Spectral Properties of the 2-DHolstein t-J Model" (High-Temperature SuperconductingConference, Beijing, China, February1997).

Silver, R.N., H. Roder, et al., "KernalPolynomial Approximations forDensities of States and SpectralFunctions," J. Comp. Phys. 124,115-130(1996).

Silver, R.N., H. Roder, et al., "TheKernal Polynomial Method Applied tothe Non-Orthogonal ElectronicStructures" (to be published in Phys.Rev. B, Brief Reports).

Silver, R.N., H. Roder, et al., "SpinCorrelation Functions in Random-Exchange S=l/2 XXZ Chains," /.Appl. Phys. 79, 4632 (1996).

Trugman, S.A., "Complex ScatteringDynamics and the Quantum HallEffect," Physica D 83, 271 (1995).

Tyson, T.A., S. Conradson, A.R.Bishop, et al., "Evidence for a LocalLattice Distortion in Ca-dopedLaMnO3" (to be published in Phys.Rev. B).

Wang, W.Z., J.T. Gammel, et al.,"Quantum Breathers in a NonlinearLattice," Phys. Rev. Lett. 73, 3598(1996).

Wang, W.Z., Y. Lu, A.R. Bishop, etal., "Dynamic Jahn-Teller Effect inFullerene C60" (to be published inPhys. Rev. B).

Zang, J., A.R. Bishop, and H. Roder,"Double Degeneracy and Jahn-TellerEffects in CMR Perovskites," Phys.Rev.BR53,l (1996).

Zang, J., A.R. Bishop, and D.Schmeltzer, "Frustrated Spin-PeierlsChains," Phys. Rev. B 52, 6723(1996).

Zang, J., H. Roder, et al., "LowTemperature Magnetic Properties ofthe Double Exchange Model" (to bepublished in J. Phys. C Lett.).



Modeling the Heat Flow and ResultingDynamics in Earth's Interior

Gary Glatzmaier

We have used computer simulationsand laboratory experiments to studythe dynamics of Earth's deep interior.Our computer models have simulatedthe flow in Earth's mantle on rela-tively small scales such as withinmagma chambers, below volcanoes,and beneath midocean ridges. Thesethree-dimensional models of localizedfeatures have demonstrated the effectsof the highly temperature-dependentviscosity of mantle material on thestructure of the fluid flow and on thetransport and mixing of differentminerals within the mantle.

Our global three-dimensionalmodels of mantle convection havealso uncovered how sensitive theglobal-scale flow structure is to thevariation of the viscosity throughoutthe mantle. In particular, we havefound that it is very likely that thelower part of Earth's mantle has amuch higher viscosity than the upperpart; our simulations that have thissame variation in viscosity producesubduction-like downflows at thesurface that are very much like thoseseen on Earth at the boundariesbetween tectonic plates (see accompa-nying figure).

We have also conducted severallaboratory experiments of convectionin viscous fluids to complement ourcomputer modeling studies andprovide further insight into convectivemixing. In addition, we are usinggeochemical observations of Earth toconstrain the dynamics of ourcomputer models by estimating theamount of mixing that has occurred inEarth's mantle.

A snapshot of our global simulation ofconvection in Earth's mantle. Theimage shows cold (dense) material asa dark shade and warm (buoyant)material as a light shade. A cutawayof the mantle shows the structuredown to the core. The long andnarrow dark regions on the surfaceresemble subduction zones on Earth.

Publications

Bunge, H.-R, M.A. Richards, and J.R.Baumgardner, "Effect of Depth-Dependent Viscosity on the Planformof Mantle Convection," Nature 379,436 (1996).

Jarvis, G.T., G.A. Glatzmaier, and V.I.Vangelov, "Effects of Curvature,Aspect Ratio and Planform in Two-and Three-Dimensional SphericalModels of Thermal Convection,"Geophys. Astrophys. Fluid Dyn. 79,147 (1995).

Kincaid, C , G. Ito, and C.W. Gable,"Laboratory Investigation of theInteraction of Off-Axis MantlePlumes," Nature 376,758 (1995).

Kincaid, C , J.-G. Schilling, and C.W.Gable, "The Dynamics of Off-AxisPlume-Ridge Interaction in theUppermost Mantle," Earth Planet.Sci. Lett. 137, 29 (1996).

Olson, P., and G.A. Glatzmaier,"Magnetoconvection in a RotatingSpherical Shell: Structure of Flow inthe Outer Core," Phys. Earth Planet.Inter. 92,109 (1995).

Van Keken, P.E., and C.W. Gable,"The Interaction of a Plume with aRheological Boundary: A Com-parison," /. Geophys. Res. 100,20291(1995).

Competency Development Projects—Geoscience, Space Science, and Astrophysics 207

Remote Sensing ScienceThrust:New Concepts

Siegfried Gerstl

The primary objective of thisproject is to evaluate the feasibility ofnew research ideas that are based onextrapolations of science and technol-ogy that are already at the forefront ofremote sensing science. These studieshave provided timely input forNASA's future civilian research, theNew Millenium Program, and theU.S. Air Force Scientific AdvisoryBoard.

We have looked at a promisingconcept for measuring vegetationcanopy hot-spot characteristics fromspace. The concept involves activeillumination and bistatic detection thatwould allow angular distributionmeasurements from space in asearchlight mode, which is equivalentto measuring a localized bidirectionalreflectance distribution function(BRDF). The concept comprises apointable illumination source, such asa laser operating at an atmospheric-window wavelength, coupled with anumber of high-spatial-resolutiondetectors (clustered around theillumination source in space) thatreceive photons nearly coaxial withthe retroreflection direction. Micro-wave control and command amongthe satellite cluster would allowsimultaneous orientation of thedirection of the laser beam and thetelescope detectors so that the coupledsystem can function like a searchlightwith almost unlimited pointingcapabilities. The concept is called thehot-spot search-light (HSSL) satellitecluster and is shown in the first figure.A nominal altitude of 600 km for thesatellite cluster will allow hot-spotBRDF measurements out to about an18-deg phase angle.

We have also demonstrated thefeasibility of an environmentalvolumetric imaging (EnVI) conceptthat would use active remote sensingfrom space to measure the distributionand density of foliage in a vegetation

canopy. Our model simulations andinformation retrieval algorithms showthat EnVI cannot only measure thetotal leaf area index (LAI) but also thevertical distribution of the LAI. Thesecond figure shows the results of

simulated remote measurements of acanopy from 10-km altitude on twodifferent vertical leaf distributionswith the same leaf area index. Basedon these encouraging results, we areinitiating collaborations with expertsoutside Los Alamos to develop laserremote sensing altimeters.

Hot-Spot Search-Light (HSSL) Satellite Cluster

Detector 3

• Detector distancesL = 10 to 200 km

• Command and Controlby Microwave

S Gerstl. L.ANL.March 96

The hot-spot search-light satellite concept, a free-flying constellation of acentral laser source and a surrounding cluster of detector telescopes atdistances of 10 to 200 km from the source, for an instantaneous field-of-view(IFOV) of 200 m.


Publications

Gerstl, S.A.W., "Angular Signatures,and a Space-borne MeasurementConcept," IGARRS'96 Symp. Proc. 3,1642 (1996).

Gerstl, S.A.W., "A MeasurementConcept for Hot-Spot BRDFs fromSpace" (to be published inInternational Workshop onMultiangular Remote Sensing,Beijing, Proceedings).

Priedhorsky, W.C., R.C. Smith, and C.Ho, "Laser Ranging and Mappingwith a Photon-Counting Detector,"Appl. Opt. 35, 3 (1996).

0.050 rflat LAI profile

0.050 F

(per

cm

LAI

ial

ent

diffe

r0.040

0.030

0.020

0.010

0.000 E0

100 200 300height (cm)

triangular LAI profile

400 500

100 200 300height (cm)

400 500

Simulated measurements of vertical leaf area index (LAI) distribution profileswith the environmental volumetric imaging (EnVI) concept. The leaves aredistributed uniformly over 3 m in the top panel and in a triangular distributionshape in the lower panel. The thick lines show the timing profile of the singlyreflected laser photons. The thin solid lines are the differential LAI distributionas derived from the photon counting; these match well with the inputdifferential LAIs.

Subsurface Noble Gas Transportat the Nevada Test Site

Joseph Thompson

The objectives of our research areto explain the results of a groundwaterpumping test done from 1975 to 1991at the location of the nuclear testCambric at the Nevada Test Site and,especially, to examine and understandthe subsurface transport of noble gas.The elution data from the pumpedwell showed that the appearance ofkrypton in the elution was delayedrelative to tritium and that only half ofthe calculated Kr-85 source term wasever removed. We hypothesized thatcarbon dioxide gas that evolved from

the carbonate rock around the nucleardevice contributed to the post-detonation migration of Kr-85throughout the rubble chimney abovethe collapsed crater. The distributionof krypton was thus different fromthat of tritium, which was containedin the immediate vicinity of thecavity. This initial distribution ofkrypton resulted in some losses ofKr-85 from the groundwater and in itsdelayed arrival, relative to tritium, atthe pumped well.

Our major accomplishment thisyear was to develop a three-dimen-sional model using the Los AlamosTRACR3D code that simulates themovement of tritium and kryptonthrough the groundwater as it movesto the pumped well at the Cambricsite. The model showed that thedelayed arrival and loss of kryptoncould indeed be explained but thatthere was substantial uncertaintyabout initial radionuclide distribution,hydrologic parameters, and otherfactors. In addition, we began toconsider the influence of thermallyinduced convection currents on thedistribution of radionuclides aroundthe location of the nuclear test. We areusing the TRACR3D code to simulatebuoyancy-driven flow to determine itssignificance in the Cambric study.


Analysis and Visualization of GlobalMagnetospheric Processes

Dan Winske

The purpose of this project is todevelop new computational andvisualization tools to analyze particledynamics in Earth's magnetosphere.These tools will allow us to constructan efficient global picture of particlefluxes that requires only a smallnumber of satellite measurements asinput parameters.

The visualization tools developedhave led to a better understanding ofparticle dynamics in Earth's mag-netotail in the presence of turbulentwave fields (see first figure). Theyhave also demonstrated how largeelectromagnetic pulses in the solarwind can interact with the magneto-sphere to increase the population ofenergetic particles and even form newradiation belts (see second figure).The work performed in this projecthas application to auroral, iono-spheric, and magnetospheric phenom-ena, to plasma kinetics, transport, andimpurities, and to plasma waves,oscillations, and instabilities.

Publications

Cattell, C, I. Roth, and M. Linton,"Effects of Low-Frequency Waves onIon Trajectories in the Magnetotail,"Geophys. Res. Lett. 23, 3445 (1995).

Hudson, M.K., A.D. Kotelnikov, X.Li, et al., "Modeling Formation ofNew Radiation Belts and Response toULF Waves," in Proc. Taos Workshopon Energetic Particles (AIP, NewYork, N.Y., in press).

Hudson, M.K., W. Lotko, C. Cattell,et al., "Modeling of MesoscaleProcesses in the Global GeospaceSystem," Space Sci. Rev. 71, 623(1995).

TICK HARKS EVERY 18 RE

Effect of a turbulent wave on the trajectory of a 100-eVproton with an initial pitch angle of 10° in the magnetotail. Theupper two plots show the proton's trajectory in the absence of turbulence in (a) the x-z and (b) x-y planes (x correspondsto the sun-Earth direction and is the horizontal axis in each panel, z points to the north, and y is the cross-tail direction).The small figures to the left show the orientation of the magnetic field. In these two plots, the proton's motion isessentially adiabatic, combining gyration, bounce, and magnetic-field-gradient drift motion. The lower two plots showhow a single monochromatic wave with an amplitude of 10 mV/m affects the proton's trajectory: the proton is(c) chaotically scattered in the current sheet region (near z = 0) and (d) drifts much farther in the direction of the cross-tail electric field, increasing its energy.


Proton flux

Energy (MeV)

Calculation of the proton flux that results from a large solar wind storm. The plot shows the flux intensity (white is mostintense, dark is less intense) as a function of energy and of the L shell (a ratio given in Earth radii). Such plots can becompared with data obtained directly from spacecraft, such as NASA's CRRES satellite.

Neutron Star Evolution and Emission

Richard Epstein

We have studied the physics ofcompact stellar objects. Our researchhas focused on three areas: theinternal dynamics of neutron stars,their interactions with other stars, andthe development of new techniquesfor observing them. The first focus ofour research has been the anomalousbehavior of pulsars—spinning,strongly magnetized neutron stars.We found that the observed suddenchanges in the star's spin rate, so-called "glitches," may be due tocracking of the star's hard crust thatproduces heat, thereby altering thespin rate of the star's superfluidinterior. Additionally, we found thatthe star's behavior after a glitchreveals that the crust and liquidinterior are threaded by a magneticfield of at least a trillion gauss.

The second focus was the interac-tions among stars in crowded regionsof galaxies, such as near galacticcenters. We discovered that high-velocity collisions between red-giantstars and compact objects led tosignificant mass loss. These resultsappear to explain the puzzling dearthof red supergiants near the center ofour galaxy and may provide anexplanation for the source of massthat falls into the massive black holesin quasars.

The third focus was the develop-ment of a laser-powered cryogeniccooler for spaceborne astronomicalobservations. Such reliable and long-lived devices would facilitate sensitivegamma-ray spectral observations ofgravitationally shifted nuclear linesfrom the surface of neutron stars.

Publications

Abney, M., and R.I. Epstein, "EkmanPumping in Astrophysical Bodies," /.Fluid Mech. 312, 327 (1996).

Abney, M., R.I. Epstein, and A. V.Olinto, "Observational Constraints onthe Structure and Dynamics of Vela,"Astrophys. J. 466, 91 (1996).

Epstein, R.I., B.C. Edwards, M.I.Buchwald, et al., "Observations ofLaser-Induced Fluorescent Cooling ofa Solid," Nature 377, 500 (1995).

Link, B., and R.I. Epstein, "Statisticsof Gamma Ray Burst TemporalAsymmetry," Astrophys. J. 466, 764(1996).

Link, B., and R.I. Epstein,"Thermally-Driven Neutron StarGlitches," Astrophys. J. 457, 844(1996).

Van Riper, K.A., B. Link, and R.I.Epstein, "Vortex Creep and ThermalEvolution of Neutron Stars,"Astrophys. J. 448, 294 (1995).


Remote Sensing ScienceThrust:Laser Remote Sensing

Siegfried Gerstl

The focus of our work is toextend a Raman lidar system to themeasurement of atmosphericconstituents such as aerosols andwater vapor with unprecedentedaccuracy and range resolution.This work will be applied to non-proliferation and environmentalboundary-layer science. Upgradesto the system included the additionof a line-narrowed Nd: YAG laserfor temperature measurements andimproving the command andcontrol software. To understandthe measurements, we are develop-ing a microscale boundary-layermodel with 2-m resolution. Wefielded the upgraded lidar systemin a central Pacific experiment,and we are using the data tovalidate the high-resolutionmicroscale boundary-layer model.

In March 1996, we used theadvanced scanning Raman lidar toquantify processes associated withthe ocean-atmosphere interface,including intermittency andcoherent atmospheric features inthe "warm pool" of the tropicalwestern Pacific near Manus Island.The data shows excellent verticaland horizontal, microscale spatialand temporal structure in theequatorial Marine AtmosphericBoundary Layer (MABL). Thedata included, for the first time, anobservation of microscale cellularconvective structures with hexago-nal patterns associated withRayleigh-Benard-like cells (see theaccompanying figure).

To characterize the structuresinvolved with the mass-energyexchange at the ocean-atmosphereinterface, we used the scanningRaman lidar to image the three-dimensional structures found inthe surface layer of the MABL.Although the atmospheric bound-ary layer is turbulent on small

length scales, the large-scale structuremay have length and time scalessimilar to those from linear stabilityanalysis of thermal convection in abounded thermal layer. Analysissuggests that the large-scale motionsof the equatorial MABL are consis-tent with weakly turbulent, small-scale Rayleigh-Benard-like convectiveprocesses. To address these importantissues, we will perform future lidarexperiments capable of resolving thetemporal behavior of the equatorialMABL.

In a further complementary effort,we developed an innovative methodfor determining water-vapor-columnirregularities by microwave interfer-ometry. This new method exploitsarchival radioastronomical data fromthe Very Large Array.

Publications

Cooper, D., W. Eichinger, R. Ecke, etal., "Initial Investigations of Micro-Scale Cellular Convection in anEquatorial Marine Boundary LayerRevealed by Lidar," Geophys. Res.Lett. 25 (1), 45 (1997).

Jacobson, A.R., and R. Sramek, "AMethod for Improved Microwave-Interferometer Remote Sensing ofConvective-Boundary-Layer-Turbulence, Using Water Vapor as aPassive Tracer" (to be published inRadio ScL).

-540 -S30 -6S0 -soo

Range (m)

A horizontal Raman lidar scan of water vapor acquired 10 m above the oceansurface on March 26, 1996, in the tropical western Pacific near Manus Island.


Development of the First Nonhydrostatic,Nested-Grid, Grid-Point GlobalAtmospheric Modeling System onParallel Machines

Chih-Yue J. Kao

All of the existing global atmo-spheric models suffer from one ormore of the following shortcomings:(1) lack of an interactive nested-gridcapability, which makes it difficult toevaluate the regional impact;(2) spherical spectral representation(as opposed to grid-point finite-difference) of model variables, whichhinders model performance onparallel machines; and (3) use of thehydrostatic approximation, whichmakes the models potentially ill-posed. As a result, no atmosphericmodel is capable of simulating the fullrange of spatial scales of atmosphericcirculations from global-scale wavedisturbances to microscale plumedispersion.

The goal of this work is to developa nested-grid, global atmospheric

modeling system (GAMS) with state-of-the-science physics and chemistry.This highly modularized, self-calibratable system will also provide aunique testbed for high-performancecomputing architecture.

We have successfully tested aglobal reduced-grid system in GAMSand the lower boundary conditions interms of sea surface temperature andorography in the model. We have alsostudied the intrinsic differencebetween the hydrostatic and non-hydrostatic global models and arepreparing a manuscript on this work.We have tested many three-dimen-sional elliptical equation solvers tofind a fast convergence rate of thepressure solution and decided to usethe Conjugate Gradient method.

Our prototype model runs on a widerange of computer platforms, includ-

ing an IBM R-6000 workstation, aCray Y-MP, and a highly parallel CM-5. All of the necessary physicalalgorithms have been developed,including cloud and radiationparameterizations, boundary layertreatment, and a soil module.

Publications

Kao, C.-Y.J., A. Quintanar, MJ.Newman, et al., "Climate Simulationswith NCAR CCM2 Forced by GlobalSea Surface Temperature in 1950-1989," J. Climate 9, No. 12 (1996;.

Reisner, J., and C.-YJ. Kao,"Efficiency of a Forward-in-TimeShallow Water Code on a Sphere" (tobe published in Parallel ComputationFluid Dynamics).

Smith, W.S., and C.-Y.J. Kao,"Numerical Simulations of ObservedArctic Stratus Clouds Using a Second-Order Turbulence Closure Model," /.Appl. Meteorol. 1,47-59 (1996).

Smith, W.S., and C.-Y.J. Kao,"Stratocumulus-Capped BoundaryLayer and its Diurnal Variation,"Monthly Weather Review 8,1803-1816(1996).

Production and Application ofHigh-Specific-Activity Si-32

Dennis R. Phillips

In this project we have worked toproduce the radionuclide Si-32 withunusually high specific activity and todevelop methods for using Si-32 inoceanographic field research onfactors affecting the global climate.

In collaboration with researchersfrom the University of California atSanta Barbara, we developed biologi-cal oceanographic experiments usingSi-32 as a tracer to measure silicateuptake by diatoms, siliceous phy-toplankton that require silicate as anutrient. Because of their sheervolume, the diatoms sequestersignificant amounts of atmospheric

carbon dioxide. By correlating thedata from our silicate-uptake studieswith data from studies on the uptakeof other essential nutrients, such asbicarbonate, inorganic nitrogen, andinorganic phosphorus, we can provideimportant information on the role ofdiatoms in the global climate. Fur-thermore, current theories indicatethat silicate may be the limitingnutrient in some important oceanbodies, and our data from this projectcan be used to test such models.

This year we refined our radio-analytical techniques, focusing oncalibration methods. After validating

the calibration methods, we analyzeddata collected during the 1995 CoastalOcean Processes research cruise inMonterey Bay (sponsored in part bythe National Science Foundation andthe Monterey Bay Aquatic ResearchInstitute). We completed and submit-ted for publication two papers thatdescribe the methods and the resultsof our experiments.

Publications

Brzezinski, M.A., and D.R. Phillips,"Evaluation of Si-32 as a Tracer forMeasuring Silica Production Rates inMarine Waters" (to be published inLimnology and Oceanography).

Brzezinski, M.A., and D.R. Phillips,"Silica Production in the Monterey,California, Upwelling System"(submitted to Limnology andOceanography).


Remote Sensing Science Thrust:Hyperspectral Sensing

Siegfried Gerstl

Our goal is to develop detectortechnologies using hundreds ofnarrow spectral bands for remotesensing. We are concentrating on theinfrared portion of the solar spectrumat hyperspectral resolution. We havemade proof-of-concept measurementswith a modified Fourier transforminfrared (FTIR) spectrometer,identifying gaseous species in plumesfrom passively degassing volcanoes.We used a combination of (1) passiveremote sensing with the FTIRspectrometer for multiple speciesconcentrations and/or ratios and (2)active remote sensing with the elasticlidar data to remotely quantify (10%error) plume species fluxes. We areusing these methods in parallel withtraditional COSPEC, a correlationspectrometer operating in the solarultraviolet (for SO2 flux), and directsampling methods (for total chemicalcomposition) to obtain ground-truthmeasurements of the new techniques.We successfully field-tested thesetechniques at the White Island andRuapehu volcanoes in New Zealand.

We detected the White Island plumeat a distance of 50 km and maderoutine measurements at 6 km fromRuapehu. We easily identified bothH2O and SO2 in the plumes of bothvolcanoes from distances up to 6 km.The first figure shows the SO2 and H2Ospectra obtained at Ruapehu. While thestandard HgCdTe detector providesoptimum performance in the long-waveinfrared region (8-12 |jm), the additionof an InSb detector allowed us to obtainhigh-quality spectra in the 3-5 |jmregion, thus permitting the detection ofHC1 in the White Island plume from adistance of 1 km (see the secondfigure). All FTIR measurements werecompletely passive, i.e., they did notrely on artificial infrared sources or

0.12-

iPlume against skyClean sky at same elevation278 K blackbody spectrum

4=5 20x10 -

o

O)CM

IOc.Sca

DC

800 1000 1200Wavenumber (cm"1)

1400

Passive FTIR spectra of the Mt. Ruapehu plume on May 10, 1996, obtainedfrom a distance of 6 km. (Top) Radiometrically calibrated long-wave infraredspectrum of the volcanic plume viewed against clear sky (heavy line) comparedwith a spectrum of a segment of sky at the same elevation angle but without anyplume (fine line). For reference, the dashed line shows a blackbody spectrum atthe ambient air temperature of 278 K. The most prominent divergence of thetwo spectra, the broad double-peaked feature extending from 1100 to 1200 cmr1

(9 to 8.3 jim), is due to SO2 in the plume. The bottom figure shows thedifference between the two spectra in the top figure. The many sharp linesthroughout the 800-1000 cm'1 region are due to water vapor.


known emissions of radiation from hotrocks or lava. Our detection andquantification of volcanic HC1 bycompletely passive means is a first andopens up a much greater range ofvolcanoes for study.

The incorporation of absoluteradiometric calibration by means ofspecially constructed, portable,blackbody reference sources isanother first performed in our project.Radiometrically calibrated measure-ments, combined with simultaneousCOSPEC measurements of SO2 pathdensities, allow plume temperaturemeasurement. This, in turn, allowsaccurate determination of the concen-trations of the other gases from theinfrared spectra. We found SO2/H2Oratios determined in this manner to bein good agreement with thoseobtained from direct sampling of thefumerole gases.

Publications

Christenson, B., J. Lindsay, F. Goff, etal., "Direct Sampling and COSPECResults Supporting FTIR and LIDARMeasurements of Volcanic Emissionat White Island and RuapehuVolcanoes," EOS Trans. Amer.Geophys. Union 77, F830 (1996).

Cottingame, W, D. Pettit, S. Love, etal, "Integrated LIDAR/UV/IR RemoteSensing of Volcanic Emissions atWhite Island and Mt. Ruapehu, NewZealand," EOS Trans. Amer. Geophys.Union 11, F801 (1996).

Love, S., D. Pettit, W. Cottingame, etal, "Integrated Infrared/UV/LidarRemote Sensing of VolcanicEmissions at White Island and Mt.Ruapehu, New Zealand," EOS Trans.Amer. Geophys. Union 11, F802(1996).

0.3-

0.2-

(0(0

0.1 -I

0.0-

HCI

White Island Plume(Plume minus Sky) u4/26/96 H

SO

HCI Reference Spectrum200 ppm.m in 1 atm N2

SO2 Reference Spectrum800 ppm.m in 1 atm N2

I I2500 2600 2700 2800 2900 3000

-UWavenumber (cm )

Passive FTIR of the White Island plume, midwave infrared region, illustratingthe first completely passive quantification of the ratio of HCI to SO2 in avolcanic plume. Upper curve shows the plume-sky difference, as in the firstfigure, converted to emissivity using an estimated plume temperature of 310 K.The lower two curves show laboratory reference spectra of HCI and SO2. Boththe broad SO2 feature and the regularly spaced sharp lines of HCI are clearlyevident in the plume spectrum.


Studies of Dynamical ProcessesAffecting Global Climate

Charles Keller

The objective of this project is togain a fundamental understanding ofthe interactions between Earth'satmosphere and its oceans. We arefocusing on improving models ofprocesses in four main areas: numeri-cal physics, cloud representation,water vapor observations, and theheterogeneous chemistry of aerosols.We have made advances in applyingapproximate inertial manifolds(AIMs), a method of dealing withsubgrid-scale physics, to numericalcomputations of ocean models. Wehave developed a finite-differenceversion of AIMs for the shallow-watermodel equation, resulting in a largedecrease in computing time with noloss in accuracy.

Our implementation of the nowfully developed cloud parameteriza-tion package, SUNAS, into a globalcirculation climate model, CCM2, isshowing remarkable improvement insimulating the hydrologic cycle (seefirst figure). Other parametersimproved include the following:zonally averaged precipitation; overallcloudiness and precipitation patterns,particularly in the Amazon basin andthe western Pacific; and persistentstratiform cloud decks observed in theeastern ocean basins.

We have used our shipboard lidarobservations of water vapor in theequatorial Pacific to develop the firsthorizontal, two-dimensional maps ofevaporative features in the ocean/atmosphere boundary layer. Thesemaps show alternating patterns of dryand moist air indicative of rising anddescending currents seen in laboratoryconvection experiments (see secondfigure).

We have used advanced lasertechniques to study heterogeneousprocesses on thin films that simulatestratospheric and tropospheric aerosolsurfaces. In addition, we are quantify-ing adsorption processes mimicking

polar stratospheric cloud interactionswith nitric acid trihydrate, a majorcomponent in ozone depletion.

500 mb Standing Waves (Cold Years)

90N-

I I I I I | 1 I I ! F | I I | I I | I I | I I | I I | I I

0 3 0 E 6 0 E 9 0 E 130E 150E 180 1 5 0 W 1 2 0 W 9 0 W 6 0 W 3 0 W 0

CONTOUR FROM -250 to 150 by 50I I 1 I I I I I I I I ! L

~| I I ] i I | I f | l i | I 1 |0 3 0 E 6 0 E 9 0 E 1 2 0 E 1 5 0 E 1 8 0 150W 120W 90W 60W 30W 0

CONTOUR PROM - 1 5 0 to 150 by 50

I I | I I | I I | I I | I

0 3 0 E 6 0 E 9 0 E 1 2 0 E 1 5 0 E 1 8 0 150W 120W 90W 60W 30W 0

CONTOUR FROM - 2 0 0 to 150 by 50

These simulations show departure of 500 mbfrom the zonally averagedgeopotential height (analogous to pressure) for cold years. These simulationswere made using global circulation models (a) SUNAS and (b) CCM2 and arecompared with data from (c) observations.


This plan view of water vaporconcentrations 10 m above theequatorial Pacific Oceanshows patterns of dry andmoist columns reminiscent ofclassic convection.

i85F -SSO -5S0 -5*0 -&5O -650 -640 -830 -620 -610 -600

Range (m)

Publications

Chen, F., and M. Ghil, "InterdecadalVariability in a Hybrid CoupledOcean-Atmosphere Model"(submitted to / . Phys.Oceanography).

Chen, E, and M. Ghil, "InterdecadalVariability of the ThermohalineCirculation and High-LatitudeSurface Fluxes" (submitted to J. Phys.Oceanography).

Cooper, D.I., W.E. Eichinger, S. Barr,et al., "High-Resolution Properties ofthe Equatorial Pacific MarineAtmospheric Boundary," / . Atmos.Sci. 53,2054(1996).

Elliott, S., and F.S. Rowland, "MethylHalide Hydrolysis Rates in NaturalWaters" (submitted to J. Atmos.Chem.).

Elliott, S., R.J. Cicerone, and R.P.Turco, "Influence of the Hetero-geneous Reaction HC1 + HOC1 on anOzone Hole Model with HydrocarbonAdditions" (to be published in J.Geophys. Res.).

Elliott, S., R.P. Turco, X.P. Zhao, etal., "Photochemical Numerics forGlobal Scale Modeling: Fidelity andGCM Testing," / . Appl. Meteorol. 34,694 (1995).

Elliott, S., X. Zhao, R.P. Turco, et al.,"Photochemical Numerics for GlobalScale Modeling: Fidelity and GCMTesting" (to be published in Mon.'Weather Rev. A).


Heterogeneous Reactions," Geophys.Res. Lett. 23, 1021 (1996).

Jones, D., and E.S. Titi, "ClApproximating Inertial Manifolds forDissipative Nonlinear Equations"(submitted to J. Diff. Eqns.).

Jones, D., L. Margolin, and E.S. Titi,"On the Effectiveness of theApproximate Inertial Manifolds—Computational Study" (to bepublished in Theor. Comput. FluidDynamics).

Kao, C.-Y.J., A. Quintanar, M.J.Newman, et al., "Climate Simulationswith NCAR CCM2 Forced by GlobalSea Surface Temperatures 1950-1989" (to be published in /. Climate).

Noble, C.A., and K.A. Prather, "Real-time Measurement of Correlated Sizeand Composition Profiles ofIndividual Atmospheric AerosolParticles," Environ. Sci. Technol. 30,2667 (1996).

Shao, Z., and E.S. Titi,"Parameterizing the Global Attractorof the Navier-Stokes Equations byNodal Values" (to be published inNumerical Functional Analysis andOptimization).

Smith, W.S., and C.-Y.J. Kao,"Numerical Simulations of ArcticStratus Clouds Using a Second OrderTurbulence Closure Model," J. Appl.Meteorol. 1,47(1996).

