Directions in Neutron Source Development

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Directions in NeutronSource Development

• Physics ColloquiumBrookhaven National Laboratory
  
• Thomas E. MasonLaboratory Director
• Upton, New YorkNovember 21, 2007

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Neutron sourcesHow far have we come?
SNS
1018
ESS
SNS
ILL
HFIR
NRU
MTR
ISIS
1015
LANSCE
HFBR
NRX
KENS
IPNS
ZING-P?
SINQ-II
SINQ
X-10
Tohoku Linac
1012
ZING-P
109
Thermal Neutron Flux (n/cm2-sec)
CP-2
Berkeley37-inch cyclotron
Next-generation sources
CP-1
106
Fission reactors
Particle driven (steady-state)
Particle driven (pulsed)
0.35-mCi Ra-Be source
103
trendline reactors
trendline pulsed sources
Chadwick
ORNL 97-3924f/djr
100
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
(Updated from Neutron Scattering, K. Skold and D.
L. Price eds., Academic Press, 1986)
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We have consistently managedto squeeze more out
of existing sources

• By adding cold sources to existing reactors
• NIST, JRR-3M, HFIR, etc., and more coming
• By improving target/moderator optimization
• SINQ target, Lujan coupled moderators
• Accelerators also have the potential for increase
  in beam power
• Well exploited by high-energy physicists (e.g.,
  AGS)
• Increases in current at ISIS, Lujan, PSI
• Next-generation sources (J-PARC and SNS) have
  made provision for power increases in their design

What are the prospects for iterative improvement
on the current technology base?
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The 20-year plan for SNS

• Evolve along path envisagedin Russell Panel
  specifications
• In 20 years
• Operating 45best-in-class instruments
• Two differently optimizedtarget stations
• Beam power of 34 MW
• Long WavelengthTarget Station (LWTS)and Power
  Upgrade should followa sequence that mesheswith
  deployment of initial capabilityand national
  needs
• Similar developments likely elsewhereJapan,
  China, Europe, . . .

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Power upgrade

• Increase energyby adding to SC linac
• Allows storageof more current in accumulator
  ring
• Relatively straightforward for ring and linac

3-MW linac at 6 duty factorscales to 50 MW
CW(not ours)
5 Managed by UT-Battellefor the Department of
Energy
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Meeting the H needs of the SNS power
upgradeHelicon driver for the SNS ion source

• Demanding requirements
• Beam current 7095 mA
• Pulse length 1 ms
• Duty factor 7.4
• Proof-of-principle experiment (LDRD funding) to
  combine
• VASIMR helicon plasma generator, ORNL Fusion
  Energy Division
• SNS H ion source, ORNL-LBNL
• Expected to increasemaximum source plasma
  density(by a factor of 3) at reducedrf power,
  resulting in
• Increased H current
• Reduced heat removal requirements

Helicon test facility, Building 7625
Goulding et al., AIP Conf. Proc. 933, 493496
(2007)
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One potential bottleneck Stripping H
Novel approach to laser stripping Use a
narrowband laser to convert H to protonsfor
high-power operations
Laser beam
High-fielddipole magnet
High-fielddipole magnet
H
proton
H0
a
H0
Lorentz stripping
Laserexcitation
Lorentzstripping
H ? H0 e
H0(n 1) g ? H0(n 3)
H0 ? p e
V. Danilov et al., Phys. Rev. ST Accel. Beams 10,
053501 (2007)
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Proof-of-principle experiment at SNS
Light invacuum chamber
Magnetic insertions
Laser and optics
H beamcurrent
Stripped electrons by laser light
Stripping efficiencygt 90
12
8
4
0
30
40
50
60
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Another potential bottleneck Target

• Pressure pulse mitigation
• Bubble injection (shock absorbers)
• Proton radiography bubble visualization
  experiment
• Analysis is progressing, with about 500 images
  processed
• Quantification of bubble sizes, numbers, and void
  fractionover a wide range of test conditions

pRad bubble visualizationexperiment, LANL

• Test conditions
• Mercury thickness 22 mm
• Mercury velocity 0.4 m/s
• Helium gas flow throughjet bubbler 1 140 sccm

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Original SNS-LWTS concept (Developed without
assumption of additional beam power)
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Optimizing the neutronic environment and
increasing beam power
Time-averaged neutron spectra
1.E15

• We have many knobsfor tuning moderator/
  reflector designto maximizeuseful neutrons
• Timing
• Energy
• We dont have verygood ways to tailorneutron
  direction

1.E14
1.E13
Brightness (n/s/cm2/sr/eV/MW)
Second target station
1.E12
Russell Panel
Long-Wavelength Target Station
High Power Target Station, beamline 5
1.E11
1.E05
1.E04
1.E03
1.E02
1.E01
1.E00
Energy (eV)
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Source development

• No existing or under construction source takes
  advantageof spallation process efficiency to
  make more neutrons
• We have taken advantage of spectra and time
  tailoring to make more useful neutrons

Figure courtesy K.N. Clausen, PSI
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Neutron production

• For power density limit,the ANS reactor
  designprobably representsa practical
  extreme(5? ILL)
• CW spallation sourcenot likely to have more than
  20? ILLwithout going to large target
  volume(lower flux)

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Father of all spallation sourcesLawrences
Materials Testing Accelerator

• Deuteron acceleratorfor production of plutonium
  and tritium
• NaK-cooledBe target
• 500 MeV
• 320 mA
• 160 MW

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The neutrons themselvesare becoming a problem!
15 Managed by UT-Battellefor the Department of
Energy
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What about the instruments?

