volume 104, number 2, march–april 1999 journal of research ... · contact: stephen hsu, (301)...

Volume 104, Number 2, March–April 1999Journal of Research of the National Institute of Standards and Technology

General DevelopmentsInquiries about News Briefs, where no contact personis identified, should be referred to the Managing Editor,Journal of Research, National Institute of Standardsand Technology, Building 101, Room E215, Gaithers-burg, MD 20899-2500; telephone: 301/975-3577.

GUIDE TO CALIBRATION SERVICE FORCAPACITANCE STANDARDS AVAILABLENIST is offering the first publication that provides acomprehensive description of its calibration service forcapacitance standards at low frequencies.

These standards are used by industry to calibratesecondary laboratory standards that ensure the qualityof various other capacitors contained in electrical andelectronic products. Traceability of the capacitancevalue and/or the uncertainty of the value is importantfor safety, performance, reliability and stability reasons.

NIST Special Publication 250-47 includes new infor-mation, such as improved uncertainties for the NISTcalibration of fused-silica capacitance standards, whichare gaining widespread use in industrial standards andcalibration labs. It also contains material taken fromNational Bureau of Standards (NIST’s predecessor)work dating back to the 1950s.

SP 250-47 can be ordered under stock no. SN 003-003-03549-1 from the U.S. Government PrintingOffice, (202) 512-1800; or under order no. PB 98-144587 from the National Technical InformationService, (800) 553-6847.Media Contact: Emil Venere (301) 975-5745; [email protected].

NEW DIRECTORY LISTS FEDERALCERTIFICATION AND RELATED PROGRAMSA newly revised NIST directory, distributed via theInternet, lists Federal certification and related require-ments for hundreds of products and services regulated

News Briefs

or purchased by 18 federal departments and indepen-dent agencies. An update of a 1988 edition, the newdirectory outlines requirements for items ranging frombottled water to building products, and from nuclearfacilities to narcotic test kits and other law-enforcementequipment.

For each Federal program, entries explain itspurpose, whether requirements are mandatory or volun-tary, and procedures for ensuring compliance andidentifying conformance. Additional particulars includeagency contact points, authorizing laws and regulations,inspection and testing requirements, sources of docu-mentation, manufacturer or vendor obligations, andreciprocity arrangements.

The intended audience for the directory includesindustry, government agencies (Federal, state, local andforeign) and the general public.

The Directory of Federal Government Certificationand Related Programsis one output of NIST’s efforts tobuild a comprehensive database on U.S. standards,regulations and conformity assessment programs. It canbe downloaded from the World Wide Web at http://ts.nist.gov/ts/htdocs/210/217/ 217.htm. Printed copiesof the directory will be available later this year. Formore information, contact Maureen Breitenberg, Officeof Standards Services, NIST, 100 Bureau Drive, Stop2100, Gaithersburg, Md. 20899-2100, (301) 975-4031,[email protected] Contact: Mark Bello (301) 975-3776; [email protected].

SOLIDIFICATION SENSOR FOR TURBINEBLADE CASTINGS DEVELOPEDJet engine manufacturers are concerned about thetemperature and stress performance of their system’sturbine blades. One way to ensure high performance isto monitor the blades as they are being cast to ensuresingle-crystal growth. NIST has developed a trans-mission x-ray diffraction sensor that precisely locatesthe boundary between a liquid metal and a solidifyingcrystal while they are still in a casting mold.

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Although x-ray diffraction monitoring has been triedbefore, the NIST system is unique because it employshigh x-ray energies that can sense the physical state ofthe casting through a thick ceramic mold and within avacuum furnace.

NIST has recently published a detailed, illustratedreport that describes the sensor system. It covers thetheory of x-ray interactions with matter, models of x-raytransmission diffraction, the apparatus used for high-energy transmission diffraction, and describes a numberof diffraction experiments.

The project started in 1994 as part of the NISTConsortium on Casting of Alloys, a government-industry-university collaboration with the goal ofimproving the quality and reducing the cost ofaerospace castings through advances in materialsscience.

For a single, free copy of the report,High-Energy,Transmission X-Ray Diffraction for Monitoring Turbine-Blade Solidification (NIST Technical Note 1500-3),contact Dale W. Fitting, MC853.07, NIST, Boulder, CO80303-3337; (303) 497-3445; [email protected] Contact: Fred McGehan (303) 497-3246;[email protected].

NIST’S RUMBLE ELECTED PRESIDENT OFCODATAJohn Rumble,Jr., head of the Standard Reference DataProgram at the National Institute of Standards andTechnology, was recently elected president of theCommittee on Data for Science and Technology. Estab-lished in 1966 by the International Council for Science,CODATA seeks to improve the quality, reliability,processing, management and accessibility of data ofimportance to science and technology.

Rumble hasbeen active in developing scientific data-base standards, including an international standard forindustrial data exchange. He also has helped buildseveral online property data systems.

Further information on CODATA is available on itsweb site: http://www.codata.org/codata.Media Contact: Linda Joy (301) 975-4403; [email protected].

NEW APPARATUS MEASURESTHERMAL-BARRIER COATINGS BETTERNIST researchers have developed an apparatus to mea-sure the thermal conductivity of thermal-barrier coat-ings (known as TBCs) as thin as 20mm. TBCs—used inaerospace materials, gas turbine engines and diesel en-gines—are thermal coatings applied to metal substrates

to protect these substrates from high temperatures andexcessive wear or corrosion.

Accurate measurement of thermal conductivities iscritical before new coating systems can be incorporatedinto advanced engineering designs and future applica-tions. For example, engineers want to keep loweringthermal conductivities so that TBC thickness candecrease as well.

The NIST device uses an infrared microscope tomeasure temperature differences on millimeter-sizedspecimens. The small size of the specimens allows themeasurements to be made in air—rather than in avacuum—which simplifies the apparatus needed.Another advantage is the noncontact nature of theinfrared temperature measurement. Any contactbetween a sensor and a small specimen would affect thespecimen’s temperature.

For a copy of paper 1-99 describing the thermalconductivity measuring device, contact Sarabeth Harris,MS104, NIST, Boulder, CO 80303-3337; (303) 497-3237; [email protected] Contact: Fred McGehan (303) 497-3246;[email protected].

A NOVEL WEAR TESTER FORBIOMATERIALS EVALUATIONUltrahigh molecular weight polyethylene paired with analloy of cobalt and chromium is currently the materialof choice for longer lasting orthopedic implants, such asjoint replacements for hips and knees. Though thiscombination of materials has proven to be durable andcompatible with the human body, joints made fromthese components last only about a decade, and thesearch for better materials is ongoing.

To speed up this process, NIST and four privatecompanies have joined together to design, construct,and test a new apparatus that will reduce the timerequired for testing of implant materials. Until now, ithas, for example, taken about 6 months for conventionalequipment to simulate the natural wear of artificial hips.

A computer-controlled wear tester has been designedand built by NIST scientists that has the capability ofcross-shearing motions, programmable loading cycles,and spike loads. Using materials of known wear charac-teristics, a test procedure of 1 week duration has beendeveloped that correctly predicts their ranking. Surfacetextures and wear debris morphology produced aresimilar to those from retrieval studies. The currenteffort involves a test refinement to allow different phys-iological loading cycles and spikes to be programmed.CONTACT: S tephen Hsu , (301) 975-6120 ;[email protected].

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NIST-DEVELOPED VALIDATION SYSTEMFOR TRIPLE DATA ENCRYPTION STANDARDALGORITHM APPROVED AS AMERICANNATIONAL STANDARDS INSTITUTE (ANSI)GUIDELINEIn January 1999, ANSI approved the NIST-developedModes of Operation Validation System for the TripleData Encryption Algorithm as an ANSI guideline. Thisguideline, ASC X9 TG.192Part 1: Modes of OperationValidation System for the Triple Data EncryptionAlgorithm (TMOVS), specifies the procedures involvedin validating implementations of the Triple DESAlgorithm in ANSI X9.52-1998, Triple Data Encryp-tion Algorithm Modes of Operation. Those who haveimplemented the Triple DES Algorithm and are seekingformal validation of their implementation will utilizethis ANSI guideline. Successful completion of the testscontained within the TMOVS is required to claimconformance to ANSI X9.52-1998.

The TMOVS specifies individual sets of validationtests, which must be successfully completed to validatean implementation of the Triple DES Algorithm. A sep-arate set of validation tests has been developed for theencryption and decryption processes of each mode ofoperation.

The TMOVS is composed of two types of validationtests: Known Answer Tests and Modes Tests. TheKnown Answer Tests are used to verify that implemen-tations correctly implement the components of theAlgorithm (e.g., S boxes, permutation tables, etc.). TheKnown Answer Tests operate on the idea that givenknown input, a known output must be produced.

The second type of validation test, the Modes Test,verifies that the implementation being tested has notbeen designed just to pass the Known Answer Tests. Asuccessful series of Modes Tests also gives assurancethat an anomalous combination of inputs would notresult in an error.

TMOVS testing will be performed as part of the NISTCryptographic Module Validation (CMV) Program. TheCMV Program uses laboratories accredited by NISTsNational Voluntary Laboratory Accreditation Programto test cryptographic products that conform to NISTstandards. A vendor contracts with an accredited labora-tory to perform the tests. After the testing is complete,the laboratory submits the results to NIST for validation.If the vendors implementation of the specific algorithmhas passed the tests successfully, NIST issues a valida-tion certificate to the vendor.CONTACT: Sharon S. Keller, (301) 975-2910; [email protected].

PATENT AWARDED TO NIST SCIENTISTA patent describing a new lithography process forpatterning silicon microchips that uses metastable raregas atoms for resist exposure was recently granted to aNIST scientist. Metastable rare gas atoms, instead ofphotons, electrons, or ions, are directed at the surface ofa lithographic resist. On impact, the metastable atomsrelease up to 20 eV of energy per atom into the resist,altering its chemical nature and making it susceptible toetching. The use of metastable rare gas atoms for litho-graphy makes it possible to take advantage of the newtechniques of atom optics, which can be used to focus,improve the collimation and intensity of, or modulatethe incident atoms. With these techniques, fabrication offeatures as small as 1 nm might be possible in a parallelprocess—a goal unattainable by the conventionalmethods of optical, electron beam, or ion beam litho-graphy. This invention could play a role in solving thesub-100 nm lithography challenge that will be faced bythe multibillion dollar microcircuit fabrication industryin the near future.CONTACT: Jabez McClelland, (301) 975-3721; [email protected].

PREFIXES FOR BINARY MULTIPLESThe International Electrotechnical Commission (IEC),the leading international organization for worldwidestandardization in electrotechnology,recently adopted asan IEC International Standard names and symbols forprefixes for binary multiples for use in the fields of dataprocessing and data transmission. The new prefixeswere developed by IEC Technical Committee (TC) 25,quantities and units, and their letter symbols, with thestrong support of the International Committee forWeights and Measures and the Institute of Electricaland Electronics Engineers. A NIST scientist, who is amember of Working Group 1 of IEC/TC 25, played asignificant role in the development of the prefixes.

Although the General Conference on Weights andMeasures has adopted prefixes as part of the Interna-tional System of Units or SI (the modern metric system)to form decimal multiples and submultiples of SI units,these prefixes represent exact powers of 10. On theother hand, in information technology there is a greatneed for prefixes for binary multiples, i.e., prefixesto express exact powers of two. The new prefixes forbinary multiples are in fact derived from the SI prefixesfor decimal multiples. For example, the new prefix for(210)1 = 1024 is called kibi, symbol Ki, which is to becompared with the SI prefix for (103)1 = 1000, which is

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called kilo, symbol k. Thus one kibibit is written1 Kibit = 210 bit, while one kilobit is written 1 kbit =103 bit. Similarly, the new prefix for (210)2 =1 048 576 is called mebi, symbol Mi, which is to becompared with the SI prefix (103)2 = 1 000 000, whichis called mega, symbol M. Thus one mebibyte is written1 MiB = 220 B, while one megabyte is written1 MB = 106 B. The other new prefixes are 230 = (210)3,called gibi, symbol Gi; 240 = (210)4, called tebi, symbolTi; 250 = (210)5, called pebi, symbol Pi; and 260 = (210)6,called exbi, symbol Ei. These are to be compared withthe SI prefixes for 109, 1012, 1015, and 1018, which arerespectively giga, G; tera, T; peta, P; and exa, E. Thenew prefixes will eliminate the present confusionbetween powers of 1000 and powers of 1024 since in thefield of information technology the SIprefix names andsymbols for decimal multiples are now often used torepresent binary multiples.CONTACT: Barry N. Taylor, (301) 975-4220; [email protected].

