1. Science and Project History Instrument Characteristics
Brent Fultz
Prof. Materials Science and Applied Physics
California Institute of Technology
Doug Abernathy
Instrument Scientist
Spallation Neutron Source
Kevin Shaw
Engineer
Science and Project History
Instrument Characteristics
Project Risks in 2001 and 2004
-Technical
-Management
Cost and Schedule Highlights
Software

3. (incoherent, inelastic) vs. (coherent, inelastic)

4. Inelastic

5. Magnetic Excitations
Energy of the excitations can be large, often beyond
the spectrum from reactor sources.
d- and f-electron form factors are large in r, small in k
For small Q and high Ei, forward detector coverage
must be good.

6. Examples of Magnetic Excitations
KCuF3 – a 1D
Heisenberg antiferromagnet
quantized excitations in
spin chain
calculated by field theory:
sharp dispersive modes
continuum from
free spinons (not FD or BE)

7. Phonon Scattering Thermodynamics of materials
T = 0 all internal coordinates in ground state.
T > 0 creates excitations.
Degeneracy of excitations gives entropy S = k lnW.
F = E – TS favors different structures of materials.
(Parallel thermodynamics for magnetic scattering.)

9. Everybody wants More Flux!
No inelastic neutron scattering experiment has ever
suffered from excessive flux
SNS source and p steradian detector coverage
will give ARCS new capabilities in practice:
1. Parametric studies
Present -- compare A vs. B. Future -- A(T,H) vs. B(T,H)
2. Single crystals
3. Small quantities of new materials
4. Sample environments

10. Multipurpose ARCS (mid-2001)

11. Bifurcation of ARCS (early 2002)
Full instrument had no contingency funds
Canadian CFI program prompted interest in a
second high-energy chopper instrument
International class facility should have a general
purpose and a magnetism instrument

13. ARCS Main Components Conventional Facilities Shutter Guides Software
Choppers
Sample
Isolation
System
Introduce self
Point out picture
Familiarize you with the different components
Hope that you’ll be able to see the logic that went into some of the decisions
Detector Array
Scattering
Tank
Shielding

15. McStas Simulations of Beams on Sample
ARCS source
Chopper:
63 meV
250 meV
0.3m/20*2=0.03m (Vertical, y)
0.3m/12*2=0.05m (Horizontal, x)
Ki=kf=5.5AA^-1
dQy=0.03/3*Ki=0.06AA^-1
dQx=0.05/3*Ki=0.09AA^-1
0.5 mm slits
600 Hz

16. McStas Simulation of Diffraction (1)
ARCS source
Chopper: 63 meV 1.14A
3mm slits, 480 Hz
Perfect crystal (selects neutrons of incident angle)
(004) diamond, 2q=79.6 deg
ARCS detector
Horiz = tube spacing
Vert = measured resolution
0.3m/20*2=0.03m (Vertical, y)
0.3m/12*2=0.05m (Horizontal, x)
Ki=kf=5.5AA^-1
dQy=0.03/3*Ki=0.06AA^-1
dQx=0.05/3*Ki=0.09AA^-1

17. McStas Simulation of Diffraction (2)
McStas Result:
DQhoriz = 1.6%
DQvert = 1.1%
(improves with 2q)
Get trend from
calculations assuming:
0.5 deg detector spacing
DE/E = 0.02
0.3m/20*2=0.03m (Vertical, y)
0.3m/12*2=0.05m (Horizontal, x)
Ki=kf=5.5AA^-1
dQy=0.03/3*Ki=0.06AA^-1
dQx=0.05/3*Ki=0.09AA^-1

18. Flux on Sample at 63 meV

19. Flux on Sample at 250 meV

20. ARCS

21. Project Risks 2001/2002 2004 Detectors in Vacuum
Shielding (with SEQUOIA)
Single Crystal Capabilities
Fermi Chopper
Sample Isolation
Sample Isolation
Shielding
Background
Management Technical
SNS/Caltech Interactions
Project Controls
Budget (balance: hardware vs. engineering)
Schedule

22. ARCS Project Budget Proposed Hardware: 10 M$ (spent/committed 0 M$)
Contingency: 2 M$ (20% of remaining)
Software: 2.9 M$ (spent/committed 0 M$)
Present
Hardware: 11 M$ (spent/committed 3.6 M$)
Contingency: 1 M$ (14% of remaining)
Software: 2.9 M$ (spent/committed 1.3 M$)
Software effort is 0.58 M$/year for postdoctoral fellows, professionals, graduate students, and a relatively small amount for hardware

23. Tech Risk #1 Detector Tubes in Vacuum
Modules with 8 detectors,analog and some digital electronics, readout card operated inside the instrument vacuum tank.
Base – goofy shape on later slide, out to ~25m then 5m more of narrower
Front end – out to 10m x 16ft high, heavy shielding, base is HD here, also area between shutter and chopper cavity
Stacked – on top of base, 14ft high
Focusing optics – out of line of sight, small, last ~6m
Seismic restraint

24. Test Program for Detector Tubes in Vacuum
Modules operated 3 months with no problem
Highest temperatures C above ambient
No outgassing problems or contamination of high potential surfaces
Noise figures unchanged (2 counts/minute over all 8 tubes)
Tests ongoing.
Base – goofy shape on later slide, out to ~25m then 5m more of narrower
Front end – out to 10m x 16ft high, heavy shielding, base is HD here, also area between shutter and chopper cavity
Stacked – on top of base, 14ft high
Focusing optics – out of line of sight, small, last ~6m
Seismic restraint

