n- 3 He Experiment: overview and updates
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n-3He Experiment: overview and updates
Christopher CrawfordUniversity of Kentucky
n-3He Collaboration Meeting
ORNL, TN 2010-10-16
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Outline
Introduction• n+3He reaction
Theoretical advances• Viviani – full 4-body calc.• Gudkov – reaction theory
Experimental update• Experimental setup• MC simulations• Statistical sensitivity• Systematic errors• Transverse RF spin rotator• 3He target / ion chamber
Management• FnPB approval status• Schedule• Work packages
Madison Spencer
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n-3He PV Asymmetry
~ kn very small for low-energy neutrons
- essentially the same asym.- must discriminate between back-to-back proton-triton
S(I):
4He J =0+ resonance
sensitive to EFT couplingor DDH couplings
~10% I=1 contribution(Gerry Hale, qualitative)
A ~ -1–3x10-7 (M. Viviani, PISA)
A ~ -1–4x10-7 (Gudkov)mixing between 0+, 0- resonance
Naïve scaling of p-p scattering at 22.5 MeV: A ~ 5x10-8
PV observables:
19.81520.578
Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)
nn + nn pp ppnn ppnn +pp nn pp
nnpp
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Theoretical calculations – progress
Vladimir Gudkov (USC) PV A = -(1 – 4)£10-7
• PV reaction theory (to be submitted)
Gerry Hale (LANL) PC Ay(90±) = -1.7±0.3£10-6
• R matrix calculation of PC asymmetry,nuclear structure , and resonance properties
Anna Hayes (LANL)• No-core shell model calculation with AV18 potential, etc.
Michele Viviani et al. (INFN Pisa) PV A = -(.944 – 2.48)£10-
7
• full 4-body calculation of scattering wave function• calculation of asymmetry within DDH framework• progress on calculation of EFT low energy coefficients• Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, arXiv:1007.2052 (nucl-th)
status: submitted to PRC
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Extraction of DDH couplings
np A nD A n3He Ap np n pp Az p Az
f-0.11 0.92 -0.18 -3.12 -0.97 -0.34
h0 -0.50 -0.14 -0. 23 -0.32 0.08 0.14
h1 -0.001 0.10 0.027 0.11 0.08 0.05
h2 0.05 0.0012 -0.25 0.03
h0 -0.16 -0.13 -0. 23 -0.22 -0.07 0.06
h1 -0.003 -0.002 0.05 0.22 0.07 0.06
n-3He: M. Viviani (PISA)
(preliminary)
dA=1x10-8
dA=1x10-8
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http://arXiv.org/abs/1007.2052
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Sensitivity to DDH couplings
NN-potentials:• AV18• AV18/UIX• N3LO• N3LO/N2LO
Pion-full EFT calculation?
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10 Gausssolenoid
RF spinrotator
3He target /ion chamber
supermirrorbender polarizer
(transverse)
FnPB coldneutron guide
3He BeamMonitor transition field
(not shown)
FNPB n-3He
Experimental setup
longitudinal holding field – suppressed PC asymmetry
RF spin flipper – negligible spin-dependent neutron velocity
3He ion chamber – both target and detector
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MC Simulations
Two independent simulations:1. a code based on GEANT42. a stand-alone code
including wire correlations
• Ionization at each wire plane averaged over:1. neutron beam phase space2. capture distribution3. ionization distribution (z)4. uniform distribution of proton angles
cos n¢kp/kp
• Used to calculate detector efficiency (effective statistics / neutron flux)
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MC Simulations – Results
Majority of neutron captures occur at the very front of chamber• Self-normalization of beam fluctuations• Reduction in sensitivity to A
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Statistical Sensitivity
N = 2.2£1010 n/s flux (chopped) x 107 s (4 full months @ 1.4 MW)
P = 96.2% neutron polarization
d = 6 detector efficiency
A/A ~ 5% assuming A=3x10-7
A/A ~ 26% worse case A=5x10-8
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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)
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Systematic Error constraints
Mott-Schwinger and parity conserving nuclear asymmetry
Measure longitudinal instead of transverse asymmetry
1) measure the average kn at two different places along the beam using the wire chamber
2) align the B field parallel to kn
3) align the wire planes to be perpendicular to the holding field (same as kn) to 2 degrees by dead reckoning
4) rotate the chamber by 180 degrees about the holding field and measure again to cancel small residuals
Use a magnetic compass which can measure the field direction to 0.1 deg
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Transverse RF spin rotator – n3He
extension of NPDGamma design• P-N Seo et al., Phys. Rev. S.T.
