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Proposal Update: the n- 3 He   Parity Violation Experiment

Proposal Update: the n- 3 He   Parity Violation Experiment. Christopher Crawford University of Kentucky for the n- 3 He Collaboration FnPB PRAC Meeting ORNL, TN 2010-12-16. Outline. Theoretical advances Viviani – full 4-body calc. Gudkov – reaction theory Experimental update

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Proposal Update: the n- 3 He   Parity Violation Experiment

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  1. Proposal Update: the n-3He  Parity Violation Experiment Christopher Crawford University of Kentucky for the n-3He Collaboration FnPB PRAC Meeting ORNL, TN 2010-12-16

  2. Outline • Theoretical advances • Viviani – full 4-body calc. • Gudkov – reaction theory • Experimental update • Transverse RF spin rotator • 3He target / ion chamber • Statistical sensitivity - simulations • Systematic errors • Alignment scheme • Management plan • Installation: changes from NPDG • Operation: run time and sensitivity

  3. n-3He PV Asymmetry p n p • 4He J =0+ resonance • sensitive to EFT couplingor DDH couplings • ~10% I=1 contribution(Gerry Hale, qualitative) • A ~ -.3–1x10-7 (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 20.578 19.815 n p + n + PV observables: n n n p p p ~ kn very small for low-energy neutrons S(I): - essentially the same asym. - must discriminate between back-to-back proton-triton Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992)

  4. 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 • calculation of asymmetry within DDH framework • progress on calculation of EFT low energy coefficients • Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, PRC 82, 044001 (2010), • Vladimir Gudkov (USC) PV A = -(1 – 4)£10-7 • PV reaction theory • Gudkov, PRC (in press)

  5. http://arXiv.org/abs/1007.2052

  6. Sensitivity to DDH couplings • Calculation of strong 4-body wave functions • 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 • EFT calculation in progress

  7. Sensitivity matrix for few-body reactions

  8. Experimental setup longitudinal holding field – suppressed PC asymmetry RF spin flipper – negligible spin-dependent neutron velocity 3He ion chamber – both target and detector 10 Gauss solenoid supermirror bender polarizer (transverse) FnPB cold neutron guide 3He Beam Monitor transition field (not shown) RF spinrotator 3He target / ion chamber FNPB n-3He

  9. Transverse RF spin rotator • 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 expt. • transverse horizontal RF B-field • longitudinal / transverse flipping • no fringe field - 100% efficiency • compact geometry - efficient • smaller diameter for solenoid • matched to driver electronicsfor NPDGamma spin flipper • prototype design • parasitic with similar design for nEDM guide field near cryostat • fabrication, testing at UKy – 2010 field lines end cap windings NPDGamma windings n-3He windings

  10. Prototype holding field coil • Developed for static nEDM guide field • 1% uniformity DC field

  11. Field map of DSCTC

  12. Prototype RFSF coil

  13. Custom aluminum CF flanges with SS knife-edges Macor ceramic frame,Cu wires, 200um diameter Chamber and flanges have been delivered to U. Manitoba Construction of frame / wires will be completed in 2011. 3He Target / Ion Chamber – Design M. Gericke, U. Manitoba

  14. Data Acquisition • Requirements similar to NPDGamma • 16 bit resolution, 100 kHz sample rate • Simultaneous external triggering (precise timing) • High channel density: ~144 channels • Driven by the size of the chamber and proton range • Data rate ~3x higher than NPDGamma • VME-based system • Groups of 4 IP modules mounted on CPU processorsfor data reduction with direct access to RAID disk • Alphi Technologies: $36k for 192 channels DAQ + storage

  15. New Detection Scheme under consideration Strategy: detect higher ion density of triton, not longer range of proton • Both proton and triton range out at Si wafer cell walls • Form asymmetry from ions near each side of cell • Less ions per event, but not differential measurement • σd = 2 (left/right planes) vs. σd = 6 (proton range / absorption length) • Can measure 6Li asymmetry to same level with this technique 3He gas < 1 cm Si, anodes on each side HV grid wires baffles -HV -HV -HV -HV -HV -HV