Smith, W.S., and C.-Y.J. Kao, "Usinga Turbulence Radiative-ConvectiveModel to Study the Cloud/RadiationInteraction with the FIRE Data," Mon.Weather Rev. 8, 1803 (1996).

Zhao, X., and R.P. Turco,"Parameterization ofPhotodissociation Rate forStratospheric Three DimensionalModeling" (submitted to /. Geophys.Res.).

Zhao, X.-R, R.P. Turco, et al.,"Numerical Simulation of theDynamical Response of an ArcticVortex to Aerosol AssociatedChemical Perturbations in the LowerStratosphere," Geophys. Res. Lett. 12,1525 (1996).


Transport Processes in Space Plasmas

Joachim Birn

In this project we combined effortsin space-data analysis with theory andlaboratory and computer simulationsto advance the fundamental under-standing of solar-terrestrial interactionthrough space-plasma processes.

Two-dimensional simulations of themagnetopause have shed further lighton the nature of surface waves andtheir contribution to ion diffusion inthis boundary region. In thesesimulations a curved bow shock, itsassociated foreshock, and a turbulentmagnetosheath are formed as shownin the first figure. These simulationscombine proper accounting for themicrophysics with the provision of aglobal perspective of the boundaryregion.

We have also performed the firsthigh-resolution, full-particle (implicit)simulations of the guide field tearingat the magnetopause, using large ion-to-electron mass ratios. We foundthat, in sharp contrast to previousnonlinear theories, the multimodetearing islands can grow to largeamplitudes, resulting in large trans-port of magnetic flux and mixing ofthe magnetosheath and magneto-spheric plasmas as seen in the secondfigure. We developed a new nonlineartheory of the tearing mode at themagnetopause.

We have further studied theconsequences of the electromagneticproton anisotropy instability in theterrestrial magnetosphere. We usedone-dimensional hybrid computersimulations to examine the velocitydistribution response of both hot(~10-keV) and warm (~10-eV)protons. Results are that the en-hanced fluctuations from this instabil-ity not only preserve the initiallybi-Maxwellian character of a hot-proton distribution, but also drive aninitially nongyrotropic hot distributionrapidly toward the gyrotropiccondition.

1000

100 200

X (c/cop)

300

Bow shock structure in a large-scale,two-dimensional simulation of solarwind-magnetosphere interaction. Thefigure shows the intensity of themagnetic field component By (asindicated by the color bar) in thecoordinate frame x, y. The y-axisunits (c/copj represent the ion inertialscale length.

Publications

Birn, J., "Magnetotail Stability andDynamics: Progress 1991-1993,"Surveys in Geophys. 16, 299 (1995).

Birn, J., and M. Hesse, "Details ofCurrent Disruption and Diversion inSimulations of MagnetotailDynamics," /. Geophys. Res. 101,15345 (1996).

Birn, J., S.P. Gary, and M. Hesse,"Microscale Anisotropy Reductionand Macroscale Dynamics of theMagnetotail," J. Geophys. Res. 100,19211(1995).

Birn, J., M. Hesse, and S.P. Gary,"The Role of Microprocesses inMacroscale Magnetotail Dynamics,"in Cross-Scale Coupling in SpacePlasmas, J.L. Horwitz et al., Eds.(Geophys. Monogr. Ser., AmericanGeophysical Union, Washington, DC,1995), Vol. 93, pp. 275-285.

Birn, J., M. Hesse, and K. Schindler,"MHD Simulations of MagnetotailDynamics," /. Geophys. Res. 101,12939 (1996).

Y (c/<op)

Magnetic island structure in simulations of tearing modes at the magnetopause.Left panel: single mode. Right panel: multimode with island coalescence.


Chow, V.W., and M. Rosenberg,"Electrostatic Ion CyclotronInstability in Dusty Plasmas," Planet.Space Sci. 43, 613(1995).

Chow, V.W., and M. Rosenberg,"Electrostatic Ion CyclotronInstabilities in Negative Ion Plasmas"(submitted to Phys. Plasmas).

Convery, P.D. and S.P. Gary,"Electromagnetic Proton CyclotronRing Instability: Threshold andSaturation" (to be published in J.Geophys. Res.).

Elphic, R.C., "Observations of FluxTransfer Events: A Review," inPhysics of the Magnetopause, P. Songet al., Eds. (American GeophysicalUnion, Washington, DC, 1995), pp.225-233.

Gary, S.P., V.M. Vazquez, and D.Winske, "Electromagnetic ProtonCyclotron Instability: Proton VelocityDistributions," /. Geophys. Res. 101,13327 (1996).

Gary, S.P., L. Yin, and D. Winske,"Electromagnetic Proton CyclotronInstability: Heating of CoolMagnetospheric Helium Ions," Ann.Geophys. 14, 1 (1996).

Gary, S.P., M.F. Thomsen, et al.,"Electromagnetic Proton CyclotronInstability: Interactions withMagnetospheric Protons," /. Geophys.Res. 100, 21961 (1995).

Hesse, M., J. Birn, et al., "MHDSimulations of the Transition ofMagnetic Reconnection from Closedto Open Field Lines," /. Geophys.Res. 101, 10805 (1996).

Hesse, M., D. Winske, et al., "HybridModeling of the Formation of ThinCurrent Sheets in MagnetotailConfigurations," J. Geomagn.Geoelec. 120, 749 (1996).

Karimabadi, H., D. Krauss-Varban,and N. Omidi, "Kinetic Structure ofIntermediate Shocks: Implications forthe Magnetopause," J. Geophys. Res.100, 11957(1995).

Krauss-Varban, D., H. Karimabadi,and N. Omidi, "Kinetic Structure ofRotational Discontinuities: Impli-cations for the Magnetopause," /.Geophys. Res. 100, 11981 (1995).

Kuo, H., C.T. Russell, and G. Le,"Statistical Studies of Flux TransferEvents,"/. Geophys. Res. 100, 3513(1995).

Le, G., C.T. Russell, et al., "ISEEObservations of the Low LatitudeBoundary Layer for NorthwardInterplanetary Magnetic Field:Implications for Cusp Reconnection"(submitted to J. Geophys. Res.).

Lindsay, G.M., J.G. Luhmann, et al.,"CME Characteristics in the InnerHeliosphere: Relationship to CoronaVelocity" (submitted to /. Geophys.Res.).

Maravilla, D., K.R. Flammer, andD.A. Mendis, "On the Injection ofFine Dust from the JovianMagnetosphere," Astrophys. J. 438,968 (1995).

Maravilla, D., K.R. Flammer, andD.A. Mendis, "The Nature of theOrbits of Charged Dust Injected intothe Jovian Magnetosphere during theTidal Break-Up of Comet Shoemaker-Levy 9" (submitted to Astrophys.Space Sci.).

McKean, M.E., N. Omidi, and D.Krauss-Varban, "Wave and IonEvolution Downstream of Quasi-Perpendicular Bow Shocks," J.Geophys. Res. 100, 3427 (1995).

Omidi, N., and D. Winske, "KineticStructure of the Magnetopause asInferred from 1-D HybridSimulations," /. Geophys. Res. 100,11935(1995).

Rosenberg, M., and N.A. Krall,"Modified Two-Stream Instabilities inDusty Space Plasmas," Planet. SpaceSci. 43, 619 (1995).

Rosenberg, M., and N.A. Krall, "LowFrequency Drift Instabilities in aDusty Plasma" (submitted to Phys.Plasmas).

Rosenberg, M., and D.A. Mendis,"UV-Induced Coulomb Crystal-lization in a Dusty Gas," IEEE Trans.Plasma Sci. 23, 177 (1995).

Russell, C.T., "The Structure of theMagnetopause," in Physics of theMagnetopause, P. Song et al., Eds.(American Geophysical Union,Washington, DC, 1995), pp. 81-98.

Russell, C.T., "A Study of FluxTransfer Events at Different Planets,"Adv. Space Res. 16, 4159 (1995).

Winske, D., and N. Omidi, "Diffusionat the Magnetopause: HybridSimulations," J. Geophys. Res. 100,11923(1995).

Winske, D., V.A. Thomas, and N.Omidi, "Diffusion at theMagnetopause: A TheoreticalPerspective," in Physics of theMagnetopause, P. Song et al., Eds.(American Geophysical Union,Washington, DC, 1995), p. 321.

Winske, D., S.P. Gary, et al., "IonHeating in a Dusty Plasma Due to theDust/Ion Acoustic Instability,"Geophys. Res. Lett. 21, 2069 (1995).

Yur, G., H.U. Rahman, J. Birn, et al.,"An Improved Simulation Facility forMagnetospheric Modelling," /.Geophys. Res. 100, 23727 (1995).

Yur, G., H.U. Rahman, J. Birn, et al.,"Magnetotail Structures in aLaboratory Magnetosphere"(submitted to /. Geophys. Res.).


Physical Properties and Mantle Dynamics

Thomas Shankland

Understanding the physicalproperties of minerals and rocksreveals processes in the earth andevents in its history. Because plan-etary interiors are difficult to assess,research methods that combinesophisticated techniques and associ-ated theory are essential for interpret-ing geophysical field measurements interms we need for improving ourunderstanding of Earth's temperature,composition, stress state, history, andhazards. One objective of our projectis to study minerals and rocks usingmaterials science methods; another isto develop new research methods,such as high-pressure techniques,rock physics computational codes,and nuclear-based analyses.

In the past year, we continued torefine our transient optical-gratingapparatus, which we have used todetermine sound velocities in fluidsand water ice at high pressures, and tofine-tune our single-crystal x-raydiffraction apparatus, which can beused to analyze materials at extremelyhigh pressures and temperatures.

In addition, we have designedcomputational tools for forward andinverse modeling of complex stress-strain histories of rocks. Furthermore,by analyzing the ratio of tungsten tothorium in samples of bulk silicaterocks, we determined that tungstendepletion is of the same order asdepletion of the iron and nickel thatform Earth's metallic core. This resultagrees with the hypothesis that Earthformed heterogeneously, that is, withdense materials accreting ahead oflighter ones. And finally, we haveobtained pressure-volume-tempera-ture equation-of-state measurementson single crystals and seismic velocitymeasurements on several denseminerals, which enables us to betterunderstand the composition of Earth'souter 1000 km.

Publications

Abramson, E., J.M. Brown, and J.Zaug, "Elastic Constants of SanCarlos Olivine to 17 GPa" (submittedto /. Geophys. Res.).

Anderson, O. L., "Anharmonicity ofForsterite and the Thermal Pressure ofInsulators" (to be published inGeophys. Res. Lett.).

Blackman, D.K., J.M. Kendall, P.R.Dawson, et al., "Teleseismic Imagingof Subaxial Flow at Mid-OceanRidges: Travel-Time Effects ofAnisotropic Mineral Texture in theMantle" (to be published in Geophys.J. Int.).

Brown, J.M., and LJ. Slutsky,"Thermoelastic Behavior of Olivineunder Upper Mantle Conditions ofPressure and Temperature" (submittedto /. Geophys. Res.).

Chai, M., and J.M. Brown, "Effects ofStatic Non-hydrostatic Stress on the RLines of Ruby Single Crystals" (to bepublished in Geophys. Res. Lett).

Chai, M., and J.M. Brown, "ElasticConstants of a Pyrope-Grossular-Almandine Garnet to 20 GPa"(submitted to Geophys. Res. Lett.).

Chai, M., J.M. Brown, and L.J.Slutsky, "Elastic Constants ofKilbourne Hole Orthopyroxene to12.5 GPa" (submitted to J. Geophys.Res.).

Chai, M., J.M. Brown, and L.J.Slutsky, "Thermal Diffusivity ofMantle Minerals" (to be published inPhys. Chem. Minerals).

Chai, M., J.M. Brown, and Y. Wang,"Yield Strength, Slip Systems andDeformation Induced PhaseTransition of San Carlos Olivine up toTransition Zone Pressure at RoomTemperature" (submitted to US-JapanResearch at High Pressure).

Cyan, H., J.D. Carnes, and O.L.Anderson, "Thermal Properties ofForsterite, including Cv, Calculatedfrom rxfcj. through the Entropy" (to bepublished in J. Phys. Chem. Solids).

Guyer, R.A., and K.R. McCall,"Capillary Condensation, InvasionPercolation, Hysteresis, and DiscreteMemory," Phys. Rev. B 54, 18 (1996).

Guyer, R.A., and K.R. McCall,"Superfluid Avalanches" (submittedto Phys. Rev. Lett.).

Guyer, R.A., K.R. McCall, G.N.Boitnott, et al., "QuantitativeImplementation of Preisach-Mayergoyz space to Find Static andDynamic Elastic Moduli in Rock"(submitted to J. Geophys. Res.).

Hearn, I , G. Humphreys, K. Deuker,et al., "Effect of Anisotropy on theDevelopment of OceanicLithosphere" (submitted to /.Geophys. Res.).

Kadish, A., P.A. Johnson, and B.Zinszner, "Evaluating Hysteresis inEarth Materials Under DynamicResonance" (to be published in J.Geophys. Res.).

Lutterotti, L., S. Matthies, H.R. Wenk,et al., "Combined Texture andStructure Analysis of DeformedLimestone from Time-of-FlightNeutron Diffraction Spectra" (to bepublished in J. Appl. Phys.).

McCall, K.R., and R.A. Guyer, "ANew Theoretical Paradigm toDescribe Hysteresis, DiscreteMemory and Nonlinear Elastic WavePropagation in Rock," NonlinearProcesses in Geophysics 3, 89 (1996).

McCall, K.R., R.A. Guyer, L. Zhu, etal., "Experimental Determination ofDynamic Elastic Properties of Rockfrom Quasistatic Measurements," inRock Mechanics: Tools andTechniques, M. Aubertin, F. Hassani,and H. Mitri, Eds. (Balkema,Rotterdam, the Netherlands, 1996), p.147.


Newsom, H.E., K.W.W. Sims, P.D.Noll Jr., et al., "The Abundance of Win the Bulk Silicate Earth: Constraintson Core Formation," Geochim.Cosmochim. Acta 60, 1155 (1996).

Pearson, A., and H. R. Wenk, "EBSPOrientation Imaging of Quartz in aGranodiorite Mylonite from the SantaRosa Mylonite Zone, SouthernCalifornia" (submitted to Texture andMicrostructure).

Ragan, D.D., D. Schiferl, and D.Clarke, "Silicone Fluid as a PressureMedium in Diamond-Anvil Cells"(submitted to Rev. Sci. lustrum.).

Schiferl, D. and Y. Zhao, High-Pressure/High-Temperature Diamond-Anvil Cell System for Single-CrystalX-Ray Diffraction" (submitted to Rev.Sci. lustrum.).

Shankland, T.J., A.G. Duba, E.A.Mathez, et al., "Increase of ElectricalConductivity with Pressure as anIndicator of Conduction through aSolid Phase in Mid-Crustal Rocks"(to be published in /. Geophys. Res.).

Wang, Y., M. Chai, and J.M. Brown,"Deformation Induced PhaseTransformation in San Carlos Olivineat Room Temperature" (submitted toGeophys. Res. Lett.).

Wenk, H.R., G. Canova, Y. Brechet, etal., "A Deformation-based Model forRecrystallization" (to be published inActa Metall. Mater.).

Zhao, Y, D. Schiferl, and T.J.Shankland, "Thermoelasticity ofMgSiO3 Orthoenstatite," Phys. Chem.Minerals 22,393 (1996).

Zhao, Y, D. Schiferl and J.M. Zaug,"RSCU-SOS: A Rapid IntensitySearching and Centering Routine forSingle Crystal Diffraction Studies atSimultaneous High Pressures andTemperatures," /. Appl. Cryst. 29, 71(1996).

Zhao, Y., R.B. VonDreele, TJ.Shankland, et al., "ThermoelasticEquation of State of JadeiteNaAlSi2O6: An Energy-DispersiveStudy" (to be published in Geophys.Res. Lett.).



Advanced Research Capabilities forNeutron Science and Technology—Neutron Polarizers

Robert Robinson

The purpose of this work is to applythe expertise at both Los Alamos andat the National Institute of Standardsand Technology (NIST) in polarizedgaseous 3He to research the develop-ment of new laser-driven 3Hepolarizers suitable for condensed-matter research at the Manuel LujanJr. Neutron Scattering Center(MLNSC) at Los Alamos. Helium-3polarizers are the technology ofchoice for broad-band applications atwavelengths below 2 A and for large-divergence applications at all neutronwavelengths.

This project involves developing theexperimental design, including thelaser, glass cell, magnetic shieldingand neutronics, then testing the cellboth on the surface profile analysisreflectometer (SPEAR) and on adiffractometer. By the end of theproject, we expect to know enough toimplement this technology on any of

the spectrometers or diffractometersat MLNSC, although such implemen-tation will not be covered by theproject. If successful, our work wouldallow significant improvement incapability in neutron scattering to beimplemented at Los Alamos.

So far, we have purchased all theinstrumentation necessary to polarizea cell and measure its polarization.We now have three 16-W diode laserarrays and are collaborating withNIST, Princeton University, and theTri-University-Meson Facility (BritishColumbia) for cell fabrication andfilling. Together we chose a cellgeometry suitable for condensed-matter applications and assembled allthe components for the neutron-beamexperiment. We requested beam timeon the SPEAR at MLNSC in prepara-tion for testing the polarizer early nextyear.

Competency Development Projects—Nuclear and Particle Physics 223

Biosciences

Solution Structure of thecAMP-Dependent Protein Kinase

//// Trewhella

Understanding the molecular basisfor biochemical regulation is afundamental problem in humanmedicine. Unregulated or uncoordi-nated activities generally lead topathological conditions and, if notcorrected, to uncontrolled prolifera-tion or cell death. In this project, weare addressing this fundamentalquestion by studying the cAMP-dependent protein kinase, which hasserved as the central model formodulation of cell function by proteinphosphorylation, one of the mostimportant mechanisms of cellregulation.

Protein kinase is a dimer of dimers(R2C2), where C and R designate thecatalytic and regulatory subunits,respectively. Free C is fully competentto catalyze the phosphorylation ofproteins. The catalytically inactiveholoenzyme is activated when cAMPbinds to R, which exposes thecatalytic site on C, allowing access toprotein substrates.

The three-dimensional crystalstructures of free C and R have beensolved, providing a basis for modelingthe holoenzyme using scattering data.We have succeeded in cloning andexpressing both C and R and, in thecase of R, have produced the expressed

protein in deuterated form. We havealso demonstrated that we can reconsti-tute a catalytically competent holoen-zyme from the expressed components,and we have measured x-ray scatteringdata from free C and R subunits as wellas reconstituted holoenzyme withdeuterated and nondeuterated R.

We are preparing for a neutroncontrast-variation study on theholoenzyme with deuterated R. Thisexperiment will yield the shapes anddisposition of the R and C compo-nents in the complex, giving the firststructural insights into the nature ofthe interactions between R and C.

Publications

Mitchell, R., G.A. Olah, W. Gu, et al.,"The Solution Structure of cGMP-Dependent Protein Kinase (PKG) andIts Alteration," Biophys. J. 70, 432(1996).

Development of Biosensors and BioprobesBased on Spectroscopic Monitoring ofEnzymes and Other Proteins Encapsulatedin Sol-Gel Glasses

reactions with ligands in the glasses andthe spectroscopy and kinetics of relevantmyoglobin reactions in solution.Techniques were developed for observ-ing the kinetics of reactions at elevatedpressures of gaseous ligands.

William Woodruff

This project sought to explore anddevelop new types of biosensors andbioprobes in biotechnology. Biosensorsdetect and measure analytes using theencapsulated biomolecules, whilebioprobes examine the encapsulatedbiomolecules to elucidate theirphysiological/biochemical functions orstructures. Our goal was to applyadvanced spectroscopic methods tobiosensors and bioprobes whosesensing elements consist of enzymesand other proteins encapsulated inoptically transparent sol-gel glasses.

Our specific objectives were (1) tocharacterize encapsulated biomoleculesand their interactions with a porousglass matrix and monitor the effect ofdifferent processing conditions usingspectroscopy and kinetics, (2) tosimilarly characterize interactions ofthe encapsulated biomolecules withpotential substrates or ligands, and(3) to apply the above information indeveloping sensing elements for use inbiosensors and bioprobes. Major resultsincluded the characterization ofencapsulated myoglobin and its

Publications

Bailey, J. C. James, and W. Woodruff,"Flow-Flash Kinetics of O2 Binding toCytochrome c Oxidase at Elevated[O2]: Observations Using High-Pressure Stopped-Flow for GaseousReactants," Biochem. Biophys. Res.Commun. 220 (3), 1055-60 (1996).

Decatur, S., S. Franzen, G. DePillis, etal., "Trans Effects in Nitric OxideBinding to Myoglobin Cavity MutantH93G," Biochem. 35 (15), 4939^-4(1996).

Competency Development Projects—Biosciences 225

Molecular Characterization ofFlow-Sorted Mammalian Centromeres

L. Scott Cram, Los Alamos National LaboratoryBarbara Hamkalo, University of California, Irvine

To better understand the fundamentalmechanisms underlying such cellularprocesses as the regulation of geneexpression, differential condensation,and chromosome segregation, we areinterested in isolating and identifyingthe proteins from the centromere regionof mammalian chromosomes.

The goal of our project is to employflow cytometry to isolate large quanti-ties of both intact mouse chromosomesand a chromosome fragment derivedfrom centromere regions to biochemi-cally compare the protein compositionof the two fractions. This is a novelapproach to identify proteins preferen-tially associated with centromeres thatcould play a role in centromere higher-order structure and/or function.

Initial chromosome sorts, utilizingbuffers developed by Los Alamosresearchers for genomic cloning,resulted in samples devoid of detectableamounts of protein, although theycontained measurable amounts ofDNA. Based on a series of controlexperiments, we determined thatchromosomal proteins were beingdisplaced from the DNA into thesupernatant before sorting. An exten-sive analysis of each component in thesorting buffers showed that threecomponents—EDTA, EGTA, andmercaptoethanol—were responsible forextracting all but a few chromosomalscaffold proteins. This displacementoccurred despite the fact that byfluorescence microscopy, the chromo-somes appeared to retain their structure.

We hypothesize that spermine andspermidine (two components of thebuffers) exchanged for proteins,resulting in compact chromosomalstructures.

Utilizing a 10-mM MgSO4,10-mMKC1,5-mM HEPES buffer (pH 8), theflow cytometer can sort chromosomeswithout any apparent loss of proteins.Inclusion of the reducing agentdithiothreitol in the sorting bufferimproves the resolution of chromo-somes during sorting without proteinloss. We can reproducibly observe alarge number of polypeptides, inaddition to the histones, by SDS-PAGE(sodium dodecyl sulfate-polyacryla-mide gel electrophoresis) and by silverstaining gels containing proteinsreleased from approximately 200,000chromosomes per lane.

With the results of this studycomplete, we will now characterizethese proteins and extend our methodsto recovering and characterizingproteins from other chromosome typesand regions.

Advanced Biomolecular MaterialsBased on Membrane-Protein/PolymerComplexation

Gregory Smith

The goal of this work has been to(1) develop a fundamentally new classof bioactive molecular films composedof reconstituted and native, self-assembled, membrane proteinscombined with polymers and (2) applysynchrotron-based, small- and wide-angle x-ray scattering to characterizethe structure and phase behavior, theinterlayer and macromolecular forces,and the stability of the protein-shape ofthese new materials. These materialscan be used as biosensors, selectivefilters, and light-to-chemical energyconverters.

We have completed the first series ofhigh-resolution, synchrotron, x-rayscattering studies of the purple mem-brane composed of a two-dimensional

(2-D) self-assembly of the membraneprotein bacteriorhodopsin. At highhumidity, the ordered phase of thishighly complex self-assembly exhibitsscattering characteristics of a 2-D solidwith power-law decay of positionalcorrelations. Two results of the x-rayscattering measurements are (1) thefirst measurements of a protein-latticeelastic rigidity, which is directly relatedto the protein-protein interactions, and(2) an experimental demonstration ofthe limits on the resolution of theprotein structure in 2-D protein crystal-lography (an expanding field becauseof the recent success of techniques forpreparing 2-D protein crystals).

To enhance the structural work, weinitiated a series of neutron

experiments. First we constructed asimple humidity oven with neutron-transparent windows for reflectivitystudies. We prepared thin-film samplesby spinning protein mixtures ontosilicon wafers. To hydrate the films, weplaced each in this sealed oven with areservoir of D2O (heavy water) andmeasured the room-temperature,neutron reflectivity at the High-FluxBeam Reactor at Brookhaven NationalLaboratory. In each case, thereflectivity measurement was consis-tent with a bare silicon surface. Uponoptical examination of the samples, wefound that the multibilayers haddelaminated from the silicon substrate,leaving droplets of sample on thesurface.

While the spinning technique showspromise in preparing the films neces-sary for the reflectometry experiments,these results suggest that the films mustbe deposited on etched silicon, veryclean quartz, or surfaces that have beenaltered with silane to produce a highdegree of hydrophobicity.


Similarity Landscapes: An ImprovedMethod for Scientific Visualization ofInformation from Protein and DNADatabase Searches

Norman Doggett

The focus of this project is to studythe evolution of human and simianimmunodeficiency viruses (HTV). Asthe viral genomes diverge, it is possibleto monitor the ratio of meaningful tosilent changes at the RNA level anddetermine the intensity of the selectionthat is operating on them.

This year we have developed amethod for distinguishing transitionaland transversional changes of these twotypes and find that both types of changeoften show a pattern of intense di-rectional selection that has driven the

separation of closely related viruses,particularly HIV-1. This directionalevolutionary change is concentrated inshort tripeptide motifs called sequons.These sequons are sites of n-glycosylation, and the proteins ofretroviruses have unusually largenumbers of sequons. We have foundthat sequons have evolved more rapidlyin the more virulent HTV-1 than in theless virulent HTV-2, and calculation ofthe relative rates indicates that theyhave evolved three times as rapidlycompared with the rate of substitutions

at the RNA level. We have used ourcapabilities for rapid searches of theentire database in GenBank to examinethe properties of microsatellites,regions of DNA that consist of multiplerepeats of a short (usually 2- to 6-base)sequence, in lower organisms. We havediscovered that microsatellites are farmore prevalent in lower organisms,even prokaryotes, than had previouslybeen realized, that many of thesemicrosatellites occur in reading frames,and that a large fraction of them arepolymorphic. Ten out of ten of the in-frame microsatellites examined in theyeast Saccharomyces cerevisiae werepolymorphic.

Publications

Wills, C, A. Farmer, and G. Myers,"Rapid Sequon Evolution in HIV-1"(to be published in AIDS Res. Hum.Retroviruses).

Formation of Drug-Bearing Vesiclesin Mixed Colloids of Bile Salts andPhosphatidylcholine

Rex Hjelm

We are examining novel methods offorming drug-bearing liposomes.Liposomes have proven to be effectiveas intravenous delivery systems forinsoluble drugs. We are studyingsystems that could potentially formliposomes spontaneously, such asbiological mixed colloids, as a betteralternative to the presently usedmechanical means of liposomeproduction. Because liposomes areformed spontaneously in these systems,the formulations could be stored in dryform and reconstituted by the additionof appropriate buffers, thus reducingthe need for costly equipment andprocedures and improving shelf lifeconsiderably. We need to show theconditions and drugs that do notinterfere with the spontaneous forma-tion of liposomes. The study of thesecolloids also relates to the efficacy oforal formulations, because drug-bile

interactions could be responsible forthe bioavailability of oral drug formula-tions. Therefore, we are also studyingthe particle structure in simulations ofthe intestinal mixture to test whetherthe bile salt/phosphatidylcholinesystems are good models of drug-bileinteractions in the intestine. We arestudying these systems using small-angle neutron scattering, supplementedby light scattering.

We have shown that the inclusion oftherapeutic levels of the steroidal drugs,cholesterol, progesterone, hydrocorti-sone, and deoxycorticosterone, doesnot affect liposome morphology. Theseresults support our theory that mixedcolloids have a valuable role in drugdelivery. Further, we have shown thatparticle morphology in bile salt/phosphatidylcholine particles is thesame as that found in the intestine,allowing us to test models of bile-drug

interaction in improving oral drugefficacy.

Publications

Hjelm, R.P., C. Schteingart, et al.,"Form and Structure of Self-Assembling Particles of Monoolein-Bile Salt Mixtures," /. Phys. Chem. 99,16395 (1995).

Hjelm, R.P., P. Thiyagarajan, C.Schteingart, et al., "Probing Self-Assembly in Biological MixedColloids by SANS, Deuteration, andMolecular Manipulation," in Neutronsin Biology, B. Schoenborn and R.Knott, Eds. (Plenum Press, New York,1996), pp. 175-190.

Hjelm, R.P., P. Thiyagarajan, C.Schteingart, et al., "Structure of MixedMicelles Present in Bile and IntestinalContent Based on Studies of ModelSystems," Falk Symposium on BileAcids in Gastroenterology: Basic andClinical Advances 80,41 (1995).

Mang, J., and R.P. Hjelm, "SANSInvestigation of the Pressure andTemperature-Dependent Structure ofthe Salt Lecithin System" (to bepublished in Mol. Cryst. Liq. Cryst).


Structural Biology of Disease-AssociatedDNA Repeats and Protein-DNAComplexes Involved in the Repair ofDNA Damage

Goutam Gupta

This work focused on examiningthe structural biology of the DNAtriplet repeats associated withgenetically inherited neurologicaldisorders such as fragile X, MyotonicDystrophy, and Huntington's disease.(The accompanying schematicdemonstrates how the number of suchrepeats is related to the expression offragile X syndrome.)

We have used two-dimensionalnuclear magnetic resonance spectros-copy, nondenaturing gel electrophore-sis, and digestion by single-strand-specific PI or SI nuclease to demon-strate that the triplet repeats found inthe genes causing these neurologicaldisorders adopt hairpin structures (i.e.,a single strand of DNA loops back tobase-pair with itself rather than with its

complementary strand) under physi-ological solution conditions. We havealso demonstrated that the same hairpinstructures are formed during replica-tion, leading to slippage, which in turncontributes to the observed lengthpolymorphism.

Furthermore, we have carried outbiochemical assays with humanmethyltransferase that demonstrate thatthe same hairpin structure that causesslippage and length polymorphism isalso an excellent substrate for methyla-tion, and we found that the fragile Xtriplet repeats are more sensitive tomethylation than many other DNAregions, especially when they havebeen expanded. The accompanyingsketch shows a possible mechanism ofexpansion and methylation.

Publications

Chen, X., S.V.S. Mariappan, P. Catasti,et al., "Hairpins Are Formed by theSingle DNA Strands of the Fragile XTriplet Repeats: Structure andBiological Implications," Proc. Natl.Acad. Sci. U.S.A. 92,5199 (1995).

Chen, X., S.V.S. Mariappan, S. Smith,et al., "Hairpin Induced Slippage andMethylation of the Fragile X Repeats"(submitted to /. Biomol. Struct. Dyn.).