MEDICAL PHYSICISTS PUBLISHRECOMMENDATIONS ON RADIOCHROMICFILM DOSIMETRYThe American Association of Physicists in MedicineRadiation Therapy Committee Task Group has pub-lished recommendations on radiochromic film dosime-try. The task group contained three NIST staff members,one of whom pioneered the technique some 30 years agowhen he published investigations to determine the dosi-metric properties of various forms radiochromic media.

With recent improvements in the sensitivity, accuracy,and precision of radiochromic film manufacturing,as well as the ruggedness and ease of the use ofradiochromic dosimeters themselves, such dosimetershave become increasingly popular in medical and non-medical applications. Over the past several years thedosimetric properties of radiochromic dosimeters havebeen evaluated by many investigators and an extensiveliterature on various aspects of radiochromic dosimetryhas appeared. The most common form of the mediaconsists of a thin coating, some tens of micrometersthick, on a plastic base material of the order of 0.1 mmto 0.2 mm thick. The initially colorless emulsion turnsblue upon exposure to ionizing radiation but is insensi-tive to room light and requires no processing to fix theimage as does conventional x-ray film. The intensity ofthe color change is proportional to absorbed dose, mak-ing it a nearly ideal dosimeter for applications requiringhigh spatial resolution. At present, various radiochromicdosimeters in the form not only of thin films

but also thicker films, gels, liquid solutions, and liquidcore waveguides, are used for routine dosimetry of ion-izing radiation over a wide range of absorbed dose(0.01 Gy to 1 MGy) and absorbed dose rates (up toabout 1 TGy/s). In recent years, various radiochromicdosimeters also have been used for non-clinical applica-tions such as blood irradiation, radiation processing, andas transfer standards.

Until now, there have been no comprehensive guide-lines on the use and calibration and associated densito-metric systems for clinical use. The report fills theneeds of a hospital physicist utilizing radiochromicfilms for medical applications. The report consists of(1) characteristics of available radiochromic films,(2) procedures for using radiochromic films for dosi-metry, (3) characteristics of scanning systems anddensitometers, (4) medical applications of radiochromicdetectors, and (5) future directions.CONTACT: Christopher Soares, (301) 975-5589;[email protected].

NONDESTRUCTIVE RADIOASSAYTECHNIQUE DEVELOPED BY NIST FORFLUID-FILLED BALLOON CATHETERSOne of the most active areas in both cardiology andinterventional radiology is intravascular brachytherapy(IVBT) for the prevention of coronary restenosis follow-ing percutaneous transluminal coronary angioplasty.Because this is a relatively new field of research, manydose delivery systems involving different radioisotopesand devices are under investigation by several researchgroups. To make meaningful comparisons betweenthese different techniques, it is necessary to have accu-rate knowledge of the dose delivered to the artery byeach system.

An approach being developed by NIST relates thedelivered dose to the amount of radioactivity present inthe delivery system. To do this, a method has been devel-oped to perform direct and nondestructive measure-ments of the contained radioactivity in balloon cathetersources. The technique uses a commercially availablewell ionization chamber (“dose calibrator”) and aspecial radiation shield designed by NIST researchers.The shield was designed to cut all of the radiationemanating from parts of the catheter delivery systemexcept the balloon itself, so that the response of the dosecalibrator is due only to the activity contained in theballoon. This system eliminates errors in estimating thecontained activity from incorrect assumptions about thecatheter dimensions and inhomogeneity of the fluidinside the balloon (i.e., air bubbles).

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A necessary part of the development of this systemwas its calibration, which was achieved for the first testcase, radioactive133Xe gas, using NIST calibrated am-poule sources. A calibration geometry was designed forthe system that permits an instrument calibration factorfor the balloon catheter to be derived using sourcescalibrated in a NIST standard geometry. Monte Carlocalculations of the responses in the dose calibratorchamber to133Xe gas in the standard and modified ge-ometries indicate agreement to within 3 % to 4 %. It isexpected that better agreement will be found forradionuclides that emit higher-energy radiations, suchas188Re and186Re. This technique can be applied in theclinical setting to calculate quickly and accuratelyadministered IVBT doses based on direct activitymeasurements, increasing the safety and effectivenessof the treatment procedure.CONTACT: Brian E. Zimmerman, (301) 975-5191;[email protected].

NIST DEVELOPS GLOW-DISCHARGERESONANCE IONIZATION MASSSPECTROMETRY FOR MEASUREMENTOF ENVIRONMENTAL RADIOACTIVITYFor many years, NIST has distributed natural-matrixradioactivity standards containing trace amounts ofactivation and fission products in matrices such as soilsand sediments. The extremely low concentrations ofradio-nuclides have been measured by sophisticated andtime-consuming (1 to 2 weeks for sample preparation)radiochemical analyses, which require the use ofsolvents for sample extraction. As an alternative methodof measurement, NIST physicists have developed anew resonance ionization mass spectrometry (RIMS)system. This system, which uses a glow discharge sourceand lasers to vaporize soil or sediment containing traceamounts of radioactive materials to be assayed by amagnetic sector mass spectrometer, has been developedto provide a means for establishing radioactive standardsin environmental materials useable in clean-up andremediation programs.

The advantages of a glow discharge source are many.The inherent simplicity of source handling and the vastreduction in measurement-time minimize sample prepa-ration error and improve turn-around time in the labora-tory. The accessibility for measurement of all massspecies and the elimination of some interfering molecu-lar species in the plasma allows for high sensitivity withlow background. The possibility of obtaining these highsensitivities combined with the direct interrogation ofthe source material reduces the need for extractionsolvents (with subsequent disposal requirements) sinceradiochemical processing can be bypassed. Calibration

of the system can be obtained by simple isotope dilutionof the sample with usually stable, more abundant isotopequantitation of a gravimetrically dispensed mastersolution.

The system shows great promise in the monitoring oflong-lived (half-lives in the range of 100 years or longer)radionuclides in the environment. Typically, forsuch radionuclides, measurements are required at the1310–12 level. With the high sensitivity and directmeasurement potential of RIMS, this becomes doablewithout the need to invest an inordinate amount oftime in sample preparation or funds on hazardous wastedisposal.CONTACT: Lisa Karam, (301) 975-5561; [email protected] or Leticia Pibida, (301) 975-5538; [email protected].

REAL-TIME CHARACTERIZATION OFLITHIUM TRANSPORT IN THIN-FILMSThin film “rocking-chair” type cells hold great promisefor both “smart window” and rechargeable batteryapplications by way of reversible ion transfer. Smartwindows increase or decrease their light transmissionvia the application of a small electrical bias and maybecome extremely important for energy conservation.Windows coated with such films can greatly reducecooling costs during summer in northern areas, and yearround throughout the sunbelt. Lightweight, less toxiclithium-based batteries now dominate the market forlaptop computer, cell phone, and other consumerelectronics. Market demand for all types of rechargeablecells is expected to grow at a compound rate of 11 % peryear, reaching a total of 2 billion cells by 2001, of whichthe lithium ion cell share is expected to be 440 millioncells. Thus the market for lithium ion cells will soonreach about $4 billion. In spite of this rapid commercial-ization, much of the underlying materials science is notcompletely understood; such knowledge is necessary toproduce better-performing and cheaper products.

Smart windows and many types of lithium batteriesconsist of two mixed electron/ion-conducting layersseparated by an ion-conducting, solid electrolyte layer.Variation in optical density or charge potential isachieved as lithium ions are transported from one layerthrough the electrolyte to the other layer. The techniqueof neutron depth profiling (NDP) provides a non-destructive method of measuring the analyte concentra-tion as a function of the depth in the matrix material.NDP has been employed to examine the dynamiclithium distribution in active electrochromic multilayersand has provided insight to the correlation between thedevice optical density and the lithium transfer betweenthe device electrodes. Measurements made with and

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without the electrical bias quantify the migration oflithium as it occurs. The application of these efforts intothe area of lithium batteries may explain the reasons forsuch problems as charge capacity loss with cycling,lower than theoretically attainable reversible chargecapacity, and less than theoretically attainable maximumcharging and discharging current densities.CONTACT: George P. Lamaze, (301) 975-6202;[email protected] or Heather H. Chen-Mayer,(301) 975-3782; [email protected].

NIST COMMENCES ACCREDITATION/OVERSIGHT OF COMMERCIALPROFICIENCY TESTING STUDY PROVIDERSFOR EPA/STATES WATER PROGRAMSWorking with the U.S. Environmental ProtectionAgency (EPA), states, and other public and commercialentities, NIST has established a system under whichprivate-sector and interested states can be accredited byNIST to provide proficiency testing (PT) services tothose laboratories testing drinking water and wastewaterfor regulated chemical, radiological, and microbiologi-cal parameters for EPA and state water programs.

Since the 1970s, EPA has conducted semiannual pro-ficiency testing to assess the competence of more than8000 public and private-sector laboratories to conductanalyses required by the Clean Water and the SafeDrinking Water Acts. The cost-free provision of theseservices is being replaced by a multiprovider system inwhich NIST-accredited state and private-sector entitieswill provide these PT services on a fee-basis.

NIST NVLAP is accepting applications for accredita-tion for any of 48 PT program areas in this new field,Providers of Proficiency Testing. Applicants will beassessed for their competence to develop and character-ize PT materials and to conduct proficiency test studies.Accredited providers must comply with the require-ments of NIST Handbook 150,NVLAP Procedures andGeneral Requirementsand the newly developed NISTHandbook 150-19,Chemical Calibration-Providers ofProficiency Testingfor the provision of PT studies thatmeet the needs described in EPAs “National Standardsfor Water Proficiency Testing Studies: Criteria Docu-ment.” In addition, NIST and EPA have worked with theNational Environmental Laboratory AccreditationConference (NELAC) to ensure that the PT studiesconducted by the NIST-accredited providers will meetNELAC standards for use in accrediting environmentallaboratories.

NIST accreditation and oversight of these providers andprovision of Standard Reference Materials to assistin value-assigning PT materials are critical for accep-tance of these PT assessments by the laboratories beingtested, laboratory accreditation bodies (both private- andgovernment-based), and other interested parties.CONTACT: Reenie M. Parris, (301) 975-3103;[email protected] or C. Doug Faison, (301) 975-5304; [email protected].

NEW METHOD DEVELOPED FOR ACQUIRINGINTERFACE VIBRATIONAL SPECTRANIST researchers have developed a new method foracquiring vibrational spectra of interfaces via sum-frequency generation (SFG). Vibrational spectroscopyis a powerful probe for the characterization of structureand chemical bonding; however, conventional vibra-tional spectroscopies (infrared absorption and Ramanscattering) are of limited utility for the study of inter-faces due to the presence of large background signalsfrom the bulk material. SFG is a second-order nonlinearoptical spectroscopy that is uniquely interface sensitivebecause SFG mixing is symmetry forbidden in cen-trosymmetric bulk materials such as liquids, gases, andmany solids such as silicon.

The new method developed at NIST involves the inter-action of a spectrally broad (500 cm–1), ultrashort(<200 fs) infrared laser pulse with a spectrally narrow(ø4 cm–1) visible laser pulse. Non-linear interactions atan interface result in the generation of a broad sum-frequency spectrum, the entirety of which is detectedwith a spectrometer equipped with an array detector.This allows acquisition of a spectrum over the 500 cm–1

region without tuning the infrared laser or scanning thespectrometer. The new technique has advantages inease-of-use, spectral quality, and data acquisition rateover the conventional method, which involves the inter-action of two spectrally narrow laser pulses and requirestuning of the infrared laser.

SFG vibrational spectra should provide significantinsights into critical interfaces, such as those encoun-tered in the study of biological membranes and polymeradhesion, and those underlying the technology ofbiosensors and advanced semiconductors. The newmethod was published in the Oct. 15, 1998, issue ofOptics Letters.CONTACT: Lee Richter, (301) 975-4152; [email protected].

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IRREVERSIBLE MAGNETIC FIELDDEPENDENCE OF THE MAGNETICSTRUCTURE IN GMR Co/Cu MULTILAYERSPolarized neutron reflectivity (PNR) and scanningelectron microscopy with polarization analysis(SEMPA) were used successfully to resolve a contro-versy involving the giant magnetoresistance (GMR) inCo/Cu multilayers. The GMR in these multilayersmakes them very attractive for possible magnetic-fieldsensor applications.

