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

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

n- 3 He PV Asymmetry ~ k n 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 coupling or 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 PV observables: Tilley, Weller, Hale, Nucl. Phys. A541, 1 (1992) n n + n n p p p p n n p p n n + p p n n p p n n p p

Theoretical calculations – progress  Gerry Hale (LANL) PC A y ( 90 ) = /- 0.3 x 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, (2010),  Vladimir Gudkov (USC)PV A = -(1 – 4)£10 -7 PV reaction theory Gudkov, PRC (in press)

Sensitivity to DDH couplings 1. Calculation of strong 4-body wave functions Kohn variational method with hyperspherical functions No parity mixing in this step: J π = 0 +, 0 -, 1 +, 1 - Tested against n- 3 He scattering lengths 2. Evaluation of weak matrix elements In terms of DDH potential EFT calculation in progress

Sensitivity matrix for few-body reactions

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) FNPBn- 3 He Experimental setup  longitudinal holding field – suppressed PC asymmetry  RF spin flipper – negligible spin-dependent neutron velocity  3 He ion chamber – both target and detector

Transverse RF spin rotator  extension of NPDGamma design P-N Seo et al., Phys. Rev. S.T. Accel. Beam, vol 11, (2008) TEM RF waveguide  new resonator for n- 3 He expt. 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, testing at UKy – 2010 NPDGamma windings n- 3 He windings field lines end cap windings

Prototype holding field coil  Developed for static nEDM guide field  1% uniformity DC field

Field map of DSCTC

Prototype RFSF coil

3 He Target / Ion Chamber – Design M. Gericke, U. Manitoba  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.

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 processors for data reduction with direct access to RAID disk  Alphi Technologies: $36k for 192 channels DAQ + storage

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  σ d = 2 (left/right planes) vs. σ d = 6 (proton range / absorption length)  Can measure 6 Li asymmetry to same level with this technique -HV HV grid wires Si, anodes on each side 3 He gas< 1 cm baffles

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  Majority of neutron captures occur at the very front of chamber Self-normalization of beam fluctuations Reduction in sensitivity to A

Measurement of LANSCE FP12 absolute flux

Comparison of statistics at LANSCE FP12  based on: D. Bowman, technical note, , A. Salas-Bacci, technical note, Gericke, NIMA (2009)  2.68 x 10 7 n/s cm 2 neutron flux at 100 μA, measured with FC  3.5” collimator, 87.6 μA proton current  4966 runs (after cut) x 10 4 /20 Hz  0.88 (air) x 0.90 (Al) x 0.88 (glass) x ( 3 He) transmission  0.60 capture in LH 2 x geom. factor  0.53 pol. 3 He x SF eff. / (1+0.25) bkg. Dilution δA = 1.9 x from calc. vs. 2.1 x RMS width in A γ

Runtime estimate for n- 3 He at FnPB  N = 2.2 £ n/s flux (chopped) x 10 7 s (4 full 1.4 MW)  P = 96.2%neutron polarization   d = 6detector efficiency

Systematics  Beam fluctuations, polarization, RFSF efficiency:  k n r ~ 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)

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

Scanning beam monitor B 4 C target CsI crystal 6 Li Shutter

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

Installation at FnPB  NPDG equipment: 3 He beam monitor SM polarizer Beam position monitor Radiation shielding Pb shield walls Beam Stop  New equipment: Transition guide field 4 He 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 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

Projected schedule  Jan 2011 – Jul 2012 (beam) NPDGamma data-taking  July 2012 Stage of stand, solenoid, RFSF, Ion Chamber in nEDM building  Aug 2012 Installation at FnPB Field map at FnPB  Sept 2012 (request: 1000 hrs) Beam axis scans 3 He Polarimetry  Jan 2013 (request: 5000 hrs) 3 He data-taking  Jan 2011 – July 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  Aug 2011, May 2012 test RFSF, 3 He chamber, and DAQ at LANSCE FP12 ORNL Offsite

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