Mariappan, S.V.S., X. Chen, X., P.Catasti, et al. "Hairpin and JunctionStructures of Fragile X Triplets,"Proceedings of the Ninth Conversationin Biomolecular Stereodynamics,R.H. Sarma and M.H. Sarma, Eds.(Adenine Press, 1995), pp. 105-19.

Mariappan, S.V.S., X. Chen, X., P.Catasti, et al. "Solution Structure ofthe Individual Strands of the FragileX Repeat," Nucleic Acids Res. 24, 784(1996).

Mariappan, S.V.S., L.A. Silks, P.A.Springer, et al., "Solution Structure ofthe DNA Triplet CAG Associatedwith Huntington's Disease"(submitted to /. Biomol. Struct. Dyn.).

TranscriptionStart

i'MR-I

Controlregion

Normal

Expanded

Methylation

\

Transcription of FMR-1

j/ \ ^ SuppressiunofEMR-l

i _ ;CpG islands

j j Strong methylX^^^^^X binding pratetn

f ~\ Weakmethyi^..^«.«.i v" binding protein

Y methylated CpG

f unmethylated CpG

A schematic representation of the FMR-1 gene. The location of the fragile. X repeat, (GCC)n'(GGC)n> is shown in the 5'untranslated region, although the exact location and the interrelationship of the promoter and the enhancer are not yetknown. The ranges of repeat numbers, n, are shown for normal, transmitting, and affected males.


A sketch of how the presence of atransient and mobile three-wayjunction can cause both expansionand methylation. The intrinsicpreference of hairpin formation by theGCC strand leads to a three-wayjunction with a Watson-Crick anchor.When the GGC strand acts as thetemplate, such a three-way junctionleads to expansion if the GCC hairpinescapes repair. In the GCC hairpin ofthe three-way junction, the Cs areC*C paired, rather than C*G pairedas in the Watson-Crick duplex. One ofthe Csfrom a C'Cpair is moresusceptible to being "flipped out" ofthe duplex and methylated than a Cfrom a C*G pair. The GCC hairpin ata three-way junction is also capableof slipping and sliding, which canmake the C*Gpair in a hairpin "slip"one notch to create a C*C pair.

Hairpin

Substrate

-BB-

TransitionIntermediate

Watson-CrickDuplex

Applications of Optical Trapping toSingle-Molecule DNA Sequencing

Richard Keller

We are investigating whether wecan use optical laser trapping (i.e.,optical tweezers) for single-moleculeDNA sequencing and single-moleculedetection (SMD). Single-moleculeDNA sequencing involves selectingthe fragment to be sequenced,synthesizing the complementarystrand using fluorescently labelednucleotides, attaching DNA fragmentsto host substrates (microspheres)anchored in a flow stream, sequen-tially cleaving the end nucleotide withan exonuclease to release the labelednucleotide into the flow stream, andusing laser-induced fluorescence todetect and identify the dye-taggednucleotides. We are currently using apipette to hold the microspherecontaining DNA in the flow stream.This project involves investigating theapplicability of optical laser trappingas an alternative method of holdingthe microsphere in the flow stream.We can use the radiation trapping

forces associated with a highlyfocused laser beam for this task.

We successfully demonstratedoptical trapping in laminar flowstreams and completely characterizedthe trapping process as a function offluid flow velocity, chamber dimen-sion, trapping depth, incident laserpower, and fluorescence measurementgeometry. In particular, we integratedan optical laser trap with fluorescenceexcitation/emission capability in aflow cytometric geometry so that wecould study microparticle confine-ment and off-axis fluorescencedetection. At the trapping wavelengthof 1064 nm, we simultaneouslytrapped and displaced 2-um-diamfluorescent latex microspheres by upto ±20 um; we did this by scanningthe trapping beam in directionsparallel and perpendicular to the flowstream, while we measured particlefluorescence. With fluorescencesignal-to-noise ratios in excess of

30 dB, we trapped and measuredparticles in flow streams that hadvelocities of up to 12 mm/s. Weshowed that samples can benoninvasively positioned eitherupstream or downstream from thedetection probe volume, a featureintegral to SMD implementation. In astationary fluid, we demonstratedtrapping of 2.8-|jm paramagneticbeads that were coated with lambdaDNA. However, because of significantvariations in the optical and magneticproperties of these substrates, wecould not trap DNA-coated beadsconsistently and reliably in thepresent system.

Publications

Wang, W, Y. Liu, G.J. Sonek, et al.,"Optical Trapping and FluorescenceDetection in Laminar Flow Streams,"Appl. Phys. Lett. 67, 1057 (1995).


Microbial Acquisition of Iron fromIron-Bearing Minerals

Larry Hersman

Iron is a universal nutrient require-ment for all life forms. Although thefourth most-abundant element in thegeosphere, iron is virtually insolubleunder environmental conditions(neutral pH, oxic), where it existsmainly as very insoluble oxides,hydroxides, and oxyhydroxides. Wedo not completely understand howiron is solubilized and made availablefor biological use. The overallobjective of this research was todetermine, in part, some of themechanisms used by microorganismsto acquire iron-form hematite.

In the past we have reported on thedissolution of hematite by microbiallyproduced, iron-binding ligands calledsiderophores. During this past year weinvestigated the role of other meta-bolic products on the dissolution ofhematite. Of particular interest werehigh-performance liquid chromatogra-phy (HPLC) compounds that elutedfrom a C-4 column before thesiderophores. These pre-siderophore

compounds, or peaks, were of interestbecause with increased incubationtime (of the microorganisms in thepresence of hematite), these peaksbecame larger. In other words,exposure to hematite appeared toinduce the production of thesemetabolic products.

We performed a series of assays todetermine the role of HPLC com-pounds in hematite dissolution.Specifically we investigated thepotential of these HPLC compoundsto reduce iron or to serve as electron-transport molecules (i.e., ligandbridges) between a reductant and iron.Results of these reduction assayssuggest that these compounds arecapable of serving as ligand bridgesbetween a reductant nicotinamideadenine dinucleotide (NADH) andiron. Although strictly an aerobicspecies, this particular species ofPseudomonas appears to use a specialform of reductive dissolution to

acquire iron from hematite. To ourknowledge, such a process is uniqueand previously unreported in theliterature.

Publications

Forsythe, J., P. Maurice, et al.,"Imaging the Results ofBiogeochemical Reactions withTapping Mode Atomic" (to bepublished in Goldsmidt Geochem.Conf. Proc).

Hersman, L., M. Harrington, M.Martinez, et al., "Dissolution ofHematite by an Aerobic PseudomonasSp." (Gordon Conf.: EnvironmentalSciences, June 23-29, New Hampton,N.H., 1996).

Hersman, L., P. Maurice, and G.Sposito, "Iron Acquisition fromHydrous Fe(III) Oxides by an AerobicPseudomonas Sp" Chem. Geol. 132,25-31 (1996).

Maurice, P., L. Hersman, and G.Sposito, "Application of Atomic-Force Microscopy to Studies ofOrganic and Microbial Interactions ofHydrous Fe(IH)-Oxides," Chem.Geol. 132, 3 3 ^ 3 (1996).

The Biology of Novel Animal Genes: MouseAPEX Gene Knockout

Mark Macinnes

Apurinic/apyrimidinic (AP)endonuclease (APE), sometimesknown as APEX, is involved in a keystep in the repair of spontaneous andinduced AP sites in DNA, in which aninformation-containing base is lost ordamaged, essentially breaking therungs of a cell's DNA ladder. APEremoves the damaged part of theladder so that another repair enzymecan rebuild it correctly. Efficient

repair of AP sites is essential forpreventing such mutations frombecoming stably incorporated into thecellular genome, which can cause thecell to die or become cancerous. Lossor modulation of repair enzymes suchas APE may elevate the spontaneousmutation rate in cells and may lead toa substantial increase in the incidenceof cancer.

Despite extensive biochemicalanalysis, the biological significance ofthe multiple enzymatic functions ofAPE in vivo has not been determined.The goals of this project are toconduct preliminary genetic, biologi-cal, and cellular characterizations ofmice containing a nonfunctionalversion of the APE gene—micewhose APE genes have effectivelybeen "knocked out."

Using gene targeting strategies, wehave generated mouse embryonicstem (ES) cells that are heterozygousfor a deletion mutation in the APEgene (that is, they contain one normal

230 Los Alamos FY1996 LDR.D Progress Report

and one nonfunctional APE gene). Wehave subsequently produced wholeanimals, derived directly from theheterozygous ES cells, containing thisAPE mutation. These animals areovertly normal and do not display anyadverse effects of the mutant APEallele. However, by inbreeding thesemice, we have determined thatanimals which are geneticallyhomozygous for the APE nullmutation (designated APE-/-) dieearly in gestation.

We have shown, through geneticand histological analyses of earlystage embryos (days 3.5 to 11.5 of a20-day mouse gestation period), thatloss of the APE gene product does notaffect blastocyst formation or implant-ation. However, at or around day 7.5,during a period of substantial cellulardifferentiation and expansion, APE-/-embryos begin to fail in normaldevelopment. These embryos displaya variety of abnormalities and do notprogress further than day 7.5 of

development, although embryoremnants have been identified at day9.5 of gestation. APE-/- embryos werenot found later than this period, andpreliminary evidence suggests that thedevelopmental failure in these animalsinduces apoptosis, or programmedcell death (essentially cell suicide),which results in complete embryonicdeath between 7.5 and 9.5 days ofgestation. These results underscorethe essential functional significance ofthis DNA repair gene during normalembryonic development.

Competency Development in AntibodyProduction for Cancer Cell Biology

Min S. Park

Investigating the roles that proteinsplay in complex biological processesrequires the use of antibodies againstspecific cellular proteins. Theobjective of this project is to developthe technical capabilities, includingthe use of recombinant technology,for producing high-quality antibodiesthat can be available for research oncancer development.

Our work includes both conven-tional and recombinant antibody-producing technology. The con-ventional method involves purifyingcellular proteins, or antigens, andinjecting them into an animal, whichin turn produces antibodies to theantigen. Recombinant techniquesinvolve isolating the genes that codefor the desired antigen or antibodyand inserting the genes into anexpression vector. Recombinanttechnology enables us to make largequantities of high-quality antibodies.Controlled expression of an antibodygene that is specific to tumor antigenprovides another novel approach forimmunocancer therapy.

In the past year we continued toproduce antigens and antibodiescritical to identifying and monitoringthe expression of crucial proteinsinvolved in cell-cycle checkpoints, theregulation of cell division, and therate-limiting steps of DNA repair.Specifically, we produced three moreantigens (total now is eight over theentire project period), two moreantibodies (total now is five over theentire project period), using conven-tional approaches. We also produced alibrary of antibody genes that encoderecombinant antibodies.

Publications

Knauf, J.A., S.H. Pendergrass, B.L.Marrone, et al., "Multiple NuclearLocalization Signals in XPGNuclease," Mutat. Res. 363, 67-75(1996).

Park, M.S., J.A. Knauf, S.H.Pendergrass, et al., " Ultraviolet-Induced Movement of the HumanDNA Repair Protein, Xerodermapigmentosum Type G, in theNucleus," Proc. Natl. Acad. Sci. USA93, 8368-8373 (1996).

Park, M.S., D. Ludwig, et al.,"Physical Interaction between HumanRAD52 and RPA Is Required forHomologous Recombination inMammalian Cells," /. Biol. Chem.271, 18996-19000 (1996).

Shen, Z., K.G. Cloud, et al., "SpecificInteractions between the HumanRAD51 and RAD52 Proteins," /.Biol. Chem. 271,148-152 (1996).

Competency Development Projects—Biosciences 23 I

Covariation of Mutations: AComputational Approach forDetermination of Function andStructure from Sequence

Alan Lapedes, Los Alamos National LaboratoryMelissa Cline, University of California, Santa CruzDavid Haussler, University of California, Santa Cruz

One of the foremost problems inmolecular biology is understandingprotein folding—what processestransform proteins from simple linearsequences to elaborate structures ofhelices, sheets, and turns. Manyresearchers use Newtonian-mechan-ics-based molecular dynamics toconvert amino acid sequences intothree-dimensional forms, but thisapproach is cumbersome and is not asaccurate as desired. In this project, wetake a different approach in our studyof inverse protein folding. Inversefolding approaches attempt to matchan amino acid sequence to a library ofknown structures. "Inverse," therefore,refers to the process of working"backward," using many knownstructures to determine the foldingendpoints of a new sequence. (Incontrast, most conventional ap-proaches start with amino acidsequences and little, if any, referenceto known structures.) We expect ourwork on inverse protein folding tobring to light enough new knowledgeon the relationship between structureand sequence to facilitate greatprogress on better understandingprotein folding in general.

hi the past year, we expanded thelinear Hidden Markov Model soft-ware, a probabilistic pattern recogni-tion program originally designed forspeech recognition, into a functioningprotein structure predictor. To test thesoftware, we built a model library thatcontains models for approximately1000 protein families, and we usedthis library to predict the structure ofmost of the proteins in one family. In

two cases, as part of the CASP-2structure prediction contest, wepredicted the folding of a sequencebefore its structure was determined,and in both cases, our predictionswere experimentally verified.

We have also enhanced our toolsuite to include a graphical,RASMOL-based alignment viewerand scoring options so we canaccommodate different model lengths.Upcoming features include a weight-ing scheme that builds on phyloge-netic relationships and emphasizes thealignment columns most critical to thestructure or function of a protein.

We have also continued to developa neural net method for modeling betasheet interactions. Based on a pro-tein's amino acid sequence, as well asother physical properties includingchain separation and beta strandmembership, we can estimate thelikelihood that two beta strands willbe in contact. We plan to incorporatethis beta sheet modeling capability

into our structure prediction softwareduring the next year.

Finally, we have continued ourwork on neural-net-based scoringfunctions to quantify the matchesbetween sequence and structure ininverse folding investigations byincreasing the spatial resolution andaccuracy of our models.

Publications

Barrett, C , R. Hughey, and K.Karplus, "Scoring Hidden MarkovModels" (to be published inCABIOS).

Grate, L., R. Hughey, K. Karplus, etal., "Tutorial: Stochastic ModelingTechniques: Understanding andUsing" (Third International Con-ference on Intelligent Systems forMolecular Biology, St. Louis, Mo.,June 12-15,1996).

Hughey, R., and A. Krogh, "HiddenMarkov Models for SequenceAnalysis," CABIOS 12 (2), 95-107(1996).


Structure, Dynamics, and Functionof Biomolecules

Nobel Prize winners) have givenpresentations at this series of discus-sions.

Hans Frauenfelder

Our project is aimed at enhancingLos Alamos' core competency inexperimental techniques, theory, high-performance computing, and model-ing. Our main focus is on simulatingand understanding biomolecularstructure, dynamics, and function. Inparticular, we are developing scatter-ing techniques to study the structuresof biomolecular complexes insolution.

One of our primary goals has beento increase—by a factor of 10—theintensity of the existing low-Qneutron diffractometer (LQD) at theManuel Lujan Jr. Neutron ScatteringCenter at Los Alamos. This increasewould result in a dramatic improve-ment in its application to structuralbiology studies.

We used Monte Carlo modelingmethods to design and test a numberof upgrades to the LQD that wouldincrease the flux of neutrons on ourbiological samples (see accompanyingfigure). Specifically, we designed thefollowing:• a five-hole multiaperture collima-

tor, which allows a sample to "see"a larger area of the neutron source(moderator) and, hence, to capturemore total neutrons;

Single or 5-Hole Multi-Aperture Coliimation

• the To chopper, which minimizesunwanted background; and

• the variable detector position,which allows for better optimiza-tion of resolution and neutron fluxfor individual experiments.

We will implement and test theseupgrades in the next project year.

We have also designed an LQD fora next-generation long-pulse spalla-tion source. In the area of structuralbiology applications, we have usedneutron scattering to complete workon a receptor/ligand complex as wellas a protein/DNA complex importantin DNA damage repair.

To strengthen interactions betweentheory and experiment and betweenthe biological and physical sciences,we have communicated our work andgoals at regular meetings of research-ers from all interested Laboratoryorganizations. In addition, we areconducting a distinguished lectureseries on Issues in Modern Biologyand are using the forum to discuss thedirections of the field and, in particu-lar, our work. In total, 17 distin-guished lecturers (7 of whom were

Publications

Olah, G.A., and R.P. Hjelm, "Analysisand Simulation of a Small-AngleNeutron Scattering Instrument on a1 MW Long Pulse Spallation Source"(Workshop on Neutron ScatteringOpportunities at Long PulseSpallation Sources, HMI Berlin,Germany, June 24-27, 1996).

Olah, G.A., R.P. Hjelm, and P.A.Seeger, "Small-Angle ScatteringInstruments on a 1 MW Long PulseSpallation Source" (ICANS-XIII,13th Meeting of the InternationalCollaboration on Advanced NeutronSources, 5232 Villigen PSI,Switzerland, October 11-14, 1995).

Olah, G.A., and J. Trewhella, "TheStructure of the Muscle ProteinComplex 4Ca2+*Troponin C'TroponinI: A Monte Carlo Modeling Analysisof Small-Angle Neutron ScatteringData" in Neutrons in Biology, B.Schoenborn and R. Knott, Eds.(Plenum Press, New York, 1997).

Movable 2-D Detector(64 x 64 cm2)

Liquid 2HModerator

To Chopper

Detector Rail

Gravity Focuser Schematic showing the designedupgrades to the low-Q neutron diffractometer

(LQD) at the Manuel Lujan Jr. Neutron ScatteringCenter. To date, structural biology applications using LQD

have been limited by the neutron flux on this instrument. Thedesigned improvements will result in a dramatic increase in its

application to structural biology studies.


Advanced NMRTechnology forBioscience and Biotechnology

Jill Trewhella

Nuclear magnetic resonance(NMR) technologies play criticalroles in bioscience and biotechnologyin both imaging and structure deter-mination. The major issues limitingthe application of NMR to manyimportant problems are the inherentlow sensitivity of the NMR experi-ment and the spectral resolutionrequired to study biological mol-ecules. This project addresses both ofthese issues by working on thedevelopment of (1) magnetic reso-nance force microscopy with thelong-term goal of imaging individualbiological molecules and (2) high-magnetic-field NMR with isotopelabeling to overcome current limita-tions on the size of biomoleculeswhose structures can be determinedusing multidimensional NMR.

In the past year we have developeda novel radio-frequency coil designfor NMR force microscopy applica-tions that are pushing the limits ofsensitivity in magnetic resonancedetection for imaging, and we havedemonstrated subsurface spatial

imaging capabilities. We have alsomade advances in the miniaturizationof two critical magnetic resonanceforce microscope components: themicromechanical resonator and themicromagnetic tip. In the area ofhigh-field NMR and isotope labeling,studies have been completed on themuscle protein troponin C complexedwith segments of its regulatory targettroponin I. This complex is respon-sible for the regulation of musclecontraction and is too large for studyusing conventional NMR approaches.As is the case for the vast majority ofbiomolecular complexes, the complexhas limited solubility, resulting ineven more demands on the NMRexperiment. Using state-of-the-art,high-field NMR instrumentation atPacific Northwest National Labora-tory, we have measured NMR datafrom complexes of isotopicallylabeled troponin C complexed withkey sequence segments of troponin I.We have successfully interpretedthese data in terms of structuralinformation on the troponin Icomponent.

Publications

Hammel, P.C., Z. Zhang, et al., "Sub-Surface Imaging with the MagneticResonance Force Microscope," / . LowTemp. Phys. 101, 59 (1995).

Hernandez, G., S.E. Rokop, P.A.Springer, et al., "NMR Studies ofTroponin 1(96-115): Free in Solutionand Bound to Troponin C,"Biophysics J. 70, 384 (1996).

Hoyt, D.W., J. Zhao, et al.,"Comparison of Small-Angle X-rayScattering and Gradient EncodedNMR Diffusion Experiments forAssaying the Aggregation State ofProteins in Solution" (submitted to J.Magn. Reson.).

Trewhella, J., G. Hernandez, S.E.Rokop, et al., "High-Field NMR &Stable Isotopes for Studying Ca2+-Binding Proteins and TheirComplexes," 27th Annual Southeast.Magn. Reson. Conf. Proc. 1,4 (1995).

Zhang, Z., PC. Hammel, and G.J.Moore, "Application of a Novel RFCoil Design to the MagneticResonance Force Microscope," Rev.Sci. lustrum. 67, 3307 (1996).

Nonlinear Analysis of Biological Sequences

David Torney

The purpose of this project is todevelop effective new computationaland mathematical techniques andapply them to analysis of the structureof biological sequences. We arecurrently focusing on the detectionand characterization of functionaldomains. We are also modelingmultigenic human diseases with thegoal of designing more effectiveexperiments that will discover thegenetic components of these diseases.

We have established the usefulnessof parities of subsequences forclassifying binary sequences. To usethis approach for DNA sequences, wefirst converted these subsequences tobinary sequences. We determined theaverage parities for subsequences of54-base-long coding sequences, forwhich the frame and strand wereknown, and for noncoding sequences.We found that the subsequences withthe smallest number of letters were

most discriminatory, and use of thesesubsequences yielded a correctclassification rate of 0.82 for bothtypes of sequences—the best successrate yet reported for such shortsequences. We have begun to developsophisticated statistical methods forcombining the parities from manysubsequences, since we employedseveral thousand, as a classificationtechnique. We explored cumulants,which yield an expected parity for asubsequence based upon its subse-quences, and thus enable the winnow-ing of "key" subsequences. Thesesimplest cumulants revealed novel


statistical features of coding andnoncoding sequences.

Our characterization of protein-sequence motifs, conserved throughevolution, was made much moreeffective by employing maximumlikelihood techniques. By averagingover possible evolutionary histories,we derived accurate profiles foramino acid usage. Furthermore, thisapproach allows the quantification ofcoevolution of pairs of amino acidresidues. Based on preliminarymodels, we found many morestatistically significant pairs ofcoevolving residues than are yieldedby other approaches and havecorroborated these interactionsthrough studies of molecules withknown structure.

Publications

Bruno, W.J., "Modeling ResidueUsage in Aligned Protein Sequencesvia Maximum Likelihood," Mol. Biol.Evol. 10, 1368-1374 (1996).

Huynen, M.A., "Exploring PhenotypeSpace through Neutral Evolution," /.Mol. Evol. 43, 165 (1996).

Huynen, M.A., et al., "Assessing theReliability of RNA Folding UsingStatistical Mechanics," J. Mol. Biol.43 (1996).

Huynen, M.A., et al., "Base PairProbabilities in a Complete HIV-1Genome," /. Comp. Biol. 3, 253(1996).

Huynen, M.A., et al., "Rate of Killingof HIV-Infected T-Cells and DiseaseProgression," Science 272,1962(1996).

Huynen, M.A., et al., "SmoothnessWithin Ruggedness: The Role ofNeutrality in Adaptation," Proc. Nat.Acad. Set U.S.A. 93, 397 (1996).

Torney, D.C., "Group Tests forComplex Biological Systems"(submitted to Nature).

Indigenous Bacteria as Hosts forProteins for Bioremediation

James Brainard

Successful application of engi-neered proteins for in situ bio-remediation requires efficientmechanisms to introduce and distrib-ute the enhanced biological activity atthe contaminated site. An attractivestrategy to accomplish this process isthrough the use of bacteria native tothe site as hosts for the engineeredproteins. The goal of this project is togain sufficient understanding of thecoupled biological, chemical, andphysical processes occurring atcontaminated sites in order torationally design and test this strategy.Although the project is primarilyfocused on a specific enzyme(Haloalkane dehalogenase) andspecific Pseudomonas isolates, theresults will have broad applicability to

many contaminants, unmodified andengineered proteins and genes, andmicrobial isolates.

During the first year of this project,we have made excellent progress inseveral areas: (1) isolating microor-ganisms into which to place genes forengineered Haloalkane dehalo-genases, (2) developing the toolsrequired to detect, track and measuregenes in the environment, (3) devel-oping methods to introduce andexpress broad-host-range plasmidscontaining engineered genes, and(4) using numerical simulations toidentify which parameters are mostimportant in limiting bioremediationeffectiveness.

We have selected three sites that arecontaminated with 1,2-dicholoethane

(DCA) from which to isolate indig-enous hosts for engineered and wildtype alkane dehalogenase genes. Fromone of these sites, we have begunenrichment cultures and direct platingto isolate Type I fluorescent Pseudomo-nas and other indigenous speciescapable of degrading DCA andintermediates of DCA degradation.

Publications

Herrick, J.B., and J.R. Brainard,"Design of PCR Primers for theAmplification of Unknown,Homologous Catabolic GeneSequences from EnvironmentalSamples," Abstracts of the 96thAnnual Meeting of the AmericanSociety for Microbiology N, 110(1996).

Herrick, J.B., K.S. Harris, and J.R.Brainard, "Rapid Fingerprinting ofBacteria Using ERIC PCR Primers"(to be published in PCR: EssentialTechniques, J. Burke, Ed., Bios. Sci.Publ., Oxford, England).


Landscapes and Dynamics of Proteins

Hans Frauenfelder

The goal of the project is tounderstand the energy and affinitylandscapes in physics and biology.Complex systems, such as biopoly-mers, glasses, and large martensiticcrystals, have a highly degenerateground state and can assume a largenumber of different structures. Thesecharacteristics are typically describedby a rugged energy landscape. Thedynamics within such a landscape arefar more intricate than dynamics insimple systems, displaying hysteresisand sometimes showing the multi-scale character of an avalanche or aquake. Our goal implies some newdirections in the study of nonlinearsystems and closer interactions withtheorists, computer experts, andexperimentalists at Los AlamosNational Laboratory and in a numberof universities.

The project objective for the firstyear, which we met, was to learnmore about the field from visitors,seminars, and workshops. Manyvrsitors were invited to give talks bothat the Center for Nonlinear Studies(CNLS) and also in the colloquiumseries "Issues in Modern Biology."The 16th CNLS Annual Conferencewas called "Landscapes." Theconference included reports onexperimental, theoretical, andmodeling studies in glasses, spinglasses, biopolymers, hierarchicalmaterials, neural networks, andevolution, and it attracted the bestresearchers in this field. The confer-ence was reported in Nature.

In addition to the more formaldiscussions with visitors and at theconference and workshops, manydiscussions on theoretical andexperimental aspects were held atCNLS. Partially as a result of theseinteractions, we proposed a new core-competency development thrust areafor the Laboratory on structuralbiology, which involves collaborationamong four divisions and is nowactive as an integrated structuralbiology resource.

Publications

Frauenfelder, H., "The Complexity ofProteins," in Physics of BiologicalSystems—from Molecules to Species,H. Flyvbjerg, J. Hertz, et al., Eds.(Springer-Verlag, Berlin, 1997),pp. 29-60.

Frauenfelder, H., "Komplexitat in derbelebten Materie," SchriftenreiheErnst-Abbe Kolloquium Jena 9, 1-26(1995).

Frauenfelder, H., "Proteins—AChallenging Many-Body Problem" (tobe published in Philos. Mag.),

Frauenfelder, H., "Proteins asParadigms of Complex Systems" inRoentgen Centennial, E. Umbach, Ed.(World Scientific, Singapore, inpress).

Frauenfelder, H., and P.G. Wolynes,"Picturing the Working Protein," inTheoretical and ComputationalGenome Research, S. Suhai, Ed.(Plenum Press, New York, in press).

Frauenfelder, H., et al, "Proteins andthe Physics of Complexity," in Non-linear Excitations in Biomolecules,M. Peyrard, Ed. (Springer-Verlag,Berlin, 1995), p. 177.

Johnson, J.B., D.C. Lamb, H.Frauenfelder, et al., "Ligand Bindingto Heme Proteins VI. Interconversionof Taxonomic Substates In Carbon-monoxymyoglobin," Biophys. J., 711563-1573 (1996).


Engineering Haloalkane Dehalogenasefor Bioremediation

James Brainard

Although bioremediation is poten-tially one of the most cost-effectiveenvironmental cleanup tools, presentbioremediation practices have difficultyachieving effective destruction of somecontaminants, notably halogenatedhydrocarbons. Many microorganismscontain halocarbon degrading enzymes,but these enzymes are poor catalystsrelative to other enzymes. Enzymes thatwork on zenobiotic halogenatedcontaminants suffer from poor affinityfor the contaminant and slow turnoverrates even when the contaminant isbound, and sometimes generate toxicintermediates. The goal of this projectis to develop the tools and understand-ing required to engineer enzymes withenhanced properties for bioremediationof contaminants. To do this we design,construct, express, and test enzymesbased on naturally occurring enzymesthat degrade halocarbons.

These modified proteins haveenhanced capabilities for degradingspecific halogenated alkanes and maybe optimized for in situ bioreme-diation strategies and waste streamtreatment. Although our efforts arefocused on engineering halocarbon-degrading enzymes, the results haveapplication to other contaminants, inparticular, other recalcitrant organicsand both toxic and radioactive metals.

This year we have made excellentprogress in (1) developing themolecular biology tools to allowrational and directed-evolutionapproaches to enzyme engineering;(2) developing the microbiological,analytical, and spectroscopic tools toscreen, select, and characterizeimproved enzymes; (3) theoreticalmodeling of the chemical reactions,solvent interactions, and protein

dynamics of dehalogenating enzymes;(4) developing and validating experi-mental models for understanding theeffects of heme environment onenzyme dehalogenation functions;and (5) using cryocrystallography totrap reaction intermediates of cyto-chrome P450 and characterize theirstructure.

Publications

Oprea, T.I., G. Hummer, and A.E.Garcia, "Identification of a FunctionalWater Channel in Cytochrome P450Enzymes" (to be published in Proc.Natl. Acad. Sci. U.S.A.).

Travis, B.J., and N.D. Rosenberg,"Modeling in situ Bioremediation ofTCE at Savannah River" (submitted toEnviron. Sci. Technol).


• % * *Program Development Projects

Program Development (PD) projects support R&D alignedwith future programmatic opportunities at the Laboratory asguided by the Laboratory's strategic planning process. PDprojects are selected by the Laboratory program directors toexplore and develop technologies needed for emerging mis-sion objectives in nuclear weapons, nuclear materials andstockpile management, nonproliferation and internationalsecurity, conventional defense, environmental management,industrial partnerships, and energy. This year, PD projectsaccounted for 24% of the LDRD budget and 21 % of allprojects, and they supported research in all nine technicaldisciplines.

Examples of subjects investigated by PD projects include theeffects of aging on nuclear materials, helium-3 targets fortritium production in fission systems, global nuclear materialmonitoring, sensors for detecting chemical and biologicalwarfare agents, advanced oxidation technologies for chemicaldemilitarization, advanced nuclear fuel processing and radio-nuclide separations, integrated approaches to advanced ma-chining, improved atmospheric transport in complex terrain,and subsurface directed-energy methods for groundwatertreatment.