In general, the magnetoresistance of a GMR multi-layer dramatically decreases when an external fieldreorients the in-plane magnetizations of the ferro-magnetic layers parallel to each other. The magneto-resistance is largest for systems in which the low-fieldresistance is associated with antiparallel alignment ofadjacent ferromagnetic layers. For Co/Cu multilayerswith thick Cu layers, the magnetoresistance for theas-prepared multilayer is often larger than the maximumobtained after cycling the magnetic field. The magneticstructure corresponding to this large magnetoresistancestate has been a puzzle.

Co/Cu samples prepared by a university wereanalyzed by NIST scientists using both PNR andSEMPA. PNR probes the order of the entire sample andprovides a depth profile of the magnetization, whileSEMPA produces a direct image of the magneticdomain structure within one magnetic layer at a time.The PNR and SEMPA measurements reveal that as-prepared samples show a strong antiparallel alignmentof the ferromagnetic Co domains across the nonmag-netic Cu interlayers. This antiparallel magnetic state isirreversibly destroyed by the application of a magneticfield. After field cycling, the smaller residual peaks inthe magneto-resistance are then associated with thepresence of small, randomly oriented Co domains.

Using the powerful, complementary tools of PNR andSEMPA, the investigation shows that it should be possi-ble to enhance the performance of these GMR multi-layer sensors by stabilizing the initial antiparallelmagnetic state.CONTACT: Julie Borchers, (301) 975-6597; [email protected] or John Unguris, (301) 975-3712;[email protected].

EXPERIMENTS SHOW FEASIBILITY OF NEWSCANNING-PROBE MICROSCOPE TYPE FORHIGH-RE SOLUTION IMAGING OF FIELDSENCOUNTERED IN MAGNETIC RECORDINGNIST scientists have carried out experiments leadingtoward the development of a new type of magnetic-resonance imaging microscope for applications in themagnetic data storage industry. Applications envisaged

for the instrument include meas-urements of fringingfields above the air bearing surface of recording heads,measurements of fields from bits written on recordingmedia, and field mapping on very small scales. Theinstrument is a scanning probe microscope thatmeasures the magnetic force between a magneticresonance specimen and a magnetized probe. Severallaboratories in the United States and abroad are tryingto develop similar instruments, which are referred to asmagnetic resonance force microscopes, or MRFMs.

To test the instrument, it is necessary to use a materialthat has a strong electron spin resonance (ESR) line.The organic compound 2,2-diphenyl-1-picrylhydrazyl(DPPH) is ideal for this purpose. The experimentalconfiguration has a 5 mm DPPH particle mounted on avibrating cantilever, which, in turn, is positioned near asmall permanent magnet probe equipped with apiezoelectric-drive stage. Magnetic resonance is modu-lated so that the magnetic force between the probe andthe particle is at the cantilever resonance frequency. Thehigh mechanicalQ of the vibrating cantilever is the keyto the unprecedented sensitivity of this technique.

Electron spin resonance spectra were obtained bymeasuring the changes of the oscillation amplitude ofthe cantilever as a function of the sweeping backgroundfield at fixed points in a plane over the magnet probe.The data then were used to generate magnetic fieldmeasurements at each point above the specimen parti-cle. The resonant magnetic field is defined as theproduct of the resonance frequency and the gyro-magnetic ratio of the electron. Both are well-knownparameters for DPPH.

The cantilever force is proportional to the product ofthe DPPH particle magnetic moment and the localmagnetic field gradient. The peak cantilever force atresonance is about 1 pN in a field gradient of 100 T/mand an applied field of 30 mT for a 5mm DPPH particle.This corresponds to the detection of about 1010 electronspins in the specimen particle at room temperature.Mechanically softer micromachined cantilevers areexpected to provide better force sensitivity, and higherfield gradients are expected to improve spatial resolu-tion. The division team expects that combining thesefeatures should make it possible to use particles wellbelow 1mm size at room temperature.CONTACT: John Moreland, (303) 497-3641; [email protected].

NIST WORKS WITH INDUSTRY TO ROADMAPINFORMATION TECH NOLOGY NEEDS FORTHE ELECTRONICS INDUSTRYThe National Electronics Manufacturing Initiative(NEMI) is an industry-led consortium of more than 50

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manufacturers, suppliers, universities, and federal agen-cies dedicated to bolstering the national electronicsmanufacturing supply infrastructure and to facilitatingNorth American leadership in consumer electronicsmanufacturing. NEMI lays out a research agendathrough its suite of technology roadmaps, publishedevery two years, and initiates projects to address identi-fied gaps where no similar efforts exist. NIST has co-ledand contributed to several of the working groups thatrecently published updated Technology Roadmaps. Oneof the key technologies charted by NEMI is that ofFactory Information Systems.

Factory Information Systems (FIS) form the nervoussystem of a manufacturing facility, analyzing data anddelivering information to the machines and people whoneed it to make information-based decisions. Due to thegrowing trend by major manufacturers to outsourcetheir operations to first-tier suppliers, a group that isgrowing at a compounded annual rate of 25 %, informa-tion systems are required to interface and integrate withsystems outside the four walls of a single organization.

The FIS Working Group identified the followingdrivers of expanded, distributed FIS capability:

• Shorter production cycle times, higher volumes, andsmaller lot sizes mean production managers wantand need to manage by exception. However, currentFIS products are not integrated and, therefore,cannot provide the timely, integrated factory viewneeded by managers to take preemptive correctiveaction.

• Short product life cycles are pressuring manufactur-ers to move rapidly from design prototypes tovolume production, making monitoring and optimiz-ing a new product introduction (NPI) process a highpriority.

• Increased outsourcing requires the two-way transferof manufacturing data between manufacturers andtheir supply chain. While large manufacturerscurrently may be able to replicate their suite ofin-house FIS applications at their contractors site,replication does not scale to the entire industry andwill not remain practical in even isolated cases.

CONTACT: James St. Pierre, (301) 975-4124; [email protected].

STANDARDS IN TRADE WORKSHOPSHOSTED FOR LATIN AMERICANIST hosted two Standards in Trade Workshops forLatin America last fall. Participants included represen-tatives of Central America, the Caribbean, Belize,Guyana, and Suriname. Twenty-five private-sector and

government participants attended the workshop forCentral America and the Dominican Republic, held inearly fall 1998. Twenty-one participants from the publicand private sectors of Antigua and Barbuda, theBahamas, Barbados, Dominica, Grenada, Guyana,Haiti, Jamaica, St. Kitts and Nevis, St. Lucia, Suriname,and Trinidad and Tobago attended the workshop for theCaribbean in November 1998.

The agendas for both workshops included briefingsand panel discussions with public and private-sectorparticipants, followed by question-and-answer opportu-nities, NIST laboratory visits, and field visits. Topicsincluded U.S. standards development, product certifica-tion, conformity assessment, metrology, laboratoryaccreditation, the U.S. regulatory process, and theNational Center for Standards and CertificationInformation (NCSCI), which is the U.S. inquiry pointfor notifying the WTO (World Trade Organization)secretariat of proposed technical regulations that mightsignificantly affect trade and receiving notificationsfrom other countries. Site visits to enhance classroombriefings included a trip to the Fresh Fields Commis-sary, where participants observed food production andpackaging and implementation of the Hazard AnalysisCritical Control Point plan, a comprehensive techniqueto evaluate a food firms ability to produce safe andquality products.

A highlight during the workshop for the CentralAmerican group was the NIST-ANSI (AmericanNational Standards Institute) Standards Summit heldat the Ronald Reagan International Trade Center inWashington, DC on Sept. 23, 1998. The participants inboth workshops want future exchanges and focusedsectoral workshops, especially in conformity assess-ment. Invaluable personal and professional relationshipswere established on which to continue to build trust andfrom which to draw for future collaboration.CONTACT: Libby Parker, (301) 975-3089; [email protected].

CRADA SIGNED TO EVALUATE NISTULTRASONIC TRANSDUCERNIST has signed a Cooperative Research and Develop-ment Agreement (CRADA) with a private company inHartford, CN. The company is interested in findingpractical ways of measuring surface residual stressprofiles by nondestructive means. NIST researchers,have developed an ultrasonic transducer that thecompany believes would be useful for accomplishingthis. The CRADA’s objectives are to evaluate the utilityof the NIST-developed line-focus transducer for themeasurement of surface residual stress in an aluminumalloy and to evaluate modifications to the transducer for

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improving its sensitivity for detecting such stresses. Inreturn for NIST providing a working copy of its line-focus transducer to the company, it will supply NISTwith a set of shot-peened aluminum alloy specimenswhose surface stresses have been characterized, bymeans of destructive profile analyses, on like represen-tative samples. NIST and the company will exchangeultrasonic data obtained on the specimens developed inthis program.CONTACT: Gerry Blessing, (301) 975-6627; [email protected].

BETTER BOXES MAY MEAN REDUCEDFIRE LOSSESAs part of its programs in industrial fire safety systemsand material flammability and in cooperation with theAmerican Forest and Paper Association and a privatecompany, NIST is exploring practical means to reducethe flammability of corrugated paper containers used inwarehouse storage. Improved fire performance of corru-gated paper products may represent a competitiveadvantage for U.S. paper manufacturers, but it does notdrive the industry. The private company is helping NISTevaluate the idea of using nanocomposites to reduce theflammability of corrugated paper while continuing tosatisfy the important competitive concerns of the paperindustry, which are cost and material properties, such asstrength, reducing water uptake in a humid atmosphere,and re-pulpability (for recycling). A number of differentclays have been sent to the private company for process-ing and testing. NIST already is working with thethermoplastics industry, to use clay nanocomposites toreduce the flammability of commodity plastics.CONTACT: Anthony Hamins, (301) 975-6598;[email protected] or Jeff Gilman, (301) 975-6573; [email protected].

COLLINS ELECTED ILAC CHAIRAt the annual meeting of the International LaboratoryAccreditation Cooperation (ILAC) meeting in Sydney,Australia, last October, Belinda Collins, director of theTS Office of Standards Services, took office as theILAC Chair. The ILAC members represent laboratoryaccreditation bodies in some 50 countries, plus threemajor regional organizations. ILAC aims to achieveglobally accepted criteria for the recognition of thecompetence of accreditation bodies and the developmentof regional and worldwide mutual recognition arrange-ments based on the needs of laboratories and theirclients and the importance of comprehensive audits andperiodic proficiency testing.CONTACT: Belinda L. Collins, (301) 975-4000;[email protected].

Y2K HELP CENTER IS OPEN FOR BUSINESSSmall manufacturers and other small businesses lookingfor free help in finding and assessing problems causedby the year 2000 computer problem now can contact theY2K Help Center for Small Business by calling (800)Y2K-7557 (925-7557), sending electronic mail [email protected], or visiting the center’s web site aty2khelp.nist.gov.

The Y2K Help Center will provide technical supportto users of Conversion 2000: Y2K Self-Help Tool,developed by NIST. The Y2K Self-Help Tool software,available in both Microsoft Access and Excel, canhelp small businesses conduct an inventory of equip-ment, identify core business systems and rate their im-portance to the survival of the business; develop contin-gency plans; and plan and manage remediation projects.The Y2K Help Center also can provide information ondatabases of Y2K compliance information.

The Y2K Self-Help Tool is available on the Y2K HelpCenter web site or from NIST around the country bycalling (800) MEP-4MFG (637-4634).Media Contact: Jan Kosko (301) 975-2767; [email protected]

CONFERENCE GOAL: MAKING THE WEB ALOT LESS TANGLEDMaking World Wide Web sites more accessible andmore useful to average, nontechnical people has manybenefits. For example, companies whose web sites areparticularly attractive and easy to navigate often have anadvantage over competitors in the electronic commercearena. In contrast, web sites that confuse customers in alabyrinth of links may lose business to firms with easilytraversed pages.

Within an organization, solid web design also makesa difference. Internal web sites where information iseasily accessed, understood, and retrieved can helpimprove employee efficiency, increase production,foster collaboration, and raise morale. Difficult-to-usesites can lead to higher costs, production mistakes andworker frustration.

