rare isotope accelerator ria opportunities & challenges · target ion source unit ion optics...
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Rare Isotope AcceleratorRIA
Opportunities & Challenges
Richard C. YorkOctober 2004
MIT
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RIA Status
• Strong Nuclear Science community support• Nuclear Science Advisory Committee Long
Range Plan (April 2002) – RIA highest priority new facility• “The Rare Isotope Accelerator (RIA) is our
highest priority for major new construction…”
• Tied for third position for near term priorities in DOE 20-year plan (November 2003)
• RIA CD-0 – done early 2004• RIA RFP expected ??
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DOE 20-Year Facilities OutlookNear-Term Priorities
1. ITER 2. UltraScale Scientific Computing Capability 3. Tie for 3
• Joint Dark Energy Mission • Linac Coherent Light Source Protein Production & Tags• Rare Isotope Accelerator (RIA)
7. Tie for 7• Characterization & Imaging of Molecular Machines
8. CEBAF 12 GeV Upgrade 209. Energy Sciences Network (ESnet) Upgrade 2010. National Energy Research Scientific Computing Center Upgrade11. Transmission Electron Achromatic Microscope12. BTeV
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RIA Benefits
• Important benefits for basic & applied science• Study properties of a large number of isotopes
that heretofore only existed in cosmos• Quantitative information for theories of stellar
evolution & formation of elements in cosmos• Support space-based astronomical observations by
providing quantitative comparisons with theoretical predictions of stellar evolution
• Experimental data to refine theories for predicting properties of nuclei with unusual neutron-to-proton ratios
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RIA Benefits - cont’d
• Support stockpile stewardship• Only way to obtain important reaction cross
sections on unstable isotopes & to improve theoretical models
• Improved diagnostic tools via isotopic analysis of materials from underground nuclear tests
• Produce almost any isotope for radio-medical research
• Materials Science & other applications• Implantation for wear & corrosion studies• Space radiation effect studies• Material modifications – doping & annealing
techniques
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RIA Scale
• RIA project cost (in FY2001 dollars)• TEC = ~$695 M ($550 M w/o contingency)• TPC (TEC + Pre-ops, etc) = ~885 M$ over ~7-8
years• Operations - ~80 M$/year – similar to JLab
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Production of Rare Isotopes at RestTarget Fragmentation
1. Random removal of protons and neutrons from heavy target nuclei by energetic light projectiles (pre-equilibrium and equilibrium emissions).
2. Extraction of rare isotopes by diffusion; ionization and acceleration: beams of high quality.
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Classical ISOL Facility Concept• Excellent beam quality and low beam energies are possible• Limited to longer lifetimes (τ > 1s)• Isotope extraction and ionization efficiency depend on
chemical properties of element: difficult, element-specific development paths
• The most neutron-rich isotopes will have too low intensities and too short lifetimes to be suitable for re-acceleration
Postaccelerator
Isotope / isobarseparator
Thick, hot target
Transfer tube Ion source
Radioactive ion beam
Production beam
Productionaccelerator
Experiment
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Production of Rare Isotopes in Flight