Materials ScienceFundamental and Applied Studies ofHelium Ingrowth in Plutonium

Michael Stevens

The overall objective of this projectis to begin development of new toolsand techniques for characterizing theeffect of radiolytic aging on the prop-erties of weapons-grade plutonium.To accomplish our goal, we must de-sign new techniques for directly mea-suring helium transport in agedmaterial; develop ion-beam tech-niques for artificially aging plutoniumthrough combined helium/heavy-ionimplantation as well as develop meso-scopic microstructure simulations topredict helium/point defect energeticsand segregation tendencies; conductab initio, total-energy calculations todevelop a better understanding aboutthe way in which group IIIB elementsstabilize the delta phase; and developspall codes and techniques for mea-suring dynamic properties of materi-als under shock conditions by usingthe laser-driven miniflyer technique.

The thermal effusion work for mea-suring helium transport has success-fully progressed this year. We now

have a functional system in place formeasuring, with high sensitivity, he-lium release from small plutoniumcoupons. Experiments will begin thiscoming year on coupons secured fromthe Laboratory's Pit Surveillance Pro-gram. In the area of "artificial" aginginduced by ion-beam implantation,this year we succeeded in using radia-tion damage codes to simulate alpha-decay damage in plutonium. Weselected and synthesized a gold-silveralloy simulant to begin the ion-beamimplantation studies. Helium implan-tation has been successful, but we en-countered problems with heavy-ionimplantation because, in this case,surface sputtering occurred instead ofimplantation.

Mesoscopic structure modeling ef-forts resulted in calculated energiesfor a variety of defects in delta pluto-nium, such as certain orientation grainboundaries, faults, and vacancy andinterstitial-point defects. Further workshowed that certain clusters of five tosix vacancies may be energetically

more stable than free vacancies, pro-viding incipient traps for the diffusionof helium. Total-energy calculationshave indicated that Pu3Ga compoundsmay be the ground-state preferredphase in this system, which suggeststhat fine-scale precipitation of thisphase over time may be possible inaged materials. This year, we havealso performed calculations to deter-mine local relaxations around a gal-lium atom in delta-phase plutonium,and next year we will refine these cal-culations. Moreover, we have com-pleted measurements of chargedensities and potentials for the Pu3Gaphase. To predict spall in planar(layered) microstructures, we havedeveloped a one-dimensional, finite-difference code that will allow us tostudy model alloys and, eventually,plutonium. Finally, this year we havedesigned a special chamber for as-sessing plutonium films under shockconditions.

Publications

Becker, J.D., J.M. Wills, et al.,"Electronic Structure of PuCompounds with Group IIIB Metals:Two Regimes of Behavior," Phys. Rev.B 54 (24), 17265-17268 (1996).

Cost-Effective Development ofThin Films for Flat-Panel Displays

Joysree Aubrey

We have used an integratedconcept-to-prototype process formodeling and fabricating thin filmsfor applications in flat-panel displays.The approach for developing "thinfilms by design" has proved to be in-valuable in materials research. Theproject included personnel from threedivisions at Los Alamos: AppliedTheoretical Physics, MaterialsScience and Technology, and

Theoretical. These personnel workedtogether to develop thin-film semicon-ductors and conductors with superiorqualities.

We deposited films using a state-of-the-art, flow-through ion gun andcharacterized the samples with anextensive array of diagnostic equip-ment. Theoretical support consisted ofsimulation of the performance of theion gun, development of adaptive pro-

cess-control methods, and materialsand device modeling for the films andtheir applications.

We reached a number of significantmilestones during the course of theproject: (1) deposition of orientedfilms of zinc oxide, indium tin oxide,and silicon; (2) characterization of thefilms; (3) mesh set-up and simulationof the ion-gun performance using thetwo-and-one-half dimensional codeMERLIN; (4) evaluation of depositionparameters for use in the developmentof adaptive-control techniques; and(5) initiation of materials and devicemodeling and development of a de-vice-modeling code, FEDPIX.

Program Development—Materials Science 241

Development of High Magnetic Fieldsfor Energy Research

Joe D. Thompson

The goal of this project is to dem-onstrate the feasibility of building a100-T magnet for high-magnetic-fieldresearch. If successful, this projectwould enable us to meet a longer-termgoal of establishing the technologicaland scientific bases upon whichDOE/Office of Basic Energy Scienceswill form a strategic alliance with theNational Science Foundation to builda revolutionary 100-T, nondestructivemagnet. This magnet will providehigh magnetic fields for furtheringenergy-related science and technologyimportant to the DOE mission. Inpreparation for the 100-T magnet, wehave been developing diagnostics andhave begun some high-field materialsresearch measurements at 50 T.

This year we have designed (1) acapacitor bank for a 50-T insert and(2) the signal sequencing patterns tocontrol a 50-T outer magnet of a com-bined 100-T magnet. We have alsomade extensive electrical simulationsfor a variety of 100-T magnet designs.

In parallel with the magnet work,we have used molecular-beam epi-taxial growth of GaAs to fabricatelarge-area, very thin (100-nm thick)cantilevers that can be used forultrasensitive micromagnetometryfrom room temperature to 30 mK inarbitrarily high magnetic fields. Wehave also discovered what appears tobe quantum oscillations in the magne-toresistance of "nonmagnetic"YbInCu4 and evidence for substan-

tially different field dependencies ofthe charge and spin gaps in Kondoinsulators at fields to 50 T. In addi-tion, we have taken high-field thermo-dynamic and transport measurementsof Ceg7La03Pd3 to test theoretical pre-dictions for Kondo-hole behavior.

Publications

Boenig, H.J., LJ. Campbell, K.R.Eberl, et al., "Design Status of the US100-Tesla Non-Destructive MagnetSystem" (submitted to 7th Inter-national Conference on MegagaussMagnetic Fields).

Harris, J.G.E., D.D. Awschalom, etal., "Fabrication and Characterizationof 100 mm Thick GaAs Cantilevers"(submitted to Rev. Sci. Instrum.).

Lawrence, J.M., T. Graf, M.F.Hundley, et al., "Kondo-HoleBehavior in Ce 97La 03Pd3," Phys. Rev.5 53,12559(1996).'

Advancing the Technology Base forHigh-Temperature Membranes

Robert Dye

This project tackles major issuesbarring the implementation of high-temperature membranes to separa-tions and catalysis that might have alarge impact for the DOE and forindustry. Advances made in thisproject have moved the state-of-the-art toward high-temperature mem-brane viability and improved overallenergy efficiency.

We have accomplished modelingand data analysis of permeation ratesthrough composite metal membranes.The model accounts not only for thewell-understood Sievert's law regimebut also for the less-understood"surface-effects" regime. In the

Sievert's law regime, permeation rateis controlled by the diffusion ofatomic hydrogen through the bulkphase. In the surface-effects regime,permeation rate is controlled by oneor more of several mechanisms fortransporting gaseous hydrogen, asatomic hydrogen, into the bulk phase.We have been very encouraged bytests of the multimetal membranes ina reformed fuel mixture. Without opti-mization, the membranes produced ahydrogen flux of 17 standard cmVcm2

at 286°C, with a partial pressure of0.5 atm of hydrogen across the mem-brane. After performing a 27-h life-time test using the gas mixture of

74% hydrogen, 25% carbon dioxide,and 1% carbon monoxide, we foundthat the membrane still performedwell.

We have applied for a patent on thecomposite metal membrane and havesuccessfully licensed this metal mem-brane technology to industry.

Publications

Peachey, N.M., R.C. Dye, P.D. Ries,et al., "Pulsed Laser Deposition ofZeolitic Thin Films: Novel Structuresfor Molecular Recognition," J. PorousMater. 2, 331 (1996).

Peachey, N.M., R.C. Snow, and R.C.Dye, "Composite PdVTa MetalMembranes for HydrogenSeparation," J. Membrane Sci. I l l ,123 (1996).


Giant Magnetoresistance Materials forMagnetic Recording Technology

Robert Hejfner

This work focused on a class oftransition-metal-oxide (TMO) materi-als (LaMnO3 doped with calcium,barium, or strontium); these materialsexhibit an insulator-to-metal transi-tion near their ferromagnetic phase-transition temperatures. Thistransition from a paramagnetic insula-tor to a ferromagnetic metal yields avery large magnetoresistance. Thus,these materials may have importantuses as magnetic sensors in a varietyof applications, ranging from auto-mobiles to read heads for magneticstorage. Practical use of these mate-rials depends upon learning to controlthe synthesis parameters (principallytemperature, pressure, and composi-tion) to achieve a specific carrier con-centration and/or mobility. A secondchallenge is the high magnetic fields(greater than 1 T) currently requiredto achieve a large change in resis-tance. We conceived of two novelapproaches to this field-sensitivityproblem; these approaches involvedeveloping multilayers of the TMO

materials. We are also exploring theuse of epitaxial strain to change thetransport properties in thin-filmmultilayers.

Using thermogravimetric analysison materials synthesized at differentoxygen pressures and temperatures,we have developed a phase diagramfor ideal growth conditions. We havestudied the effects of lattice substrateepitaxy by depositing (La,Ca)MnO3

materials on several lattice-matchedisostructural substrates: lanthanumaluminate, strontium titanate, andneodymium gallate. X-ray diffractionstudies of these films indicate thatlarge amounts of coherent interfacestrain can be produced. We havesuccessfully adapted a semiconductorstrain-layer approach and have fabri-cated multilayer superlattices bydepositing alternating layers ofLao 67Cao 33MnO3

a nd strontium titan-ate perovskites. These stacks exhibitmultiple x-ray satellite reflections thatare indicative of a highly orderedsuperlattice structure with a period of

250 A and d-spacing corresponding toa highly strained material.

Publications

Hawley, M.E., CD. Adams, P.N.Arendt, et al, "CMR Films' Structureas a Function of Growth andProcessing" (to be published in /.Crystal Growth).

Hawley, M.E., X.D. Wu, P.N. Arendt,et al., "Microstructural Study of CMRFilms as a Function of Growth,Temperature, as Deposited andAnnealed," Mat. Res. Soc. Symp.Proc. 401, 531(1996).

Hundley, M.F., J.J. Neumeier, R.H.Heffner, et al., "Transport andMagnetism Correlations in Thin-FilmFerromagnetic Oxides," /. Appl. Phys.79, 4535 (1996).

Louca, D., EX. Brosha, and T. Egami,"Observation of Polaronic LatticeDistortion in Laj xSrxMnO3 by PulsedNeutron Diffraction" (submitted toPhys. Rev. Lett).

Louca, D., W. Dmowski, T. Egami, etal., "Evidence of Lattice Polarons inLax xSrxMnO3 by Pulsed NeutronDiffraction" (submitted to Phys. Rev.Lett.).

Characterizing Mechanical Effects ofAging Damage

Philip M. Howe

Our goal is to use molecular-levelspectroscopic data and theoreticalinformation from atomistic calcula-tions in the parameterization of amicromechanical model designed toassess aging effects on the propertiesof particle-filled composites. Theresults will be used in the develop-ment of a micromechanics-basedconstitutive model for such materials.The main emphasis is on Plastic-Bonded Explosive 9501 (PBX-9501)and its constituents, high-meltingexplosive (HMX) and Estane binder.

During the reporting period, weestablished shipping arrangementsand experimental standard operatingprocedures to allow studies of explo-sive materials and made initial spec-troscopic measurements for fresh andaged samples of both the pure binderand PBX-9501. Spectra for the freshand aged samples differed, indicatingchanges due to aging, and we con-cluded that spatially resolved data willbe required for an improved under-standing of the aging behavior. Wepurchased software for atomistic

studies of polymeric systems and per-formed preliminary calculations of theelastic constants for the amorphouscomponent of Estane; calculations forpure HMX are also underway. We willextend these studies to provide esti-mates of the adhesion strength betweenthe HMX and binder.

We computed micromechanics-based stress-strain curves as a func-tion of "binder" concentration for amodel composite system that crudelymimics an explosive formulation. Wepredicted reasonable behavior and aremaking refinements. Finally, we in-corporated advances in a constitutivetheory for particle-filled compositesinto a computer model and predictedmuch of the known characteristicbehavior.


High-Magnetic-FieldCollaborations

Research

Johndale Solem

The purpose of this project is toexploit the research potential of thepulsed magnetic fields that might bepossible with PEGASUS andexplosive-driven flux-compressiongenerator sources to explore com-pletely novel ideas in condensed-matter physics and chemistry. Theproject links the Laboratory to theacademic and industrial communitiesby involving those communities inour research programs, whichenhances the technical vitality of theLaboratory, benefits the broaderscientific community, and creates abroader constituency for science-based stockpile stewardship.

The initiative brought togetherAmerican, Russian, Australian, andJapanese researchers from around theworld. We started with a campaign ofexperiments (Dirac series) using high-explosive-driven flux-compressiongenerators. The Dirac series includedfour -150-T experiments using a lin-ear explosive-driven flux-compressiongenerator designed at Los Alamos andthree -1000-T experiments using acylindrically imploding, explosive-driven flux-compression generatordesigned at Arzamas-16.

Our experiments explored quantumlimit phenomena in two- and three-dimensional organic metals, semi-metals, transition metals, and electrongases; chemical-bond manipulation;and nonlinear Faraday rotation. Theseexperiments have been described indetail by other documents on theLDRD program. We are still analyz-ing much of the data.

Publications

Brooks, 1, et al., "Quest for theQuantum Limit in Three DimensionalMetals" (Seventh InternationalConference on Megagauss MagneticField Generation and Related Topics,Sarov [Arzamas-16], Russia, August5-10, 1996).

Clark, R., et al., "The ExtremeQuantum Limit of Dilute 3D ElectronSystems: Experimental Probe ofTransport in Semiconductors andSemimetals to 500 Tesla" (SeventhInternational Conference on Mega-gauss Magnetic Field Generation andRelated Topics, Sarov [Arzamas-16],Russia, August 5-10, 1996).

Sheppard, M., et al., "Multi-Megagauss Field Generation UsingCapacitor Banks" (Seventh Inter-national Conference on MegagaussMagnetic Field Generation andRelated Topics, Sarov [Arzamas-16],Russia, August 5-10, 1996).

Solem, J., "Basic Science at theExtreme States of Matter," Bull. Am.Phys. Soc. 41, 929 (1996).

Solem, J., "Overview andIntroduction to Dirac" (Seventh Inter-national Conference on MegagaussMagnetic Field Generation andRelated Topics, Sarov [Arzamas-16],Russia, August 5-10, 1996).

Solem, J., and M. Sheppard,"Experimental Quantum Chemistry atUltrahigh Magnetic Fields: SomeOpportunities" (submitted to Int. J.Quantum Chem.).

Solem, J., and M. Sheppard,"Quantum Chemistry at UltrahighMagnetic Fields" (Workshop onProperties of Molecules in StrongMagnetic Fields, University ofFlorida, Gainesville, Fla., October24-27, 1996).

Solem, J., et al., "DIRAC: aCampaign of Experiments to StudyPhysics and Chemistry at UltrahighMagnetic Fields" (Seventh Inter-national Conference on MegagaussMagnetic Field Generation andRelated Topics, Sarov [Arzamas-16],Russia, August 5-10, 1996).

Ceramic/Polymer, Functionally GradedMaterial (FGM), Lightweight Armor System

John Petrovic

Significant improvement in bodyarmor has been listed as one of theDepartment of Defense's (DoD's) "TopTen Tough Problems." Requiredadvances in lightweight body armor tomeet the DoD's needs can no longer bemet through incremental advances inpost-Vietnam-era armor systems basedon Kevlar-type fabric vests and willrequire the incorporation of lightweightceramics. The approach that providesthe most opportunity for improvementin performance is to employ FGMs inwhich the surface intercepting the bul-let is made of a very hard ceramic thatcan break up the bullet. This ceramic isthen graded into an energy-absorbingpolymer or metal to absorb energy andbullet fragments.

The critical step for developingceramic/polymer FGM armor is devel-oping a graded-porosity, boron carbide(B4C) ceramic that can then be liquid-infiltrated with a polymer material or ametal such as aluminum. We havefocused our efforts on developing agraded-porosity, B4C ceramic. Becausewe have chosen the B4C/A1 system as abenchmark to gauge the performanceof the B4C/polymer armor, our second-ary focus has been on establishing pro-cedures for infiltrating aluminum intothe B4C ceramic. We have establishedthat gradients in carbon-induced B4Cdensification and gradients in particle-size distribution are the two most prom-ising approaches for developing FGMarmor.


NewAnion-Exchange Polymers forImproved Separations in Nuclear andIndustrial Applications

Gordon Jarvinen

The objective of this work is toimprove our understanding of how thestructure of a new class of anion-exchange polymers controls the bind-ing of anionic actinide complexesfrom solution. This kind of fundamen-tal data is needed to develop practicalseparation systems that will reducethe cost of actinide-processing opera-tions within the DOE complex. Thesesystems will separate actinides fromboth process and waste solutions. Inaddition, anion exchange is widelyused in industry, and these new mate-rials may have much broader applica-tions in areas such as water treatment,pollution-control technology, andpurification of chemical products.

We designed and synthesizedseveral new series of bifunctional,anion-exchange polymers, and wetested their ability to remove threeactinides—plutonium(IV),americium(III), and uranium(VI)—from nitric acid. The polymerscontain a pyridinium site derivedfrom the host poly(4-vinylpyridine)and a second cationic site (eithertrimethylammonium, pyridinium, ortrimethylphosphonium) attachedthrough a chain of two to six methylenegroups. The new polymers removedplutonium 4-10 times more efficientlythan can the best commercial materialspresently available. The sorption kinet-ics and distribution coefficients forplutonium(iV) were generally bestwhen the two cationic sites were

separated by a five-methylene spacer.The order of affinity for plutoniumfrom 1-M nitric acid was pyridinium >trimethylphosphonium > trimethyl-ammonium. Replacing the centralmethylene group in a five-unit spacerwith an ether oxygen further en-hanced the sorption of plutonium.Compared with other separationtechniques, our new polymers offerthe prospect of removing plutoniummore effectively from many nitrateprocess and waste solutions whiledecreasing the volume of secondarywaste generated.

Publications

Marsh, S.F., G.D. Jarvinen, and R.A.Bartsch, "New Bifunctional AnionExchange Resins for Nuclear WasteTreatment" (to be published in React.Polym.).



Detection of UndergroundStructures and Tunnels

Joseph Mack

The primary objective of thisproject is to assess electromagnetic(EM) and gravitational methods fordetecting underground structures. Wealso considered methods for detectingland mines and improving under-ground communications.

Using an improved means of elec-tromagnetic scattering, we obtainedexcellent agreement between ourtheoretical predictions and experimen-tal results when sensing a grounded#14-gauge wire buried 10 m. We alsowere able to detect the presence of an~30-m-deep, 7.3-m-diameter,conductor-carrying tunnel. We per-formed these experiments at SandiaNational Laboratories, New Mexico,

and the Nevada Test Site (NTS),respectively.

It is believed that undergroundcommunications using low-frequencyEM waves coupled to any longitudi-nal conductor propagate as a surfaceguided wave with no cutoff frequency.We successfully demonstrated thishypothesis at ~300-m depths at theLyner Facility at the NTS.

We have used resonant microstrip-patch antennas to detect and imageantipersonnel mine mockups in bothdry and wet soil, and we also estab-lished clutter sensitivities.

In addition, emphasizing quasi-analytic techniques, we developed acomputer code to model EM detection

of deeply buried tunnels. We havesuccessfully modeled critical aspectsof tunnel detection.

Through another buried-wire ex-periment in which we used low-tem-perature superconducting quantuminterference devices (SQUIDs), wedetermined that more design andhardware development is necessaryfor successful gravity-gradiometrydetection of underground structures.High-temperature SQUIDs show newpromise as this new technology be-comes interlaced with noise-controlelectronics.

We assessed other tunnel-detectiontechnologies in conjunction with theexperiments performed by other insti-tutions. Of note was detecting tunnelpresence with a magnetometermounted on the unmanned, airborneCYPHER vehicle, which was flownover the Yucca Mountain tunnel(7.3-m diameter, -30 m below thesurface).

Active Noise and Vibration Controlfor Vehicular Applications

Paul Lewis

In this project we planned todevelop a benchtop demonstration ofa semiactive suspension system basedon real-time nonlinear control of amagneto-rheological (MR) shockabsorber. We embarked on this projectbecause of the Laboratory's interac-tions with General Motors (GM)Delphi in the area of active noise andvibration control and because of theDefense Advanced Research ProjectAgency's (DARPA's) interest in MRtechnology for military applications.

We carried out background researchand a literature search on semiactivesuspensions and controllable shockabsorbers, and we developed andadapted numerical models and simula-tions of alternative nonlinear controlalgorithms for use with an MR shock.(In an MR shock, friction is controlledrather than dampened.) We specifiedand assembled the control system con-sisting of a 486-based personal com-puter (PC) that has a special-purposedigital signal-processing board(TMS320C31) to handle the control

loop. We designed a mechanicaldemonstration fixture to hold thedamper/spring assembly, and wespecified and procured a custom-made MR shock from MR Tech-nologies. (MR shocks are still adeveloping technology and are notreadily available.) To characterize theperformance of the MR shock, wetook measurements, which were satis-factory. However, the device leakedMR fluid and had to be repaired byMR Technologies; it subsequentlybegan to leak again.

Because interests at both GM andDARPA changed, we did not imple-ment the benchtop demonstrationdesign. However, we have docu-mented the design, simulation, andmeasurements in the project's finalreport.

Program Development—Engineering and Base Technologies 247

Study of Possible Detector Geometriesfor Detection of Radioactivity in MovingVehicles

Robbie York

The security plans for many DOEfacilities require monitoring of pedes-trians and vehicles to control themovement of special nuclear material(SNM). Vehicle monitors often pro-vide the outermost barrier against thetheft of SNM. The standard SNMvehicle monitors consist of two pillarsthat the vehicles drive through. Thetwo pillars contain both large plastic

scintillators and decision-makingelectronics. These automatic monitorsdetermine the presence of SNM bycomparing the gamma-ray and neu-tron intensities of the occupiedvehicle monitor to the backgroundradiation level of the unoccupiedmonitor.

The sensitivity of these monitorsvaries for different types of vehicles

Overhead detector

Vertical pillars

Lower detector

A sketch showing the configuration of the four-pillar detector that we tested.

and depends on the size, spacing, andnumber of detectors in the monitor.For a given detector configuration andvehicle, two of the dominant sensitiv-ity factors are the occupancy back-ground suppression and the shieldingprovided by the components of thevehicle. The goal of this project is toevaluate different detector configura-tions as a means of improving the sen-sitivity of these instruments to achievea vehicle monitor that is economical,practical to install, and sensitiveenough to be an effective barrier toillegal transportation of SNM.

The most severe shielding locationsin a vehicle are between the doorposts, above the engine block, andbelow the engine. By placing detec-tors above and below the vehicle (seefigure), we minimized variations inthe sensitivity caused by gamma-rayshielding. With the source betweenthe two door posts, the sensitivity ofthe side detectors was very poor, butthe sensitivity of the lower detectorwas high. However, with the sourceabove the engine block, the situationwas reversed. We found that addingthe overhead detector did not increasethe worst-case sensitivity. Summingthe count rates of the side and lowerdetectors decreased the minimumdetectable mass by a factor of 3.However, when we summed all threedetector groups, the sensitivityimproved by a factor of 5, while thenuisance-alarm rate remainedconstant.

Environmentally Conscious CoalCombustion: Development of ProcessMonitors and Improved Numerical Models

Donald D. Hickmott

Many inhabitants on the Navajoreservation use free subbituminouscoal in home-scale coal stoves fortheir home heating. Coal is used forsimilar small-scale combustion inmany developing nations, particularlyChina. The principal coal-combustion

need on the Navajo reservation, andpotentially in the developing world, isfor a high-efficiency, smokeless stovethat burns diverse feedstocks (i.e.,coal, wood, biomass). In this projectwe evaluated the contaminants pro-duced during coal combustion in aNavajo home-scale coal stove and the

possible engineered controls on thosecontaminants.

Unlike utility-boiler combustion,home-coal combustion emits contami-nants cyclically. Only low levels of sul-fur dioxide and other contaminants areproduced, but they are potentially highenough to exceed Environmental Pro-tection Agency standards for ambientair because of winter atmosphericinversions that occur in the neighboringtown of Shiprock, New Mexico. Weevaluated several engineering controlson home-coal-stove emissions, such assmall-scale scrubber systems and im-proved-efficiency stoves.


Establishing the Operational Durabilityof Polymer Light-Emitting Diodes

Ian Campbell

Recently discovered polymer light-emitting diodes (PLEDs) have thepotential to revolutionize display tech-nology for defense and civilian appli-cations. Displays are expected to bemajor drivers in both the computerand the high-definition televisionindustries in the near future. At LosAlamos we are collaborating withHewlett-Packard Company, UniaxCorporation, the University of Texasat Dallas, and the University ofCalifornia at Santa Barbara to developPLED technology.

Our ongoing collaborative researchprogram has made it clear that PLEDs

have all the device attributes (effi-ciency, emission colors, and operatingvoltage) required to build a successfuldisplay technology. We initiated thisproject to establish meaningful deviceoperating lifetimes and to understandPLED failure mechanisms with thegoal of controlling device reliabilityand ultimately producing a viablecommercial product.

We established a PLED lifetimetesting facility to measure the changein PLED light output and drive volt-age at constant current bias as a func-tion of time for different current biaslevels, operating temperatures, and

device (polymer) thicknesses. Wehave identified that the dominant fail-ure mechanism of the PLEDs isdelamination of the electron-injectingmetal contact, which occurs at lessthan 1000 hours of operation. Thisyear we developed a new electro-absorption technique to measure theelectric field distribution inside thePLEDs. We used this technique toassess relative device reliability.

Publications

Campbell, I.H., M. Joswick, et al.,"Measuring Internal Electric Fields inOrganic Electronic Devices UsingElectroabsorption Spectroscopy" (tobe published in Polym. Adv. Technol).

Smith, D.L., S.M. Kogan, et al.,"Acousto-Optic Modulation of III-VSemiconductor Quantum Wells,"Phys. Rev. B 53, 1421 (1996).

Helium-3 Targets for Tritium Productionin Fission Systems

Brian James

Neutron irradiation of 3He is apotentially attractive method for pro-ducing tritium. Should this method beimplemented, experimental, defense,and power reactors could provide acontingency supply of tritium. How-ever, the safety of putting 3He in areactor has always been questioned—the loss of 3He would result inincreased reactivity. Moreover, con-tainment of the tritium produced is aconcern under both normal operatingand accident conditions. The objectiveof our project is to develop innovativedesigns of reactor targets for produc-ing tritium by neutron irradiation of3He. The new targets should overcome

the technical problems associatedwith tritium production.

We have invented a target thatreduces or eliminates the additionalreactivity resulting from a loss of 3He;this target makes the use of 3He inreactors a viable option for supple-mental or contingency production oftritium. In the inherently safe target(1ST), 3He normally "cloaks" an addi-tional strong solid absorber such asboron-10. If the 3He gas should leakout of the target canister, the reactorflux will immediately "see" the solidabsorber. The target canister can bedesigned so that the reactivity shift ona loss of 3He is negligible or negative.

The special target design is an engi-neered, passive safety feature.

Our new concept for a reactor targetwas successfully tested in the solutionhigh-energy burst assembly at LosAlamos. Targets of the type wedesigned could be used for supple-mental or contingency tritium pro-duction in existing DOE reactors—the advanced test reactor (ATR) atthe Idaho National EngineeringLaboratory and the Fast Flux TestFacility (FFTF) at the Hanford Site—or in commercial light-water reactors.ISTs could also be used in flowing3He systems at FFTF and ATR withon-line tritium extraction that allowscontinuous removal of tritium from3He and thus lessens containmentproblems. Such use would greatly re-duce the inventory of tritium at risk,and it would significantly reduce per-meation of tritium into the reactorcoolant. Finally, it would also sim-plify shipment of tritium for use atSavannah River.


Explosives Detector Using the OpticalSignature of Deflagrating ExplosiveParticipates

Herbert 0. Funsten

Because of the stickiness of explo-sives, surfaces coming in contact withan explosive will become contami-nated with explosive particulates.These particulates, which will exist inpossibly large amounts on the explo-sive packaging and environs, providean important avenue for detecting thepresence of explosives.

In the past year, we developed aunique technique for detecting explo-sives residue. This technique detectsthe rapid burn of explosives, whichhave a higher oxygen content and amore rapid breakup of molecules incomparison with nonexplosives. Thedetection apparatus consists of (1) asample surface, (2) a heat source thatinitiates deflagration, (3) a photomul-tiplier tube that detects the optical sig-nature resulting from deflagration,and (4) a signal analyzer. Our tests ofthe explosives detector show that thelight output from the burning residueof explosives is rapid and intense,which contrasts with the emberlikeburn of nonexplosives.

The accompanying figure showspulse signatures from 5-ug gunpow-der particulates (used in 45% of bombsand devices used or confiscated in theUnited States), engine oil, and nonex-plosive particulates such as paper and

household dust. The optical signaturefrom the gunpowder is short and in-tense, whereas the signatures from theengine oil and nonexplosives are dimand long. Since the pulse magnitudeand width are anticorrelated, the ratioof the magnitude to the width enablesa simple but extremely sensitive tech-nique for differentiating explosivesfrom nonexplosives. Advantages ofthis detection technology includefewer false-alarm rates, faster sampleanalysis, less costly instrumentation,and higher sensitivity.

IO-4

Gunpowder

Engine OilNonexplosives(Paper, vacuumed

paniculate)

io-3 io-2 10° 101lO"1

Time (s)

A comparison of the optical output from explosive and nonexplosive materials.

Directed-Light Fabrication—A LaserMetal-Deposition Process for Fabricationof Near-Net-Shape Components

Gary Lewis

Directed-Light Fabrication (DLF)is a direct metal-deposition processdeveloped at Los Alamos NationalLaboratory and is a revolution inmanufacturing technology. The DLFprocess is the first rapid-prototyping,free-form fabrication process thatdeposits metals directly to near netshape. It is a material-independentprocess capable of processing any

powder material that can be melted.Our studies proved feasibility withany metal that can be made intopowder form and with intermetalliccompounds.

Our assembly work on a five-axisDLF machine in this project was anextension of earlier efforts that hadbeen limited to the three-axis DLFmanufacture. The transition to the

five-axis capability allows true three-dimensional replication of metal com-ponents as designed on a computer;by contrast, the three-axis machineis capable of only two and one-halfdimensions.

During the year we succeeded inassembling and testing the five-axissystem, including assembly and testof a support structure and powder-feed apparatus. The system has fourpowder feeders that can be run indi-vidually or simultaneously to providematerials to the focal zone of thelaser, where they are fused into thedesired component. This accomplish-ment is a significant advance incapability.


Modeling and Assessment of Concreteand the Energy Infrastructure

George Guthrie

Concrete is an essential componentof our energy infrastructure. It is theprimary material used by the energyand transportation sectors (for ex-ample, in roads, bridges, runways,dams, reactor containment vessels,and radioactive- and metal-waste-disposal). The strength and durabilityof concrete, which are the propertiesthat determine its effectiveness in anyof these applications, result fromchemical and structural changes thatoccur during the minutes to years thatfollow the pouring of a particular con-crete structure. These chemical andstructural changes are controlled by avariety of geochemical and mineral-ogical processes that also occur insome geological environments.