To address this new area of research, NIST is hostingthe Fifth Conference on Human Factors and the Web onJune 3, 1999. The theme for the meeting is “the futureof Web applications.” It will provide a forum for sharinginformation among a community of human factorengineers, designers, and developers from industry,academia, and government agencies. Among the pos-sible topics for discussion are: usability studies ofdynamic, customizable web sites; innovative applica-tions, especially for electronic commerce and enter-prise-wide operations; case studies of legacy systemsre-engineered for the web; database-enabled sites and

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transaction-based applications; usable design with newweb technologiessuch as XML and Java; tools for webusability testing and evaluation; and accessibility.

More information about the conference is available onthe web at www.nist.gov/hfweb or by sending electronicmail to [email protected]. The final conference programwill be available on the web site by April 20, 1999.Media Contact: Philip Bulman (301) 975-5661;[email protected].

NEW TRANSFER STANDARD IMPROVESCALIBRATIONS FOR OPTICAL METERSScientists at NIST have developed and evaluated atransfer standard for the calibration of optical fiberpower meters over the wavelength range of 750 mm to1800 nm. The transfer standard is an optical-trap detec-tor consisting of two germanium photodiodes and amirror. The photodiodes and mirror are contained in apackage that is thermally stable and accepts a varietyof optical fiber connectors. Benefits of this transferstandard versus previous standards include high optical-to-electrical conversion efficiency, reasonable cost andimproved spatial uniformity.

As a transfer standard, the detector is robust andconvenient to use in different laboratories, the scientistsreport. They will continue to evaluate the standardto establish a calibration history and to determine theeffects of aging on the photodiodes and mirror.

More information on the standard is available fromJohn H. Lehman, (303) 497-3654, [email protected]. A paper, no. 2-99, explaining thestandard is available from Sarabeth Harris, MS104,NIST, Boulder, Colo. 80303-3337; (303) 497-3237;[email protected] Contact: Fred McGehan, (303) 497-3246;[email protected].

NIST SCIENTISTS DEMONSTRATE HIGHLYDIRECTIONAL ATOM LASERAtoms in a Bose-Einstein condensate can be manipu-lated with light to form a highly directional atom laser,NIST physicists reported in the March 12, 1999, issueof Science.The NIST device represents a significantstep forward from the first atom laser demonstrated in1997 in that its atoms stream forward in a chosen direc-tion as a very narrow beam. The direction of the earlieratom laser beam was determined by gravity and had alarge spread due to the tendency of the atoms to repeleach other.

“The atom laser is as different from an ordinary atombeam as an optical laser is from a flashlight. It now givesyou for atom beams what you have had with laser light,”says Nobel Laureate William D. Phillips, leader of theLaser Cooling and Trapping Group in the NIST PhysicsLaboratory.

Although practical uses of the atom laser could beyears away, scientists are excited about the NIST inven-tion and its potential. Researchers anticipate being ableto create holographic images producing any picture orpattern desired on a flat surface. This eventually maylead to improvements in lithography, the manufacturingtechnique for making exquisitely small features oncomputer chips.

For more information and to see images of the atomlaser, go to the NIST Physics Laboratory’s news page onthe World Wide Web at www.physics.nist.gov/atomoptics.Media Contact: Linda Joy, (301) 975-4403; [email protected].

DOORS OPENED TO NEW CHEMISTRYBUILDING AND NIST’S FUTURENIST took its first step into the 21st century withthe March 8, 1999, dedication of the new AdvancedChemical Sciences Laboratory (ACSL) in Gaithersburg,MD. The $75 million, 18 588 m2 (200 000 ft2) ACSL—the first major construction in nearly 40 years at theMaryland site—was built to house the researchprograms of NIST’s Chemical Science and TechnologyLaboratory (CSTL).

Research by CSTL scientists long has benefited ourNation’s health and environment, as well as industrialproductivity and international trade. The new state-of-the-art ACSL features advanced designs that will helpNIST meet 21st-century needs for accurate chemicalmeasurements, standards and methods used for pharma-ceutical manufacturing, medical diagnosis, pollutionmonitoring and clean up, nutritional analysis, and otherchemistry-related endeavors.

Among the features of the ACSL are 162 laboratorymodules that can be reconfigured to meet special needs,131 office modules, precise temperature and humiditycontrol, high-capacity ventilation systems, an uninter-ruptible power supply, a high-purity water system, fiveclean rooms, two cold rooms, five non-metallic labs, andadvanced data transmission wiring.Media Contact: Michael E. Newman, (301) 975-3025;[email protected].

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1999 NATIONAL INFORMATION SYSTEMSSECURITY CONFERENCEComputer experts from around the globe will convergein the Washington, DC, area this fall to address thehottest information security issues of the approachingmillennium.

The 22nd National Information Systems SecurityConference, co-sponsored by NIST and the NationalSecurity Agency, is expected to attract more than 1600participants. The annual conference is one of the largestand most significant computer security gatherings in theworld. Expected to draw a wide range of industry andacademic participants as well as government experts,the conference will take place at the Hyatt RegencyCrystal City in Arlington, VA, Oct. 18-21, 1999.

Panel discussions and papers will cover a diverse setof topics such as electronic commerce, Internet security,research and development, security testing and evalua-tion, and public key infrastructure technology. Confer-ence goals include educating participants about majorinformation security issues and provoking debate andaction on these issues.

More information about the conference is available athttp://csrc.nist.gov/nissc.Media Contact: Philip Bulman, (301) 975-5661;[email protected].

NIST PROPOSES TRIPLE DESOn Jan. 15, 1999, NIST published aFederal Registerannouncement that proposes changes to the existingFederal Information Processing Standard (FIPS) 46-2,Data Encryption Standard (DES), to recommend the useof a stronger technique to protect sensitive, unclassifiedinformation, known as Triple DES. Triple DES is amethod of using the DES algorithm in three operations,which will provide the additional security needed forfederal applications. It is specified in AmericanNational Standards Institute (ANSI) Standard X9.52. Inaddition to the adoption of Triple DES, the proposedFIPS 46-3 recommends that:

• For existing systems, government organizations areencouraged to migrate to Triple DES based on a prudentstrategy that matches the strength of the protective mea-sures against the associated risk; and

• New procurements should use Triple DES. Informa-t ion on Triple DES may be found at http: / /www.nist.gov/encryption. A 90 day public commentperiod for the approval of the proposed revised standardclosed on April 15, 1999.

The Data Encryption Standard was first adoptedin 1977 as FIPS 46 for the encryption of sensitive,unclassified computer data. The standard was re-affirmed in 1983, 1987, and 1993 as FIPS 46-2 and hasbeen used to protect Federal Government informationand, on a voluntary basis, many private-industryapplications. As technology has advanced, the relativestrength of DES has declined, thus highlighting the needto find a replacement. Therefore, in 1997, NIST initiatedthe design and development of the Advanced EncryptionStandard (AES). Completion of the AES will require asubstantial amount of time; final approval is notexpected until 2001. See http://www.nist.gov/aes for in-formation about the AES development.CONTACT: Elaine Barker, (301) 975-2911; [email protected].

NIST FACILITATES DEVELOPMENT OFELECTRONIC BOOKSNIST is playing a pivotal role in the continuing saga ofelectronic books. An electronic book is a portabledevice that integrates display, microprocessor, andstorage technologies resulting in a reading appliancewith significant functionality over paper-based books.NIST developed a prototype electronic book that incor-porates desired functions like font resizing, touch-screencontrol, electronic dictionary, and voice activation.Last fall, NIST hosted the worlds first conferenceon electronic books, which attracted more than 400attendees ranging from publishers, electronic bookmanufacturers, display fabricators, software developers,and end users. Members of the industry met to form theOpen Electronic (E-Book) Standards Committee; NISTwas asked to assist in this effort.

In January 1999, NIST co-organized the first workingmeeting of the Open Electronic Book StandardsCommittee, which met in San Francisco. The purposeof the meeting was to review and comment on a draftspecification. Specific topics discussed at the meetingcentered on the adoption of an XML-HTML commonformat, the use of standardized metadata, and the abilityof the standard to adopt future multimedia components,e.g., picture (jpeg, bmp), and video file formats. Partic-ipants agreed that the proposed straw-man draft neededfurther review, and the industry requested NIST to headan authoring group to review the scope and purpose ofthe proposed standard. NIST offered the use of its proto-type electronic book as a reference implementation oncethe standard is finalized. The Open E-Book StandardsCommittee agreed to meet again in the spring of 1999.NIST also participated with the Electronic Book

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Exchange Group (EBX) that is developing standards forcopyright protection of electronic content as it is trans-mitted from publisher to e-book holder.

NIST continues to conduct further research with itsprototype, looking to integrate writable DVD storage,thus giving the electronic book full multimedia capa-bilities. Also, the NIST prototype will incorporatespeech, making it a “talking book.”CONTACT: Victor McCrary, (301) 975-4321; [email protected].

INDUSTRY SUCCESSFULLY EVALUATINGFIREWALL PRODUCTS BASED ON PROFILESDEVELOPED BY NIST AND THE NATIONALSECURITY AGENCY (NSA)Two private companies have successfully completedevaluations of their firewall products against version 2.0of the Common Criteria, an international standard (ISO15408) for security evaluation criteria. Both productsdemonstrated compliance to the Common Criteria aswell as to the Federal Governments family of firewallprotection profiles. As a result, these products receivedCommon Criteria certificates at the recent RSA DataSecurity Conference in January 1999, marking the be-ginning of a new standard of quality for this productclass. Other firewall vendors are expected to undergoproduct evaluation and receive a similar certificatein the near future. An estimated 60 % to 75 % of thecollective firewall market share is represented by theproducts that have completed evaluation or are in evalu-ation. Firewalls serve as part of an organizations overallsecurity defense by isolating an organizations internalnetwork from the Internet or other external networks.

Jointly representing the United States, NIST and NSAwere among the original six national sponsors (UnitedKingdom, Netherlands, France, and Canada) of theCommon Criteria, and under the National InformationAssurance Partnership (NIAP) developed the Govern-ments firewall protection profiles. More information onthe Common Criteria and NIAP can be found at thefollowing web sites: http://csrc.nist.gov/cc/, http://www.radium.ncsc.mil/tpep, and http://niap.nist.gov.CONTACT: Timothy Grance, (301) 975-4242; [email protected] or Wayne Jansen, (301) 975-3359;[email protected].

NIST’S INTERACTION AUTOMATIONSOFTWARE USED AT THE SOUTH POLEExpect, NIST’s interaction automation software, is inuse at the South Pole(www.spole.gov) through theNational Science Foundations SPIREX (SouthPoleInfrared Explorer) and Australias AASTO (Automated

Astrophysical Site-Testing Observatory). Experimentsat the pole are difficult and expensive but significant dueto unique conditions—for instance, the extreme coldmeans that the sky is much darker in the infrared wave-lengths and the dryness means that there is little watervapor to absorb interesting wavelengths. Since livingconditions are harsh, the goal is to build an observatorythat needs no human intervention to run for a year atambient temperatures down to –808C. Expect facilitatesthis goal by allowing control of astronomical equipmentvia embedded controllers over the Internet. Pictures ofthe site are available at http://www.phys.unsw.edu.au/~mcba/aasto.html. Expect is in use at a number of otherobservatories around the world such as Siding SpringObservatory and Kit Peak National Observatory.CONTACT: Don Libes, (301) 975-3535; [email protected].

COMPUTER MODEL PREDICTIONS AID INDECISION TO IGNITE SHIPPredictions from a computer program developed byNIST fire researchers were used to evaluate the impactof intentionally igniting the fuel on theNew Carissa,afreighter grounded on the coast of Oregon. Igniting thefuel on the ship could reduce the quantity of oil reachingthe water and impacting natural resources and wildlifein the area. The National Oceanic and AtmosphericAdministration response team on site requested predic-tions from ALOFT-FT, which was developed specifi-cally for situations involving the intentional burning ofoil spills. The predictions gave authorities confidenceabout the limited spread of the downwind smoke plumeover populated areas. ALOFT-FT provides detailedthree-dimensional predictions of the downwind distribu-tion of smoke particulate and combustion products fromlarge outdoor fires. The ignition of the fuel on the shipwas the first use of intentional burning of oil at sea offthe coast of the continental United States and the firstuse of ALOFT-FT in response to an incident. Photo-graphs of the smoke plume from the ship fire agreefavorably with the predictions from the model.CONTACT: Doug Walton, (301) 975-6872; [email protected].

