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The n-3He Experiment
Christopher Crawford University of Kentucky
for the n-3He Collaboration
FnPB PRAC ORNL, TN 2013-01-23
Outline
Physics • Reaction & observable • EFT calculation • Statistical sensitivity • Systematic effects
Experimental design • Experimental setup • Installation at FnPB • Commission & run plan • ES&H issues
Collaboration • Organization / Manpower
WBS subpackages • Neutron beamline • Stand / Alignment • Magnetic field • RF Spin Rotator • Target Chamber • Preamps • Data Acquisition
Project • Timeline • Resources
n-3He PV asymmetry
Sensitive to isoscalar couplings (I=0) of the Hadronic Weak Interaction
Complementary to NPDGamma (I=1) and p-p scattering (I=0 & 2)
Large asymmetry A = 1.15 x 10-7
Viviani, et al., PRC 82, 044001 (2010),
PV observables:
19.815 20.578
Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)
n + n p p n p n +p n p
n p
Theoretical calculations – progress
Gerry Hale (LANL) PC Ay(90) = -1.7 +/- 0.3 x 10-6
• R matrix calculation of PC asymmetry, nuclear structure , and resonance properties
Michele Viviani et al. (INFN Pisa) PV A = -(.248 – .944)£10-7 • full 4-body calculation of scattering wave function
- Kohn variational method with hyperspherical functions - No parity mixing in this step: Jπ = 0+, 0-, 1+, 1-
- Tested against n-3He scattering lengths • evaluation of weak <J-|VPV|J+> matrix elements
- In terms of DDH potential Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, PRC 82, 044001 (2010) Girlanda, Kievsky, Marcucci, Pastore, Schiavilla, Viviani, PRL 105 232502 (2010)
Vladimir Gudkov (USC) PV A = -(1 – 4)£10-7 • PV reaction theory Gudkov, PRC 82, 065502 (2010)
Michele Viviani et al. (INFN Pisa) PV VNNEFT, a0 – a5
Viviani, PAVI (2011), preliminary
EFT NN potential revisited to NNLO
Viviani et al., preliminary (PAVI 11) • (a) Q0 h1
π gπ(r) • (CT) Q1 C1,2,3,4,5 Z(r) • (b,c) Q2 zero • (e,h) Q2 renorm./absorb in h1
π • (d), Q2 h1
π+C3 (triangle) L(r) • (f,g,g’) Q2 h1
π (box) H(r)+L(r)
Azn3He (prelim) using N3LO (Emtem & Macheleidt) + 3N N2LO (Navratil)
Λ = 500: a0=-0.15 a1=.026 a2=.021 a3=0.11 a4=-.043 a5=-.0022
10 Gauss solenoid
RF spin rotator
3He target / ion chamber
supermirror bender polarizer
(transverse)
FnPB cold neutron guide
3He Beam Monitor
FNPB n-3He
Experimental setup
longitudinal holding field – suppressed PC nuclear asymmetry A=1.7x10-6 (Hales) sn kn x kp suppressed by two small angles
RF spin flipper – negligible spin-dependence of neutron velocity
3He ion chamber – both target and detector
MC Simulations
Two independent simulations: 1. a code based on GEANT4 2. a stand-alone code
including wire correlations
• Ionization at each wire plane averaged over: • neutron beam phase space • capture distribution • ionization distribution β(z) • uniform distribution of proton angles
cos θ = σn·kp/kp
• Used to calculate detector efficiency (effective statistics / neutron flux)
MC Simulations – Results
Majority of neutron captures occur at the very front of chamber • Self-normalization of beam fluctuations • Reduction in sensitivity to A
Runtime estimate for n-3He at FnPB
N = 1.5x1010 n/s flux (chopped) x 107 s (116 days)
P = 96.2% neutron polarization
σd = 6 detector efficiency
15% measurement in 1 beam cycle (without contingency), assuming Az= 1.15 x 10-7
= 1.6 x 10-8
Systematics
Beam fluctuations, polarization, RFSF efficiency:
knr ~ 10-5 small for cold neutrons
PC asymmetries minimized with longitudinal polarization
Alignment of field, beam, and chamber: 10 mrad achievable
Unlike NPDG, NDTG: insensitive to gammas (only Compton electrons)
Commissioning / run plan
1. Scan beam profile upstream and transfer centroid to crosshairs
2. Scan beam profile downstream
3. Align theodolite to crosshairs
4. Align B-field to theodolite