The experimental and modelingcapabilities that we developed forgeological systems such as YuccaMountain are useful in our work toimprove the design of next-generationconcrete. Our first goal is to under-stand the geochemical processes thatlead to the alkali-silica reaction(ASR), which is one of the mainimpediments to durable concreteworldwide. ASR is an interactionbetween alkalis in the fluid and somesilica-rich components of the aggre-gate. It results in the formation of agel that causes the concrete to frac-ture, greatly reducing the concrete'sstrength and longevity.

As part of our scoping activities, weproduced an inexpensive and environ-mentally friendly set of stains that candetect deleterious reaction productsassociated with ASR. This method isin contrast to the one currently usedby highway departments, which isbased on uranyl acetate. The uranylacetate method produces uranium-contaminated wastes, exposes person-nel unnecessarily to radioactivity, isdifficult to use, and may result inambiguous information about thenature of ASR in a particular con-crete. We also obtained promisingresults when we used nonlinearresonance ultrasound spectroscopyto evaluate fractures in concrete.

We are developing this work inconjunction with the Alliance forTransportation Research, which re-cently assembled a national expertpanel that conducted a successfulindependent, external review of ourefforts.

Global Nuclear Material Monitoring

Jo Ann Howell

To facilitate the development of thenuclear material monitoring system ofthe future, we are working to design adetailed plan for advanced integratedfacility monitoring. We will identifythe necessary components, the appro-priate demonstration facility, and theenabling technologies.

We identified the following majorcomponents: material-tracking sensorsystems, personnel-tracking sensorsystems, information managementsystems, measurement systems to per-form assay, analysis tools to processthe collected data, and software to tieall of the above functions togetherinto one system.

We have identified several neces-sary technologies. Some of those thatpresently exist include interface build-ing, visualization, authentication,

pattern recognition, radiation sensordesign, portal monitor sensor design,digital video production, and facilitysimulation. Some of the technologiesthat we still need to develop includeanomaly detection for particular safe-guards applications; integration ofdatabases with analysis systems,alarm systems, and displays; anddesign and implementation of smartsensors, data-mining tools, and recon-ciliation tools.

We have initiated a publicationseries about Los Alamos globalnuclear-material-monitoring projects.The first document to be produced inthe series will be about monitoring atthe Japanese facility, Monju. We haveidentified simulation as an area that isnot often exploited in facility monitor-ing systems. Facility simulations can

be run in parallel with actual facilityoperations to improve the capabilityfor detecting departures from standardoperating conditions. We alsoenhanced the computerized LocalArea Network Material AccountingSystem (LANMAS) to incorporateaccess control and authorization.

Publications

Howell, J.A., "Analysis of Facility-Monitoring Data" (to be published inNucl. Mater. Manage.).

Howell, J.A., H.O. Menlove, P.E.Argo, et al., "Global Nuclear MaterialMonitoring with NDA and C/S Datathrough International FacilityMonitoring" (to be published in Nucl.Mater. Manage.).

Proceedings of The FacilityMonitoring Workshop, J.A. Howell,Ed., Los Alamos, N. Mex., September19-21, 1995, Los Alamos NationalLaboratory document LA-CP-95-251.


Frequency-Resolved Optical Gating:A Diagnostic for the Characterizationof Optoelectronic Materials and Devices

Antoinette Taylor

Frequency-resolved optical gating(FROG) is an ultrafast diagnostictechnique that measures the full elec-tric field, both instantaneous ampli-tude and phase, of an arbitraryultrashort pulse. Because FROG is ageneral, broad-band optical diagnos-tic, it can be used in research areas forwhich characterizing the full electricfield of an optical pulse would pro-vide critical insight into physicalprocesses. One area in which FROGcould have an enormous impact is inunderstanding the coherent interactionbetween optical pulses and optoelec-tronic materials and devices. Theobjective of this research is to addressissues relevant to high-speed opto-electronic materials and devices usingFROG.

We have demonstrated FROG as atechnique to determine basic proper-ties of optical materials such asdispersion, nonlinear refraction, two-photon absorption, and cross-phasemodulation by measuring the phasechange of the optical pulse withFROG after the pulse traverses thematerial. The emphasis of thisresearch is to determine the types andaccuracy of measurements possiblewith FROG. We have completed athorough set of measurements of thenonlinear index, «2> in a variety ofoptical materials using FROG. Theaccompanying three figures exhibittypical intensity and phase dataderived from the FROG spectrogramsused to determine n2. We have demon-strated that FROG accurately mea-sures n2 in optical materials, with theerror dominated by the uncertainty inthe fluence measurement. We are cur-rently completing a second set ofmeasurements on cross-phase modu-lation in optical materials.

-200 -150 -100 -50 0 50

Time (fs)

1.0

0.8 -

0.6 -

0.4 -

0.2 -

-

- •

-

<Kt)

/ '

/ ;

A \

N>- :0.0-200 -150 -100 -50 0 50

Time (fs)

Publications

Taylor, A.J., G. Rodriguez, and T.S.Clement, "Determination of the n2

through Direct Measurement of theOptical Phase," Opt. Lett. 21, 1812(1996).

Normalized intensity andphase for a pulse with nosample in the beam. Thepulse width is 130 fs. Thephase (§) varies almostlinearly with time overthe pulse and hencerepresents a nearlytransform-limited pulse.

Normalized intensity andphase of the pulse after ittraverses 0.95 cm of fusedsilica (Corning 7940),with apeak intensity of5.2 x 1010 W/cm2. Thephase follows the intensityenvelope, indicating thepresence of significantself-phase modulation dueto the n2 interaction in thesample.

100 150 200

100 150 200

0.0 -

-0.2 -

-0.4 -

-0.6 -

-0.8 -

-1.0

- iCt)

- A ;

-200 -150 -100 -50 0 50

Time (fs)

100 150 200

Phase change—A^(t)—is plotted for this data along with a fit (solid line) thatinvolves simply scaling the measured normalized temporal intensity profile to fitA(f>(t). (To obtain A(])(t), the calculated value for linear dispersion in the sampleis added to the phase data with no sample present before subtracting the phasesmeasured with and without the sample in the beam.) This fit yields a constantthat is proportional to A(|)(t)/I(t) and from which n2 can be determined. This setof data yields n2 = 2.45 x 10~16 cm2/W for fused silica at 804 nm.


Neutron-Based, Land-MineDetection System Development

Thomas McDonald

The goal of this project was toexamine the feasibility of developinga buried land-mine detection systemby detecting and analyzing promptgamma-rays induced by neutron inter-rogation. This is a mature concept;however, it has not been successfullyapplied to the buried-mine detectionproblem because of lack of both asuitable neutron source and a detec-tion system having a sufficiently highsignal-to-noise ratio. Most studiesindicate that a source strength in therange of 109-10n n/s would be neces-sary to achieve a reliable detectioncapability requiring interrogationtimes of only a few seconds.

We considered two neutron sourcesthat have the potential of neutronfluxes in the neighborhood of10u n/s: the inertial electrostatic con-finement source (see schematic

diagram below) and the intense ion-beam source (see schematic diagramon p. 26). The advantage of thesesources is that they can be turned offwhen not in use and can be used overa wide range of operating modes fromsteady state to pulsed. We alsoreviewed alternative detection tech-niques and carried out preliminarymeasurements using mock high-explosive material.

We found that the primary advan-tage of the neutron-based detectionapproach for nonmetallic mines is thatthe approach is a powerful discrimina-tor. Other approaches, such asground-penetrating radar and infrareddetection, can detect buried objects;however, these objects may or maynot be mines. The neutron-basedapproach, on the other hand, detectsexplosives and differentiates between

inert objects and explosive-containingmines. Our approach of using a con-trolled, high-flux neutron sourceincreases the speed of detection andallows a longer standoff distance. Avehicle is still needed to transport thesystem, and we project that costs willbe relatively high compared withcosts of metal-detection techniquescurrently in use. We believe that theneutron-based approach can be usedmost effectively in conjunction withother approaches in a suite of comple-mentary detection sensors.

Publications

Davis, H.A., G.E. Remnev, et al.,"Intense Ion Beam Treatment ofMaterials," Bull. Mater. Res. Soc. 21(8), 58 (1996).

Davis, H.A., J.C. Olson, W.A. Reass,et al., "Progress Toward a Micro-second Duration, Repetitive, IntenseIon Beam for Active SpectroscopicMeasurements on ITER," Rev. Sci.lustrum. 68, 332 (1996).

14 cmK2 (Emitter * 2 ,

Cathode)

X62 (ExtractorGrid *2)

Shell (Grounded)

15 cm

Schematic of an inertial electrostatic neutron sourcedesign for supplying 10n n/s, pulsed or steady. Thedesign is a series of spherical, concentric grids andan outer shell approximately 30 cm in diameter. Weestimate the power requirements to be approximately20 kW.

G1: (Outer Grid)

600 V

G2(Intermediate

Grid)

XG1 (ExtractorGrid *1)

K1 (Emi t ter* ! ,Cathode)

G3 (Central Cathode)-50 KV, 300 ma


Development of the Transient-ReactorAnalysis Code (TRAC) for Real-TimeApplications

G. Niederauer

Traditionally, nuclear-plant trainingsimulators have employed simplethermal-hydraulics codes because ofthe demands to run in real time andwith limited computing power. Therehas always been a desire to increasethe flexibility of such training systemsand to increase the fidelity of modelsin the simulators. Although TRAC isthe most advanced code for suchapplications, many issues need to beaddressed to take such a complexcode from a batch engineering envi-ronment to real-time environments.

The object of this project was toinvestigate the feasibility of usingTRAC in a simulator.

We have worked extensively withGSE Systems, Inc. to write an infor-mal discussion paper on the real-timeapplications of TRAC. Together weoutlined technical issues relating totaking a batch code into real time anda staged approach for developingwhat we would call TRAC-RT, start-ing with a proof of concept. LosAlamos provided the expertise on

TRAC, while GSE provided theexpertise on real-time systems. Dis-cussions then expanded to (1) real-time software design techniques tointegrate TRAC into a real-time simu-lator and (2) ways to modify engi-neering plant models for use in asimulator.

We also worked on the so-calledRobinson plant model, modified it forsimulator use, and ran several tran-sients cases to characterize TRAC'sperformance in real time. We identi-fied areas where run-time could beimproved and explored means formodifying TRAC to achieve suchimprovement. We investigated inter-faces between TRAC and a real-timesystem, including data structures,graphical user interfaces, and real-time executive control.

Rapid Prototyping of HazardousMaterials Using the Directed-LightFabrication Process

Gary Lewis

In the past, fabricating componentsfrom hazardous materials such asberyllium has been difficult and ex-pensive because of both the numberof processing steps necessary to getfrom the raw material to the finishedproduct and the controls necessary toprocess the materials safely withoutcontaminating the environment. Now,however, the directed-light fabrication(DLF) process that we developed atLos Alamos can produce, in a singlestep, near-net-shape (within a fewthousandths of an inch) metal compo-nents that are fully dense. The processis nearly waste-free, and it eliminatesor contains all contaminants producedwith conventional methods.

DLF uses tool paths generated fromdigitally designed solid models toaccurately trace the cross section of a

part with a laser beam that meltsmetal powder particles entering thefocal zone. Upon solidification, themetal forms a deposit representing aplanar cross section of the part.Multiple cross-sectional layers areformed in succession until the part iscomplete. The DLF system we cur-rently use has five axes of motion,allowing us to fabricate three-dimensional components and todeliver up to four different powders atthe same time or in succession. DLFcan be used for depositing any metalor intermetallic compound.

The goal of this project has been toapply DLF technology to fabricatefully dense beryllium components(that is, beryllium components havingfull theoretical strength). To reducecosts, we modeled the process using

steel as a surrogate, with the intent ofapplying the knowledge gained fromthe steel modeling and depositionexperiments to fabricating a berylliumcomponent. We anticipate that it willbe straightforward to assemble aspecial system with the necessaryengineered controls for handlingberyllium or other hazardous materials.

Using DLF process parameters andinformation about the physical prop-erties of stainless steel as input to aheat-flow code, we modeled finiteheat flow in steel. Unfortunately, be-cause we did not have a complete setof beryllium thermophysical proper-ties, we were unable to apply themodel to a beryllium component forcomparison. From the steel models-,we determined that we could controlthe thickness of the deposited layers ifwe used heat-flow gradients to helpoptimize the DLF process parameters.We will correlate the theoretical datafrom these models with experimentalresults and will eventually incorporatethe data into control loops for real-time process control.


Reactor-Based Tritium Production

Michael Houts

Los Alamos National Laboratory isresponsible for stockpile stewardship.As part of its stockpile stewardshipresponsibilities, Los Alamos mustassure that the United States has anadequate supply of tritium for defensepurposes. In that context, the goal ofour project was to evaluate options forproducing reactor-based tritium.Much of our effort focused on evalu-ating the Fast Flux Test Facility(FFTF). We selected the FFTFbecause little independent work had

been done related to that option, and ithas the potential for providing signi-ficant amounts of defense-relatedtritium.

A major accomplishment of theproject was our development of aninherently safe 3He-based tritiumproduction target designed for use infast-spectrum reactors (such as theFFTF). Although the basic operatingpremise is the same, the target issignificantly different from the inher-ently safe targets we had previously

designed for thermal-spectrum reac-tors. We are currently applying forpatents for both the fast-spectrum tar-get and the thermal-spectrum target.

In addition, we assessed all aspectsof the tritium production cycle, fromtarget fabrication to extraction oftritium to getting the tritium into theform required by the Department ofDefense. The use of flowing 3Heloops (for which FFTF is well suited)could greatly reduce the cost ofprocessing and shipping targets. Theuse of static 3He targets rather thanflowing 3He would also reduce costs.If the option for FFTF tritium produc-tion is funded, Los Alamos is in anexcellent technical position to partici-pate in numerous aspects of thisoption.

Methods for the Rapid On-Line Detectionof Biological and Chemical Weapons

Philip Hemberger

Our objective is to develop technol-ogy for the detection (using surro-gates) of chemical and biologicalwarfare agents. The project consistsof three tasks: (1) to modify a trans-portable mass spectrometer for thedetection of chemical agents; (2) todemonstrate the detection of specificbacterial DNA sequences using afluorescence-based, single-copy genedetector; and (3) to upgrade a surface-acoustic-wave measurement station.

In the past year, we modified anexisting transportable mass spectrom-eter for the field detection of chemicalwarfare (CW) agents. The detectiontechnology is based on the combina-tion of membrane sampling and ion-

trap mass spectrometry. We installed amembrane interface on the transport-able mass spectrometer and adapted theinstrument for the detection of surro-gates of chemical warfare agents. Theinstrument and sampling system aremounted in a 20-in. x 20-in. x 36-in.transportable container. The instrumentalso requires a small cylinder ofhelium and a rotary vacuum pump,which are mounted externally on thecontainer. We also developed pre-liminary methods for detecting CWsurrogates. The surrogates includedchlorobenzene, cyclohexanol,dimethyl methyl phosphonate, anddimethyl sulfoxide. These compoundswere detected at approximately

100 ppb by volume in air. The detec-tion of these compounds satisfied thedeliverable of demonstrating theinstrument for the detection of CWsurrogates.

In addition, we developed a tech-nique for the rapid, direct detection—with high sensitivity andspecificity—of pathogenic DNA. Themethod consists of adding two DNAprobes to a sample containing thetarget DNA. The sample is thenanalyzed by a laser-based, ultra-sensitive fluorescence system capableof detecting single molecules at twodifferent wavelengths. If the target ispresent, the two probes will bind to it,and their signals will appear simulta-neously in time and space. Using thesystem, we detected single copies of aspecific DNA sequence from Bacillusanthracis with a signal-to-noise ratioof 20 in only 400 s in an excess ofunrelated DNA material.


Night-Vision Device TechnologyDevelopment

Herbert 0. Funsten

The U.S. military extensively usesnight-vision devices that utilizeimage-intensification tubes. Thesetubes have two significant problemsthat can critically compromise theiroperation: (1) the field of view is re-stricted due to aberrations introducedby the flat-image plane and, (2) light-sensitivity (gain) loss occurs when abright-light source lies within the fieldof view. A wide field of view is criti-cal to aviators who need peripheralvision for motion cues and detectionof nearby obstacles, obstructions, or

aircraft. Bright-spot suppression iscrucial to night missions in an urbanor other well-lighted environment(one with streetlights, flares, head-lights).

In this project we are developingtechnology to overcome these prob-lems. First we are designing a curved-image plane, using recently developeddetector technology that enables awide field of view. We have per-formed optic and electro-optical simu-lations to allow up to 80 degrees field

of view. For the bright-spot suppres-sion, we have designed a segmentedmicrochannel-plate scheme that sup-presses the gain in only that segmentilluminated by a bright light source,while it retains full gain across allother segments. In this way, dimobjects within the field of viewremain visible.

We finished a design and procured anexperimental, curved-microchannel-plate tube based on the wide-anglework in the first year. Currently we arewaiting for delivery of the fabricatedtube. We also finished a prototype for asegmented microchannel-plate designand now are planning a laboratorydemonstration of the concept.

Integrated Approach to Advanced Machining

Robert D. Day

The goal of this project was to mea-sure the residual stresses induced bymachining as a function of the depth ofcut and the cutting tool's sharpness.The sample for these experiments con-sisted of a titanium alloy that contained6% aluminum and 4% vanadium. Weperformed cutting tests on this samplein the as-received condition and after astress-relieving heat treatment. The firstfigure shows cutting and thrust forces

for Ti-6A1-4V specimens. Kennemetaldonated tools (both dull and sharp) forthis project. We measured the tools'sharpness radii at Los Alamos beforemachining, using interferometry, anddetermined them to be nominally 1 nmfor the sharp tools and 10 |am for thedull tools.

We measured the residual stressesinduced by x-ray diffraction using therotating anode located at the Los

Alamos Neutron Scattering Center.These measurements revealed that thehoop stress increased with depth of cut;however, the radial stress decreasedwith depth of cut. An elastic-plasticmodel provided a possible explanationfor this behavior. For small depths ofcut, the tool makes multiple passesthrough the damaged subsurface layer,which causes both residual stress com-ponents to increase; however, the radialstress increases by a much greateramount than the hoop stress. Thesecond figure compares the calculatedresidual stress with the measuredvalues.

EE

0.1

1000 -

100 -

1 0 -

1—

o

•

o

X

1—

1 1—1— 1 1 1 j i 1 !—1—111

Sharp tool thrust force per unit width

Sharp tool cutting force per unit widtr

Dull tool thrust force per unit width,

Dull tool cutting force per unit width,

—1 1—i 1 1 1 1 | 1 1 1—h^-^-H

1 1 1—1 M i l -

N/mm

, N/mm

N/mm

N/mm

-

i* -$

1 1 1—1 M i l -

1 10Depth of cut,rrm

100

Cutting and thrust forces for heat-treatedTi-6Al-4V specimens. The average isplotted. The uncertainty bars indicate themaximum and minimum measured forcevalues.


e-

u--100-

-200-

-300-

-400-

-500-

-600 -

-700 -

-800-

1 : I 1 I l l l | 1 1 1 1 1 I i i i . -

'--

Ii

o Sharp tool hoop residual stress, N/mm2

n Sharp tool calc hoop stress N/mm2

-.-

-_-

--

--

, l0.1 1 10

Depth of cut, (nm)

a)

100

0 -

-100-

-200-

-300-

-400-

-500-

-600 -

-700-

-800-

1 1 I I I l l l | 1 1 I 1 M l l | H -

I Ji

o Sharp tool radial residual stress, N/mm2

p Sharp tool calc radial stress N/mm2

1 1 1 1 1 1 H-

i ij

f ::-i-

-

0.1 1 10Depth of cut, (|xm)

100

b)

JoS

0 -

-100-

-200-

-300-

-400-

-500-

-600-

-700-

-800-

1 1—i—i-r !• i i

c

| 1 I I 1 1 I M |

\ Ii f

o Dull tool hoop residual stress, N/mm2

D Dull tool calc fioop stress N/mm2

—h- \ 1—1 l-i-H- -

d>

0.1 1 10Depth of cut, (jim)

c)

100

0 -

100-

200-

300-

400-

500-

600-

700-

800-

u

i j

Io Dull tool radial residual stress, N/mm2

o Dull too! calc radial stress N/mm2

J [

-+-

0.1 1 10Depth of cut, (um)

100

d)

Measured and calculated residual stresses. The average value is plotted. The uncertainty bars for the measured residualstresses are the combination of the variation in the measurements at four locations around each ring and themeasurement uncertainty. The uncertainty bars for the calculated values come from the variation in the forcemeasurements that were used in the data analyses: (a) sharp tool hoop stress, (b) sharp tool radial stress, (c) dull toolhoop stress, (d) dull tool radial stress.



Subsurface, Directed-Energy Methods forGroundwater Treatment

John Coogan

A critical issue in pump-and-treatapproaches to groundwater reme-diation is the limited mass transport ofsubsurface organics, especially densenonaqueous-phase liquids (DNAPLs).We are evaluating a novel conceptusing acoustic waves to enhance thetransport and extraction of subsurfaceorganics from leaking undergroundstorage tanks. Until now the majorityof research in this area has beenfocused on improving production indeclining oil and gas reservoirs, andthe underlying physical mechanismsfor enhanced transport have not beenthoroughly investigated.

During the reporting period weexplored two research paths. First wedemonstrated that acoustic energy canenhance the solubility of DNAPLs,specifically trichloroethylene (TCE),in both sand and Pajarito tuff. Experi-mental work has clearly shown thatthe proposed process is real (seefigure), with removal efficienciesincreased by orders of magnitude inboth static and flowing systems. Thiswork also suggests several potentialmechanisms for the effect. Second,we used cavitation and the resultingsonochemical reactions produced at

higher ultrasound intensities todestroy DNAPL surrogates in sandand soil. Although we discovered thatsoil can act as a reaction fluidizedbed, greatly enhancing sonochemical

reaction rates over those found insimple fluids, the scaling to subsur-face remediation is not promising, andthe work will not continue.

For the next fiscal year, we willextend the research in enhanced trans-port under more controlled laboratoryconditions to identify mechanisms,and we will use the knowledge gainedto evaluate a field-ready prototype.

Effects of Ultrasound (US) on TCE Transport

10000

_ 1000

Q.•S

100

-9/25 US vial

O 9/25 control vial

-9/10 US transport vial

9/10 control vial

Saturationconcentration

10 20

Time (hours)

30

TCE concentration measured as a function of time with and without ultrasonicenhancement. Data for both controls and samples are shown. We appliedultrasound to samples at time - 22 hours. The production of TCE levels abovethe solubility limit suggests that emulsions may be formed.

Program Development—Plasmas, Fluids, and Particle Beams 259

Plasma Source Ion Implantation forAdvanced Manufacturing

Jay Scheuer

Plasma source ion implantation(PSII) and plasma immersion ionprocessing (PHP) can be used toprovide economical surface modifica-tion to satisfy industrial and DOEstockpile support needs. PSII is a non-line-of-sight ion implantation techniquethat reduces the complexity and cost oftraditional ion implantation. PHP is alogical extension of PSII that combinesion bombardment with plasma deposi-tion, thus allowing deposition of con-formal, adherent coatings withthicknesses of tens of microns. Ourproject is dedicated to developing anddemonstrating PSD/PHP processes.

We have performed processdevelopment and characterization in

support of the industrial implants listedbelow. A new system dedicated to thedevelopment of PUP processes is nowoperational. We have performed dem-onstration implants on actual industrialcomponents and are currently field test-ing these components. We have con-ducted implantation experiments athigh temperature in collaboration withthe Institute of Electrophysics and theInstitute of Metal Physics inEkaterinburg, Russia. A PSH/PUPprocess for the deposition of adherentdiamondlike carbon films on steels isalmost fully developed. We have com-pleted the design and fabrication of asolid-state insulated-gate bipolar tran-sistor (IGBT) modulator that will be

capable of operation at 20 kV with acurrent capability of 2 kA. This modu-lator does not suffer from switchingstorage delay or temperature effectsand permits system operation overlarge temperature extremes.

Publications

Reass, W.A., "Progress Toward a20 kV, 2 kA PSH Modulator forAutomotive Production" (22nd Int.Power Modulator Symposium, BocaRaton, Fla., June 24-27,1996).

Walter, K.C., M. Nastasi, and C.P.Munson, "Adherent Diamond-likeCarbon Coatings on Metals via PSII"(submitted to Surface Coatings andTechnology).

Walter, K.C., K.T. Kern, J.R. Tesmer,et al., "Nitrogen and Boron IonImplantation into ElectrodepositedHard Chrome" (submitted to SurfaceCoatings and Technology).

Magnet Design Concepts for the100-MeV Isotope-Production Facility

E. Wadlinger

If an isotope-production (IP) facil-ity is to be viable at the 100-MeVregion of the Los Alamos NeutronScience Center (LANSCE) accelera-tor, an efficient extraction system isrequired. The greatest uncertaintiesare associated with the kicker magnetneeded to divert portions of the beaminto any new beam line. This magnetmust fit into a rigidly defined spacewithin the transition region of the ac-celerator and must operate in concertwith the current accelerator operationssystems. In addition, it must in noway degrade beam quality when the

beam is directed to other areas ofLANSCE. Because of these con-straints, the magnet must be specifi-cally designed and built for thisintended application. Project objec-tives were to evaluate design conceptsfor the kicker magnet and its powersupply and to assess the feasibilitiesof various design alternatives.

We have developed a conceptualdesign for a kicker magnet and powersupply to be placed in the availablespace in the transition region to pro-vide a proton beam for a proposed IPfacility. Our design study shows the

technical feasibility for delivering therequired 100-MeV beam to the IPfacility and still delivering therequired beam to the proposed long-pulse spallation source (LPSS) facil-ity, the weapons neutron researchfacility, and the proton storage ring(PSR) at the Manual Lujan Jr. Neu-tron Scattering Center. LPSS requiresproton-beam macropulses of 60 ppsand PSR requires 20 to 30 pps of pro-tons, leaving 30 to 40 pps for otherusers. At the LPSS-proposed 21-mApeak proton-beam current and 1-mspulses, the IP facility would only need12 pps to get the required 250-uAbeam. The power supply design isbased on a proven and working designfor the RIKI (ring-injector kicker)magnet that switches the 800-MeVbeam into the PSR.


Advanced Ignition of Jet Turbine Engines

James Early

During the past year we have dem-onstrated several innovative technolo-gies for applying lasers as an alter-native to capacitive discharge for theignition of jet turbine engines. Thisproject focused primarily on two ar-eas essential to the implementation ofa practical laser igniter: (1) develop-ing energy-efficient, laser-inducedfuel-ignition methods that are effec-tive and reliable, and (2) developingtechniques to maintain the transpar-ency of optical surfaces that isolatethe laser from the hostile combustion-chamber environment.

Laser-based ignition concepts em-ploy many laser-wavelength andpulse-format mechanisms to increaseboth the rate and duration of laserenergy delivery. We found thatincreasing the time the laser light isapplied to the fuel medium assists thegrowth of a stable flame kernel. At thesame time, it reduces both laser peak-power requirements and inefficiencyin energy utilization.

We used plasma pumping, directlight absorption by fuel componentsand laser light/material surface inter-actions as energy-coupling mecha-nisms. We showed that theseinnovative ignition methods reliablyignited jet-fuel aerosols over a broadrange of fuel/air mixtures and at fueltemperatures as low as -40°F. Asshown by the jet-fuel ignition profilesin the accompanying figures, this kindof ignition is superior to conventionallaser-spark ignition. We also devel-oped a laser-based method that effec-tively removes opaque deposits of fuelhydrocarbon combustion residuesfrom laser window surfaces. To date,this R&D effort has resulted in threepending patents, one provisionalpatent, and one invention disclosure.

s8

0

.10 -8 -6 4 -2 0 2 4 6 8 10

Radial Initiation Location in Fuel Cloud (mm)

With the same laser energy (144 mJ), the reliability of jet-fuel ignition issubstantially improved by applying the dual laser pulse/plasma pumpingmethod (curve A) over that of conventional laser-spark ignition (curve B).

120

£ 80 -

ae

20 -

0

# With Preheat

• Without Preheat

-10-8 -6 -4-2 0 2 4 6 8 1012Radial Initiation Location in Fuel Cloud (mm)

The laser-prevaporization method provides a significant enhancement to jet-fuel-aerosol ignition. Fuel droplets are vaporized by the direct absorption oflow-peak-power (30 kW), 3-mm light provided by a free-running Er:YAG laser.The fuel vapor is subsequently ignited by a laser spark produced by a focused,91-mJ, Q-switched Nd:YAG laser pulse.


Removal of Transuranic Materials fromContaminated Equipment Using PlasmaDecontamination

Carter Munson

The primary goal of this project is todevelop and demonstrate the utility ofplasma-based processes for the removalof transuranic (TRU) contaminationfrom targets of interest to the DOEcomplex. The first stage of the processhas been to design, fabricate, and per-form initial tests of a prototype plasma-decontamination system using surro-gate materials.

We have designed, fabricated, andintegrated a small system (-0.5 m3)with a two-stage, cryogenic trappingand recovery system. Examination ofthe etching characteristics of variousgases (CF4, NF3, SF6, etc.) led to the

selection of NF3 as the plasma precur-sor gas because of the reduced potentialfor particulate formation and nonvola-tile material deposition. We conductedexperiments to examine the removal ofvarious surrogate materials in a numberof different target geometries.

We have also conducted a very largescale test (~3-m2 target area) in anotheravailable facility. This test examinedthe removal of a very hard, chemicallyresistant, amorphous carbon materialfrom the surface of an extremely com-plex aluminum target. We used an oxy-gen plasma in this case as an analoguefor the fluorine-based plasma that

would be used to volitalize and removeplutonium or uranium from contami-nated surfaces.

Experiments with NF3 and tungsten(as the TRU surrogate) have demon-strated material-removal rates in a mild,reactive-ion-etching (RIE) mode. Theserates are nearly an order of magnitudefaster than the material-removal rateswe observed in the plasma-immersionmode. We expect significant additionalincreases in removal rates when thesystem operates in the combined RTF,and sputtering mode.

Publications

Munson, C, E.P. Chamberlin, et al.,"Development of Plasma-BasedDecontamination of Large MetallicObjects" (23rd InternationalConference on Plasma Science,Boston, Mass., June 3-5, 1996).

Supporting Technologies for a Long-PulseSpallation Source

Joey Donahue

We are investigating the acceleratormodifications, target-moderator-reflector concepts, neutron-scatteringinstrumentation, and facility modifi-cations necessary to design a long-pulse spallation source (LPSS) at LosAlamos. We are building on lastyear's efforts and incorporating tech-nologies and ideas from synergisticactivities at the Los Alamos NeutronScience Center (LANSCE), such asthe Accelerator Production of TritiumProject, the LANSCE ReliabilityImprovement Project, and Accelera-tor-Driven Transmutation Technolo-gies. Major emphasis is on evaluatingconcepts from an engineering per-spective to establish a basis for as-sessing the technical as well as costand schedule risks for the proposedLPSS facility.

