Managed by UT-Battelle for the Department of Energy Directions in Neutron Source Development Physics Colloquium Brookhaven National Laboratory Thomas E

Managed by UT-Battellefor the Department of Energy

Directions in NeutronSource Development

Physics ColloquiumBrookhaven National Laboratory

Thomas E. MasonLaboratory Director

Upton, New YorkNovember 21, 2007

2 Managed by UT-Battellefor the Department of Energy

Neutron sources:How far have we come?

1920

Ther

mal

Neu

tron

Flu

x (n

/cm

2 -sec

)

1018

1015

1012

109

106

103

100

1930 1940 1950 1960 1970 1980 1990 2000 2010 2020

NRX

X-10

CP-2

CP-1

0.35-mCi Ra-Be source

(Updated from Neutron Scattering, K. Skold and D. L. Price: eds., Academic Press, 1986)

Chadwick

Tohoku Linac

KENSIPNS

LANSCE

SINQZING-P

ZING-P

SINQ-II

ESSSNSSNS

ISISILLHFIR

HFBR

NRUMTR

Next-generation sourcesFission reactorsParticle driven (steady-state)Particle driven (pulsed)trendline reactorstrendline pulsed sources

ORNL 97-3924f/djr

Berkeley37-inch

cyclotron

Brookhaven_0711


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?

Brookhaven_0711


Evolve along path envisagedin Russell Panel specifications

In 20 years:– Operating ~45

best-in-class instruments

– Two differently optimizedtarget stations

– Beam power of 3–4 MW

Long WavelengthTarget Station (LWTS)and Power Upgrade should followa sequence that mesheswith deployment of initial capabilityand national needs

Similar developments likely elsewhere:Japan, China, Europe, . . .

The 20-year plan for SNS

Brookhaven_0711


Power upgrade

Increase energyby adding to SC linac– Allows storage

of more current in accumulator ring

Relatively straightforward for ring and linac

5 Managed by UT-Battellefor the Department of Energy Brookhaven_0711

3-MW linac at 6% duty factorscales to 50 MW CW

(not ours)


SNS external antenna H– source

Ions

Heliconplasmagenerator

Meeting the H– needs of the SNS power upgrade:Helicon driver for the SNS ion source

Demanding requirements:– Beam current: 70–95 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, 493–496 (2007)

Brookhaven_0711


H– protonH0

Lorentz stripping

Laserexcitation

Lorentzstripping

High-fielddipole magnet

High-fielddipole magnet

H– H0 + e– H0(n = 1) + H0*(n = 3) H0* p + e–

Laser beam

H0*

One potential bottleneck: Stripping H–

Novel approach to laser stripping: Use a narrowband laser to convert H– to protonsfor high-power operations

V. Danilov et al., Phys. Rev. ST Accel. Beams 10, 053501 (2007)

Brookhaven_0711


0

4

8

12

30 40 50 60

Magnetic insertions Laser and opticsLight in

vacuum chamber

H– beamcurrent

Stripped electronsby laser light

Proof-of-principle experiment at SNS

Stripping efficiency> 90%

Brookhaven_0711


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

Another potential bottleneck: Target

Test conditions

Mercury thickness: 22 mm

Mercury velocity = 0.4 m/s

Helium gas flow throughjet bubbler 1: 140 sccm

Brookhaven_0711


Original SNS-LWTS concept (Developed without assumption of additional beam power)

Brookhaven_0711


Second target stationRussell PanelLong-Wavelength Target StationHigh Power Target Station, beamline 5

Optimizing the neutronic environment and increasing beam power

We have many knobsfor tuning moderator/ reflector designto maximizeuseful neutrons– Timing – Energy

We don’t have verygood ways to tailorneutron direction

Time-averaged neutron spectra1.E+15

1.E+14

1.E+13

1.E+12

1.E+11

1.E–05 1.E–04 1.E–03 1.E–02 1.E–01 1.E–00Energy (eV)

Brig

htne

ss (n

/s/c

m2 /s

r/eV/

MW

)

Brookhaven_0711


Source development

Figure courtesy K.N. Clausen, PSI

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

Brookhaven_0711


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)

Fission 180–200 MeV/neutron Average kinetic energy ~ 2 MeV

Spallation 35–50 MeV/neutron Average kinetic energy ~ 2–5 MeV

Fusion >17.6 MeV/neutron Average kinetic energy 14 MeV and 3.5 MeV

Other routes(e.g., LENS, bremsstrahlung, . . .)