5. Field map in RFSR/Target region
6. Align the position / angle of target with theodolite / autocollimator
7. Tune RSFR / measure polarization
8. Measure physics asymmetry
ES&H Issues
Radiation much lower than from NPDGamma • IRR will cover 3 activities:
- Front and back beam scans 3He detector + 6Li aperture - Polarimetry 3He polarizer + 3He monitor - Physics data run 3He target/detector
• Beam friendly materials - Aluminum windows transparent to neutrons - 3He, 6Li have large cross section with no γ radiation
• Graduate student will create MCNP model based on NPDG - Will be validated by radiation group
No other safety concerns • No HV, pressure, vacuum, cryogenics, ladders, …
n-3He collaboration
Spokespersons D. Bowman, M. Gericke, C. Crawford
Local Project Manager S. Penttila
Project Engineer Rick Allen
Work Subpackage Leaders M. Gericke Beam monitors G. Greene Polarimetry L. Barrón Magnetic fields C. Crawford Spin rotator M. Gericke Target chamber J. Hamblen Preamplifiers I. Novikov Data acquisition D. Bowman Alignment J. Calarco Shielding
Neutron beamline
Scope: • FnPB guide, polarizer, beam monitors (existing, NPDG) • Beam profile scanners, polarimetry
Status: • All equipment exists except aluminum aperture / crosshair • Must design shielding to accommodate xy-scanner • Must design mount for 3He analyzer
Alignment
Scope: • Aperture / crosshairs for beam scan • Support stand and xy-adjustment for theodolite • Alignment V-block for trimming B-field • Optical system and adjustable mount for target
Progress: • Conceptual design
Saturday, January 05, 201310:37 PM
Tech Review Page 1
Magnetic field
Scope: • Magnetic field simulations to verity adiabatic spin rotation and uniformity • Design and construct longitudinal solenoid and frame • Map fields at UNAM before delivery to SNS
Status: • Conceptual design, preliminary calculations indicate adiabaticity
15 coils, 15 cm apart, 35 cm radius, 150 A turns
Transverse RF spin rotator
Resonant RF spin rotator • P-N Seo et al., Phys. Rev. S.T.
Accel. Beam 11, 084701 (2008)
Properties suitable for n-3He expt. • Transverse horizontal RF B-field • Longitudinal or transverse flipping • No fringe field - 100% efficiency • Real, not eddy currents along outside
minimizes RF leaked outside SR • Doesn’t affect neutron velocity • Compact geometry • Matched to the driver electronics
of the NPDGamma spin flipper
Construction • Development in parallel with similar
design for nEDM neutron guide field • Few-winding prototype built at UKy;
Production RFSF being built now
field lines end cap windings
NPDGamma windings
n-3He windings
Inner / outer coil design
Windings calculated using scalar potential • Uniform transverse RF field inside • Zero leakage field enforced by B.C.’s • Copper wires run along equipotentials 1. Inner region:
2. Intermediate:
3. Outer region:
4:1 inside / outside winding ratio • By choosing
appropriate radii • Perfect cos theta
windings inside & out • 48 inner loops of
18 AWG wire
Electrical specifications – compatible with NPDG
Holding field:
Resonant frequency:
Inductance: 4.5 mH Capacitance: 7.5 nF Resistance: 5.1 Ω
Maximum voltage:
Stored energy:
Dissipated power:
Quality factor: Q=151
R&D: test 3 winding patterns with same field in high-frequency limit INNER INNER/OUTER OUTER
easiest to wind no eddy currents no copper in beam
Progress & Schedule
Design completed in 2011
Resonator machined except wire grooves
March 2013: Finish machining
May 2013: Finish winding
September 2013: RF field map
November 2013: Test with preamps and DAQ system
Target Chamber
Chamber design finished in 2010 • delivered to U. of Manitoba, Fall 2010
All aluminum except for the knife edges. • 4 feedthrough ports (200 readout channels) • 2 HV ports + 2 gas inlets/outlets • 12 inch Conflat aluminum windows (0.9 mm thick).