Accel. Beam, vol 11, 084701 (2008)• TEM RF waveguide
new resonator for n-3He experiment• transverse horizontal RF B-field• longitudinal / transverse flipping• no fringe field - 100% efficiency• compact geometry - efficient
- smaller diameter for solenoid• matched to driver electronics
for NPDGamma spin flipper
prototype design• parasitic with similar design for
nEDM guide field near cryostat• fabrication and testing at UKy – 2009
NPDGammawindings
n-3Hewindings
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RFSF winding: designed from the inside out
Standard iterative method:Create coils and simulate field.
New technique: start with boundary conditions of the desired B-field, and simulate the winding configuration
1. Use scalar magnetic potential (currents only on boundaries)
2. Simulate intermediate region using FEA with Neumann boundary conditions (Hn)
3. Windings are traced along evenly spaced equipotential lines along the boundary
red - transverse field linesblue - end-cap windings
Magnetostatic calculation with COMSOL
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Prototype RFSF
Developed for static nEDM guide field
1% uniformity DC field
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3He Target / Ion Chamber – Considerations
Must measure proton asymmetry in current mode directly in target
Can distinguish back-to-backproton and triton by their range• Ep:Et = mt:mp = 3:1• Must let protons range out: rp~5 cm• Neutron mean free path should be < rp/2
Current-mode• HV: 1 – 3 kV• 200 Al wires
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3He Target / Ion Chamber – Design
M. Gericke, U. Manitoba
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Data Acquisition
Requirements similar to NPDGamma• 16 bit resolution, slow 100 kHz• Simultaneous external triggering (precise timing)
High channel density: 20 x 19 channels or less• Driven by the size of the chamber and proton range• Simultaneous measurement of AL, AT
• Data rate ~10x higher than NPDGamma
VME-based system• Groups of 4 IP modules mounted on CPU processors
for data reduction with direct access to RAID disk
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Projected schedule – old
Jan 2011 – Jul 2012• NPDGamma data-taking
Aug 2011 – Dec 2011• Construction of solenoid• Test of field uniformity,
alignment procedures
Aug 2012 – Dec 2012• Installation at FnPB• Commissioning
Jan 2013 – Dec 2013• 3He data-taking
Jan 2011 – May 2011• Construction of new RFSF
resonator at UKy• Construction of 3He ion
chamber at Univ. Manitoba• DAQ electronics and software
production at Univ. Kentucky
May 2011, May 2012• test RFSF, 3He chamber, and
DAQ at LANSCE FP12
window of opportunity forthe n-3He experiment between NPDGamma and Nab
ORNL Offsite
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Work Packages
Theory - Michele Viviani
MC Simulations - Michael Gericke / ?
Polarimetry - Stefan Baessler / Matthew Musgrave
Beam Monitor - Rob Mahurin
Alignment - David Bowman / Geoff Greene
Field Calculation - Septimiu Balascuta
Solenoid / fieldmap - Libertad Baron Palos
Transition, trim coil - Pil-Neyo Seo
RFSF - Chris Crawford
Target / detector - Michael Gericke
Preamps - Michael Gericke / ?
DAQ - Nadia Fomin / Chris Crawford
Analysis - Nadia Fomin / Chris Crawford
System integration/CAD - Seppo?
Rad. Shielding / Tritium - John Calarco
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Organization
Collaboration meetings after NPDG meetings
Regular phone conferences: ~monthly
Collaboration email list: [email protected]
PRAC in December: submit request for beam time
Installation target date: July 2012