Brookhaven_0711


Deuteron acceleratorfor production of plutonium and tritium

NaK-cooledBe target

500 MeV

320 mA

160 MW

Father of all spallation sources:Lawrence’s Materials Testing Accelerator

Brookhaven_0711


The neutrons themselvesare becoming a problem!



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)



Spacefor future second magnet

Magnet

Neutronguide

Existingbuildings

Detectors

Choppers

SNS Target Building

Preliminary concept: High magnetic field (≥30 T)

instrument on SNS beamline 14

We shouldn’t ignore non-neutronic improvements: ZEEMANS beamline

Johns Hopkins, SNS, National High Magnetic Field Laboratory, others

Ze Extreme MagneticNeutron Spectrometer

Brookhaven_0711


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 handling

of accelerator/significant parts of instruments,target + higher speed detectors with correspondinglysegmented electronics

– Current “limit” on regional-scale scientific facilityis $1–2B (or Euros, Oku Yen, etc.)

– Global model (ILC/ITER) might provide another orderof magnitude, but doesn’t work so well when capacityis as much an issue as performance

Current (3rd-generation?) spallation source technologywill scale to 3–5 MW with reasonable progressin ongoing R&D

Likely another order of magnitude in a 4th-generation(short pulse, long pulse, or CW: TBD)



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 community’s log plot world only applies to useful x-rays

Our success in arranging our neutronsmore usefully in time begs a question:What is the optimal time structure for scattering?

– Current debate is constrained by the accelerators

– Also: What can we do about spatial distribution?

Brookhaven_0711


Update on SNS:Exceeding early power ramp-up goals

0

40

Actual

Commitment

Inte

gra

ted

Bea

m P

ow

er (

MW

-ho

urs

)

160

Oct Nov Dec Jan Feb Mar Apr

FY 2007

May Jun Jul Aug Sep Oct

80

120

Brookhaven_0711


SNS is now the world’s most powerfulpulsed neutron source

Brookhaven_0711


We are on schedulefor commissioning instruments

Brookhaven_0711


Backscattering spectrometer

Brookhaven_0711


Holmium titanate spin icedoped with nonmagnetic(La) voids: Ho1.6La0.4Ti2O7

SNS at 150 kW, 30 Hz

Spectra: 10 h

0 < Q < 1.8 Å–1

(Q-independentspin dynamics)

Georg Ehlers, SNS

Backscattering spectrometer:Measurement of a “spin ice”

Are the spin dynamics thermally activated or defect assisted?

Brookhaven_0711


TL = 223 K

Backscattering spectrometer:Hydration-water-induceddynamic transitions in lysozymes

Sow-Hsin Chen, MIT

1013

1012

1011

1010

109

108

2.6 3.0 3.4 3.8 4.2 4.6 5.0

1,000/T (K-1)

1/D

(sec

/m2 )

Irrev

ersib

le d

enat

ured

Reve

rsib

le

Cpmax

TD

Bulk waterWater-lysozyme h = 0.3VFT fitArrhenius fitVFT fit

Strong-to-fragiledynamic crossoverin protein hydration water is conjecturedto initiate reversible protein denaturation

Native

Brookhaven_0711


Backscattering spectrometer:Hydration-water-induceddynamic transitions in lysozymes (continued)

Brookhaven_0711

27 Managed by UT-Battellefor the Department of Energy 27

ReflectometersReflectometers



Sample Multilayer consisting of

– Poly(methacrylic acid) [PMAA]water-soluble acid

– Quaternized poly(vinylpyrolidone)[PVP] salt (ionic)

Deuterated d-PMAA markersevery fifth bilayer

Liquids reflectometer:pH-responsive weak poly-electrolyte multilayers

Kharlampieva and Sukhishvili (Stevens Institute of Technology) and Tao, Halbert, and Ankner (SNS), submitted to Phys. Rev. Lett.

Goals Determine how film reacts

to changes in pH

First step to controlling release in vivo

Brookhaven_0711


0.03 0.06

1E-4

1E-3

0.01

0.1

1

-40000 -20000 0 20000 40000-6.0x10-4

-5.0x10-4

-4.0x10-4

-3.0x10-4

-2.0x10-4

-1.0x10-4

0.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4

T = 300K

M (emu/cm2)

H (Oe)

T = 5K

Si3N4

Mn

Si

Si3N4 10

Magnetism reflectometer:Where does the ferromagnetism reside?

H. Ambaye, R. Goyette, A. Parizzi, F. Klose, and G. Felcher

Brookhaven_0711



Documents

Managed by UT-Battelle for the Department of Energy Directions in Neutron Source Development Physics Colloquium Brookhaven National Laboratory Thomas E