Frame Design and Construction
Chamber frame design finished in 2012
Received 50 Macor wire frames (up to 25 signal and 25 HV) $30K
Final feature machining planned for early this year at UT shop.
Platinum-Gold thick film wire solder pads on Macor to be completed early this year by Hybrid Sources Inc..
Frame Assembly and Signal Readout
The frame mounting structure is designed • pieces will be ordered in the spring
Two options for frame mounting: • Mount into exit flange with threaded rods • Insert into existing exit window flange
Signal readout via circuit board traces • Single HV connections • Guide wires to feedthroughs with PMT-
inspired stand-offs and ceramic beads
Target Chamber Assembly Schedule
February 2013: Have test frame finished by Hybrid Sources and verify measurements.
March 2013: Complete feature machining at UT shop.
April 2013: Order remaining parts for frame assembly and feedthroughs.
June-July 2013: Completed solder pad deposition by Hybrid Sources.
October 2013: Complete chamber assembly
December 2013: Test with RFSF and DAQ
Preamps
Scope • 4 boxes with 32 channels each $41k • Design and fabricate circuit, and mechanical enclosure • Connector to Target Chamber port and cabling to DAQ module
Status – on critical path – need resources soon! • Have preliminary design (from NPDG preamps) • Must modify circuit for n-3He (high channel density, 10x larger signal)
Data Acquisition
Scope: • 128 channels of 16/24 bit ADC, > 60 KS/s $51k
data acquisition software; RAID storage array $25k
Status – need resources soon to begin development and testing! • selected candidate system D-tAcq CQ196CPCI-96-500 • Each card 96 sim. channels + antialiasing filters + FPGA signal proc.
runs Linux on 400MHz XScale processor with Gigabit Ethernet • Inexpensive cPCI chassis used only for power and cooling • DAQ software included with hardware – turn-key system • awaiting funds to purchase and test system
Equipment summary
FnPB / NPDG hardware • 3He beam monitor • SM polarizer • Beam position monitor • Radiation shielding • Pb shield walls • Beam Stop
New equipment • Longitudinal field solenoid mounted on stand • Longitudinal RFSF resonator mounted in solenoid • 3He target/ion chamber mounted in solenoid • Preamps mounted on target • Data acquisition system + RAID storage
NPDG electronics • B-field power supply • RFSF electronics • Trigger electronics • SNS / chopper readout • Fluxgate magnetometers • Computer network
Timeline
Construction of subsystems in parallel • Will be ready for beam at beginning of cycle Aug 2014 • Critical path: preamp design and construction (possibly DAQ) • Will stage experiment in EDM building and perform
dry run of field map, beam map, and alignment procedures • See Gantt chart for details
Milestones • 2014-04-21 Begin assembly and testing in EDM building • 2014-07-18 Begin installation in FnPB cave • 2014-10-27 IRR – begin commissioning phase • 2015-02-?? Physics data taking at beginning of beam cycle
Time budget • 76 days commissioning (all equipment pre-assembled) • 15 days PC transverse asymmetry 1.7 x 10-6 ± 0.5 x 10-7
• 116 days PV longitudinal asymmetry 1.15 x 10-7 ± 1.6 x 10-8
Resources
All equipment funded except Preamp, DAQ, RAID ($117k) • UNAM: (CONACYT $31k) Solenoid and support stand • U. Kentucky: (NSF $23k) RF spin rotator • U. Manitoba: (NSERC $111k) Target chamber
Minimal utilization of SNS crafts • Most equipment mounted on single support structure,
staged in the EDM building, craned onto NPDG det. support • 3D solid model will be drafted by graduate (Mark McCrea),
reviewed by SNS engineer, and incorporated into SNS model • MCNP radiation simulation will created by UKy graduate,
validated by radiation group • Machining will be done at university shops • Alignment is relative to beam scan
Total P-Division operations budget request ($200k) • $117k for DAQ + $83k for Engineering/Radiation/Craft support • See budget spreadsheet for details