A NEW LUBRICANT CONCENTRATIONMEASUREMENT TECHNIQUE FOR POOLBOILINGNIST scientists have demonstrated the feasibility of anew in situ technique for measuring the concentrationof lubricant on a boiling heat transfer surface. Theproposed technique relies on the fluorescence of thelubricant to determine the amount of lubricant that has

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accumulated on the heat transfer surface. Fluorescenceoccurs when the incident light is at a shorter wavelengththan the light emitted from the surface.

The heat transfer performance of a boiling surface inrefrigeration equipment is a strong function of both thetype of lubricant and its concentration in the refrigerant.After boiling of the refrigerant, excess lubricant residesin a very thin layer on the surface. Severe boiling perfor-mance degradation can occur in evaporators when highconcentrations of lubricant reside in a very thin layer onthe surface. In measurements of 10 lubricant samples inspecial test equipment, researchers found that lubricantconcentration on an aluminum “stepped” target surfacewas a linear function of fluorescence intensity and thereflected harmonic from the surface. The next step ofthe research will be to test the concept on an existingpool boiling rig using a bifurcated optical bundle withboth excitation and emissions detection in a singlecable. The goal of the research is to enable manufactur-ers to chose lubricants that both lubricate the compres-sor and improve the heat transfer performance of theevaporator.CONTACT: Mark A. Kedzierski, (301) 975-5282;[email protected].

ANALYZING NEUTRON POLARIZATIONWITH POLARIZED 3HeNIST researchers recently demonstrated polarizationanalysis on the NG3 Small Angle Neutron Scattering(SANS) spectrometer using polarized3He gas. Polar-ized 3He analyzers (and polarizers) rely on the largespin dependence of the cross section for absorption ofneutrons by polarized3He gas. Cold and thermal neu-trons are excellent probes of materials. They penetratematter much more than charged particles, and theirwavelengths are well matched to the characteristic sizeand dynamics of atoms.

The NIST polarized 3He program includes twodifferent optical pumping methods of producing sam-ples of 3He gas with spin-polarized nuclei: spin-exchange and metastability-exchange. To simplify thistest experiment, cells full of polarized gas were preparedby each method and transported to the SANS instru-ment. Because polarized gas is sensitive tomagnetic field gradients, the cells were transported in abattery-powered solenoid and another solenoid was usedat the SANS instrument. The polarization was suffi-ciently large and long-lived to permit a demonstration ofa classic use of polarization analysis: separating coher-ent scattering from incoherent scattering.

This proof-of-principle experiment was the firstapplication of polarized3He to neutron scattering in theUnited States. Further development and successfulapplication of polarized3He spin filters also could havea profound impact on the currently planned SpallationNeutron Source (SNS) at Oak Ridge National Labora-tory. Polarizing monochromators are used at reactorsources for polarizing thermal neutrons, but a broad-band polarizer such as polarized3He is better suited tothe pulsed neutron beams produced by spallationsources because neutron energy information is extractedby time-of-flight. The next step for the NIST researchersis to use polarization analysis techniques to separatemagnetic and nuclear scattering.CONTACT: Tom Gentile, (301) 975-5431; [email protected] or Charlie Glinka, (301) 975-6242;[email protected].

ANALYZING IMAGES FROM NEAR-FIELDOPTICAL MICROSCOPYNIST researchers have developed accurate, efficient,computational models for understanding and analyzingimages made by near-field optical microscopy (NSOM).NSOM is being studied intensively in two NIST compe-tence programs to achieve optical spatial resolutionmuch better than the diffraction limit. To do so,nanometer-scale apertures and sharp tips are used tolocalize probe fields. The improved spatial resolution isrealized when the sample is placed in the probe near-field. However, strong near-field coupling between thesample and probe greatly complicates image analysis.Detailed modeling is required to understand images andclearly separate probe and sample contributions to theseimages.

NSOM is a challenge to model. Electromagnetic fieldpropagation and scattering is modeled on length scalesthat must cover two to three orders of magnitude toinclude all processes that affect image formation. Theresearchers have developed models and algorithms thatare powerful enough to capture the essential physics ofimage formation, yet are still computable in reasonabletimes. They have used these models to analyze NSOMimages made in collaboration with researchers at theNaval Research Laboratory, and two universities. Asdescribed in a recentPhysical Review Bpublication,they have developed analytical models to analyzeimages made of nanochannel glass arrays. Modeling theentire process of image formation is critical for correctlyinterpreting the images. The researchers find that theNSOM images reveal detailed information about thephotonic modes of these glass arrays. In another study,

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they have used the coupled dipole approach to modelNSOM images made of Au nanoparticles. These imagesreveal detailed information about the fields near the endof the NSOM probe. Such information is a critical inputfor modeling other images made with these probes. Theimages in these two examples provided very differentinformation. Modeling was necessary to successfullyextract the content of these images.

Currently, the NIST researchers are extending thiswork to improve the models and enhance the efficiencyof the algorithms. They now are using these modelsto better understand imaging of thin films, includingbiological and polymer films, refractive index profiling,and imaging of optical waveguides, routers, andcouplers.CONTACT: Garnett Bryant, (301) 975-2595; [email protected].

NIST ADVANCED RADIOMETER SELECTEDFOR NASA’S TRIANA MISSIONTwo NIST scientists have been selected to lead thedevelopment of a spaceflight instrument, the Scripps-NIST Advanced Radiometer (NISTAR), which isscheduled to fly as part of the National Aeronautics andSpace Administration’s (NASA) Triana Mission. TheTriana spacecraft is expected to be launched in Septem-ber 2000 aboard the space shuttle and subsequently willbe placed in an orbit about L1 (the Lagrange libration,or neutral gravity point between the Earth and the Sun),about 1.53106 km from Earth. At that position, animaging camera and NISTAR will have a continuous,nearly full disk, sunlit view of the Earth. NISTAR willmake measurements of the reflected solar and emittedthermal radiation from the Earth. These measurementswill be traceable to NIST’s HACR (high-accuracyradiometer), the Nations primary standard for opticalpower measurements. NIST is working with a privatecompany to develop the NISTAR instrument to meet thescience requirements of the Scripps Institution ofOceanography, University of California at San Diego,and install the Triana spacecraft at NASA’s GoddardSpace Flight Center in Greenbelt, MD.CONTACT: Steven Lorentz, (301) 975-2311; [email protected].

HIGH PRECISION AND SENSITIVITYACHIEVED USING MIDINFRARED CAVITYRINGDOWN SPECTROSCOPYIn a collaborative effort, scientists from NIST and auniversity have developed a high sensitivity and highfrequency precision absorption technique based on theobservation of saturation dips in the midinfrared usingcavity ringdown spectroscopy (CRDS). CRDS has

generated much recent interest for sensitive concentra-tion measurements of trace contaminates in gas samplesand for the absolute measurement of very small molecu-lar absorption cross sections. The absorption cell inCRDS consists of a confocal Fabry-Perot optical cavitymade of very high reflectivity mirrors, which alloweffective optical pathlengths on the order of kilometersto be achieved. Previously, the technique had been basedin the near-infrared and visible spectral regions wherehigh-reflectivity mirrors and a variety of tunable lasersare available.

A midinfrared cavity ringdown spectrometer hasbeen developed by using a tunable laser based onnonlinear mixing of a CO2 laser and microwave radia-tion in a CdTe modulator. The midinfrared region of thespectrum offers significant advantages for CRDS sincevirtually all molecules strongly absorb in this spectralregion. The scientists have taken advantage of theselarge absorption strengths to observed nonlinear satura-tion of a transition with the technique. The nonlinearabsorptions have linewidths on the order of 1 MHz, orless, or approximately 2 % of the full Doppler width.The technique also offers potential analytical chemistryapplications, since saturation signals were observedusing gas partial pressures as low as 0.004 Pa. Potentialapplications include the absolute measurement of theabsorption cross sections for unstable molecules andcharacterization of the atmospheric water continuum.CONTACT: Gerald Fraser, (301) 975-3797; [email protected].

FIRST ACCURATE VACUUM UV REFRACTIVEINDEX MEASUREMENTS OF CALCIUMFLUORIDENIST researchers have made the first and only accuratemeasurements of the index of refraction, its dispersion,and its temperature dependence of calcium fluoride inthe vacuum ultraviolet near 157 nm. These results werepresented at the International SEMATECH 157 nmWorkshop in Phoenix, AZ, in February 1999. Thesemeasurements are crucial for the design of opticalsystems for 157 nm excimer-laser-based optical lithog-raphy tools, which are projected to be used for thefabrication of future-generation integrated circuits(around 2005). Since these are the only measurementsavailable, all major semiconductor lithography compa-nies in the United States, Europe, and Japan are usingthese results in their optical designs.

The index measurements were made by the minimumdeviation method with a relative uncertainty of 10–5,using a precision goniometer in a nitrogen purge atmo-sphere. The dispersion was determined using line emis-sion radiation near 157 nm from a deuterium lamp, with

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wavelengths calibrated using a vacuum ultravioletFourier-transform spectrometer. Temperature control ofthe sample and surrounding medium to 0.058C enabledan accurate determination of the temperature depen-dence of the index.CONTACT: John Burnett, (301) 975-2679; [email protected].

A FREE-FALL DETERMINATION OF G, THENEWTONIAN CONSTANT OF GRAVITATIONDeterminations ofG, the Newtonian constant of gravita-tion, initially seen as a way to measure the mean densityof the Earth, go back to Isaac Newton. Yet afterhundreds of years of research, the relative uncertaintywith which this fundamental constant is known issurprisingly low—only 1.5310–3. A few years ago, acarefully carried out measurement ofG reported anumber that disagreed with the accepted (CODATA)value by more than 40 standard deviatons. In the hopeof addressing this inconsistency, NIST scientists deviseda novel new approach to the problem—an approach thatresulted in the only laboratory measurement ofG usingan unsupported test mass. They used a well-character-ized 500 kg tungsten standard of mass (in the shape ofa ring) to either increase or decrease the rate of fall ofa small test body dropped in a vacuum. By measuringthe acceleration difference for these two cases, theyobtained a new value forG. Their value, which has arelative uncertainty of 1.4310–3, lies 1.5 times thevalue’s uncertainty above the CODATA value. Since thisresult was reached using a completely new method, thisagreement should help rule out the possibility thatprevious meas-urements suffered from some commonsystematic bias.CONTACT: James E. Faller, (303) 492-6807; [email protected] or Joshua Schwarz, (301) 975-8129;[email protected].

HEXAPOD KINEMATIC ERRORS REDUCEDRapid production of quality contoured parts requiresmachine tools that combine speed, accuracy, stiffness,and multiaxis versatility. A new class of parallel-actuated machine tools based on the Stewart platformmechanism presents new possibilities for meeting theseneeds; however, much remains to be learned about thecharacteristics of these “hexapod” machine tools beforethey will see widespread production application. Thus,in May 1995, NIST researchers began working with oneof these machines.

Extensive simulation and iterative characterizationtests were necessary to identify its most significanterrors. The main difficulty is that in a parallel-actuated

machine, such as the Hexapod, there is not a one-to-onecorrespondence of an observed error to a single prob-lem. In other words, the measured error map does notoffer many clues as to the source(s) of error.

It was therefore necessary to develop several simula-tion tools, as well as the required Hexacluster metrologyinstrument, to carry out the studies. An active HexapodUsers Group has been incorporating NISTs knowledgebase into tools and procedures for this new class ofmachine tools. One such development has been a newtest part analogous to the circle-diamond-square,expressly designed for traditional machine tools. Boththis test part and the calibration procedures are formingthe basis for new standards and inputs to the ISO 230and ANSI/ASME B5 committees.CONTACT: Hans Soons, (301) 975-6474; [email protected] or Tom Wheatley, (301) 975-3449; [email protected].

NIST RESEARCHERS DEVELOP ADVANCEDMICROMACHINING PROCESS THAT ALLOWSCOMPANIES WITHOUT ON-SITE FABRICATIONFACILITIES TO MANUFACTURE MEMSNIST and an industrial partner have developed a newsilicon micromachining process to fabricate CMOSmicroelectromechanical systems (MEMS). The newprocess enables companies that do not have on-siteintegratd circuit (IC) fabrication facilities to fabricateCMOS MEMS structures. Such structures vary widely,ranging from micro-heating elements for micro-hotplate gas sensors and thermal flat panel displays topassive microwave components for microwavecoplanar transmission lines and power sensors. Onemajor advantage of the process is that it providesimproved understanding and control of silicatechemistries in the use of tetramethylammoniumhydroxide (TMAH) to anisotropically etch (micro-machine) silicon. The researchers found that the processwas remarkably sensitive to reagent concentration andneeded extensive laboratory development. Anothermajor advantage of the process is that it preservesexposed metallization at wire bond pads over very longperiods of etching time, which, in turn, means higheryield and increased compatibility with a productionenvironment.