Our initial work was directed to-ward modeling the physics of targetsystem and neutron-scattering instru-ment performance, which was neededto establish the scientific case for theLPSS. We also investigated the accel-erator modifications necessary toachieve the 21-mA peak currentrequired for a 1-MW LPSS. We had asuccessful 32-h accelerator develop-ment run at 800 kW of beam powerwith the LPSS beam structure. Thisrun demonstrated that the LANSCElinac can already deliver 80% of thepower needed for a 1-MW LPSS.These efforts supported the LPSSproposal, its preliminary cost andschedule estimates, and a preliminaryengineering layout for the targetstation.

Several external review committeeshave examined the technical progressof our activities. Based on feedbackfrom the committees, we began toaddress some of the supporting engi-neering issues of the target-moderator-reflector system and target station inthe latter half of the fiscal year. Theseinclude target thermohydraulics andthe choppers that are used to shapethe neutron pulses. The results of thiswork have been documented in publi-cations, conference proceedings, andinternal Laboratory reports.

Publications

Fitzsimmons, M.R., "Reflectometry atContinuous Wave and Pulsed-NeutronSources" (to be published in Nucl.lustrum. Methods).

Fitzsimmons, M.R., and R. Pynn,"The Performance of Reflectometersat Continuous Wave and Pulsed-Neutron Sources," ICANS-XIII: Proc.13th Meeting Int. Collaboration onAdvanced Neutron Sources (1995).


Olah, G.A., RA. Seeger, and R.P.Hjelm, "Small-Angle ScatteringInstruments on a 1 MW Long PulseSpallation Source," ICANS-XIII:Proc. 13th Meeting Int. Collaborationon Advanced Neutron Sources (1995).

Pitcher, E.J., G.J. Russell, et al.,"Performance of Long-Pulse SourceReference Target-Moderator-ReflectorConfiguration," ICANS-XIII: Proc.13th Meeting Int. Collaboration onAdvanced Neutron Sources, 323-329(1995).

Pynn, R., and L.L. Daemen, "ThePerformance of NeutronSpectrometers at a Long-PulseSpallation Source," ICANS-XIII:Proc. 13th Meeting Int. Collaborationon Advanced Neutron Sources (1995).

Pynn, R., and D. Weinacht, "AProposal for a Long-Pulse SpallationSource at Los Alamos NationalLaboratory," ICANS-XIII: Proc. 13thMeeting Int. Collaboration onAdvanced Neutron Sources (1995).

Russell, G.J., E.J. Pitcher, and P.D.Ferguson, "Coupled ModeratorNeutronics," ICANS-XIII: Proc. 13thMeeting Int. Collaboration onAdvanced Neutron Sources, 495-509(1995).

Russell, G.J., E.J. Pitcher, and P.D.Ferguson, "Neutronic Performance ofa Benchmark 1-MW LPSS," inProceedings of the Workshop onNeutron Instrumentation for a Long-Pulse Spallation Source (LawrenceBerkeley Laboratory report LBL-37880, Berkely, Calif., 1995).

Russell, G.J., E.J. Pitcher, et al.,"Long-Pulse Spallation SourceNeutronic Performance" (Workshopon Neutron Scattering Opportunitiesat Long Pulse Spallation Sources,Berlin, Germany, June 24-27, 1996).

Waters, L.S., E.J. Pitcher, et al.,"Shielding Calculation for the Long-Pulse Source Facility" (AmericanNuclear Society 1996 RadiationProtection and Shielding DivisionTopical Meeting, No. Falmouth,Mass., April 22-25, 1996).


Chemistry

Advanced Oxidation Technologies forChemical Demilitarization

Louis A. Rosocha

Safely demilitarizing chemical-warfare (CW) agents is a high-priorityproblem for the Department of De-fense (DoD). Historically, the DoDhas preferred to destroy CW agents byincinerating them. However, becauseincineration has many drawbacks(such as leaks, hazardous air emis-sions, and large secondary-wastestreams), the DoD is currently lookingfor alternative methods that are highlyefficient at destroying these extremelytoxic chemicals.

Our main objective was to establishan innovative, advanced oxidation

system as a viable process for de-stroying CW agents, thereby provid-ing a basis for future programdevelopment. We focused on testing asystem concept in which we first vola-tilize (and/or oxidize or pyrolize) asurrogate liquid CW agent using athermal packed-bed reactor (PBR)and then further process the PBR off-gas with a second-stage nonthermalplasma (NTP) reactor (see schematicdiagram). We designed this two-stagesystem for closed-loop operation toachieve extremely high degrees ofagent destruction and to collect and/orcontrol all by-products from the pro-cess.

In preparing the apparatus and ex-periments, we established a projectedmass balance for the two-stage unit(based on previous data related tophosphate esters) and compared thisprojection to incinerator-based pro-cessing. We evaluated various CWsurrogates and chose the pesticidemalathion as our primary simulant.We then designed and constructed alab-scale PBR/NTP reactor, consist-ing of a liquid-injection system, aninjection-rate meter, an electric fur-nace, condensers, chemical traps,plasma reactors, power supplies, andchemical diagnostics. In addition, wecarried out combined PBR/NTP pro-cessing experiments and completedpreliminary chemical-processing cal-culations on carbon dioxide traps, re-action chemistry, by-productdistributions, and phase equilibria.

Chemical- Feed

Schematic diagram of an advancedoxidation system for chemicaldemilitarization with a PBR and anNTP reactor that is based on silent-discharge plasma (SDP). Our systematomizes liquid CW-agent surrogatesand then injects them into the PBR,where they are oxidized or pyrolized.The PBR off-gas is then fed to theSDP cells (the NTP stage) for furtherprocessing. Because we can operatethe system in closed-loop mode, wecan achieve an extremely high degreeof destruction and can capture the by-products of the process. A particularlyattractive feature of the system is itsability to operate with oxygen-freefeed gases.

ir.^1

Program Development—Chemistry 265

Advanced Nuclear Fuel Processing

Larry Avens

The goal of the project is to deter-mine unique approaches where LosAlamos' expertise in separations andnuclear materials operations can beapplied to spent fuel reprocessing.The first figure shows an overview ofthe technical goals of this proposal.We intend to develop alternative pro-cessing technologies and conceptsnecessary to understand critical ele-ments such as separation efficiencies,material and equipment requirements,and waste generation.

This year we reviewed several sepa-ration technologies. These were

(1) distillation-based separations;(2) pyrochemical separations in metalalloy systems; (3) metal solvent sys-tems for actinide/lanthanide separa-tions; (4) salt-environment methodssuch as halide slagging; and (5) use ofceramic materials that are constructedto selectively transport or capture ele-ments. Our approach uses chloridesalt distillation and recycle methodsfor plutonium electrorefining salts.Using selective transformations likeoxidation and distillation, we havedesigned a process that separatescesium and strontium from the

actinides, performs a lanthanide/ac-tinide separation, and recovers ura-nium from the other actinides asillustrated in the second figure.

Initial experiments have shown thatsignificant quantities of actinides, lan-thanides, and fission products can bedissolved in a LiCl/KCl eutectic mix-ture when heated. More importantly,the chloride salts of many of thesemetals can be converted to their re-spective oxides by addition of sodiumcarbonate. We are also investigatingthe selective halogenation of the lan-thanides over the actinides. We havebegun investigating tungsten hexa-chloride and other chloride melts todetermine their ability to maintain thedesired complex in a low-meltingmedium.

Destiny of the actinides, fission products, and activation products from spent fuel processing.

I La/Ac/Fp + Na2CO3/LiCl J

Distillation

Ac = Th, U, Np, Pu, Am

FP = Cs, Sr, Tc

La = Ce, Eu, Yb, Lu

Proposed chloride-based, molten-salt separation scheme.


Chemical-Biological Treatment ofHeterogeneous Wastes

James Brainard

Heterogeneous wastes (HW)—defined here as wastes containingbulk solids contaminated with one ormore components subject to ResourceConservation and Recovery Act(RCRA), Comprehensive Environ-mental Response, Compensation, andLiability Act (CERCLA), Toxic Sub-stances Control Act (TOSCA) orradiation restrictions—are difficult totreat by any single conventional ordeveloping technology. Included inHW are decontamination and decom-missioning (D&D) wastes (for ex-ample, soil, clean-up debris, andpaint-stripper waste); petroleumwastes (hydrocarbons and contami-nated soils, metals, and sludges);waste-treatment sludges and combus-tibles; and filter materials (paper,cloth, wood, solvents, and metals).

Conventional chemical and physicaloxidation technologies are not effec-tive in treating these wastes becauseof problems with one or more of thefollowing: permitting, cost, publicperception, and performance.

Using integrated business and tech-nical development activities, we areworking to develop, demonstrate, andimplement chemical-biological tech-nologies for the treatment of hazard-ous HW. During the past year weobtained permits and treated actualplutonium-containing D&D wasteobtained from storage at TechnicalArea (TA)-54. We also obtained mass-transfer kinetics equilibrium data andbiodegradation kinetics data for thedestruction of organic paint-strippersolvents in the modified gas-loopbioreactor that is part of our treatment

system. We applied these data to buildand validate a numerical model tosimulate the coupled physical andbiochemical processes in thebioreactor. In addition, we demon-strated the applicability of HW treat-ment strategies to the recycle/reuse ofEnvironstrip™ paint-stripper blastmedia.

Publications

Twary, L.V., R.K. Gmmbine, T.M.Foreman, et al., "Integrated Chemical/Biological Treatment of Paint StripperMixed Waste," Proc. of the ThirdBiennial Mixed Waste Symposium(Cognizant CommunicationCorporation, Elmsford, N.Y, 1995),p. 1171.

Twary, L.V., K. Steenhoudt, B. Travis,et al., "Biodegradation of PaintStripper Solvents in a Modified GasLoop Bioreactor" (to be published inBiotechnol. Bioeng.).

Radionuclide Separations Using PillaredLayered Materials

Norman Schweder

The objectives of this project are todevelop pillared layered materials(PLMs) that can efficiently sorbradionuclides, such as strontium-90,from liquid nuclear wastes stored inunderground tanks at DOE facilitiesand from mixed wastes stored at LosAlamos; to characterize the mostpromising of these PLMs and testthem on actual wastes; and to investi-gate their sorption mechanisms.

PLMs are layered, inorganic ionexchangers propped apart by metaloxide pillars. This year, we preparedlarge batches of chromium-,titanium-, and silicon-pillared tanta-lum tungstate (TaWO6) materials. Tocharacterize these materials, we used

titrations, surface area measurements,pore size distributions, and capacitymeasurements. The active sites inthese materials were probed withelectron paramagnetic resonance,europium fluorescence, and infraredmeasurements conducted before andafter the sorption of gases.

A general conclusion obtained fromour data is that there are at least twoactive sites responsible for cation ex-change in these materials. A tentativeinterpretation of how these active sitesfunction is that one is active at low pHand operates purely by an ion ex-change process; the other site is activeat high pH, operates by a sorptionmechanism, and gives these materials

their strong affinity for strontium. Thedistribution coefficients (Kj values)for Ca2+, Sr2+, and Ba2+ onto thepillared TaWO6 compounds were de-termined as a function of ionicstrength, pH, surface area, and ionicradius.

The data we obtained show a strongpH dependence and Kd values for thethree cations increasing to > 104 abovepH 12. Although PLMs removed>99.999% of the strontium fromnuclear waste simulants, their sorp-tion of strontium from actual wastewas disappointing. Our analysis indi-cates that complexants in the actualwaste compete effectively againstPLMs for the strontium. Destructionof the complexants would make fea-sible the application of PLMs to theHanford waste.


Integration of Advanced, Nuclear MaterialsSeparations Processes

Gordon Jarvinen

We are investigating the fundamen-tal chemistry issues that affect the in-tegration of several promising newseparations technologies into nuclearmaterials synthesis and processing.One of these technologies, hydrother-mal oxidation, uses water and an oxi-dant at high temperature and pressureto efficiently and safely destroy com-bustible materials. The water streamthat results can then be partitioned togive optimal product or waste forms.The successful development of thesenew technologies will lead to greatlyreduced generation of solid wastesfrom nuclear materials operations.

One focus during this year was onthe plutonium(VI) carbonate chemis-try (including solubility and specia-tion of plutonium) expected to controlthe fate of plutonium after hydrother-

0.6

0.5

mal oxidation of plutonium-contain-ing combustible materials. To mea-sure the solubility of Pu(VI) fromoversaturation in carbonate media, weneeded a well-characterized, solid-limiting phase. We prepared 500 mgof 239PuO2(CO3) and characterized itby powder x-ray diffraction, extendedx-ray absorption spectroscopy, anddiffuse reflectance spectroscopy. Weinitiated solubility experiments usingthis solid in 0.1- and 5.0-MNaCl so-lutions under 100% CO2. We col-lected a set of spectrophotometrictitration data, some of which areshown in the accompanying plot. Apreliminary fit gives formation con-stants for the tris- and biscarbonatocomplexes to be log b130 = 17.7 andlog b120 = 13.6, respectively.

0.4

0.3

0.2 -

0.1 -

pH 10.430

pH 10.430

500 600 700 800Wavelength (nm)

900 1000

A subset of absorption spectra used to determine the formation constants ofPu(VI) carbonate complexes. Experimental conditions were [PuO^] =4.45 fflM, [CO3

2~] = 12.0 mM, ionic strength = 0.1-M NaClO4, temperature =25°C, andpH = 7.059—10.430. The spectroscopic peaks clearly shift to higherwavelengths as the pH increases. To determine the formation constants, we fitthese peak shifts to a model in which the formation constants and spectra of theindividual complexes are free parameters.

A second focus was on implement-ing a capability for hydrothermalR&D on plutonium-containing mate-rials using small-batch reactors. Wedesigned and built several hydrother-mal batch reactors (see accompanyingdiagram) that we will install in aglove box at the Plutonium Facility.We will conduct plutonium-speciationexperiments on 2- to 2.5-mL mixturesof solution and solids at pressures ofup to 6000 psi and temperatures of500°C-600°C in these reactors. Whenwe tested these batch reactors on non-radioactive solutions, we found thathydrothermal processing conditionsoxidized Ce(III) to Ce(IV) and Cr(III)to Cr(VI), supporting our expectationthat plutonium compounds will beoxidized to Pu(VI).

Schematic drawing of a hydrothermalbatch reactor that we constructed forthis project. We will install it in aplutonium-handling glove box.


Catalysis for Alternative Feedstocks

William Tumas

In this project we focused on tech-nical and program development workin catalysis and supercritical fluidchemistry to strengthen theLaboratory's capabilities and to posi-tion Los Alamos for future programs.The program development activitiesfocused on working closely with in-dustry, DOE, and the EPA to launchnew initiatives in catalysis for nextyear and beyond. We expect the tech-nical work on catalytic processes insupercritical carbon dioxide to yieldinnovative, environmentally benign

processes utilizing carbon dioxide asa solvent and a potential reagent. Thiswork focused on two classes of reac-tions that are industrially significantand could lead to extensive wasteminimization/solvent replacement:(1) palladium-catalyzed reductivecarbon-carbon bond-forming reac-tions (Heck reaction) to producepharmaceutical intermediates, asshown in the first figure, and(2) cobalt-catalyzed air oxidations ofcyclic hydrocarbons to produce poly-mer intermediates, as shown in thesecond figure.

Our work on the Heck reaction re-vealed supercritical carbon dioxidecan be used as an alternative solventfor the Heck reaction. We examined anumber of catalysts for the reaction ofiodobenzene with styrene in the pres-ence of triethylamine. Perfluorinatedphosphine catalysts dramatically in-creased conversions to 99% after 12hours at 90°C and 5000 psi. We havefound CO2 to be an effective cosol-vent for the direct cobalt-catalyzed airoxidation of cyclohexane and cyclo-hexanone to adipic acid. Oxidation ofcyclohexane at 95°C produced adipicacid with selectivities higher thanthose of conventional solvents (>80%)at low conversions (up to 4%). Directair oxidation of cyclohexanone pro-ceeds at higher rates.

PhiPd(OAc)2,Et3N,L

P h 5000 psi

Ph

Ph

Ph

L = Ligand

none

Time TfC) Conversion trans-Stilbene ds-Stilb*ne

12 h

4d

12 h

90°C

90°C

90°C

19%

37%

14%

>99%

93%

>99%

12 h 90°C

24 h 40°C

7%

99% 94%

51% 94% 6%

Summary of palladium-catalyzed carbon-carbon bond forming (Heck reaction), illustrating higher conversions usingfluorinated phosphine ligands.

100

80 -

£T 60 -

o

Oxidation of cyclohexane at 95°C in CO2/HOAc,illustrating high selectivity for the formation ofadipic acid at conversions up to 6%.

20 -

; Adipic acid selecti

; w s ^ Conv

• i i i r ^ T i i • i i

fity N

ersion

•

•

•

10

10 15

Time (hr)

- 8

6 ?

- 4

- 2

20


Separation Science and Technology:Membrane-Based Separations andDestruction Processes

Barbara F. Smith

This project combines advancedseparations and destruction technolo-gies with the objective of adaptingthem to industrial needs. Specifically,our research focuses on the followingareas: synthesizing new extractantsfor removing valuable or hazardousmetal ions from industrial waste andprocess streams or from ground-waters, producing membranes thatwill selectively separate industrialgases, and designing membrane orsupported systems that will selec-tively oxidize or destroy hazardousorganics.

Our first goal was to prepare water-soluble, chelating polymers that couldbe used to remove or recover valuableor toxic metals from a variety of pro-cess or waste streams. Industry is in-terested in advanced, metal-ionseparations because these technolo-gies lead to lower operating and wastetreatment costs. This year, we pre-pared nine new, water-soluble, metal-binding polymers, and some haveshown selectivity for certainoxyanions (such as tungsten, molyb-denum, arsenic, and selenium), evenin the presence of a high salt concen-tration (for example, 1-MNaCl).

Another goal was to separate fissionproducts such as cesium and stron-tium from high-level radioactivewastes or from contaminated ground-waters using a specific extractant,cobalt dicarbollide. As a soft anion,cobalt dicarbollide will selectivelybind cesium and strontium and pullthem from an aqueous phase into anorganic phase. Current processes relyon hazardous solvents such as nitro-benzene; we modified the process touse diethylbenzene, an environmen-tally benign organic solvent, in placeof nitrobenzene. We demonstratedsimultaneous cesium and strontium

removal from high-level waste surro-gates using this new system.

We were also interested in develop-ing advanced electrochemical reactorsthat would improve our ability toseparate and treat waste. We success-fully demonstrated a new electro-chemical-cell design in which the cellvoltage at a current density of300 mA/cm2 was just 1.7 V; the cellvoltage in commercial units is 3.2 V.The resulting systems can providemore-energy-efficient organic de-struction than the commercial unitscan.

Another area we studied was ad-vanced membrane materials for sepa-ration of industrial gases such ashydrogen. We installed a polymer-spinning unit that produces hollowfiber membranes, a favored membranegeometry for efficient separations. Weused this unit to spin membrane mate-rials, such as polysulfone andpolyaniline, into microporous andultraporous hollow fibers, and weevaluated the spun systems for gasseparations. We also compared theseparation properties of these fiberswith the separation properties ofhigh-strength, highly conductive(>50 S/cm), polyaniline solid fibers.In addition, we demonstrated the fea-sibility of producing ultraporous andmicroporous polyetheretherketoneflat-sheet membranes.

We are also developing "smart" fil-ters, which will selectively bind and,if designed properly, potentially de-stroy organic materials. We success-fully synthesized a number of hostpolymers for organic materials, andwe demonstrated that these host poly-mers have the nanoporosity necessaryto absorb organic contaminates fromwater. We measured the equilibrium

constants of the host polymers for anumber of systems and successfullyfabricated optical-quality membranesfrom these polymers.

Our final goal was to develop insitu photocatalytic reactors for selec-tive oxidation of organics. These sys-tems may allow a valuable oxidizedorganic product to be synthesizedfrom an organic waste stream. We arefocusing our organic-oxidation studieson phenolic materials in aqueousstreams and arenes in the gas phase.Currently, we are collaborating withBechtel on applying species-selectiveoxidation technology to its industrialsymbiosis goals and on extrapolatingthe technology to metal removal.

Publications

Balaich, G.J., S.A. Fino, et al.,"Synthesis of an OrganometallicPolyamide of Cobalt Dicarbollide"(submitted to Inorg. Chem.).

Chamberlin, R.M., B.L. Scott, et al.,"Butyllithium Deprotonation VersusAlkali Metal Reduction of CobaltDicarbollide" (submitted to Inorg.Chem.).

Rais, J., D.V. Mason, and S.D. Abney,"Use of PVC Plasticized Membranesfor Uptake of Radioactive Cesium andStrontium" (to be published inSeparation Sci. Technol).

Smith, B.F., T.W Robison, M.E.Cournoyer, et al., "Polymer Filtration:A New Technology for SelectiveMetals Recovery" (SUR-FIN95Conference of the AmericanElectroplaters and Surface FinishersSociety, Baltimore, Md., June 26-29,1995).

Winokur, M.D., J. Maron, and B.R.Mattes, "Processing Induced Changesin the Local Structure of AmorphousPolyaniline Using RDF Analysis,"Macromolecules 28 (13), 4475(1995).


Microwave Processing Improvements forMethane Conversion to Ethylene

Ray Stringfield

The objective of this project was toinvestigate microwave-enhancedcatalysis. Published work by othershad demonstrated improved selectiv-ity in microwave-driven catalytic con-version of 2-methylpentane to itsisomers.

Our accomplishment was repro-ducing their experiment and discover-ing that there is no improvement inselectivity using microwaves. The se-lectivity at a given conversion was thesame for both microwave-heated andconventionally heated catalyst beds.Meetings with the authors of the ear-lier work led to the conjecture that

their catalyst had not been preparedproperly, which led to anomalous, lowselectivity for their conventional heat-ing runs. Even though we found noimprovement in selectivity with mi-crowaves, microwave processing stilloffers the promise of rapid heatingadjustments and low thermal inertia—aids to quality manufacturing.

We developed and characterized anoptical temperature diagnostic suit-able for use on a microwave applica-tor in this project. This pyrometer canmeasure the temperature of small-scale features on the catalyst bed. Inaddition, it has a fast response that

can follow the rapid heating often en-countered in a microwave processingsystem. We studied the behavior ofthe microwave applicator system anddeveloped theoretical models thatyield insights about the stability andcontrol of the system.

Publications

Nelson, E.M., "Enhancement ofThermal Stability in MicrowaveApplicators by Mismatching andDetuning," 31st Microwave PowerSymp. Proc. 31,108 (1996).


Mathematics andComputational Sciences

Data Resources and Sample Applicationsfor Information Analysis in Chemical andBiological Warfare Defense

Kevin Buescher

The Laboratory has extensive infor-mation analysis capabilities. Our goalin this project was to identify repre-sentative applications for these in thearea of chemical and biological war-fare defense. In particular, we focusedon developing methods for detectingthe outbreak of diseases and for pre-dicting their evolution. In particular,we examined existing mathematicalmodels for the statistical progression

of infected individuals from a dy-namical systems viewpoint. We foundthat we could express a number ofdisease models in a common form andthat we could transform these modelsin a way that allows us to perform on-line estimates of their model param-eters in a computationally efficientmanner. Using this technique, wecould track diseases in an automatedand cost-effective manner.

After reviewing the literature andtalking with experts in the field, wehave determined that the greatest needin this area is for epidemiologicalmodels that account for spatial andtransport aspects of disease spread.The Laboratory's simulation capabili-ties might help to address this need.For example, we could link transpor-tation and climate simulations to amodel of infection mechanisms tobetter predict the evolution of an out-break.

In addition, the Laboratory's analy-sis capabilities could prove to be veryuseful in mining morbidity and dis-ease data to locate similar cases thatcould indicate the onset of an epi-demic or an attack.

Information-Handling/Data-FusionTechnologies to Extract and AnalyzeExport Information

Harry Forehand

Proliferant nations generally do nothave the technical capability and in-dustrial infrastructure to producenuclear weapons without assistancefrom nuclear weapons states or ad-vanced-technology countries. Hencethey may procure the technology, bothmaterial and hardware. We planned todevelop an information-handling/data-fusion tool to extract and analyzeexport information to look for at-tempts by proliferant countries to

acquire such technology. Exportinformation, both dual-use, export-controlled, and Schedule B {StatisticalClassification of Domestic and ForeignCommodities Exported from the US)are generally available electronically.This project was intended to investi-gate automated data-handling and link-analyses tools to develop techniquesfor rapid evaluation of technology-transfer mechanisms via export infor-mation.

We researched commercially avail-able databases containing export com-modities information for applicationto our investigation and had extensivediscussions with the Department ofCommerce (and other organizationsinvolved in export-controls-data re-view). Yet it became clear that thedata sources we needed did not con-tain sufficient and necessary informa-tion to derive indicators of proli-feration. In addition, none of thecommercially available data containedsufficient detailed data to do the jobadequately, nor was the data likely tobe available in the near future. Theproject was therefore terminated be-fore its normal term.

Program Development—Mathematics and Computational Sciences 273

Intelligent Controllers for BattlefieldSimulations

Chris Barrett

In this project we are developing,testing, and demonstrating new meth-ods for producing intelligent com-puter-generated forces, battlefieldsimulations in which computer codesdecide the behavior of military forces.These battlefield simulations are anarea of growing importance and inter-est to the Department of Defense(DoD). Our new methods are basedon two advanced simulation technolo-gies: intelligent control and adaptivesystems. In intelligent control tech-nology, we formally emulate the con-trol process of the real system using arule-based, expert systems approachthat improves over time by addingnew rules. In adaptive systems tech-nology, the adaptive systems softwarelearns and adapts its tactics from syn-thetic battlefield experiences gener-ated by the simulation.

The simulation environment we areusing is called JointSim; the AirForce, Army, and DoD have been de-veloping this environment over thepast few years, and it serves as an ex-cellent test bed and proving ground tointroduce the Laboratory's researchadvances in battlefield simulations tothe DoD. In FY96 we developed acommand and control architecturethat the joint U.S./U.K. workinggroup on command and control stan-dardization accepted as their standardreference model. We also developed agenetic algorithm that learns new tac-tics for systems not yet in the DoDforce structure.

Publications

Barrett, C , M. Wolinsky, and M.Olesen, "Emergent Local ControlProperties in Particle Hopping TrafficSimulations" (Traffic and GranularFlow, Julich, Germany, October 9-11,1995).

Nagel, K., C. Barrett, and M. Rickert,"Parallel Traffic Microsimulation ofTraffic by Cellular Automata andApplication" (submitted toTransportation Res. C).

Rasmussen, S., C. Barrett, and M.Olesen, "Dynamical Hierarchies: ASummary" (First InternationalConference on Artificial Life andRobotics, Oita, Japan, February 2-10,1996).

Reidys, C, "Mappings in RandomStructures" (submitted to SIAM J.Discrete Math.).

Stroud, P., "An Adaptive AirborneLaser Flight Controller" (submitted toIEEE Trans. Systems, Man, andCybernetics).

Stroud, P., "Simulation-BasedLearning in Knowledge-BasedControllers" (1996 InternationalSymposium on Intelligent Control,Dearborn, Mich., September 1996).

Visualization Capability forNonproliferation and Emergency Training:A "Poor Man V Virtual-Reality System

George Papcun

We have developed means to takean ordinary photograph or video im-age and rapidly transform it into athree-dimensional virtual-reality envi-ronment of what is shown in the im-age. This capability can be applied tonuclear nonproliferation, to emer-gency management, and to relatedsituations. For example, if a photo-graph can be obtained of some loca-tion that has dangerous chemicalsstored in it, a virtual-reality environ-ment would let workers carry outpractice runs for dealing with thechemicals without exposure to thedangers of the actual environment. Totake another example, let us supposethat a limited number of photographsare available of clandestine locationswhere nuclear materials may bestored or manufactured. In such situa-tions, a virtual-reality representationwould allow inspectors to make mea-surements, determine what additionalinformation is needed, and so on.

Our system provides the operatorwith a set of computer programs thathe or she can use to transform theimage into its three-dimensional rep-resentation. Included in the system isa tutorial that teaches the operatorhow to use the system. Because oursystem runs on an ordinary personalcomputer, it is relatively inexpensiveand portable.

In the course of our research, wehave developed new means to makemeasurements of complex shapes,such as faces. This aspect of our workcan be applied to recognizing imagesof people.


Modeling for Environmentally ConsciousManufacturing

Richard LeSar

This project focused on creating anintegrated approach for developingsimulation tools for environmentallybenign manufacturing. We developedcasting simulations that would yieldan accurate prediction of materials'microstructures and properties, which,in turn, would enable development ofnear-net-shape casting methods withlittle waste. The specific objectives ofthis project were to develop method-ology to couple microscopically basedsolidification models to fluid flow andto implement these techniques withinexisting computational fluid dynamicscodes. Progress this year was made inthe following three areas.

Modeling of Equiaxed EutecticSolidification. We developed a modelof equiaxed eutectic solidification thatcouples the microstructural level(nucleation, growth, and impingementof the grains) with the macroscopiclevel of heat flow. The principal out-puts of the model are temperature andsolid fraction fields and detailed pic-

tures of the microstructure, which en-able us to analyze any microstructuralparameters of interest as a function ofcooling rate and other processing con-ditions.

Modeling of Quiescent Crystalliza-tion of Semicrystalline Polymers. Wedeveloped a multiscale model for thecrystallization of polymers that ac-counts for heat diffusion at the macro-scopic scale; grain nucleation, growth,and impingement at the mesoscopicscale; and fibrils growth at the micro-scopic scale.

Direct Modeling of DendriticGrowth. We developed a model thatreproduces the growth of solutal den-drites, i.e., the destabilization of aspherical nucleus into a dendriticgrain with primary, secondary, andtertiary dendrite arms.

We are planning to implement thesesuccessful microstructural modelswithin a new casting code being de-veloped under the Accelerated Strate-gic Computing Initiative.

Publications

Charbon, Ch., and R. LeSar, "A2DFully Coupled Model of EquiaxedEutectic Solidification," inSolidification and Processing,I. Ohnaka, and D.M. Stefanescu, Eds.(TMS, Warrendale, Pa., 1996).

Charbon, Ch., and R. LeSar, "A 2DMicro-Macro Model of EquiaxedEutectic Solidification" (to bepublished in Modeling and Simulationin Mater. Sci. Engin.).

Charbon Ch., and S. Swaminarayan,"Modeling the MicrostructureEvolution of ThermoplasticComposites" (submitted to Mater. Sci.Engin.).

Charbon Ch., and S. Swaminarayan,"A Multiscale Model of PolymerCrystallization I: Growth ofIndividual Spherulites" (submitted toPolymer Engin. Sci.).

Charbon Ch., and S. Swaminarayan,"A Multiscale Model of PolymerCrystallization II: Crystallization of aMacroscopic Part" (submitted toPolymer Engin. Sci.).