  16. MC Simulations • Two independent simulations: • a code based on GEANT4 • a stand-alone code including wire correlations • Ionization at each wire plane averaged over: • neutron beam phase space • capture distribution • ionization distribution (z) • uniform distribution of proton angles cos n¢kp/kp • Used to calculate detector efficiency (effective statistics / neutron flux)

  17. MC Simulations – Results • Majority of neutron captures occur at the very front of chamber • Self-normalization of beam fluctuations • Reduction in sensitivity to A

  18. Measurement of LANSCE FP12 absolute flux

  19. Measurement of LANSCE FP12 absolute flux

  20. Comparison of statistics at LANSCE FP12 • based on: • D. Bowman, technical note, 2010-09-24, • A. Salas-Bacci, technical note, 2010-10-14 • Gericke, NIMA 611 239 (2009) • 2.68 x 107 n/s cm2 neutron flux at 100 μA, measured with FC • 3.5” collimator, 87.6 μA proton current • 4966 runs (after cut) x 104/20 Hz • 0.88 (air) x 0.90 (Al) x 0.88 (glass) x 0.346 (3He) transmission • 0.60 capture in LH2 x 0.3017 geom. factor • 0.53 pol. 3He x 0.989 SF eff. / (1+0.25) bkg. Dilution δA = 1.9 x 10-7 from calc. vs. 2.1 x 10-7RMS width in Aγ

  21. Runtime estimate for n-3He at FnPB • 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

  22. 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)

  23. Alignment procedure • Suppression of 1.7 x 10-6 nuclear PC asymmetry • longitudinal polarization: sn . kn x kp doubly suppressed • Symmetric detector • Rotate 180 deg about kn during data taking • Align B field with detector axis to 1 mrad • Vant-Hull and Henrickson windblown generator • Minimize Bx, By by observing eddy currents in generator • Align detector/field with neutron beam to 1 mrad • Perform xy-scans of beam at 2 z-positions before/after target • NPDG: B4C target in beam with CsI detector, 6Li chopper

  24. Scanning beam monitor 6Li Shutter CsI crystal B4C target

  25. 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 / field map - 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

  26. Installation at FnPB • NPDG equipment: • 3He beam monitor • SM polarizer • Beam position monitor • Radiation shielding • Pb shield walls • Beam Stop • New equipment: • Transition guide field • 4He flight path from SMpol to RFSF (reuse 6Li shielding) • Longitudinal field solenoid mounted on stand • Longitudinal RFSF resonator mounted in solenoid • 3He target/ion chamber mounted in solenoid • Preamps mounted on target • DAQ: single-board computers + ADC modules + RAID array • NPDG electronics: • B-field power supply • RFSF electronics • Trigger electronics • SNS / chopper readout • Fluxgate magnetometers • Computer network

  27. Jan 2011 – Jul 2012 (beam) NPDGamma data-taking July 2012 Stage of stand, solenoid,RFSF, Ion Chamberin nEDM building Aug 2012 Installation at FnPB Field map at FnPB Sept 2012 (request: 1000 hrs) Beam axis scans 3He Polarimetry Jan 2013 (request: 5000 hrs) 3He data-taking Jan 2011 – July 2011 Construction and field mapping of solenoid at UNAM Construction and testing of RFSF resonator at UKy Assembly of 3He ion chamber at Univ. Manitoba DAQ electronics and software at UKy / UTK / ORNL Aug 2011, May 2012 test RFSF, 3He chamber, and DAQ at LANSCE FP12 Projected schedule Offsite ORNL

  28. Conclusion • Published 4-body calculation • EFT calculation under way • Experimental progress • Prototype RFSF resonator • Target chamber delivered • Systematics under control • Scheduled to immediately follow NPDG

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