• We still have lotsof room to improve
• Optics
• Sample environment
• Detector speed, resolution, efficiency, background

• We are bumping upagainst the limitin terms of
  steradians(and space)

16 Managed by UT-Battellefor the Department of
Energy
17
We shouldnt ignore non-neutronic improvements
ZEEMANS beamline
Ze Extreme MagneticNeutron Spectrometer
SNS Target Building
Choppers
Neutron guide
Existing buildings
Magnet
Detectors
Spacefor future second magnet
Preliminary concept High magnetic field (30 T)
instrument on SNS beamline 14
Johns Hopkins, SNS, National High Magnetic Field
Laboratory, others
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Limits to growth

• Intrinsic difficulties of dealing with extremely
  high neutron flux (radiation/activation,
  detectors) will ultimately limit useven if we
  solve the energy density problems through
  ingenuityor even more efficient production
  (fusion)
• Solvable to some extent with money Remote
  handlingof accelerator/significant parts of
  instruments,target higher speed detectors with
  correspondinglysegmented electronics
• Current limit on regional-scale scientific
  facilityis 12B (or Euros, Oku Yen, etc.)
• Global model (ILC/ITER) might provide another
  orderof magnitude, but doesnt work so well when
  capacityis as much an issue as performance
• Current (3rd-generation?) spallation source
  technologywill scale to 35 MW with reasonable
  progressin ongoing RD
• Likely another order of magnitude in a
  4th-generation(short pulse, long pulse, or CW
  TBD)

18 Managed by UT-Battellefor the Department of
Energy
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Overcoming the limits

• Beyond a 4th generation of spallation
  sources(plus continued use of reactors when
  there is synergywith nuclear energy or isotope
  interests),things get harder
• We may be hitting the neutron limit with either
  100? SNS spallation or a fusion source, unless
  the economicsof science policy undergoes a
  fundamental shift
• This highlights the importance of continuing to
  developways to make more useful neutrons
• The x-ray communitys log plot world only applies
  to useful x-rays
• Our success in arranging our neutronsmore
  usefully in time begs a questionWhat is the
  optimal time structure for scattering?
• Current debate is constrained by the accelerators
• Also What can we do about spatial distribution?

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Update on SNSExceeding early power ramp-up
goals
160
Actual
120
Commitment
Integrated Beam Power (MW-hours)
80
40
0
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
FY 2007
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SNS is now the worlds most powerfulpulsed
neutron source
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We are on schedulefor commissioning instruments
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Backscattering spectrometer
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Backscattering spectrometerMeasurement of a
spin ice

• Holmium titanate spin icedoped with
  nonmagnetic(La) voids Ho1.6La0.4Ti2O7
• SNS at 150 kW, 30 Hz
• Spectra ?10 h
• 0 lt Q lt 1.8 Å1(Q-independentspin dynamics)

Are the spin dynamics thermally activated or
defect assisted?
Georg Ehlers, SNS
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Backscattering spectrometerHydration-water-induc
eddynamic transitions in lysozymes
1013
TL 223 K
1012
Bulk water
Reversible
1011
Water-lysozyme h 0.3
1/D (sec/m2)
VFT fit
Cpmax
Arrhenius fit
Irreversible denatured
1010
TD
VFT fit
Strong-to-fragiledynamic crossoverin protein
hydration water is conjecturedto initiate
reversible protein denaturation
109
Native
108
2.6
3.0
3.4
3.8
4.2
4.6
5.0
1,000/T (K-1)
Sow-Hsin Chen, MIT
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Backscattering spectrometerHydration-water-induc
eddynamic transitions in lysozymes (continued)
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Reflectometers
27 Managed by UT-Battellefor the Department of
Energy
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Liquids reflectometerpH-responsive weak
poly-electrolyte multilayers

• Sample
• Multilayer consisting of
• Poly(methacrylic acid) PMAAwater-soluble acid
• Quaternized poly(vinylpyrolidone)PVP salt
  (ionic)
• Deuterated d-PMAA markersevery fifth bilayer

• Goals
• Determine how film reacts to changes in pH
• First step to controlling release in vivo

Kharlampieva and Sukhishvili (Stevens Institute
of Technology) and Tao, Halbert, and Ankner
(SNS), submitted to Phys. Rev. Lett.
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Liquids reflectometerpH-induced structural
change

• As-grown
• pH 5
• Layered
• dPMAA markers

• Released
• pH 7.5
• Mixed
• 38 of PMAA dissolved

• Reabsorbed
• pH 5
• Mixed
• PMAA redeposited

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Magnetism reflectometerWhere does the
ferromagnetism reside?
H. Ambaye, R. Goyette, A. Parizzi, F. Klose, and
G. Felcher
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31 Managed by UT-Battellefor the Department of
Energy