Thoma, D.J., Ch. Charbon, et al.,"Directed Light Fabrication of Iron-Based Materials," Mat. Res. Soc.Symp. Proc. 397, 341 (1996).

Low-Speed Flow Hydrodynamics

John H. Cerutti

This project has led to the develop-ment and application of a new tool,called Telluride, for the simulation ofcasting processes. Our efforts have al-lowed Telluride to model key processespresent in Los Alamos foundries.

We formulated and implemented asecond-order-accurate algorithm for therobust solution of the incompressibleEuler equations. We incorporated aRunge-Kutta time-integration scheme(ideally suited for unstructured meshes)into our volume-tracking algorithm. Wealso devised and tested in two dimen-sions a new "full remap" time-integra-tion scheme. The volume-tracking andfluid-flow algorithms give Telluride a

unique interfacial flow capability, asdemonstrated by our simulations of adrop splash and the filling of a box. Inaddition, we implemented an interfa-cial-surface-tension model (essentialfor mold-filling scenarios) and devisedand implemented a novel back-diffusion model for alloy solidification.Efficient (>90%) parallelization of ouralgorithms was demonstrated on sev-eral multiprocessor platforms.

We performed isothermal "mold-filling" simulations (neglecting heattransfer) with conditions representativeof our foundries (e.g., a top fill of a boxmold). We are presently simulating thefill of a copper chalice cast in our

foundries. We also performed heattransfer/solidification simulations of agravity-poured, cast-uranium cylindri-cal shell; we were successful in repro-ducing experimental solidificationtimes.

Because of our successes in this third(and final) year of the project, the Ac-celerated Strategic Computing InitiativeProgram has provided funding for fur-ther Telluride development.

Publications

Brackbill, J.U., and D.B. Kothe,"Dynamical Modeling of SurfaceTension" (Third Microgravity FluidPhysics Conference, Cleveland, Ohio,June 13-17,1996).

Rider, W.J., and D.B. Kothe, "VolumeTracking Reconstructed" (submitted to/. Comput. Phys.).


A New Model to Estimate RegionalEmissions Inventories

Michael Williams and Michael Brown

With collaborators from the Univer-sity of Southern California (USC), weare optimizing a new model for com-puting gridded air-pollution emissionsby integrating meteorological, photo-chemical, and hybrid receptor models.At present, estimating gridded emis-sions inventories is seen as the weak-est link in air-quality evaluations. Ourmodel, called SITEOF for SourceIdentification through Empirical Or-thogonal Functions, uses existing am-bient concentration measurements ofpollutants and then runs "backwards"to derive the pollutants' source loca-tion and strength. By applying a sta-tistical empirical-orthogonal-eigenfunction approach, SITEOFproduces emissions inventories over

an entire city on 1-km2 grids (see firstfigure).

Since emissions inventories are notknown with any certainty in the realworld, we have tested our new modelwith synthetic concentration fields(see second figure). These fields areproduced by a Laboratory-developedair-quality modeling system—thehigher-order turbulence model for at-mospheric circulation (HOTMAC)and the random particle transport anddispersion (RAPTAD) model—withuser-specified emissions inventories.Using 30 days of model-computedsynthetic hourly concentration fields,we are investigating the most effectiveways to construct gridded emissionsfrom the assumed inventories. With

our USC collaborators, we are alsodetermining the optimum location andnumber of measurement sites neededto calculate an emissions inventory.

As a prelude to the next step indeveloping our SITEOF model, wecoordinated an extensive volatileorganic compounds (VOCs) canisterstudy as part of a larger field experi-ment in the El Paso/Ciudad Juarezregion. The field experiment was ajoint effort with the Texas NaturalResource Conservation Commissionand the US Environmental ProtectionAgency. Measurements show signifi-cant correlation between carbonmonoxide and both acetylene andtrans-2-butme (see third figure), indi-cating that routinely measured COmight be used as a surrogate for otherVOCs and thus be used as an inputparameter to the SITEOF model whenstudying reactive species.

0 -

1 -

2 -

3 -

O 9°

0.0-

I0

I1

I2

I3

I4

grid no.

I5

I6

17

18

Example of gridded emissions fieldsgenerated with SITEOF fromsynthetic concentration fieldsproduced by a simple Gaussiandispersion model. The gray boxrepresents an emissions source of 8units strength; the contours depict thecomputed emissions inventory.Agreement is good for this simplecase; we are using HOTMAC andRAPTAD data to optimize theSITEOF model for more realistic(complicated) scenarios.


Sept. 2, 0300 1st

A one-hour average concentrationfield computed with the HOTMAC/RAPTAD modeling system for a 1-km2

area source of a nonreactive pollutant(CO) in the El Paso/Ciudad Juarezregion. Near the source, the plumetravels close to the ground and istransported to the south-southeast bylow-level winds; as the plume mixesupwards, it bends to the south-southwest and is carried along byupper-level winds. Thirty days ofhourly synthetic concentration, wind,and boundary-layer-depth fields wereproduced and fed into the SITEOFstatistical model. The computedemissions inventory was thencompared with the known emissionsinventory that was input intoHOTMAC/RAPTAD. The white dots inthe figure are monitoring stations.

3546

3498

338 346 354 362 370 378utmx, km

1 I ' I ' I ' I ' I ' I ' I ' I '0 10 20 30 40 50 60 70 80 90 100

concentration, micrograms/m**3

GC measurements

Gas chromatograph measurements ofcarbon monoxide (a nonreactive airpollutant) and trans-2-butene (ahighly reactive ozone precursor)taken in El Paso during an extensivefield experiment this past summer. Thehigh correlation between the two setsof measurements indicates that theroutinely measured CO can be usedas a surrogate for VOCs like trans-2-butene, which are seldom measuredfor thirty consecutive days at multiplelocations. From the data collected, wewill determine statistical relationshipsbetween CO and relevant VOCs.

I • I • I ' I • I • I • I

CO, ppm


Improving Industrial Performance throughIntegrated Process Simulation, Control,and Optimization: Modeling Atoms toEnterprise

Anne D. Henriksen

The goals of this project were asfollows: (1) develop an integrated,object-oriented system model of thetop three layers of the atoms-to-enter-prise hierarchy; (2) develop processmodels of selected steel-productionunit operations and molecular-levelmodels of selected steel-making pro-cesses for eventual integration into themodel of the top three layers; (3) es-tablish relationships with members ofthe steel industry; and (4) generateexternal funding from either DOE orcooperative research and developmentagreements (CRADAs) for follow-onwork.

We have divided the accomplish-ments of this project into two catego-ries: technical and program develop-

ment. Technical accomplishmentsinclude the following. We developedan object-oriented system simulationof selected processes on the top twolevels of the atoms-to-enterprise hier-archy and integrated them with all theelements on the third (i.e., manufac-turing) level. We developed severalmodels, including a blast-furnace,mass-balance process model (at theunit-operations level) for integrationwith the system simulation; a basicoxygen-process (BOP), carbon-end-point model (at the unit-operationslevel) based on nonlinear-model, pre-dictive control; and a BOP kineticsmodel (at the molecular level) for pre-dicting carbon endpoint, which wewill integrate with the nonlinear, pre-dictive-control model.

Under program development ac-complishments, we visited three steelcompanies (Inland, DOFASCO, andBethlehem) and established a workingrelationship with DOFASCO. We alsoestablished a relationship with theAssociation of Iron and Steel Engi-neers (AISE), the steel industry pro-fessional organization, with thefollowing outcomes: we (1) obtaineda prioritized list of three proposalsthat AISE was willing to fund forjoint work with Los Alamos;(2) hosted a meeting of over 30 AISEmembers at Los Alamos to present theLaboratory's metals- and modeling-related work; and (3) obtained fund-ing from DOE for a follow-on projecton blast-furnace stove control.

Publication

Henriksen, A.D., "A Framework forHierachical Object-OrientedSimulation Modeling of a SteelManufacturing Enterprise," in The 1996Object-Oriented Simulation Conf.Proc, C. Roberts and J. Wallace, Eds.(Society for Computer Simulation, SanDiego, Calif., 1996), pp. 123-131.

National Environmental/EconomicInfrastructure System Model

Robert Drake

We are working to develop a newmethodology for the macroeconomicmodeling of national environmentaland economic problems. We are doingthis because the current suite of thenation's best macroeconomic forecast-ing models is well known for its failureto produce accurate analyses. In thepast, the computational complicationsof simultaneously linking all of thenation's economic activities have pre-vented researchers from designing ad-equate policy analysis tools. This yearwe have explored, studied, and synthe-sized the current literature concerningthe microbehavioral foundations ofmacroeconomic analysis; we focusedespecially on the linkages of naturalresource markets and environmentalpolicy to the national economy.

We have produced a new approachfor the macroeconomic modeling ofnational environmental and economicproblems. The concept is based on theintegration of microsimulation method-ologies with the new microfoundationsof macroeconomic theory. This year wecompleted the background analyticalresearch, and we briefed Laboratoryprogram and division office leaders onour project goals and technical pros-pects. We have generated significantinternal technical support and programinterest, and we have established exter-nal contacts with the U.S. intelligencecommunity and the Department ofState. We investigated a related projectthat uses massively parallel processingat Sandia National Laboratories, andwe negotiated with them concerning

possible coordination of our organiza-tions' efforts.

We investigated the development ofan environmental technology evalua-tion tool that uses simulation sciencetechniques. We experimented at mak-ing such a tool, trying out various ideasfrom other similar projects, such as ourTransportation Analysis and SimulationSystem (TRANSEVIS) models. Wedemonstrated that the prospects for ap-plying simulation techniques to macro-economic modeling are viable. DOEEnvironmental Managementpolicymakers as well as Laboratoryenvironmental decision-makers haveexpressed interest in further develop-ment and use of the tool. They are in-terested in immediately applying it todetermine the most cost-effectivemethod of paying for the DOE com-plex cleanup within a competitive mar-ket framework. We have alreadydeveloped a very simplified model tosimulate the Laboratory's transuranicsolid-waste stream.


Global Nuclear Material Flow Model

Jared S. Dreicer

The goals of this project are to(1) characterize the global inventoryof nuclear weapons material (pluto-nium and highly enriched uranium),(2) characterize the safeguards ac-counting and management and controlmethodologies and enumerate theassociated resource requirements,(3) develop macro-system analyticalcapabilities to estimate future quanti-ties of nuclear material, estimate theimpact on material inventory of dispo-sition options, and estimate futureresource requirements for nuclearmaterial management and control,(4) develop a visual representation ofthe information related to nuclearfacilities and sites and the nuclearmaterial flow among and within coun-tries, and support the development ofother pertinent algorithmic capabili-ties necessary to undertake furtherglobal nuclear material-related stud-ies.

Our results include the following: Aprototype analytical model has beendeveloped to enable systems analysisof a variety of global, nuclear materialmanagement issues. The model can

assess future quantities and disposi-tion of nuclear material, estimatefuture resource requirements fornuclear material management andcontrol, address material-transferissues, and examine nuclear fuel-cycle, facility-specific issues. We canrepresent visually the global disposi-tion of plutonium and highly enricheduranium as well as facility-specificdata.

We have completed two nuclear-proliferation studies. The first studyindicated potential areas that requirestrengthening in the InternationalAtomic Energy Agency's SafeguardsCriteria. We specifically showed thatthere could be proliferation activitythat might go undetected under thecurrent safeguards criteria. In thesecond study we estimated theamount of plutonium likely to havebeen produced in a North Koreanresearch reactor during the entireperiod it operated.

Publications

Dreicer, J.S., and D.A. Rutherford,"Fissile Material Disposition andProliferation Risk" (InternationalSpent Nuclear Fuel and FissileMaterial Management, Reno, Nev.,June 16-20,1996).

Dreicer, J.S., and D.A. Rutherford,"Fissile Material Proliferation Risk,"Nucl. Mater. Mgmt. XXV (1), 30(1996).

Dreicer, J.S., and D.A. Rutherford,"Global Estimation of UnreportedPlutonium Production in ThermalResearch Reactors," Nucl. Mater.Mgmt. Proc. XXX, 1050 (1996).

Dreicer, J.S., and D.A. Rutherford,"Global Nuclear Material ControlModel" (International Spent NuclearFuel and Fissile Material Manage-ment, Reno, Nev., June 16-20,1996).


Atomic andMolecular Physics

Measurement Criteria Analysis forKrypton, Xenon, and Hydrogen(Hydrogen/Deuterium/Tritium) Isotopesand Concentration Variability at Distance

Bryan Fearey

Our goal is to assess the feasibilityof and technology for remotely sens-ing noble-gas fission products emittedfrom reactors in order to determinethe reactors' operating parameters andhistory. The importance of measuringxenon and krypton isotopic ratios hasincreased substantially as concernsabout global nuclear proliferationhave grown in recent years.

We have modeled and performed asystems analysis for the productionand atmospheric dilution of noble-gasfission isotopic ratios, addressing suchissues as the relative isotopic variationas a function of nuclear fuel composi-tion and reactor history and type. Ofparticular importance in our analysiswas the question of how to back-calculate process parameters given

noble-gas isotopic data. We also ana-lyzed the effect of measurement un-certainties on the estimatedparameters. The results of our workindicate that noble-gas monitoringshould be experimentally feasible.

Publications

Nakhleh, C.W., W.D. Stanbro, L.N.Hand, et al., "Noble-Gas AtmosphericMonitoring for InternationalSafeguards at Reprocessing Facilities"(to be published in Science andGlobal Security).

Program Development—Atomic and Molecular Physics 281


The Carpinteria ReservoirRedevelopment Project

Richard P. Kendall

The central goal of this project wasthe development of a Web-based, res-ervoir-management system that wouldallow multi-user access to large vol-umes of complex data and remote ac-cess to common user software tools.The objective was to greatly enhancethe quality of analysis that could bedone on complex systems such as anoil field by a small team of profes-sionals like those found in a typicalindependent oil- and gas-producingcompany (there are about 8000 suchcompanies in the United States).

We successfully developed a client-server system that can support the useof best-of-class petrotechnical soft-ware. A distributed-object data storeformed the "backplane" of this sys-tem. This data store (a data model anda collection database) complies withindustry standards (PetrotechnicalOpen Software Corporation), can bequeried from remote sites via theWeb, and can be maintained by the"owners" of the data at remote sites.

We tested the reservoir manage-ment system and actually used it toevaluate new field-development plansfor the Carpinteria offshore field.Carpinteria was chosen as the locationfor first application of the manage-ment system because the field has ex-perienced a production decline ofmore than 10 years duration—typicalof some 20 offshore California fields.The management system we designedsupports professionals (geoscientistsand engineers) at five separate loca-tions (Long Beach, Carpinteria,Ventura, Houston, and Los Alamos).In effect, the system enabled theseprofessionals to form a "virtual enter-prise" for the reservoir-managementstudy, and they have used the toolsand approaches developed in theproject to formulate and evaluate al-ternative oil recovery strategies for theCarpinteria field. This project is agood example of the use of the rapidlyevolving National Information Infra-structure to support a technicalproject.

Publications

Kendall, R.P., M.B. Lee, A.G. Sgro, etal., "Tools for the Oil & Gas VirtualEnterprise" (SPE 72nd AnnualTechnical Conference and Exhibition,San Antonio, Tex., October 5-8,1997).

Kendall, R.P., E. M. Whitney, R. Paul,et al., "A Simulation-Based ReservoirManagement Program" (SPE 72ndAnnual Technical Conference andExhibition, San Antonio, Tex.,October 5-8, 1997).

Kendall, R.P, E. M.Whitney, R.Webster, et al., "Advanced ReservoirManagement for Independent Oil &Gas Producers" (SPE 72nd AnnualTechnical Conference and Exhibition,San Antonio, Tex., October 5-8,1997).

Kendall, R.P., E. M. Whitney, R.Webster, et al., "Improved OilRecovery for Independent Oil & GasProducers" (SPE 72nd AnnualTechnical Conference and Exhibition,San Antonio, Tex., October 5-8,1997).

Sgro, A.G., R.P. Kendall, J.M. Kindel,et al., "Improved Oil Recovery forIndependent Oil and Gas Producers"(SPE Improved Oil RecoverySymposium, Tulsa, Okla., April 21,1996).

Voskanian, M.M., R.P. Kendall, E.MWhitney, et al., "A Simulation-BasedReservoir Management Program"(SPE Western Regional Meeting,Anchorage, Alaska, May 22-24,1996).

Program Development—Geoscience, Space Science, and Astrophysics 283

Satellite-Based Laser Windsounder

John Schultz

Our objective for this project is toassess the technical feasibility of us-ing satellite-based laser wind mea-surement systems to improve pro-liferation detection capabilities. Atpresent, much of the United States'ability to detect proliferation dependson physically sampling wind-borneeffluents from suspected facilities, butthe effectiveness of this technique isseverely limited by inadequate knowl-edge of wind patterns. From our inter-actions with the relevant operationalproliferation detection organization,we confirmed that better wind mea-surements would contribute greatly tolong-range and regional proliferationdetection. We also obtained enthusias-tic programmatic support and usefulassessments of measurement require-ments and priorities from the opera-tional users.

We evaluated four potential laserwind-sensing techniques and selectedthe incoherent Doppler technique. It

uses an interferometer to measure theDoppler shift in near-ultraviolet laserlight scattered from aerosols and par-ticulates entrained in the atmosphere.Our choice was based on the simplic-ity and maturity of the required lasersand interferometers and on the poten-tial for using the same system to mea-sure other atmospheric parameters ofinterest, such as water vapor content,temperatures, and various cloudproperties.

We completed a conceptual designstudy to identify the technical chal-lenges inherent in a relatively inex-pensive, low-risk, proof-of-conceptsmall-satellite mission appropriate toLos Alamos' technical capabilities.The major challenges that we identi-fied were the system's weight, powerconsumption, laser scanning patternand pointing knowledge, and tech-niques for assimilating measured datainto atmospheric transport models.Our conceptual design was based onthe Fabry-Perot interferometer tech-

nology that has been used for allknown incoherent Doppler lidar sys-tems to date. During the course of thestudy, however, it became apparentthat much simpler optical systemsbased on Mach-Zehnder interferom-eters promise equivalent performancewith substantially reduced weight andpower consumption. At the conclusionof the study, we built a breadboardMach-Zehnder interferometer-basedsystem and used it to qualitativelyverify these predictions. To quantita-tively verify the benefits of systemsbased on Mach-Zehnder interferom-eters, we have developed detailedplans that include constructing andtesting a fieldable ground-based windmeasurement system in collaborationwith the University of Wisconsin andperforming numerical data assimila-tion studies.

Publications

Czuchlewski, S.J., MJ. Brown, G.H.Nickel, et al., "Preliminary Analysisof Lidar Techniques for RegionalMeteorological Studies," Proceedingsof the Gas Lasers Conference, SPIE2702, 52-64 (1996).

Conditioning Geological ReservoirRealizations with Time-Dependent Data

Richard P. Kendall

The goal of this project was to pro-vide a preliminary geostatistical char-acterization of the Carpinteria off-shore field in order to support thefuture stochastic simulation of its geo-logical attributes. This oil reservoir istypical of some twenty offshore fieldsnear the California coastline. Most ofthese fields are experiencing a seriousdecline in oil production, which we

can hope to stem only with the appli-cation of the most advanced recoverytechniques. One such technique isgeostatistics to reduce the inherentuncertainty in the geological descrip-tion of the field.

The most important finding of thiswork was the identification of poten-tial "pay" layers of the field, based onthe underlying statistics of the field

measurements (primarily well logs).These layers have the highest oil stor-age capacity and conductivity. Thestudy also suggests that reservoir at-tributes correlate over distances of atleast 500 ft. Since the median distancefrom a well to its nearest neighbor isabout 250 ft, this means that improve-ments in modeling can be expected ifstochastic simulation methods areused.


Improved Atmospheric Transport for RiskAssessment in Complex Terrain

Daniel Cooper

Our objective is development ofreliable and useful risk-assessmentmethods for problems involving therelease of atmospheric contaminants.These methods require a combinationof quality and simplicity. Qualitymeans accurate and timely estimatesof the likely transport trajectories andthe dilution, deposition, and transfor-mation of the material during travel.Simplicity means user-friendliness

and ability to implement the estimateswith available computing tools.

The development of a micro- andmesoscale, convective, turbulent at-mospheric model is well underway.Some initial testing has been per-formed with very promising results.We used data acquired by the Ramanwater-vapor lidar showing plumestructure over the ocean as a test forvalidation of the model. Initial results

are very promising, including the abil-ity to model 2- to 5-m structures inthe surface layer of the atmospherefor the first time. Furthermore, themodel appears to give the structuralinformation observed by the lidar.

The biggest hurdle for the model isthe improved code development re-quired for the model to operate onworkstation computers, since thepresent software requires extensivemainframe time. The next step is toimprove the model and perform acomplete evaluation of the model'sability to simulate complex plumedynamics in the surface-atmosphereinterface.

Reservoir Enhancement on theImpermeable Margins of ProductiveGeothermal Fields: Integrated ResourceDevelopment and Management

James Albright

The objective of our project for thepast year was three-fold. First, wewanted to identify, collaborate, andpartner with members of the geother-mal industry in evaluating the applica-tion of microseismic mappingtechnology for assessing the role offracture permeability in developingand managing geothermal productionfields. Second, we planned to preparea proposal for submission to DOE forthe evaluation and assessment ofmicroseismic mapping technology.Third, we intended to reassemble aborehole seismic instrumentationpackage used in research at LosAlamos 10 years ago and retrofit it

with contemporary electronics andsensors. This package would then beused to conduct assessments of themapping hardware in producingfields.

In June 1996 in Santa Rosa,California, we introduced the poten-tial for microseismic mapping torepresentatives of the geothermal in-dustry at a DOE-sponsored workshopon "Subsurface Permeability Detec-tion and Mapping." Representativesfrom 80% of the major producersattended the workshop. We identifiedthree potential industrial collabora-tors, visited their geothermal fields,assessed the reservoir development

and management needs, and devel-oped work plans. Two of the collabo-rators accepted our invitation toparticipate in preparing a proposal forthe evaluation of the technology. Wesubmitted this proposal to DOE inSeptember 1996.

In the past year, we also designedthe seismic instrumentation package.We reassembled the package fromsalvaged parts, machined and fabri-cated missing mechanical parts,designed and fabricated improvedelectronics circuitry, and procured andinstalled state-of-the-art sensors. Wetested the entire package in a high-temperature well and deemed theinstrument fit for service.

Program Development—Geoscience, Space Science, and Astrophysics 285


Disposition of Plutonium as NonfertileFuel for Water Reactors

Kenneth Chidester

In this project, we are studying thepotential for reducing global pluto-nium inventories by creating specialfuels, especially nonfertile fuels, forburning in conventional reactors. Ourproject continued to build upon theinitial investigations of nonfertile fu-els and concentrated on examiningevolutionary mixed-oxide (EMOX)fuels consisting of the mixed oxidesurania, plutonia, and a nonfertile com-ponent (currently, calcia-stabilizedzirconia). The nonfertile componentreplaces some of the fertile uranium,lowering the amount of plutoniumproduced through breeding and result-ing in a net destruction—over the irra-diation cycle—of plutonium in thefuel. We performed detailed reactorphysics calculations to determine thebehavior of the EMOX fuel under avariety of parameters. We also con-ducted fabrication experiments to de-termine the feasibility of usingstandard, commercial processes forfabricating nuclear fuel to produceEMOX fuel with the desired composi-tions.

The results of the calculations indi-cate that net reduction of core-aver-aged plutonium inventories can beaccomplished using plutonium load-ings of greater than 6% (PuO2 in UO2-PuO2) with a nonfertile fraction of30% (amount of fuel that is thenonfertile component). The nuclearreactor is loaded with a one-third core

of EMOX fuel (the other two-thirdscontains standard low-enriched ura-nium fuel). Loading a core entirelywith EMOX lowers the plutonium-loading requirement to less than 3%.Plutonium destruction rates increasewith increasing plutonium loadingand an increasing core fraction ofEMOX. Additionally, EMOX exhibitsreactivity coefficients nearly identicalto those of standard MOX.

We used the solid-state reactionmethod to fabricate a number ofnonfertile and EMOX fuel pellets ofvarying compositions. The source ofreactor fuel was PuO2 derived fromthe hydride-dehydride process forconverting weapons-grade plutoniummetal to oxide. Specifically, we fabri-cated a nonfertile fuel with a compo-sition of PuO2 (2.69 wt %), ZrO2

(87.19 wt %), and CaO (10.12 wt %).The nonfertile fuel was sintered to89.7% of theoretical density. In addi-tion, we fabricated an EMOX fuelwith a composition of PuO2

(10.97 wt %), UO2 (83.94 wt %), andZrO2 (4.63 wt %). The EMOX fuelwas sintered to 96.8% of theoreticaldensity. No fabrication difficultieswere encountered.

Publications

Beard, C.A., J.J. Buksa, et al.,"Development of Evolutionary MixedOxide Fuel," I996ANS/ENS WinterInt. Meeting Trans. 75, TANSAO 751-490(1996).

Buksa, J., S. Eaton, and J. Toevs,"Disposition of Plutonium as MixedOxide Nuclear Fuel," Fourth Int.Conf. Nucl. Eng. (ICONE-4) 4, 453(1996).

Eaton, S.L., C.A. Beard, and J.J.Buksa, "Evolutionary Mixed OxideFuel Performance in PressurizedWater Reactors," 1996ANS/ENSWinter Int. Meeting Trans. 75,TANSAO 75 1-490 (1996).

Ramsey, K.B., and H.T. Blair,"Fabrication of a Non-Fertile Fuel forthe Disposition of WeaponsPlutonium," Fourth Int. Conf. Nucl.Eng. (ICONE-4) 4, 499 (1996).

Ramsey, K.B., and K. Chidester,"Fabrication of Non-Fertile andEvolutionary Mixed Oxide Fuels,"1996ANS/ENS Winter Int. MeetingTrans. 75, TANSAO 75 1-490 (1996).

Program Development—Nuclear and Particle Physics 287

An Ultracold Neutron Facility at theManual Lujan Jr. Neutron ScatteringCenter

Thomas Bowles

Ultracold neutrons (UCNs) are neu-trons whose wavelengths are so longthat they can undergo total internalreflection from a variety of materials.This makes it possible to confineUCNs in a bottle for more than 100 s,making a compact source for use infundamental physics research.

A UCN capability is seen as an es-sential component if Los Alamos is toexecute a strong and ongoing experi-mental program that would be amongthe world's foremost in fundamentalneutron physics. This project is in-tended to develop and demonstrate afirst experimental UCN source at theManuel Lujan Jr. Neutron ScatteringCenter (MLNSC). This experimentalsource will be based on a Doppler-shifted, Bragg-scattered source andwill use a rotor to select beam pulsesfrom the accelerator.

The UCN source uses Flight Path11 at MLNSC. A guide tube trans-ports the cold neutrons out to theUCN converter, which is a set of micacrystals on the end of a rotor that ro-tates in synchronism with the beampulse rate (20 Hz). UCNs are pro-duced at the rotor and pass through ashutter to be transported by the guide

tube to the experiment. A UCN bottlewith filter plates at the ends has beenconstructed to allow a differentialmeasurement of the UCN velocityspectrum.

Some of our accomplishments thisyear were the installation and align-ment of the guide tube and shutterassembly on Flight Path 11; detailedcalculations of the shielding and theshielding design, procurement, andinstallation; tests of the algorithms forthe phasing of the rotor-drive motor tothe 400-m/s cold neutrons from theMLNSC liquid hydrogen source; andthe assembly and testing of the rotorsystem, UCN guide tubes, and UCNbottle. Some small modifications tothe system to improve operations arecurrently under way.

Other accomplishments were theinstallation of the instrumentation forsafe operation and monitoring of thesystem; measurements of thereflectivity and mosaic spread of themica crystals used in the UCN source;design and building of the crystalpackage using the parameters ob-tained from Monte Carlo calculations;and detailed Monte Carlo calculations

of the predicted UCN rate using mea-sured parameters as input. These cal-culations agree well with ouranalytical predictions of the UCNrates. More-detailed Monte Carlo andanalytical calculations are now underway to better understand the micro-scopic production processes.

We have also assembled the entiresystem on the beam line. The systemincludes the source, monitoringequipment, shielding, and data acqui-sition electronics and the UCN guide,bottle, filters, and detector. We arewaiting for the new liquid hydrogensource to become available at theMLNSC to start the first experimentalmeasurements.

Publications

Seestrom, S.J., TJ. Bowles, et al.,"Plans for an Ultra Cold NeutronSource at Los Alamos" (Tsukuba,Japan, Hadron Project Workshop—Nuclear Physics and FundamentalPhysics with Neutrons, March 1996).

Seestrom, S.J., T.J. Bowles, R. Hill,et al., "Development of an Ultra ColdNeutron Source at the Los AlamosSpallation Source" (to be published inProc. 14th Int. Conf. Appl. Accel. Res.Ind.).

Seestrom, S.J., T.J. Bowles, R. Hill, etal., "Development of an Ultra ColdNeutron Source at MLNSC" (to bepublished in Proc. Int. Conf. Appl.Nucl. Tech.).

Measurement of Fissile Material in SpentFuel and Alternate Nuclear Materials

Mark Pickrell

We investigate neutron interroga-tion methods for measuring spent fuelagainst high-radiation backgrounds.Two applications of these methods arethe measurement of fissile content inspent fuel and the measurement offissile material in alternate nuclearmaterials. In our experiments, weused a deuterium-tritium neutron gen-erator developed for borehole logging.

The time control of the neutronsignal and the data acquisition elec-tronics that we have developed forand used in the experiments are en-tirely novel. Instead of using a shortneutron pulse, as has been done con-ventionally, we used a square-waveneutron signal and implemented adigital lock-in amplifier by using apersonal computer and digital time

sealers. Compared with conventionaltechniques, ours yields significantlyimproved signal-to-noise ratios bothfrom the interrogating neutrons andfrom the background radiation.

Our new method can be applied tomeasuring the fissile content and thereactivity of spent fuel for safeguardsand safety. Our project led directly toa fully funded program to develop ahigh-fluence neutron source as theinterrogating driver. The high-fluencesource will also be used to furtherimprove the signal-to-noise ratio ofour measurements.


Biosciences

A Consortium for Biomedical Applicationsof Single-Molecule Detection

Richard Keller

Our goal is to perform basic re-search and explore applications inultrasensitive fluorescence detectiontechnology in collaboration with theUniversity of New Mexico (UNM)and private industry. The Laboratoryleads the world in developing tech-niques for ultrasensitive fluorescencedetection in flowing streams. We havedemonstrated the detection of indi-vidual fluorescent molecules as theyare transported through a laser beam.Applications include DNA sequenc-ing, DNA fragment sizing, sensitiveassays for randomly generated phar-maceuticals, and assays for ligands toorphan receptors. We anticipate addi-tional applications in the areas ofarcheology and ecology.

