The n- 3 He Parity Violation Experiment Christopher Crawford University of Kentucky for the n- 3 He Collaboration NSAC Review Meeting Chicago, IL,

Outline  Scientific Motivation Reaction and PV observable Theoretical calculations Previous experiment  Experimental setup Transverse RF spin rotator 3 He target / ion chamber  Sensitivity Statistical sensitivity, simulations Systematic errors Alignment scheme  Management plan Work packages, level of effort Installation at FnPB Projected schedule

n- 3 He PV Asymmetry S(I):  sensitive to I=0 and I=1 couplings  PV A ~ 1.1 x (Viviani)  PC A ~ 1.7 x (Hale) Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992) n n 3 He p p 3H3H 3H3H θ ~ k n very small for low-energy neutrons - the same asymmetry - must discriminate between back-to-back proton-triton PV observables: GOAL:  A = 1.3 x 10 -8

Theoretical calculations  Gerry Hale (LANL) PC A y ( 90 ) = /- 0.3 x R matrix calculation of PC asymmetry, nuclear structure, and resonance properties  Vladimir Gudkov (USC)PV A = -(1 – 4) x PV reaction theory Gudkov, PRC 82, (2010)  Michele Viviani et al. (INFN Pisa)PV A = x Full 4-body calc. of strong scattering wave functions J π = 0 +, 0 -, 1 +, 1 - Eval. of weak matrix elements in terms of DDH potential Work in progress on calculation of EFT low energy coefficients Viviani, Schiavilla, Girlanda, Kievsky, Marcucci, PRC 82, (2010)

n- 3 He PV experiment in 1981 Neutron flux: 6 x 10 7 n/s Polarization: 97% (transverse) PV: A p = 0.38 ± 0.49 x PC: A p = ± 0.57 x JETP Lett, 33, 411 (1981)

10 Gauss solenoid RF spin rotator 3 He target / ion chamber supermirror bender polarizer (transverse) FnPB cold neutron guide 3 He Beam Monitor transition field (not shown) FNPB (already exists) n- 3 He (new equipment) Experimental setup  longitudinal holding field – suppressed PC asymmetry  RF spin flipper – negligible spin-dependent neutron velocity  3 He ion chamber – both target and detector  record ionization signal in each wire; spin asymmetry -> A p shim coils (not shown)

Transverse RF spin rotator  Resonant RF spin rotator P-N Seo et al., Phys. Rev. S.T. Accel. Beam 11, (2008)  Properties suitable for n- 3 He expt. Transverse horizontal RF B-field Longitudinal or transverse flipping No fringe field - 100% efficiency 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 currently being tested Full size RFSF to be built this year field lines end cap windings

The chamber is made completely from aluminum except for the knife edges. Detector / Ion Chamber The chamber design was finished in 2010 and the completed chamber was delivered to U. of Manitoba in the Fall of The chamber has: 4 data ports for up to 200 readout channels. 2 HV ports 2 gas line ports 12 inch Conflat aluminum windows (0.9 mm thick).

Preliminary wire frame and readout design The chamber is large enough to completely cover the SNS beam profile, even without collimation. We are currently optimizing the competing issues of frame size and wire spacing vs. frame rigidity and material cost. Macor would be best, but very expensive. Other possibilities include Peek (pure too soft), carbon or glass filled peek.

Also shown are initial ideas for readout and HV distribution boards above and below to frames. Preliminary wire frame and readout design Current options being explored: 1) 6.4 mm thick frames with 18 HV and 17 signal wires (alternating). 8 wires per signal frame 9 wires per HV frame ~ 2 cm wire spacing 136 signal wires 2) 4.8 mm thick frames with 23 HV and 22 signal wires. 10 wires per signal frame ~1.5 cm wire spacing 220 signal wires total (omit the last two frames).

