1. The n- 3 He Experiment Christopher Crawford University of Kentucky for the n- 3 He Collaboration FnPB PRAC ORNL, TN 2015-11-10

2. Outline  Introduction Experimental setup Long. vs. trans. asym Timeline & beam time Statistics & sensitivity  Components Chopper – window tune RFSF – polarimetry Ion Chamber – scans DAQ – instrumental asym.  Simulations Status of simulations MC Validation  Physics analysis L/R wire pair asym. U/D singles asym.  Conclusion

3. Experimental setup 10 Gauss Holding field RF spin rotator 3 He target / ion chamber FnPB cold neutron guide 3 He Beam Monitor FNPB n- 3 He Super-mirror polarizer Collimator y z x

4. Longitudinal vs. transverse PV asymmetry  Initial design: measure a longitudinal PV asymmetry Insensitive to misalignment: L/R – U/D mixing Problem: chamber not self-normalizing Solution: flip spin half-way during TOF of pulse  Reconsideration: measure transverse PV asymmetry Factor of 2x better sensitivity to PV asymmetry: -No dilution due to the opposite sign of asymmetry coming from upstream vs. downstream of sense wire -Can decrease pressure so ions make it out of beam We decided to run both PC and PV in transverse mode

5. Timeline – Installation & Commissioning: 2014  Spring – construction: Solenoid, RFSF, Ion Chamber, Preamp, DAQ  June – removed NPDG from FnPB  July – construction: barrier wall, mounting hardware tuned solenoid, tested major components  Aug – installation of solenoid / frame in FnPB  Sept – transverse fieldmap; ISSR tritium safety meeting  Nov – commissioning without beam; IRR 1 review filled Ion Chamber with 3 He, tested  Dec – beam profile scans; RFSF tune / polarimetry Accomplished installation and commissioning (except for IRR 2 and L/R asymmetry) on schedule during Fall 2014.

6. Timeline – Data collection: 2015  Jan 21 – IRR 2 approval; tune RFSF / polarimetry; initial PV data  Feb 10–Feb 16 – PC data collection : 116 hr @ 900 kW δA= 6.8x10 -8  Feb 16 – tuned chopper, began PV collection in final configuration  June 26–Aug 13 – summer shutdown 1920 MW hr RUN 1  Sept 26–Oct 14 – SNS target failure 1040 MW hr RUN 2  Oct 14– Dec 22 – production expect~1300 MW hr RUN 3 δA=1.1x10 -8 JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 4520 hr = 1.6x10 7 s @ 1.07 MW ave

7. Optimization of Chopper, RFSF, DAQ window Chopper efficiency Unchopped single-pulse neutron spectrum Chopped spectrum TOF x 60 Hz Neutron Flux [arb. units] Chopped 60 Hz beam Ion chamber TOF signal Chopper efficiency Dropped pulse every 10 s

8. Solenoid Definition of σ n direction – Adiabatic rotation from transverse to longitudinal spin – 10 mG, 0.1% uniformity Univ. Nacional Autónoma de México

9. Transverse RF Spin Rotator  Double-cosine-theta coil Fringeless transverse RF field Longitudinal OR transverse Designed using scalar potential Univ. Tennessee / Univ. Kentucky

10. 3 He transmission polarimetry Larmor Resonance Rabi Oscillation Polarization of 3 He Cell Beam Polarization Spin Flip Efficiency

11. Target / Ion Chamber 3 He for both target and ionization gas –Macor frames with 9 x 16 sense wires, 8 x 17 HV wires –All aluminum chamber except for knife edges, 0.9 mm Al windows –7 psi pure 3 He –16 mCi tritium over life of experiment University of Manitoba

12. Measured ion yield in target chamber

13. Garfield / gmsh / Elmer simulation of ion drift Ion collection across diagonal

14. Readout electronics Ionization read out in current mode – 144 channels read out simultaneously – Low-noise I-V preamplifiers mounted on chamber – 24-bit, 100 kS/s, 48 channel Δ-Σ ADC FMC modules Oak Ridge National Lab, Univ. Kentucky, Univ. Tennessee Electronic Tests: Instrumental false asymmetry measurements

15. False electronic asymmetries

16. MC Simulations  Three independent simulations: 1.GEANT4 with white source – Manitoba 2.C-code with McStas ntuple source – UKy 3.C-code with FnPB measured source – UTK Ionization weighted averages: Used to calculate detector efficiency (effective statistics / neutron flux) ionization yield yield covariance geometry factor

17. Test of MC simulation – ionization deposit  Three independent simulations: 1.GEANT4 with white source 2.C-code with McStas ntuple source 3.C-code with FnPB measured source Event - weighted averages: ionization correlation geometry Used to calculate detector efficiency (effective statistics / neutron flux) PRELIMINARY – work in progress

18. Test of MC simulation – correlations PRELIMINARY – work in progress Difference of correlation: MC - experiment

19. PC Asymmetry analysis  Single-wire asymmetry, 30 hr. data subset

20. PC Asymmetry analysis  Single wire asymmetries – offset due to beam asymmetry

21. PC Asymmetry analysis  Wire pair asymmetry – does not include correlations

22. Covariant – weighted analysis Histogrammed extracted physics PC asymmetry from each good run (746 total = 86 hr) used full covariant weighting of each wire pair to extract the PC asymmetry PRELIMINARY – work in progress G. Hale, R-matrix theory (PV Workshop, Madison, WI 2008)

23. PV asymmetry – wire 2

24. Conclusion  Sensitivity of data collected by December Expect 1.1 x10 -8 statistical uncertainty in PV asymmetry  Preliminary analysis of PC asymmetry 7 x10 -8 statistical uncertainty in 5 days of data taking Data appear statistically consistent  Analysis of PV asymmetry underway Investigating some inconsistencies  Preliminary MC validation Still needs work

25. n 3 He Collaboration Duke University, TUNL Pil-Neo Seo INFN, Sezione di Pisa Michele Viviani University of Kentucky Chris Crawford Latiful Kabir Aaron Sprow Western Kentucky University Ivan Novikov Los Alamos National Laboratory Gerry Hale University of Manitoba Michael Gericke Mark McCrea Carlos Olguin University of New Hampshire John Calarco Universidad Nacional Autónoma de México Libertad Barrón José Favel Andrés Ramírez Oak Ridge National Laboratory David Bowman Vince Cianciolo Paul Mueller Seppo Penttilä Jack Thomison University of South Carolina Vladimir Gudkov Matthias Schindler Young-Ho Song Middle Tennessee State University Rob Mahurin University of Tennessee Noah Birge Chris Coppola Nadia Fomin Irakli Garishvili Connor Gautham Geoff Greene Chris Hayes Serpil Kucuker Eric Plemons Mae Scott University of Tennessee at Chattanooga Josh Hamblen Jeremy Watts Caleb Wickersham University of Virginia Stefan Baessler