CMOS MEMS are manufactured in commercial ICprocesses. The IC process creates device structures(precursors) that are then processed into the finalMEMS structures. The TMAH process is cleaner, safer,and easier to implement than the ethylenediaminepyrocatechol (EDP) process commonly used to performthe post-process function.CONTACT: Loren Linholm, (301) 975-2052; [email protected].

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EXPERIMENTAL RESULTS DEMONSTRATETHAT POWER ELECTRONIC INTERCONNECTPARASITICS CAN BE ACCURATELYCHARACTERIZED WITH TIME DOMAINREFLECTOMETRYRecent experiments by a NIST scientist have demon-strated, for the first time, the use of time domain reflec-tometry (TDR) to characterize the interconnect para-sitics of a prototype power converter. The componentsof this prototype high-power inverter include insulatedgate bipolar transistor (IGBT) power modules, a busbar,and a high-voltage dc capacitor. The experiments provedthat the internal interconnect impedances of the IGBTmodule can be extracted completely using TDR. Resultsalso indicated that the busbar can be modeled by uni-form transmission line segments between connectionpoints, and that the dc capacitor contained a significantseries interconnect inductance. Moreover, the TDRmethod also may be used to characterize any otherpower electronics devices or components, such as theinterconnects for microprocessor power-supply regula-tors.

Without adequate metrology for characterizing inter-connects, the electromagnetic wave propagation proper-ties of interconnects are often approximated usinganalytical or computational methods that do notadequately predict the nonideal behavior of real inter-connects. These methods have some fundamentallimitations because the physical properties, parameters,and structures of the conductor materials are notgenerally known, and assumptions must be made incomputations.

A measurement-based method such as TDR is criticalfor the characterization of the transmission line proper-ties of the interconnect parasitics because they cannot beconsidered as ideal lumped elements (resistors, capaci-tors, inductors), but must be represented as distributedtransmission line elements having transmission linecharacteristic impedances and propagation delays. Inaddition, the transmission line characteristics typicallyare not uniform along the interconnect and must berepresented using several transmission line segmentshaving different characteristic impedances and propaga-tion delays.

The electrical behavior of module and circuit boardinterconnects is also becoming increasingly moreimportant in determining the behavior of digital andanalog systems due to the increasing speed and powerrequirements and decreasing operating voltages. Amajor impediment to the development of the next-gener-ation microprocessor modules is the lack of power-supply stability caused by the interconnects between themicroprocessor chip, its power-supply bypass capacitor,

and its power-supply voltage regulator. The primaryreason for this is that power requirements have changed;the power-supply voltage has changed from 3.3 V forpresent systems to 1.1 V for future systems, the voltagecompliance requirements have changed from 5 % forcurrent systems to 2 % for future systems, and therequirement for rate-of-change of power-supply currentduring power-up has changed from 1 A/ns to 5 A/ns.Given that the characteristic impedance is a key parame-ter in the present and next generation voltage regulatordesign, improved interconnect metrology is essential.CONTACT: David G. Seiler, (301) 975-2074; [email protected].

ITERATIVE IR APPROACH FOR EXTRACTINGVALUES OF INTRINSIC OPTICAL CONSTANTSOF SILICON REDUCES UNCERTAINTY BY AFACTOR OF 10Infrared (IR) spectroscopy is a powerful techniquethat has been used extensively by industry to analyze avariety of materials, but, up to now, the use of IR probesto characterize semiconductor materials has beenlimited by a lack of reliable optical data, models, andtest methods. Of these limitations, the most critical isthe lack of accurate values for the intrinsic opticalconstants,n(v ) and k(v ), for silicon. At present, thepublished values ofn(v ) possess relative uncertaintiesof about 10–3, while the reported values ofk(v ) vary bya factor of 2 or even greater, in some cases.

NIST researchers have developed a new iterativemethod that leads to a reduction in the uncertainty ofn(v ) by a factor of 10. Using this method, the uncer-tainty ofk(v ) is also significantly reduced. Further, themeasurements have brought to light a systematic errorin the published values ofn(v ), which could be asignificant source of error in prior IR analyses.

The method developed by the researchers extractsaccurate values for the midinfrared (450 cm to4000 cm–1) optical constants,n(v ) andk(v ), of silicon.Two Fourier transform infrared (FTIR) spectra wereused: a high-resolution spectrum (Dv = 0.5 cm–1)yielding a typical channel spectrum, dependent mainlyon the sample thickness andn(v ); and a low-resolutionspectrum (Dv = 4.0 cm–1) yielding an absorptionspectrum, dependent mainly on the sample thicknessandk(v ). Independent analyses of each spectrum gaveinitial n(v ) andk(v ) estimates. The estimated valuesthen were used as the starting point for an iterative fit ofthe high- and low-resolution spectra successively. Theimproved accuracy of the values for the intrinsic opticalconstants will allow semiconductor manufacturers to

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further refine the IR spectroscopic analytical limits forimpurities and thin insulator layers needed to producelarger and more tightly specified 300 mm wafers.CONTACT: Thomas J. Schaffner, (301) 975-8009;[email protected].

INTERNET-BASED TEST SERVICE ENABLESCUSTOMERS TO INTERACT WITH NIST STAFFWHILE CALIBRATIONS ARE PERFORMEDMultifunction calibrators, which are used to test andverify the accuracy of digital multimeters (DMMs), areused in a wide variety of industrial applications. Inmany cases, these calibrators require traceability tonationally and internationally accepted electricalstandards. Like DMMs, calibrators operate over a widerange of ac and dc voltage, current, and resistance, andit is virtually impossible to test all available outputsignals. In the past, several approaches have beendevised to test these instruments reliably and efficiently.

One approach is to calibrate them using a few electri-cal-standard artifacts and rely on self-calibrationsoftware in the calibrator to compensate for errors overthe entire operating range. Another approach is tocalibrate as many points as possible (more than 200)using standard artifacts (Zener references, resistors, andthermal converters), and then interpolate between pointsto estimate uncertainties over the operating range. Mostusers are more comfortable with the second method,but, even with semi-automated systems, it can take askilled technician up to a week to complete such a test.A third approach, one that is gaining popularity, is to usea transportable DMM that has been characterized usingan artifact-calibrated calibrator or reference calibratormaintained at a national laboratory or an accreditedstandards laboratory. This approach limits the laboriousartifact calibrations to a few laboratories with the timeand resources to devote to the task. Traceability isprovided through a test report for the transportableDMM.

A new service is evolving at NIST that offers signifi-cant value-added benefits to the latter approach. Mostimportant of these is that a customers calibrator can bemonitored by NIST staff as the test is performed at thecustomers site. The new service will employ the Internetto expand present capabilities, making the process notonly more efficient and less time consuming but alsomore collaborative. A customer-owned DMM will betested using the customers test calibrator, shipped toNIST where it will be tested using a NIST referencecalibrator, and returned to the customer for follow-uptests. An interactive Internet link between NIST and its

customers will be established to improve communica-tions, enable rapid transfer of test data, and allow thecustomer to download test protocols and software forsystem evaluation.

With both audio- and video-capability, NIST will beable to provide real-time consultation and assist withtroubleshooting during the test. The customer’s “before”and “after” data will be sent electronically to NISTwhere the data analysis will be performed. Oncecompleted, a password-accessible report (that expressesthe test calibrator errors and uncertainties in terms of theNIST reference calibrator) may be posted on a NISTweb site. In addition, an interactive database of testsystems with historical data and instrument modelingshould make it possible to predict performance (basedon periodic comparisons between the customers calibra-tor and DMM), to increase or extend the calibrationinterval, and to update the test report. If successful,this approach could be applied to many other areas ofmeasurements at NIST and throughout the metrologycommunity.

This work also is tied closely to the InteramericanMetrology System Network (SIMNET), a new programto use the Internet to enhance international comparisonsof measurement standards within this hemisphere.CONTACT: Barry A. Bell, (301) 975-2419; [email protected].

REFRACTIVE INDEX PROFILING OF OPTICALFIBERS AND PLANAR WAVEGUIDES WITHUNPRECEDENTED RESOLUTIONNIST scientists have built and demonstrated a refractednear-field (RNF) system, which measures with excep-tional resolution, the two-dimensional refractive indexprofile in both optical fiber and planar waveguides. TheRNF technique probes a waveguide with 635 nm laserlight focused to a point on the entrance face of thewaveguide. The waveguide is placed in contact with amaterial of nearly equal refractive index, allowing lightto escape from the side of the waveguide. Measuring thepower of the escaping light gives a precise measurementof the index of refraction at the focal point of thelaunched light. The relative uncertainty of this tech-nique is generally limited by the uncertainties of thecalibration artifacts to about 10–3 to 10–4. However, theresearchers are able to make measurements with arepeatability of 4.3310–5. This is about an order ofmagnitude smaller than the resolution achieved in otherpublished RNF results.

Since the lightwave propagation in a waveguidedepends on the index of refraction profile within theguide, it is important to have an accurate knowledge of

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the details of that profile. The RNF technique allows awaveguide manufacturer to verify that the manufactur-ing process yields the expected profile or to quantify theoutcome of a new fabrication technique. For example,this RNF system is being used currently to measureindex profiles of ion exchange waveguide structures todetermine the diffusion coefficient of the dopant ionsinto the waveguide.

To the waveguide designer, the index profile measure-ment provides the propagation characteristics of theguide and allows theoretical performance to be com-pared to measured results. Index profile measurementsfacilitate accurate waveguide modeling, which in turnimproves waveguide performance and manufacturingyield. For example, a particular area of interest amongmanufacturers is the ability to measure residual strain inthe waveguide. Residual strain can affect the indexprofile or it can alter the polarization of the light; ineither case, it will have a deleterious effect on the perfor-mance of the device. RNF measurements offer thepossibility of mapping the strain-induced birefringencein the waveguide by controlling the polarization state ofthe input light. The NIST RNF system is being modifiedto allow these measurements as well.CONTACT: Paul A. Williams, (303) 497-3805;[email protected].

NEUTRON SCATTERING REVEALS THEMECHANISM BEHIND THERMALCONTRACTIONAt the NIST Center for Neutron Research (NCNR),scientists from NIST, a university, and a privatecompany are exploring the atomic structure and dynam-ics of the rare examples of solids that contract uponheating. Engineers always have been forced to contendwith unwanted thermal expansion of solids. Railroadengineers got around the problem by leaving spacesbetween tracks, but in modern information technologytolerances are much tighter and this necessitates a searchfor materials whose dimensions do not vary withtemperature. One way to accomplish this is bycombining materials with opposite coefficients ofthermal expansion in suitable ratios to form compositeswith temperature-independent dimensions. Unfortu-nately, almost all solids expand with temperature andvery few contract over a significant temperature range.

ZrW2O8, a material that does contract with increas-ing temperature, consists of octahedral and tetrahedralmetal oxide molecules, that form an open and highly

under-constrained structure. Neutron scattering revealeda very low energy molecular twist mode, which is aconsequence of this structure and which causes thermalcontraction because twisting molecules tug on theirsurroundings. ZrW2O8 already is being used by theprivate company to compensate thermal expansion infiber-optic gratings. The discovery of the mechanismbehind this effect was possible only through the use ofneutrons and state-of-the-art instrumentation as is avail-able at the NCNR. This work will help to identify othersubstances that can be used to produce composites thathave no thermal expansion for applications wherethermal expansion cannot be tolerated.CONTACT: Collin Broholm, (301) 975-5179; [email protected].