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  (z) uniform distribution of proton angles cos  n ¢k p /k p Used to calculate detector efficiency (effective statistics / neutron flux)

MC Simulations – Results  N = 2.2x10 10 n/s flux (chopped) x 10 7 s (4 full 1.4 MW) P = 96.2%neutron polarization  d = 6detector efficiency  Majority of neutron captures occur at the very front of chamber Self-normalization of beam fluctuations Reduction in sensitivity to A

Backgrounds  Wraparound neutrons BACKGROUND: < 0.02%,  Compton electrons from Gammas 10% gammas/neutron from SNS -Conservative, assuming E=.5 MeV 2.4% probability of Compton scattering from Al window 10% ionization current from e - vs. p + BACKGROUND: < 0.02%, NO false asymmetry  Betas from Al decay – 2.4 min lifetime b thermal neutron cross section 0.9 mm thick Al window 0.25% capture probability; half of decays go through chamber 10% ionization current from e - vs. p + BACKGROUND: < 0.015% Al asymmetry measured for NPDGamma Rob Mahurin, technical note Primary window Wrap-around neutrons Neutron flux vs. Wavelength neutrons gammas x 18 Neutron & Gamma flux vs. Position

Systematics  Beam fluctuations, polarization, RFSF efficiency Only systematic beam fluctuations contribute (A<<1) Self-normalizing detector – forward wires sensitive to flux only  Parity allowed asymmetries minimized with longitudinal polarization Alignment of field, beam, and chamber: 1 mrad achievable  k n r ~ small for cold neutrons

Alignment procedure  Suppression of 1.7 x nuclear PC asymmetry longitudinal polarization doubly suppresses s n. k n x k p 1. Symmetric detector Rotate 180 deg about k n during data taking 2. Align B field to detector within 1 mrad Vant-Hull and Henrickson windblown generator Minimize B x, B y by observing eddy currents in generator 3. Align detector and neutrons to 1 mrad Perform xy-scans of beam at 2 z-positions before/after target B 4 C target in beam with CsI detector, 6 Li chopper B 4 C target CsI crystal 6 Li Shutter

Work Packages  Theory- Michele Viviani  MC Simulations- Michael Gericke  Polarimetry- Geoff Greene  Beam Monitor- Rob Mahurin  Alignment- David Bowman  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- Chris Crawford  Analysis- Nadia Fomin  System integration/CAD- Seppo Pentilla  Rad. Shielding / Tritium- John Calarco

Effort Estimate for n- 3 He Collaborators (Percentage of research time) InstitutionResearcherCategory Duke University, Triangle Universities Nuclear Laboratory Pil-Neo SeoResearch Staff10 Istituto Nazionale di Fisica Nucleare, Sezione di Pisa Michele VivianiResearch Staff15 Oak Ridge National Laboratory Seppo PentilläResearch Staff David BowmanResearch Staff TBDPostdoc University of Kentucky Chris CrawfordFaculty3035 TBDGrad Student50100 Western Kentucky University Alex BarzilovFaculty5570 Ivan NovikovFaculty5570 TBD * 2Undergraduate100 University of Manitoba Michael GerickeFaculty Shelley PageFaculty20 10 WTH. Van OersFaculty 2010 Rob MahurinPostdoc V. TvaskisPostdoc 2010 Mark McCreaGrad Student D. HarrisonGrad Student80100 Universidad Nacional Autónoma de México Libertad BaronFaculty2530 TBDGrad Student 100 University of New Hampshire CalarcoFaculty50 University of South Carolina Vladimir GudkovFaculty10 5 Young-Ho SongPostdoc10 5 TBDGrad Student Univeristy of Tennessee `Geoff GreeneFaculty10 S. KucukerPostdoc20 University of Virginia S. BaesslerFaculty51520

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

Projected schedule  July 2012 Stage stand, solenoid, RFSF, Target/Ion Chamber in nEDM building  Dec 2012 Installation at FnPB Field map at FnPB  Feb 2013 Beam axis scans 3 He Polarimetry  Apr – Dec He data-taking  Jan – Dec 2011 Construction and field mapping of solenoid at UNAM Construction and testing of RFSF resonator at UKy Assembly of 3 He ion chamber at Univ. Manitoba DAQ electronics and software at UKy / UTK / ORNL  Jan – May 2012 test RFSF, 3 He chamber, and DAQ at HFIR SNS Offsite Beam time request: 5000 hrs.

Conclusion  Theoretical progress Full 4-body calculation published, EFT calculation under way Test of consistency of DDH or EFT within few-body systems  Experimental progress Prototype RFSF resonator designed and built Target chamber delivered, instrumentation under way  Sensitivity Statistics: ±A = 1.3 x 10 -8, low background levels Systematic effects suppressed with longitudinal polarization  Will be ready to commission and run after NPDGamma