25. Tech Risk #2: Shielding Biological shield effectiveness
(we can meet the 0.25 mR/hr)
Crosstalk between instruments
(heavy T_0 choppers)
Background
(difficult to calculate well)

26. Tech Risk #2: Shielding Design
MCNPX Calculations
E. Iverson, D. Abernathy
Dose rates outside
beamline 0.1 mrem/hr
Optimization possible
Cans cover top, bottom, sides, all around
Cost is major consideration
Wax cans heavy
Polyethylene lighter because no cans
Future design issue is restraining shielding, attach to tank? Self supporting?
blue: steel
yellow: HD concrete
red borated poly
turquoise: regular concrete

27. Tech Risk #2: Background?
Neutron dose rates:
with steel sample, choppers open
without sample, Fermi chopper closed

28. Tech Risk #2: Background?
Neutron count rates:
with steel sample, choppers open
without sample, Fermi chopper closed

29. Tech Risk #3 3-Axis Cryogenic Goniometer
Sumitomo cryocooler
Kohzu components
Designed for first operations on Pharos instrument at LANL
180o
10o
10o
Base – goofy shape on later slide, out to ~25m then 5m more of narrower
Front end – out to 10m x 16ft high, heavy shielding, base is HD here, also area between shutter and chopper cavity
Stacked – on top of base, 14ft high
Focusing optics – out of line of sight, small, last ~6m
Seismic restraint
Heavy copper Litz wire
Sample
Thermal isolator

30. Tech Risk #4 Fermi Chopper System
Moveable Fermi choppers
Two independent control units
Can move while spinning if accelerations and jerk are low
Open beam also
Base – goofy shape on later slide, out to ~25m then 5m more of narrower
Front end – out to 10m x 16ft high, heavy shielding, base is HD here, also area between shutter and chopper cavity
Stacked – on top of base, 14ft high
Focusing optics – out of line of sight, small, last ~6m
Seismic restraint

31. Tech Risk #4 Fermi Chopper System
Finite element stress calculations in elastic range
All material below yield stress

32. Tech Risk #5 Sample Isolation System

33. Tech Risk #5 Sample Insertion (Pharos)

34. Tech Risk #5 Sample Isolation System
opening
closed
main
vacuum
Base – goofy shape on later slide, out to ~25m then 5m more of narrower
Front end – out to 10m x 16ft high, heavy shielding, base is HD here, also area between shutter and chopper cavity
Stacked – on top of base, 14ft high
Focusing optics – out of line of sight, small, last ~6m
Seismic restraint

35. Tech Risk #5 Sample Isolation System

36. Mgmt. Risk #1 - SNS/Caltech Interactions
MOA (signed in 1 day by Caltech Provost)
Visitor Status of Doug Abernathy
Purchasing through Caltech
- small items: office staff
- evaluated procurements: buyers and lawyers
Project communications adequate
Shielding –
Chopper cavities
Optics carousel
Chamber –
Inserts –
Interface –
Other –

37. Mgmt. Risk #2 - Project Controls
Data reporting with project plan started working at Argonne
New system at ORNL -- follow the SING instruments
Today’s review kick-started the ORNL project controls support.
Shielding –
Chopper cavities
Optics carousel
Chamber –
Inserts –
Interface –
Other –

38. Mgmt. Risk #3 - Funding Channels
DOE BES
ANL
ORNL
WFO
Hardware
Software
[various]
Engineering
[FY]
Installation
Caltech
Shielding –
Chopper cavities
Optics carousel
Chamber –
Inserts –
Interface –
Other –

39. Budget Profiles 2001/2002 Aug. 2004 Target Bldg.
Ready for Equipment: 9/1/03
Beneficial Occupancy: 6/1/04
Beneficial Occupancy: March 05
1 yr
Budget Profiles
2001/2002
Aug. 2004

40. Major Procurements - Highlights
Completed or Contract Issued
Detector tubes
Fermi Choppers
Core vessel insert and shutter insert
Guide in shutter
Shielding (poured in place)
Request for Proposals Imminent (specs under review)
Main guide
Sample isolation system
Vacuum tank/pumping system
T0 chopper
Engineering Underway
Shielding around tank
Sample hutch
Shielding –
Chopper cavities
Optics carousel
Chamber –
Inserts –
Interface –
Other –

41. Software Roadmap v. 1.0

42. Data Reduction Data Modeling Full Simulations
Third generation code for polycrystalline samples
First generation for single crystal data reduction. Needs data from real experiments.
Visualization needs attention (commercial packages?)
Data Modeling
Full suite of phonon dynamics codes
Classical magnetics dynamics
Full Simulations
McStas bindings for Pyre framework underway.

43. Software Milestones Software Baseline Design January, 2003
Software First Build July, 2004
Software Beta Release March, 2005
Software Release February, 2006
End ARCS Project September, 2006

44. DANSE NSF has funded 1 yr design ($ 985,000)
Construction proposal in preparation

45. Summary Cost (comfortable) Schedule (tight but possible)
What it will be in Sept. 2006:
- Working instrument (parameters essentially as promised, but energy resolution depends on moderator modeling)
- Probably with a complete detector array
- More than basic data reduction and visualization
- Some single crystal capability
- Limited time to minimize background
Shielding –
Chopper cavities
Optics carousel
Chamber –
Inserts –
Interface –
Other –

46. End of Presentation