OPTICAL SPECTROSCOPIC METHOD FOUNDUSEFUL IN DETERMINING PHASESEPARATION IN INDIUM GALLIUM NITRIDEFILMSA new generation of short-wavelength, blue to ultra-violet, light-emitting devices is being developed fromthin films of the group III nitrides, AlN, GaN, InN andtheir alloys. These devices will be used for applicationsranging from high-density optical data storage systemsto outdoor lighting and instrument panels. The activeregion of a typical blue-emitting nitride thin film deviceconsists of a stack of ultrathin (2 nm to 4 nm) indiumgallium nitride (InxGa1–xN) layers, alternating withGaN, and sandwiched between thicker (100 nm to1000 nm) GaN layers. Since the wavelength of theemitted light is determined by the indium fraction,control of the alloy composition is critical to producingdevices with reproducible, optimal properties. Compo-sition control is difficult, however, because alloys in theInN-GaN system have a tendency to phase separate byspinodal decomposition at the typical film growthtemperatures of 6008C to 8008C. Raising the growthtemperature is not feasible, because, at higher growthtemperatures, sufficient indium cannot be incorporatedinto the InxGa1–xN layers.

Although these films are intended for optical applica-tions, little work has been done to examine the effects ofphase separation and compositional inhomogeneity ontheir optical properties. In a collaboration with a univer-sity scientist, NIST researchers are using several opticalspectroscopic methods to examine films with indiumamount of substance fractions fromx = 0.06 tox = 0.50.Using optical transmittance, photoluminescence

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excitation, cathodoluminescence, and Raman spec-troscopy, they have found that the different opticalprobes respond differently to the compositionalchanges, but that all of the techniques suggest thepresence of increased inhomogeneity and, possibly,multiple phases as the indium fraction increases. Theseresults suggest that optical spectroscopic methods canprovide a simple (in terms of sample preparation)and nondestructive probe of the occurrence of phaseseparation in InxGa1–xN layers.CONTACT: Lawrence H. Robbins, (301) 975-5263;[email protected].

PROCEEDINGS OF THE NATO- AND NIST-SPONSORED MEETING ON DNA DAMAGEAND REPAIR PUBLISHEDThe book containing the proceedings of the recentN A T O - a n d N I S T - s p o n s o r e d m e e t i n g o n“DNA Damage and Repair; Oxygen Radical Effects,Cellular Protection and Biological Consequences,”has been published by Plenum Publishing Corp.,New York.

This meeting, also called a “NATO Advanced StudyInstitute,” was organized by Miral Dizdaroglu ofCSTL’S Biotechnology Division and took place inAntalya/Turkey on Oct. 13-24, 1997. It was sponsoredby NATO, NIST, and, in part, the Danish Center forGerontology, Scientific and Technological ResearchCouncil of Turkey and the Turkish Society of Toxi-cology. The meeting was attended by 37 invited lectur-ers from NATO countries and Japan as well as 75 otherparticipants from 23 different countries, includingNATO countries and NATO Cooperation Partner coun-tries such as Russia, Bulgaria, Romania, Poland,Lithuania, Ukraine, and Armenia. The volume isentitled “Advances in DNA Damage and Repair;Oxygen Radical Effects, Cellular Protection andBiological Consequences.” It contains 37 chapterswritten by well-known international experts andencompasses the state-of-the-art knowledge and recentdevelopments on various aspects of oxidative DNAdamage and its cellular repair and on the pertinence ofthis research field to human health. Further, more than80 abstracts of the works presented during the meetingby the participants as oral contributions or papers areincluded.CONTACT: Miral Dizdaroglu, (301) 975-2581;[email protected].

Standard Reference Materials

NIST STANDARD REFERENCE MATERIAL(SRM) USED BY THE INTERNATIONALATOMIC ENERGY AGENCY TRAININGPROGRAMSRadionuclides have permeated and resided in theenvironment since the formation of the Earth, and, ingeneral, human radiation exposure from this primordialradioactivity does not cause untoward human healthrisk. However, enhanced release of radionuclides intothe environment through human action can result inaddi-tional and meaningful radiation exposure that hassignificant financial consequences and impact onhuman health. In these elevated radiation areas, it isnecessary for environmental management to assessaccurately the damage, develop cost-effective remedia-tion strategies, evaluate the effectiveness of the remedi-ation activity, and monitor the cleaned-up site into thefuture. To make this possible, NIST has gone to enor-mous efforts to develop natural matrix environmentalradioactivity SRMs, which can be used in the determi-nation of radioanalytical performance.

Many labs have helped NIST certify 13 nuclides inthe natural matrix SRM, Rocky Flats Soil (SRM 4353).Soil SRMs, such as Rocky Flats, are important becausethey are representative of desert soils and have minimal,yet measurable, quantities of plutonium isotopes. Asvarious national and international agencies have betterdefined their roles in environmental remediation andcompliance activities, there has been a growing need totrain personnel in proper radioanalytical techniques andto demonstrate the quality of analytical data. TheInternational Atomic Energy Agency (IAEA) laborato-ries in Seibersdorf, Austria, which conducts trainingprograms for radiochemists from member states,recently held a training program for radiochemists fromvarious countries, and SRM 4353 was used as a testanalyte by the students.

NIST continues to collaborate with the IAEA labora-tories—most recently in development of OceanSediment SRM 4357. This will provide a convenientmaterial in training radiochemists in radionuclidemeasurements in marine sediments, another potentialconcentration “sink” for radioactive contamination.CONTACT: Lisa Karam, (301) 975-5561; [email protected].

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Standard Reference Data

NEW INFRARED SPECTRAL DATABASEINTRODUCED TO SUPPORT REMOTESENSING APPLICATIONSNIST researchers recently developed NIST StandardReference Database 79 (SRD 79) “Quantitative InfraredDatabase,” which contains absorption coefficient datafor 21 hazardous air pollutants. Over the last decade,growing concerns about the environment in general andair quality in particular have stimulated the developmentof improved, cost- effective field monitoring methods.In Fourier transform (FT) infrared-based technologiesdeveloped for real-time monitoring of airborne chemi-cal contaminants, an infrared source is aimed at a retro-reflector placed at some distance away, and the resultingreflected beam is passed through an FT spectrometer.Multiple compounds can be measured simultaneously—because each molecular species has a unique infraredspectrum—with sensitivities at the 1310–9 level. The insitu and real-time nature of this approach offers severaladvantages over traditional point source monitoringtechniques for applications such as determining fugitiveemissions and chemical contaminants from industrialprocessing plants, hazardous waste and municipal land-fills, water treatment plants, oil refineries, and chemicalplants. Following successful testing of FT infraredmethods during remediation of several Superfund sites,the U.S. Environmental Protection Agency (EPA) hasissued a protocol (TO-16) for FT infrared open-pathremote sensing. Successful implementation of thisprotocol is highly dependent on the availability of high-quality reference spectral data from a definitive sourcesince molar absorptivity data in the literature widelydiffer.

SRD 79 data are based on NIST primary gravimetricstandards prepared with starting materials of assessedpurity and procedures that minimize contamination. Theinitial 0.12 cm–1 resolution data were processed togenerate data at a number of different resolutions andapodizations to provide users with data that closelymatch their experimental parameters. SRD 79 data areprovided in a standard JCAMP-DX format on a CD-ROM. A digital signature accompanying each data fileallows users to ensure the integrity and source of thedata file and traceability to NIST. Intercomparisonswith a number of expert laboratories, including theNational Physical Laboratory of the United Kingdom,were used to assure the quality of the NIST data. Futureplans are to expand the intercomparisons of NISTprimary standards and molar absorptivity data with

additional national metro-logy institutes to facilitate theuse of this database in issues of global interest andimpact.

The current version of SRD 79 can be obtainedthrough the NIST Standard Reference Data Program. Atits completion, this database will include manyadditional compounds listed in the EPA Clean Air Act aswell as those that are of concern in global warming andemissions trading issues. Updates to the NIST SRD 79will be available over the Internet as additional spectraare added.

A validated quantitative database traceable to nationalmeasurement standards is a critical part of the in-frastructure required for establishing emerging infrared-based monitoring technologies. This newFT-infraredtechnology, coupledwith the NIST spectral database,provides both industry and EPA with a tool for assessingregulatory compliance that is both cost effective and lessinvasive.CONTACT: Pam M. Chu, (301) 975-2988; [email protected] or Frank R. Guenther, (301) 975-3939;[email protected].

NIST RESEARCHERS DEVELOP STANDARDREFERENCE DATA FOR IMPORTANTPLASMA PROCESSING GASNIST researchers recently completed the determinationof a set of standard reference data for electron interac-tions with chlorine gas (Cl2). This gas is of significanttechnical importance to the semiconductor industrywhere it is used in various etching processes to fabricatemicroelectronic devices. Many reactor models haveutilized electron collision cross sections for Cl2 thatwere based upon a cross section set derived morethan 10 years ago. This set has been shown to containsignificant inaccuracies.

The standard reference data for Cl2 derived at NISTwere determined from a thorough assessment of theelectron interaction data available in the scientificliterature. This is the sixth gas to be investigated in anongoing NIST project to provide reliable electron inter-action data to the semiconductor industry. The dataassessment for Cl2 was particularly complex becauseof the large amount of data in the literature and thequestionable reliability of much of the data due to thereactive properties of the gas. The reference data for Cl2

contain cross sections for total electron scattering,momentum transfer, total vibrational excitation, elec-tronic excitation, total dissociation into neutrals, totalionization, total electron attachment, and ion-pair for-mation. Reference data for various electron transportparameters also were determined, along with electron

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interaction data with other species commonly found inCl2 plasmas, such as Cl, Cl+, and Cl. These new refer-ence data provide a sound basis upon which plasmamodelers can base their calculations. The reference datawill be posted on the World Wide Web for easy accessby industry.CONTACT: James K. Olthoff, (301) 975-2431; [email protected].

DATABASES NOW ON THE JOB TO HELPKEEP GAS FLOWINGEngineers in the natural gas industry will be interestedin a new paper from NIST that describes three comput-erized databases which provide thermophysical proper-ties for pure fluids, mixtures of fluids, and a predictivepackage emphasizing hydrocarbon systems.

The pure fluids database, known as the NIST12 Data-base, includes natural gas components such as methane,ethane, propane, andiso- and n-butane. Each fluid isrepresented by a highly accurate equation of state; corre-lations also are provided for viscosity, thermal conduc-tivity and dielectric constant. A separate program forhelium covers both the superfluid and normal fluidstates. The DOS-based, interactive database is menudriven and user friendly.

The NIST14 Database provides accurate thermophys-ical properties of 17 pure fluids and their mixtures. Thisdatabase emphasizes accurate density calculations, yetprovides excellent results for other properties. NIST hasbeen working on new models for mixture properties,and these will be incorporated into future versions ofNIST14.

The NIST4 Database (NIST SUPERTRAPP) empha-sizes prediction of thermophysical properties for a largenumber of fluid systems that have not been adequatelymeasured to establish standard property surfaces. Theinteractive, DOS-based database allows calculations for192 pure fluids and their mixtures of up to 20 compo-nents. The fluids include hydrocarbons up to carbon-24,as well as common impurities such as carbon dioxide,nitrogen, oxygen, and hydrogen sulfide. TheFORTRAN source code for property prediction also isincluded, so that a user may link it with other software.

Copies of the databases may be ordered from theStandard Reference Data Program, NIST, 100 BureauDr., Stop 2310, Gaithersburg, MD 20899-2310; (301)975-2208; [email protected]. Copies of paper 3-99explaining the data-bases are available from SarabethHarris, MS104, NIST, Boulder, Colo. 80303-3337;(303) 497-3237; [email protected] Contact: Fred McGehan, (303) 497-3246;[email protected].

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May 25–26, 1999UNDERSTANDING THE DIGITAL ECONOMY:

DATA, TOOLS, AND RESEARCH

Location: U.S. Department of CommerceWashington, DC

Sponsors: National Economic Council, Office ofScience and Technology Policy, National ScienceFoundation and the U.S. Department of Commerce.Audience: Business, government and academia.Format: Major panel sessions in auditorium, andbreakout sessions.Purpose: To fulfill a presidential directive to under-stand the scope and direction of change in the U.S. andinternational economy due to growth of the internet andworldwide web.Topics: Macroeconomic assessment, access, smallbusiness, organizational change, market structure andcompetition, and employment and the workforce.Technical Contacts: Ronald Levin, U.S. Departmentof Commerce International Trade Administration,Office of Trade and Economic Analysis, Room 2815,Washington, DC, phone: 202/482-1678,fax: 202/482-4614,email: [email protected] Homepage:http://www.ita.doc.gov/industry/otea/utde/index.html.Electronic Registration: https://sales.nist.gov/conf/secure/CONF115/conf_register.htm.