hot participant zone
projectile fragment
1. Random removal of protons and neutrons from heavy projectile in peripheral collisions.
projectile
target
2. Cooling by evaporation.
projectile fragment
“radioactive beam”
Projectile Fragmentation
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Schematic of a Projectile Fragmentation Facility
• High-energy beams (E/A > 50 MeV) of modest beam quality
• Physical method of separation, no chemistry• Suitable for short-lived isotopes (τ > 10-6 s)• Low-energy beams are difficult
• Solution – stop in gas cell & reaccelerate
Fragment separator
Thin productiontarget Radioactive ion beam
Heavy ionaccelerator
Experiment
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Example Fragment Separation Technique (NSCL)
Wedge locationD = 5 cm/%R = 2500 p/∆p
100 pnA 86Kr5 kW Beam power
8 msr∆p = 5%
65% of the 78Ni is transmitted
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The Rare Isotope Accelerator (RIA) Concept
• Combines advantages of projectile & target fragmentation techniques• Use all tools developed for rare isotope research
worldwide
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General Comments
• Technical Risks• No “Show Stoppers” but significant challenges
• ~5 years - significant efforts on the driver linac -• Optimization strategies & detailed
considerations• Relatively less activity on the target and
experimental areas• Recently these arenas have seen dramatic
increase in focus• Significant challenges and issues recognized
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RIA Layout• Driver linac straight or folded (shown) – decision
based on optimization
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RIA at MSU• Over 5000 acre campus – potential sites within 5 minutes of classroom• Next generation scientists & multi-discipline synergies
North
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Driver Linac Sample Beam List• Design goal - Constant beam power
• 100 kW minimum • 400 kW if ion source capable
• Multiple charge state acceleration for >Xe
Ion A Z Final Energy(MeV/u)
H 1 1 1028 3He 3 2 777 D 2 1 622 O 18 8 560 Ar 40 18 566 Kr 86 36 510 Xe 136 54 470 U 238 92 400
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Comparison of Rare Isotope Intensities
neutron number
possible locationof neutron dripline
pro
ton
nu
mb
er
10: comparable100100 - 10,000larger than 10,000
Approximate Intensity Gains of RIA over NSCL
stable isotope
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Driver Linac Front End
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Superconducting Driver Linac
• Design driven by 400 MeV/nucleon uranium• 28+ & 29+ U injected into SC linac at 292 keV/u• Segment I
• Accelerated to ~12 MeV/u & stripped • Segment II
• 5 charge states (73±2) accelerated to ~90 MeV/u• Segment III
• Stripped and 3 charge states (88 ±1) accelerated to 400 MeV/u
I II III
Fold point
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Superconducting Structures
ßopt=0.04180.5 MHz
LegnaroMSU
ßopt=0.08580.5 MHz
ßopt=0.285322 MHz
MSU
ßopt=0.49805 MHz
MSU/JLAB
ßopt=0.63805 MHz
SNS
ßopt=0.83805 MHz
SNS
Tested – 2003Exceeded Specs.
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Superconducting Segments
6 cavity types
Cavity Type βopt f
(MHz) T
(K) Linac
Segment# Of
Cavities λ/4 0.041 80.5 4.2 I 18 λ/4 0.085 80.5 4.2 I 104 λ/2 0.285 322 2 II 208
Ellip. 0.49 805 2 III 68 Ellip. 0.63 805 2 III 64 Ellip. 0.83 805 2 III 32
Total 494
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Driver Linac Stripping Chicanes
• High symmetry – good higher-order corrections• Positioned to support longitudinal matching at
frequency changes
X XY YZ ZEntrance Exit
1st Stripping Chicane
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Transit Time Factors & Energy Gain
Stripping locations
U
H
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NSCL SRF Facility Layout
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NSCL SRF Chemistry Facility
BCP Pumping System
Temperature <15 CHeat Exchanger 5 kW Filtration 4 microns Speed 8 gpm
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NSCL SRF R&D Facility
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Segments I & II Cryostats
• Isolated vacuum• Superconducting solenoid focusing
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Low-β Cryomodule Prototype
HWR,ßopt=0.285
QWR,ßopt=0.085
0.6 T Quadrupole
9 T Solenoid
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Segment III Cryostats
Two-cavity β=0.49 prototypeTested Spring 2004
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βopt=0.49 elements
He Vessel
Tuner
PowerCoupler
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β= 0.49 Prototype Systems Test
Top Plate
Support Link
He Supply
He Return
Power Coupler
Tuner
Ti Rails
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Natural Modes/Mechanical Resonances
42 Hz 72 Hz
142 Hz121 Hz
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Cavity and microphonics circuit
Qext, fixed ≅ 1x107
Qext, transformer ≅ 105 to 4x109
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RIA Layout - BSY
Beam Switch Yard
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Driver Linac Switch Yard• Baseline – provide two beams (of same isotope) to
two targets simultaneously (µ-bunch)
-1.0
-0.5
0.0
0.5
1.0
Volta
ge
Time
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RIA Layout - Target Area
Target Area
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ISOL Target Area Concepts• 400 kW beam power – Many R&D Issues
