n- 3 He Experiment: overview and updates Christopher Crawford University of Kentucky n- 3 He Collaboration Meeting ORNL, TN

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

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 ~ -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: 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  Vladimir Gudkov (USC)PV A = -(1 – 4)£10 -7 PV reaction theory (to be submitted)  Gerry Hale (LANL) PC A y (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: (nucl-th) status: submitted to PRC

Extraction of DDH couplings np A  nD A  n 3 He A p np  n n  pp A z p  A z f  hr0hr hr1hr h2h h0h h1h n- 3 He: M. Viviani (PISA) (preliminary) dA=1x10 -8

Sensitivity to DDH couplings  NN-potentials: AV18 AV18/UIX N3LO N3LO/N2LO  Pion-full EFT calculation?

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

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

Statistical Sensitivity  N = 2.2 £ n/s flux (chopped) x 10 7 s (4 full 1.4 MW)  P = 96.2%neutron polarization   d = 6detector efficiency   A/A ~ 5% assuming A=3x10 -7   A/A ~ 26% worse case A=5x10 -8

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)

Systematic Error constraints  Mott-Schwinger and parity conserving nuclear asymmetry  Measure longitudinal instead of transverse asymmetry  1) measure the average k n at two different places along the beam using the wire chamber  2) align the B field parallel to k n  3) align the wire planes to be perpendicular to the holding field (same as k n ) 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

Transverse RF spin rotator – n3He  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-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 NPDGamma windings n- 3 He windings

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 (H n ) 3. Windings are traced along evenly spaced equipotential lines along the boundary red - transverse field lines blue - end-cap windings Magnetostatic calculation with COMSOL

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

3He Target / Ion Chamber – Considerations  Must measure proton asymmetry in current mode directly in target  Can distinguish back-to-back proton 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

3 He Target / Ion Chamber – Design  Custom aluminum CF flanges with SS knife-edges  Macor ceramic frame supporting pure copper wires, 200um diameter  Being designed and constructed at the University of Manitoba  Similar to the design that was used for the NPDGamma beam monitors  Chamber and parts have been ordered M. Gericke, U. Manitoba

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 A L, A T 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

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 He data-taking  Jan 2011 – May 2011 Construction of new RFSF resonator at UKy Construction of 3 He ion chamber at Univ. Manitoba DAQ electronics and software production at Univ. Kentucky  May 2011, May 2012 test RFSF, 3 He chamber, and DAQ at LANSCE FP12 window of opportunity for the n- 3 He experiment between NPDGamma and Nab ORNL Offsite

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

Organization  Collaboration meetings after NPDG meetings  Regular phone conferences: ~monthly  Collaboration list:  PRAC in December: submit request for beam time  Installation target date: July 2012