n- 3 He Experiment: overview and updates

1. n-3He Experiment: overview and updates Christopher Crawford University of Kentucky n-3He Collaboration Meeting ORNL, TN 2010-10-16

2. 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

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 ~ -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 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 • 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

5. Extraction of DDH couplings n-3He: M. Viviani (PISA) (preliminary) dA=1x10-8 dA=1x10-8

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

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

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. 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)

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

11. 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

12. 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)

13. 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

14. 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 electronicsfor NPDGamma spin flipper • prototype design • parasitic with similar design for nEDM guide field near cryostat • fabrication and testing at UKy – 2009 NPDGamma windings n-3He windings

15. RFSF winding: designed from the inside out Magnetostatic calculation with COMSOL • Standard iterative method:Create coils and simulate field. • New technique: start with boundary conditions of the desired B-field, and simulate the winding configuration • Use scalar magnetic potential (currents only on boundaries) • Simulate intermediate region using FEA with Neumann boundary conditions (Hn) • Windings are traced along evenly spaced equipotential lines along the boundary red - transverse field lines blue - end-cap windings

16. Prototype RFSF • Developed for static nEDM guide field • 1% uniformity DC field

17. 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

18. 3He 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

19. 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 processorsfor data reduction with direct access to RAID disk

20. 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 Projected schedule – old Offsite ORNL window of opportunity for the n-3He experiment between NPDGamma and Nab

21. 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

22. Organization Collaboration meetings after NPDG meetings Regular phone conferences: ~monthly Collaboration email list: n3he@pa.uky.edu PRAC in December: submit request for beam time Installation target date: July 2012