June 3, 1999FIFTH CONFERENCE ON HUMAN

FACTORS AND THE WEB:THE FUTURE OF WEB APPLICATIONS

Location: National Institute ofStandards and TechnologyGaithersburg, MD

Sponsors: NIST, AT&T Labs, and Oracle.Audience: Usability engineers, web designers anddevelopers, and human factors researchers.Format: Conference.

Calendar

Purpose: The purpose of this conference is to providea forum for sharing information among a community ofhuman factors engineers, designers, and developers whoare interested in producing web sites that are moreuseful and usable.Topics: Web design and usability.Technical Contact: Sharon Laskowski, NIST, 100Bureau Dr., Stop 8940, Gaithersburg, MD 20899-8940, phone: 301/975-4535, fax: 301/975-5287,email: [email protected] Homepage:http://zing.ncsl.nist.gov/hfweb/Electronic Registration: http://zing.ncsl.nist.gov/hfweb/register/actualform.en.html.

June 20–25, 1999NATO ADVANCED RESEARCH WORKSHOP

ON POLYMER STRUCTURE AND TRANSPORTIN CONFINED SPACES

Location: Punchner CastleBikal, Hungary

Sponsors: NIST/Biotechnology Division, North At-lantic Treaty Organization (NATO), and Avanti PolarLipids.Audience: The meeting will be directed towardspolymer scientists, physicists, biologists, biophysisists,theoreticians, and industries interested in the physicalproperties of RNA and DNA as well as the mechanismsby which proteins and DNA are transported across cellmembranes.Format: The meeting is a four-day workshop withlectures and poster sessions.Purpose: This workshop seeks to advance the scien-tific and technological state-of-the-art of the physical,mechanical, and transport properties of polymers inbiological systems. Emphasis will be placed on under-standing the biology and physics of polymer structureand transport in highly confined geometries. Emergingtechnologiesthat could benefit from these studies willalso be discussed.Topics: I) Protein transport in biological systems;protein biochemistry. II)Polymer transport throughnanometer-scale pores. III) Theoretical approaches to

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polymer structure, transport and dynamics; molecularrecognition; intermolecular forces. IV) DNA-proteinand protein-protein interactions. V) Spectroscopy;single molecule detection, characterization, andmanipulation. VI) Applications.Technical Contact: Dr. John J. Kasianowicz, NIST,100 Bureau Dr., Stop 8311, Gaithersburg, MD 20899-8311, phone: 301/975-5853, fax: 301/330-3447,email: [email protected] Homepage:http://www.cstl.nist.gov/nist831/NATO99/

October 18–21, 199922ND NATIONAL INFORMATION SYSTEMS

SECURITY CONFERENCE

Location: Hyatt Regency Crystal CityArlington, VA

Sponsors: NIST and National Computer SecurityCenter of the National Security Agency (NCSC/NSA).Audience: Government, industry, commercial, andacademic communities.Format: Tracks, tutorials, and panels with a separatevendor exposition.Purpose: To address today’s hottest informationsystems security issues.Topics: Information systems security issues. For infor-mation on submitting conference papers and paneltopics, email: [email protected] Contact: Pat Toth, NIST, 100 Bureau Dr.,Stop 8930, Gaithersburg, MD 20899-8930, phone: 301/975-5140, fax: 301/948-0279, email: [email protected] Homepage: http://csrc.nist.gov/nissc/welcome.htm.

October 18–22, 1999CONFERENCE ON BIOASSAY,

ANALYTICAL AND ENVIRONMENTALRADIOCHEMISTRY (BAER ‘99)

Location: National Institute ofStandards and TechnologyGaithersburg, MD

Sponsor: NIST.Audience: Radiochemistry industry, commerciallaboratories, academia, regulatory agencies, nationallaboratories, and international laboratories.

Format: Conference, workshops, and poster sessions.Purpose: Informal forum for presentation of newdevelopments, lessons learned, innovations, technicaltips, problem solving, training, building contact net-works, and discovering sources of expertise in the areaof bioassay, analytical and environmental radio-chemistry.Topics: Bioassay, analytical and environmental radio-chemistry.Technical Contact: Kenneth G. W. Inn, NIST, 100Bureau Dr., Stop 8462, Gaithersburg, MD 20899-8462, phone: 301/975-5541, fax: 301/869-7682, email:[email protected].

November 1–2, 1999INDUSTRIAL VIRTUAL REALITY

SYMPOSIUM

Location: University of IllinoisChicago, IL

Sponsors: NIST, University of Illinois at Chicago, andthe American Society of Mechqnical Engineers(ASME).Audience: Industry and academia.Format: Invited speakers, paper presentations, videopresentations, research demonstrations, exhibits, work-shops, and round table discussions.Purpose: To present what is being done in the area ofindustrial virtual reality and how research institutionsand industries ar contributing towards developing thistechnology as well as itsapplications.Topics: Computational aspects of VR applications inmanufacturing, current state of software technologies,current state of hardware technoligies, distribution andlogistics applications in manufacturing, layout andlocation applications in manufacturing, manufacturingeducation, manufacturing process design, prodictdesign and prototyping, telepressence and telerobotics,and volumetric visualization.Technical Contact: Pat Banerjee, University ofIllinois, Dept. of Mechanical Engineering (M/C 251)3029 ERF, 842 W. Taylor, Chicago, IL 60607-7022,phone: 312/996-5599, fax: 312/413-0447, email:[email protected].

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U.S. Department of Commerce

Technology Administration

National Institute of Standards and Technology

The International System of Units (SI)The Modern Metric System

Uncertain about the InternationalSystem of Units (universally abbreviatedSI), the modern metric system usedthroughout the world? Do you need toknow the proper way to express the resultsof measurements and the values of quanti-ties in units of the SI? Do you need to knowthe NIST policy on the use of the SI? Thenyou need the 1995 edition of the NationalInstitute of Standards and TechnologySpecial Publication 811,Guide for the Useof the International System of Units (SI).

The 1995 edition of the National Institute of Standards and Technology Special Publication 811,Guide for the Use of the International System of Units (SI), by Barry N. Taylor, is now available.

The 1995 edition of SP 811 corrects a number of misprints in the 1991 edition, incorporates asignificant amount of additional material intended to answer frequently asked questions concerningthe SI and SI usage, and updates the bibliography. The added material includes a check list forreviewing the consistency of written documents with the SI. Some changes in format have alsobeen made in an attempt to improve the ease of use of SP 811.

The topics covered by SP 811 include:• NIST policy on the use of the SI in NIST publications.• Classes of SI units, those SI derived units that have special names and symbols, and the SI

prefixes that are used to form decimal multiples and submultiples of SI units.• Those units outside the SI that may be used with the SI and those that may not.• Rules and style conventions for printing and using quantity symbols, unit symbols, and prefix

symbols, and for spelling unit names.• Rules and style conventions for expressing the results of measurements and the values of quan-

tities.• Definitions of the SI base units.• Conversion factors for converting values of quantities expressed in units that are mainly unac-

ceptable for use with the SI to values expressed mainly in units of the SI.• Rounding numbers and rounding converted numerical values of quantities.

Single copies of the 84-page SP 811 may be obtained from the NIST Calibration Program,100 Bureau Dr., Building 820, Room 236, Stop 2330, Gaithersburg, MD 20899-2330, telephone:301-975-2002, fax: 301-869-3548.

Special Publication 811

1995 Edition

Guide for the Use of the International

System of Units (SI)

Barry N. Taylor

United States Department of Commerce



Evaluating and Expressing the Uncertaintyof Measurement Results

Uncertain about expressing measure-ment uncertainty? Do you need to knowhow NIST states the uncertainty of its mea-surement results and how you can imple-ment their internationally accepted methodin your own laboratory? Then you need thenewly available 1994 edition of theNational Institute of Standards and Tech-nology Technical Note 1297,Guidelinesfor Evaluating and Expressing the Uncer-tainty of NIST Measurement Results.

The 1994 edition of the National Institute of Standards and Technology Technical Note 1297,Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, by BarryN. Taylor and Chris E. Kuyatt is now available.

The 1994 edition of TN 1297 includes a new appendix—Appendix D—which clarifies and givesadditional guidance on a number of topics related to measurement uncertainty, including the useof certain terms such as accuracy and precision. Very minor word changes have also been madein a few portions of the text of the 1993 edition in order to recognize the official publication inOctober 1993 by the International Organization for Standardization (ISO) of theGuide to theExpression of Uncertainty in Measurementon which TN 1297 is based. However, the NIST policyon measurement uncertainty, Statements of Uncertainty Associated with Measurement Results,which is reproduced as Appendix C of TN 1297, is unchanged.

It is expected that the 1994 edition of TN 1297 will be even more useful than its immediatepredecessor, the 1993 edition, of which 10 000 copies were distributed worldwide.

Those United States readers who wish to delve into the subject of measurement uncertainty ingreater depth may purchase a copy of the 100-page ISOGuidefrom the Sales Department of theAmerican National Standards Institute (ANSI), 105-111 South State Street, Hackensack,NJ 07601. Copies may also be purchased from the ISO Central Secretariat, 1 rue de Varembe´,Case postale 56, CH-1211 Gene`ve 20, Switzerland.

Single copies of the 20-page TN 1297 may be obtained from the NIST Calibration Program,100 Bureau Dr., Building 820, Room 236, Stop 2330, Gaithersburg, MD 20899-2330, telephone:301-975-2002, fax: 301-869-3548.

NIST Technical Note 1297

1994 Edition

Guidelines for Evaluating and Expressing

the Uncertainty of NIST Measurement Results

Barry N. Taylor and Chris E. Kuyatt

United States Department of Commerce



NISTTechnical PublicationsPeriodical

Journal of Research of the National Institute of Standards and Technology—Reports NIST researchand development in those disciplines of the physical and engineering sciences in which the Institute isactive. These include physics, chemistry, engineering, mathematics, and computer sciences. Papers cover abroad range of subjects, with major emphasis on measurement methodology and thebasic technologyunderlying standardization. Also included from time to time are survey articles on topics closely related tothe Institute’s technical and scientific programs. Issued six times a year.

Nonperiodicals

Monographs—Major contributions to the technical literature on various subjects related to theInstitute’s scientific and technical activities.Handbooks—Recommended codes of engineering and industrial practice (including safety codes) devel-oped in cooperation with interested industries, professional organizations, and regulatory bodies.Special Publications—Include proceedings of conferences sponsored by NIST, NIST annual reports, andother special publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

National Standard Reference Data Series—Provides quantitative data on the physical and chemicalproperties of materials, compiled from the world’s literature and critically evaluated. Developed under aworldwide program coordinated by NIST under the authority of the National Standard Data Act (PublicLaw 90-396). NOTE: The Journal of Physical and Chemical Reference Data (JPCRD) is publishedbimonthly for NIST by the American Chemical Society (ACS) and the American Institute of Physics (AIP).Subscriptions, reprints, and supplements are available from ACS, 1155 Sixteenth St., NW, Washington, DC20056.Building Science Series—Disseminates technical information developed at the Institute on buildingmaterials, components, systems, and whole structures. The series presents research results, test methods, andperformance criteria related to the structural and environmental functions and the durability and safetycharacteristics of building elements and systems.Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment ofa subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of thesubject area. Often serve as a vehicle for final reports of work performed at NIST under the sponsorship ofother government agencies.Voluntary Product Standards—Developed under procedures published by the Department of Commercein Part 10, Title 15, of the Code of Federal Regulations. The standards establish nationally recognizedrequirements for products, and provide all concerned interests with a basis for common understanding ofthe characteristics of the products. NIST administers this program in support of the efforts of private-sectorstandardizing organizations.

Order thefollowing NIST publications—FIPS and NISTIRs—from the National Technical InformationService, Springfield, VA 22161.Federal Information Processing Standards Publications (FIPS PUB)—Publications in this seriescollectively constitute the Federal Information Processing Standards Register. The Register serves as theofficial source of information in the Federal Government regarding standards issued by NIST pursuant tothe Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat.1127), and as implemented by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 ofTitle 15 CFR (Code of Federal Regulations).NIST Interagency Reports (NISTIR)—A special series of interim or final reports on work performed byNIST for outside sponsors (both government and nongovernment). In general, initial distribution is handledby the sponsor; public distribution is by the National Technical Information Service, Springfield, VA 22161,in paper copy or microfiche form.

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