We made significant progress in ourapproach to DNA sizing; we are nowusing our flow cytometry approach tosize large PI artificial chromosomeclones and extended our sizing rangedown to 217 base pairs and up to167,000 base pairs. A small DNA-sizin apparatus has been built andtested. We have developed muchfaster, more accurate algorithms forsingle-molecule detection that provideinformation not previously available.We designed a pressure loading sys-tem that reduced sample loading timeby a factor of 20. We also refined ourmeasurements on the photobleachingof single molecules of phycoerythrinand submitted the data for publica-tion. In related work, we have devel-oped an assay to find different ligandsto promote cell growth in chemo-therapy patients. For his contributions

to advancing single-molecule detec-tion, Richard Keller received theLester W. Strock Award from theSociety for Applied Spectroscopy.

In addition to basic research, wedeveloped secondary applications forlaser and instrument manufacturers,chemical producers, and testinglaboratories.

Publications

Affleck, R.L., W.P. Ambrose,J.N. Demas, et al., "Reduction ofLuminescent Background in Ultra-sensitive Fluorescence Detection byPhotobleaching," Anal. Chem. 68,2270 (1996).

Ambrose, W.P., R.L. Affleck,P.M. Goodwin, et al., "ImagingBiological Molecules with SingleMolecule Sensitivity Using Near-Field Scanning Optical Microscopy,"Exp. Technol. Phys. 41, 237 (1995).

Ambrose, W.P., P.M. Goodwin, J.Enderlein, et al., "FluorescencePhoton Antibunching from SingleMolecules on a Surface" (submitted toPhys. Rev. Lett.).

Enderlein, J., and R.A. Keller,"Comparison of One and Two FocusSet-up in Single Molecule DetectionExperiments" (submitted to Appl.Spectrosc).

Goodwin, P.M., W.P. Ambrose, andR.A. Keller, "Single MoleculeDetection in Liquids by Laser-induced Fluorescence" (to bepublished in Acct. Chem. Res.).

Goodwin, P.M., W.P. Ambrose, et al.,"Spatial Dependence of the OpticalCollection Efficiency in FlowCytometry," Cytometry 21,133(1995).

Goodwin, P.M., R.L. Affleck, W.P.Ambrose, et al., "Detection of SingleFluorescent Molecules in FlowingSample Streams," in ComputerAssisted Analytical Spectrometry,Steven D. Brown, Ed. (Wiley andSons, New York, 1996).

Huang, Z., J.T. Petty, B. O'Quinn,et al., "Large DNA Fragment Sizingby Flow Cytometry: Application tothe Characterization of PI ArtificialChromosomes (PAC) Clones,"Nucleic Acids Res. 24, 4202 (1996).

Keller, R.A., W.P. Ambrose,P.M. Goodwin, et al., "SingleMolecule Fluorescence Analysis inSolution," Appl. Spectrosc. 50,12A(1996).

Roslaniec, M.C., C.S. Bell-Prince,H.A. Crissman, et al., "New FlowCytometric Technologies for the 21stCentury" (submitted to Hum. Cell).

Wu, M., P.M. Goodwin, et al.,"Photochemistry and FluorescenceEmission Dynamics of SingleMolecules in Solution: B-Phycoerythrin?' /. Phys. Chem. 100(1996).

Program Development—Biosciences 289

Cancer Risk Assessment

Bruce Lehnert

Creating new, mechanisticallybased biotechnological methods forassessing the risk of cancer develop-ment in individuals who have been ormay be exposed to environmental car-cinogens is the objective of thisproject. Extensive evidence indicatesthat cancer risk is related to the exist-ence of specific "susceptibility genes"that are heterogeneously distributedamong humans. However, an indi-vidualized assessment of cancer riskhas not been previously possible be-cause of major gaps in understandingthe basic mechanisms involved in car-cinogenesis.

The scientific focus of this projecthas been to identify those critical

genes and gene products that renderindividuals more susceptible to expo-sures to carcinogens, especially ioniz-ing radiations. The initial specificaims of our mechanistically basedeffort have been to identify and char-acterize potential cancer-susceptibilitygenes that are involved in cell-cycleregulation and DNA repair and to de-velop advanced flow-cytometry as-says for those genes that arecandidates for cancer susceptibility.Longer-term goals of the project areto establish relationships between sus-ceptibility gene products and cancerrisk and to develop bioassays for as-sessing the risk posed by the suscepti-bility genes and gene products.

This year, we have successfully cor-related nuclear regulating factors withcell-cycle checkpoints; we haveproved that alpha particles, such asthose emitted by radon and radonprogeny, cause Gl and G2 cell-cycledelays in normal cells; we have foundthat alpha particles can induce thegeneration of DNA-damaging extra-cellular factors that may be exploitedas biomarkers of exposure; we havedemonstrated that wild-type and mu-tant p53 differentially alter the cell-cycle and apoptotic responses to DNAdamage; and we have demonstratedthat poly (ADP-ribose) polymerase isassociated with the products of someDNA-repair proteins. Finally, we havedemonstrated that phase-sensitiveflow cytometry can distinguishbetween immunofluorochrome-labeled antigens and cellularautofluorescence.

Human Brain Mapping: Experimental andComputational Approaches

Charles Wood

Our project combines novel sen-sors, data acquisition techniques, andhigh-performance computing to ad-vance noninvasive brain imaging. Theexperimental component emphasizesoptimization of spatial and temporalresolution of functional brain imagingby combining structural magneticresonance imaging (MRI) of brainanatomy; functional MRI of bloodflow, oxygenation, and volume; andmagnetoencephalography (MEG) ofneuronal population currents. Thecomputational component emphasizesdevelopment of a high-resolution,three-dimensional volumetric modelof the brain based on anatomicalMRI; this model integrates structuraland functional information from mul-tiple forms of brain images.

In the past year, we made four ma-jor accomplishments. First, we com-pleted and published the results of ourinitial experiments using functionalMRI (fMRI) and MEG to compare

brain activation under comparableexperimental conditions. These ex-perimental comparisons used pat-terned visual stimulation foractivation of striate and extra-striatevisual cortex in the two functionalimaging modalities. In both fMRI andMEG, we observed multiple foci ofactivation, which is consistent withpredictions of brain activation fornonhuman primates. We are perform-ing additional analyses to determinethe precise degree of correspondencebetween the two activation measures.

Second, we completed and pub-lished the results of our MEG studiesof retinotopic organization of thehuman visual cortex. This analysisdemonstrated small but systematicdepartures from the conventional"cruciform" model. These data willform the base for further comparisonsof fMRI and MEG.

Third, we made significant progresson developing algorithms and soft-

ware for constrained modeling andintegration of anatomical MRI, fMRI,and MEG. These same techniqueswill be extended to integration withother functional imaging modalities.

Finally, we continued trade-offstudies between boundary elementmodels for the electromagnetic in-verse problem and the widely usedand simpler spherical and spherical-shell models. Boundary element mod-els can, in principle, provide greateraccuracy at the cost of increased com-putational complexity. However, nei-ther the extent of the theoretical gainsin accuracy nor the associated degreeof additional computational cost havebeen thoroughly explored.

Publications

Aine, C.J., et al. "RetinotopicOrganization of Human VisualCortex: Departures from the ClassicalModel," Cerebral Cortex 6, 354(1996).

George, I.S., et al., "MappingFunction in the Human Brain withMEG, Anatomical MRI, andFunctional MRI," /. Clin.Neurophysiol. 12, 406 (1995).


Universal Biological-Agent Point-SensorProgram Development

Gary Salzman

The three objectives for this projectwere (1) to upgrade our biology labo-ratory to Biosafety Level 2 (BL2) andto provide organisms and toxins toinvestigators in the Life Sciences Di-vision and other Laboratory organiza-tions, (2) to help develop and then touse a DNA-fragment-sizing flowcytometer (here called a microflowcytometer) to determine whether

bacteria can be identified by the massspectrum of a DNA fragment obtainedusing a set of restriction enzymes, and(3) to develop flow-cytometric meth-ods for identifying toxins.

This year we completed the BL2upgrade and obtained 25 microorgan-isms. We also developed a microflowcytometer for DNA-fragment sizing.The flow cytometer uses a 532-nm,

solid-state laser, a microchannel flowchamber, and a photon-counting de-tector. We obtained DNA fragmentsusing restriction enzymes and stainedthe fragments with POPO-3, a dyethat is stoichiometric for DNA con-tent. We then analyzed the fragmentsample with the microflow cytometer.The response was linearly propor-tional to DNA content from 384 to167,000 base pairs. We obtainedDNA-fragment spectra from A,-phageDNA and from bacteria artificialchromosomes. We also developedbead-based sandwich assays forbotulinum toxins A and B, ricin, andanthrax.

Sensors for Point Detection ofChemical and Biological Warfare Agents

Thomas Zawodzinski

The goal, of this project was todevelop sensors that detect airbornechemical warfare (CW) agents. Dur-ing this year we progressed in demon-strating electrochemical sensors forCW agents and in developing surfacecoatings for surface acoustic wave(SAW) and optical sensors for CWagents. In addition to sensing CWagents, we can also chemicallymodify, and thus destroy, CW agentsusing either our electrochemical orour SAW and optical technologies.

We demonstrated electrochemicalsensors for quantifying HCN (a bloodagent) and have also demonstrated apossible electrochemical approach forquantifying sulfur mustards. Usingboth enzymatic and enzyme-mimickingcatalytic sensors, we could senseHCN in the part-per-billion range.The enzyme-mimicking catalytic ap-proach involves replacing the enzyme

with an organometallic complex thatmimics the enzyme function. Thisapproach adds considerable robust-ness to our sensor while retaining theamplification from electrocatalyticreactions. The HCN sensors are alsoreversible. We are preparing severalpatent applications stemming fromthis work.

Our specific goals for the SAW andoptical sensors were to (1) developnew self-assembled linker layers toenhance thin-film densities andstabilities, (2) develop new ap-proaches to multilayer thin films forenhanced sensitivity, and (3) measurethe SAW response of cyclodextrin(CD) and calixarene (CA) thin filmsto CW-agent simulants.

First, we developed and tested new,high-density, well-ordered linkerlayers based on bifunctional self-assembled thin films. These linker

layers resulted in an approximately25% improvement in the density ofreagent molecules. This higher den-sity led to increased sensitivity andmore stable films. We also used thesenew linker layers as reference films inSAW measurements. Second, we de-veloped a new polyelectrolyte deposi-tion method to quickly preparemultilayer thin films with control atthe molecular level. So far, we havetested this approach on CA and nickelphalocyanine thin-film reagents andwill soon test it on CD reagents.These thin films are quite stable andreproducible. We also developed anew sol-gel approach to prepare mul-tilayer films with excellent control ofthe reagent chemistry. New multilayerfilms prepared in this manner haveshown excellent sensitivity and stabil-ity. Third, we began testing CD andCA monolayer films against CW-agent simulants. We also developed atest bed for Zeeman interferometryand initiated tests using our CD andCA thin films.


Molecular Medicine for the 21 st Century:A Computational Basis for Design andCritique of Vaccines and Therapeutics

Alan Lapedes

The kissing-loop RNA motif, inwhich the loops of two stem-loopstructures base-pair with each other, isthought to modulate steps in the lifecycle of retroviruses such as HIV (seeaccompanying diagram). Using anRNA-folding protocol developed forthis project, which takes into accountinformation on possible base pairingsand structural constraints resultingfrom connectivity requirements, weare studying the folding of a potentialkissing-loop motif in HIV. Specifi-cally, we are modeling the structureand the flexibility of this motif, andwe have worked out three possiblestructures with low conformationalenergies (see accompanying figureshowing molecular models).

Following on our earlier work, inwhich we analyzed correlated muta-tions (also known as nonindependentmutations) in the V3 loop of HIV, wehave developed an evolutionary modelthat incorporates these mutations at

different positions in model se-quences. (A correlated mutation is amutation at one site that affects a mu-tation at another site.) Our evolution-ary model takes into account how thephylogenetic tree affects the analysisof mutations, and it shows a highercorrespondence of correlated posi-tions with structurally adjacent posi-tions in the model than do previousanalyses.

Furthermore, using patient data andsimple models, we have begun ana-lyzing and have published the firstquantitative estimates of the dynamicsof HIV in vivo. We found that 10 bil-lion viral particles are produced andcleared each day in a typical mid-stage AIDS patient and that the vastmajority (99%) of virus is producedby cells that live only about 1.5 days.These estimates suggest that if HIVreplication can be completely stoppedby potent drug combinations, then allHIV and infected cells might beeliminated from the body after two tothree years of treatment.

Publications

Perelson, A.S., A.U. Neumann, M.Markowitz, et al., "HIV-1 DynamicsIn Vivo: Virion Clearance Rate,Infected Cell Lifespan, and ViralGeneration Time," Science 271, 1582(1996).

helix 1

A""~\

G

C

helix 3

5'

C:U:C:G:G:

G•

C (

- UGUCG

5'

G^AGCC

\G U C•

- A G

: /:C:A:G:C

hairpin 1

helix 2

hairpin 2

The sequence and secondary structureof HIV TAR-TAR* kissing-loop motif.

* " • " • •**

Three predicted structures of the HIV TAR-TAR* kissing-loop motif. Helices 1 and 2 are shown in light gray, and helix 3is in medium gray. The two single-stranded loops (p-A-p, p-U-p) are plotted in dark gray.


Distributed Telemedicine for the NationalInformation InfrastructureTestbed

David Forslund

TeleMed is an advanced data man-agement tool that uses object-basedcomputing, distributed data reposito-ries, advanced graphical user inter-faces, visualization tools, andinnovative concept extraction of im-age information for storing and ac-cessing medical records. More than astandard client/server application,TeleMed has a multitiered architec-ture in which there are multiple serv-ers between the persistent storage ofdatabases and the clients.

In the original deployment ofTeleMed, we used a Sybase productcalled Gain Momentum for the clientbecause of its powerful multimediauser-interface capabilities. Becausethe Java programming language wasso widely and rapidly accepted on thebasis of its portability and its usabilityon the Internet, we have elected tomove away from Gain Momentum.

This year we began the transitionfrom the Gain Momentum client to aJava-based client, extended the infra-structure to support relational data-bases, and worked with industry tobegin the process of deploying tech-nologies similar to TeleMed through-out the nation. We coordinated thework of several organizations tocollaboratively sponsor two work-shops on the Master Patient Index foruse throughout the healthcare indus-try. The system was also deployed andtested at the National Jewish Centerfor Immunology and RespiratoryMedicine in Denver, Colorado, and atthe National Institutes of Health inBethesda, Maryland. Our proposal towork with the National InformationInfrastructure Testbed was rejected bythat organization, which is now calledthe InfoTest. However, our work inthis area has caught the interest of a

potential commercial partner, and theUnited States Army has given usfunding to deploy TeleMed in its vari-ous testbeds. We have also workedsuccessfully with Northern NewMexico Community College to findways of making TeleMed available forrural healthcare, including the awardof a two-year grant by the NationalTelecommunications & InformationAdministration of the Department ofCommerce.

Publications

Forslund, D.W., "What CORBA CanDo: an Example of a New SystemDeveloped with Object Technology,"Proceedings: Toward an ElectronicPatient Record^ (II), 255 (1996).

Forslund, D.W., and D. Kilman, "TheVirtual Patient Record: A Key toDistributed Healthcare and Tele-medicine," First Class Magazine VI(II), 14 (1996).

Forslund, D.W., R.L. Phillips, et al.,"Experiences with a DistributedVirtual Patient Record System," J.Am. Medical Informatics AssociationProceedings Symp. Supple., 483(1996).

Deformable Human Body ModelDevelopment

William Wray

Our goal is to develop a realistic,fully accessible, deformable humanbody model that is applicable to auto-mobile design by integrating existinganthropomorphic dummy models withexisting detailed biomechanical com-ponent models.

We have conducted extensive studyof human body anatomy and mechan-ics and determined that the criticaljoints that are sufficiently movable to

require representation in the deform-able human body model include themajor synovial joints of the upper andlower limbs, the synovial joints of therib cage, and the cartilaginous jointsof the vertebral column.

The major synovial joints of theappendicular skeleton include theball-and-socket joints of the shouldersand hips and the hinge joints of theelbows and knees. The sternocostal

and costovertebral joints of the ribcage are gliding synovial joints, ex-cept for the first sternocostal joint,which is cartilaginous. The cartilagi-nous joints of the cervical, thoracic,and lumbar vertebrae are of a typecalled symphysis.

We have developed methods of rep-resenting the three types of synovialjoints (gliding, hinged, and ball-and-socket) and one type of cartilaginousjoint (symphysis) in finite-elementcodes. These joint representationmethods will provide a means forlinking detailed biomechanical mod-els to the baseline anthropomorphicdummy models.


Detection and Characterization ofBiological-Weapons Agents by Matrix-Assisted Laser Desorption/lonizationMass Spectrometry

Charles Wilkerson

The objective of this project was todevelop and demonstrate a field-deployable point sensor, based onmatrix-assisted laser desorption/ion-ization (MALDI) mass spectrometry,to unambiguously identify biologicaltoxins. Specifically, our goals were to(1) develop a MALDI source capableof coupling with either a time-of-flight (TOF) mass spectrometer or anion-trap (IT) mass spectrometer,

(2) characterize the MALDI sourcefrom instrumental and applicationperspectives, (3) implement method-ologies for identifying biological tox-ins and verifying their structures, (4)critically compare experimental re-sults obtained when the MALDIsource is used in combination with aTOF or IT mass spectrometer, and(5) design a field instrument based on

the detection system that produced thehighest-quality data.

During this year we constructedinstrumentation to perform MALDI-TOF mass spectrometry on proteins.In addition, we wrote and tested dataacquisition and analysis software. Wesuccessfully detected the proteinsgramicidin S (-1150 Da) and bovineinsulin (-5300 Da), but technical ob-stacles prevented us from observinglarger species, such as anthrax toxins(80,000-90,000 Da) and botulinumtoxin A (-150,000 Da). Over thecourse of the year, we modified theinstrument, continually improving itscapabilities. We also modeled thebehavior of ions in the spectrometerto help extend our high-mass capabili-ties.

Novel Gene Complex StructureDetermination by Neutron and X-RayScattering

Joe Gatewood

There are in excess of 200,000genes in each cell in the human body.Most of these genes are inactivatedwhile specific genes remain func-tional. The packaging of genes intohigher-order chromatin is a funda-mental factor in determining geneactivity. The basic unit of chromatin isthe core particle, which consists ofDNA wrapped around a protein as-sembly of the four core histones. Twocopies of each of the four core his-tones combine to form a proteinoctamer, which binds 146 base pairsof DNA. A fifth linker histone (his-tone HI) interacts with DNA extend-ing from the core particle to form thenucleosome. The proteins in this com-plex are similar in organisms rangingfrom mouse to man. The core histonesconsist of "major" and "minor" vari-ants. The minor variants constituteless than 15% of the histones insomatic cells.

We have successfully isolated "op-erative" chromatin containing exclu-sively the minor histone variants.Histone HI is quantitatively missingfrom operative chromatin. One of theaims of this project was to determinethe proteins responsible for stabilizingoperative chromatin. This chromatinis stabilized by the microtubule pro-teins tau and tubulin. Another goal ofthis project was to characterize thestructure of operative chromatin nu-cleosomes. Using solution scattering,we examined nucleosomes containingthe minor variants and demonstratedthat these particles are structurallydistinct from nucleosomes containingthe major variants. The unusual struc-ture and stabilization of operativechromatin by microtubule proteinsprovides a possible mechanism fordirect interaction of transcriptionmachinery with specific chromatindomains.


In Situ Bioremediation ofTrichloroethylene-ContaminatedGroundwater

Nina Rosenberg

Results of bioremediation effortsare typically variable and difficult topredict. An incomplete understandingof the effects of variable site charac-teristics (notably, soil heterogeneity,indigenous microbial ecology, andcontaminant speciation) and the lackof adequate tools that would allowspecialists to predict results and mea-sure successful bioremediation strate-gies have made the implementation ofbioremediation more empirical thandesired. Our main objective for thisproject is to develop practical compu-tational tools that will enable us towork with site owners and providersof remediation services in order tosolve problems in site-specific designand in performance assessment andimplementation of bioremedationstrategies for chlorinated solvents,such as trichloroethylene (TCE), ingroundwater.

This year, we have accomplished anumber of tasks. First, we have con-ducted an extensive literature reviewof previous experiments on competi-tion between different types of mi-crobes present in soil and on preda-tion in soil microbe systems. It hasbecome clear not only that predationand competition are present at con-taminated sites, but that they also

have a significant impact on the effec-tiveness of microbial degradation ofcontaminants. Next, we created acomputer code that can be used tocharacterize microbial metabolism inlaboratory-scale bioreactors.

We conducted sensitivity analysesof key biokinetic parameters in a fieldexperiment aimed at the bioreme-diation of TCE contamination, andthen we ranked the parameters. It isknown that the degradation of TCEgenerates by-products that are toxic tothe degrading microbes. Our analysesindicated that TCE toxicity was, infact, the most important parameter.We also analyzed soil heterogeneitythrough homogenization theory. Thenaturally occurring heterogeneity insoils has not been included adequatelyin previous modeling studies ofbioremediation; that is one major rea-son for such studies not to have beensufficiently accurate. In computationalmodels, the total volume of soil en-compassed by a field site is repre-sented by a grid of small boxes, and asingle value is used for soil propertieswithin each box. As a result, subgrid-scale variability is completelysmoothed away. However, in reality,subgrid-scale heterogeneity can

modify the flow field, and thus it canstrongly affect the chemical environ-ment of the microbial population. Ourmodel removes part of this source oferror through application of homo-genization theory. Homogenizationtheory determines an equivalent ten-sor to represent subgrid-scale proper-ties. Computational experimentsindicate this is a significant improve-ment over the former use of singlescalar quantities within grid boxes.

Finally, we have prepared severalmanuscripts for submission to profes-sional journals and have submitted aproposal to the Environmental Man-agement Science Program (EMSP)competition. Our proposal wasclosely tied to a project on the geneticengineering of bacteria to more effi-ciently degrade TCE. Although ourproposal made it to the last round, itwas not funded. However, reviewswere favorable, and we plan to resub-mit an improved proposal for the nextround of the EMSP competition, aswell as for the upcoming NaturalAccelerated Bioremediation call.

Publications

Travis, B.J., and N.D. Rosenberg,"Modeling In Situ Bioremediation ofTCE at Savannah River" (submitted toEnviron. Sci. Technol.).

Vanderberg-Twary, L., K. Steenhoudt,B. Travis, et al., "Biodegradation ofPaint Stripper Solvents in a ModifiedGas Lift Loop Bioreactor" (to bepublished in Biotechnol. Bioeng.).


Index of PrincipalInvestigators

Abdallah, J. Jr. 72Albers, R. 157Albright, J. 285Alcouffe, R.E. 194Altherr, M. 119Arthur, E.D. 187Aubrey, J. 241Avens, L. 266

B

Balatsky,A. 156Baldridge, W.S. 189Barlow, D. 174Barrett, C. 274Benage, J. 40Benjamin, R. 171Berendzen, J.R. 129Bhatia,T.S. 177Bhattacharya, T. 111Bigio, I. 25,127, 129Birn, J. 92,218Bishop, A. 70,161, 191,204Booth, T.E. 190Borovsky, J. 99Bourke, M.A.M. 147, 152Bowles, T. 288Bowman, J.D. 103Bradbury, E.M. 126Brainard, J. 235,237,267Breshears, D.D. 93Brown, D.L. 61Brown, M. 276Buescher, K. 273Burns, C. 47Bystritskii, V.M. 170

Camassa, R. 65Campbell,! 159,249Campbell, L. 168Carlson, J. 105Carlsten, B. 43Casperson, D.E. 94Cerutti, J.H. 275Chamberlin, R.M. 59Chen,D. 118Chen, S. 67Chen,W. 66Chidester, K. 287Clark, T. 41Clements, B.E. 155Cline, M. 232Cobble, J.A. 44Collins, L. 71Coogan, J. 259Cooke, D.W. 9Cooper, D. 285Cort, B. 140Cram,L.S. 118,226Cranfill, C.W. 188Cremers, D. 23

Davis, H.A. 26Day,R.D. 256Devlin, D. 146Doering, C. 194Doggett, N. 227Donahue, J. 262Donohoe, R. 21, 185Doolen, G. 167Drake, 278Dreicer, J.S. 279Dunand, D.C. 152Dye,R. 14,242Dyer, R.B. 121

EarLW. 51Early, J. 261Ecke, R. 202Eckert, J. 148Elling, J.W. 23Elliott, S. 98Epstein, R. 15,211

Faber, V. 203Faehl, RJ. 41Farnum, E. 29Farrar, C.R. 31, 171Fasel, J. 199Fazio M., 37Fearey,B. 281Federspiel, F. 108Fenimore, E. 83Fitzsimmons, M. 154Flynn, E. 169Forehand, H. 273Forslund, D. 293Frauenfelder, H. 233, 236Freyer, J.P. 123Funk, DJ. 73, 172Funsten, H.O. 75, 250, 256

Garcia, A. 122Gary, S.P. 81Garzon, F. 35Gatewood, J. 294Gavrilov, E. 68Gerstl, S. 208,212,214Glatzmaier, G. 82,207Goff,F. 88Goodwin, E. 116Gosling, J. 85

Index of Principal Investigators 299

Gosnell,T.R. 33,74Gottesfeld, S. 25Gubernatis, J. 193, 198, 200, 201Gupta, G. 120,228Gupta, R. 114Guthrie, G. 251Guzik, J. 86

H

Hahn, H. 199Haight,R. 108Hamkalo,B. 226Hammel, P.C. 27, 151Haschke, J. 60Hasslacher, B. 62Haussler, D. 232Hawley, M. 144Hayden,F.G. 127Heffner,R. 147,243Hemberger.P. 255Henriksen, A.D. 278Henson, B. 58Hermes R., 59Hersman, L. 230Hickmott, D.D. 78,248Hills, J. 95Hime,A. 110Hixson, R. 11Hjelm, R. 140,227Hoffbauer, M. 14Hoffman, C. 108Holm, D.D. 30,62,63Houts,M. 255Howe, P.M. 243HowelU.A. 251Huang, J. 155Hubbard,K. 18Hughes, R. 31,34Hyman, J. 64,66

Jacobson, A. 91James, B. 249Jarvinen, G. 245,268Jen,E. 69Jia,Q. 153Johnson, P. 83Johnston, R. 30Jones, E. 76

K

Kao,C.-YJ. 80,213Kapustinsky, J. 27Keller, C. 216Keller, R. 229, 289Kendall, R.P. 283,284Kinnison,W. 104Kirkpatrick, R. 180Kocks,U.F. 143Koskelo,A. 79Kraus, R. 36Kubas, G. 54

Lackner, K. 34,183Laflamme,R. 99Lai, C.-C. 91Lamartine, B. 36Lapedes,A. 232,292Lehnert, B. 290LeSar, R. 275Lewis, G. 250,254Lewis, P. 247Li,D. 20,53LomdahLP. 192Lowe,T.C. 146

M

Machines, M. 183,230Mack,J. 247Madland, D. 111Maggiore, C. 179Mainieri, R. 35Maley, M. 160Margolin, L. 188McBranch, D. 45,159McComas, DJ. 75McDonald, T. 253McNaughton, M.W. 109Migliori, A. 19Miller, W. 100,102Milonni, P. 74Mitchell, T. 163Morel, J. 61, 189Morris, C. 175,177Mosteller,R. 201Mottola,E. 112,198Munson, C. 262

N

Nguyen, D.C. 40Niederauer, G. 254

Ott, K. 57

P

Paffett,M. 185Papcun, G. 274Park, M.S. 119,231Parkin, D. 149Pearson, J. 130Peng, J.-C. 109Perelson,A. 127Perry, F. 95Petrovic, J. 244Phillips, D.R. 213Picard, R. 195Pickrell,M. 288Poling, D. 192Prather, K.A. 184Pratt, L. 117Preston, D. 168

QQuinlan, D. 67

R

Rider, W. 196Roberts, J. 135,145Roberts, R.S. 35Robinson, B.A. 80Robinson, J.M. 84,184Robinson, R. 142,223Rosenberg, N. 295Rosocha,L.A. 170,265Ryne, R. 182


uSaltzman, J.S. 65,193Salzman, G. 291Sauer, N. 52Scheuer, J. 260Schiferl,D. 90Schiferl, S. 18Schmidt, D. 24Schmidt, S.C. 56Schoenborn, B. 120Schroeder, N. 267Schultz, J. 284Schwarz, R.B. 138Scovel, J. 63Scripsick, R. 137Seestrom, S. 179Shankland, T. 220Shashkov, M. 69Sheffield, R. 178Shi,N. 136Sickafus, K.E. 10Silks, L.A. 46, 116Sinnis, C. 113Smith, B.R 57, 270Smith, D. 19Smith, G. 137, 149, 226Soderquist, S.D. 173Solem, J. 244Sparks, W. 81Steckle,W.P. 15Stevens, M. 154,241

Ullmann, J. 108Unkefer,C. 128

Venneri, F. 174Vieira, D. 106Voter, A. 50

wWadlinger, E. 260Warren, M. 85Watkin, J. 55Wesse,F.J. 170West, G. 104White, A. 200Wilkerson, C. 294Williams, M. 276Wills, J. 142Winske, D. 102,210Wood, C. 117,290Woodruff, W. 52,60,225Wray,W. 293Wysocki, F. 42

Strauss, C.E.M. 71Stringfield, R. 271Suszcynsky, D. 78Swanson, B. 150Sze,R. 32

TTaylor, A. 28, 38, 252Terwilliger, T. 121,122Thode, L.E. 39Thoma,D. 12Thompson, J. 209Thompson, J.D. 139, 158, 242Tolmie, D. 68Torney, D. 124,234Trewhella, J. 115, 225, 234Tumas, W 48, 269

York,R. 248

zZaera, F. 185Zawodzinski, T. 51,291Zhu,Y.T. 16Zurek,W. 96,98Zweig, G. 64

USGPO 1997 573-236/33199Index of Principal Investigators 301

This report has been reproduceddirectly from the best available copy.

It is available to DOE and DOEcontractors from the Office ofScientific and Technical Information,P.O. Box 62,Oak Ridge, TN 37831.Prices are available from(615)576-8401.

It is available to the public from theNational Technical InformationService,US Department of Commerce,5285 Port Royal Rd.Springfield, VA 22616.

BACK COVER

Clockwise from upper right:• Accretion disk around a rotating black hole (W. Miller,

"Accretion onto Black Holes: The Power-GeneratingMechanism").

• Diffusion image of helium-3 gas at thermal equilibrium(D. Schmidt, "Nuclear Magnetic Resonance Imaging withHyperpolarized Noble Gases").

• Optical shadowgraph of the spiral defect chaos state in thermalconvection (R. Ecke, "Self-Organization and Pattern Formation").

• Plasmid for expressing fusion proteins (J. Trewella, "Biotechnol-ogy Approaches to Stable-Isotope Labeling for BiomolecularStructure/Function Studies").

i s> *

la-13278-pr progress report 1 l aboratory- 9 directed ... · and nitride thin films 18 texture...

Documents