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

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

Inelastic

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.

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)

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.)

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

Multipurpose ARCS (mid-2001)

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

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

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

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

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

Flux on Sample at 63 meV

Flux on Sample at 250 meV

ARCS

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

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

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

Test Program for Detector Tubes in Vacuum Modules operated 3 months with no problem Highest temperatures 10-15 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

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)

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

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

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

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

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

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

Tech Risk #5 Sample Isolation System

Tech Risk #5 Sample Insertion (Pharos)

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

Tech Risk #5 Sample Isolation System

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 –

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 –

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 –

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

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 –

Software Roadmap v. 1.0

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.

Software Milestones Software Baseline Design January, 2003 Software First Build July, 2004 Software Beta Release March, 2005 Software Release 1.0 February, 2006 End ARCS Project September, 2006

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

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 –

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