• ~10x existing designs - major technical challenge for ISOL targets
• Infrastructure proposed suitable for ultimate 400 kW• Three (possibly staged) ISOL target stations proposed
• Redundancy & beam development & R&D to higher powers
< 400 kW primary beam
beam transport matrix
to post-accelerator
target stations withpre-separator and
focal-plane switchyard
high-resolution separators
to stopped beam area
from gas stopping station
ECR
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ISOL Target Layout
Cra
ne S
ervi
ceTr
ansf
er a
rea
Hot cell
Tele manipulator stationsRemote control room
To high resolution separators Pre-separatorTarget Plug
Plug Storage
Target service docks
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ISOL Target Station
Hg loop pipes mounted on insulators
`
Isolated HG feedthroughs
HV - electrical feedthroughs
Hg spill tank
Target ion source unit
Ion optics
vacuum pumps
to prevacuum line
vacuum duct
servicechannelsfor Hg, gas, water,electric power and instrimentation
electrical wiresmounted on insulators
`
inflatable seals
focal plane beam
switchyard
to HV platforms
pre-separator dipole magnet
1 m
Laser beams
beam lines
`
Slit system+ beam diagnostics+ optics
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Services
Target area service gallery
Access plugs
RemoteControlRoom
Target shielding
ISOL Hot Cell & Service Gallery
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Facility Classification
• Category 1 – Potential for significant off-site consequences• Category 2 – Potential for significant on-site consequences• Category 3 – Potential for localized consequences
Spallation of UC2 Target1836 MeV 3He, 100 kW, Stopping Target
7-Day Irradiation, 1-Day CoolLAHET+MCNP+ORIHET
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
0 50 100 150 200 250Fragment Mass (A)
Act
ivity
(Ci)
Calculation
DOE Cat. 2 Thresh
DOE Cat. 3 Thresh
Cat 2
Cat 3
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Fragmentation Production Area
• Targets – R&D challenge• High power density - ~ 500 kW/cm3 (400 kW
primary beam)• Small spot size – reduce geometric aberrations• ~20% of beam power lost in target• Heavy ions have high dE/dX
• Pre-separator concept• Begin to isolate downstream system from very
high radiation environment• High performance & radiation resistant magnets
required – R&D challenge
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Pre-Separator
NSCL
Target
Dipole Quad-Triplet
IsotopeSlits
Wedge
BeamDump
Beam
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PHITS 1.69 Neutron Heating Calculation
Beam
400 kW beamIron heat load = 9 kWCoil heat load = 130 W
Coil dose ~ 1 MGy/yearOrganic dose ~200 MGy/year
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RIA Layout – Low Energy Area
Low Energy Area
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Low-energy Experimental Area• Important to make design compatible with very different types of targets• Mass separators with beam cooling may be better & cheaper – R&D
Required• Post accelerator ( 10 MeV/u for A up to 240, 20 MeV/u for A<60)
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RIA Layout – High Energy Area
High Energy Area
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Fragment Separators
• High acceptance design feeding helium gas stopping station• 10 T-m, 12% momentum acceptance, 10 msr
• High resolution design feeding fast beam area• 10 T-m, 6% momentum acceptance, 8 msr• Similar to NSCL design
• Pre-separator segment• Remove primary beam & most of unwanted
fragments• R&D Challenge
• Optical design with radiation resistant magnets and beam interception elements
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Fragmentation Separation Area Layout
Gas Cell
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Gas Stopping Station
• Layout • Provides beam from gas stopping to low-energy
area• Allows use of fragment separator to send beam
to high-energy area• Good R&D progress made with NSCL gas cell
• Shown ~20-50% incident ion implanted• Shown range-compression technique workable
• Outstanding R&D questions remain• What is system efficiency?• What is rate limitation?
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Gas Stopping at the NSCL
To
buncher
Gas cell RFQ 1 RFQ 2
Degraders SkimmerNozzle Orifice
Accelerationoptics
Entrancewindow
Pressure (He): ~1 bar ~ 0.1 mbar ~10-3 mbar < 10-6 mbar
Supersonicgas jet
Beam
fromA1900
RFQ 3
• Stopping/extractions of radioactive isotopes works• Systematic studies of intensity limits• Optimized ion guiding schemes and geometries
Substantial R&D still required
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Gas Stopping Efficiency
∆P/P 0.5 %, gas_cell_1.2_50
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
1650 1670 1690 1710 1730 1750 1770 1790
18 k pps
6 k pps
2 k pps
0.4 k pps
0.04 k pps
gas-equivalent
stopping /10
Total efficiency decreases with implantation rate
Glass thickness (µm)
Known implantation rate of ions [38Ca].Measured stopping fractions: 0.2 – 0.5
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High Energy Experimental Area
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Summary
• Fully general RIA facility accommodating baseline and future capabilities has been developed
• Driver linac with beam transport• Relatively detailed design• Beam transport flexibility increase remains a
challenge• Target and experimental areas
• General designs defined & issues identified• Provides for large range of possibilities for
future capabilities• R&D priorities identified