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

Outline Introduction Components Simulations Physics analysis 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

Experimental setup y x z FNPB n-3He 10 Gauss Holding field RF spin rotator 3He target / ion chamber FnPB cold neutron guide 3He Beam Monitor FNPB n-3He Super-mirror polarizer Collimator y z x ----- Meeting Notes (2013-01-23 09:38) ----- Here is a schematic of the experiment. 3

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

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 3He, 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.

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 Jan 21 – IRR2 approval Feb 16 - tuned choppers 4520 hr = 1.6x107s @ 1.07 MW ave

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

Solenoid Definition of σndirection Adiabatic rotation from transverse to longitudinal spin 10 mG, 0.1% uniformity Univ. Nacional Autónoma de México

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

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

Target / Ion Chamber 3He 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 3He 16 mCi tritium over life of experiment University of Manitoba

Measured ion yield in target chamber

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

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

False electronic asymmetries

MC Simulations Three independent simulations: GEANT4 with white source – Manitoba C-code with McStas ntuple source – UKy 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 Two independent simulations have been done of the wire chambers and detection efficiency of the asymmetry to estimate delta A and were consistent with each other. I will describe the second one. It simulated neutrons event by event, to find the average number of ions (beta_i) in each wire plane, and also the correlation between wires (beta_i,j) since the same neutron leaves a track through multiple wires. Since the physical asymmetry is small it was not simulated, only the sensitivity to the asymmetry (alpha_I or cos theta). From this we get the effective statistics of the asymmetry which goes as 1/sqrt(N) times the detection efficiency sigma_d, which is about 6 for the optimal neutron wavelength range.

Test of MC simulation – ionization deposit Three independent simulations: GEANT4 with white source C-code with McStas ntuple source 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 Two independent simulations have been done of the wire chambers and detection efficiency of the asymmetry to estimate delta A and were consistent with each other. I will describe the second one. It simulated neutrons event by event, to find the average number of ions (beta_i) in each wire plane, and also the correlation between wires (beta_i,j) since the same neutron leaves a track through multiple wires. Since the physical asymmetry is small it was not simulated, only the sensitivity to the asymmetry (alpha_I or cos theta). From this we get the effective statistics of the asymmetry which goes as 1/sqrt(N) times the detection efficiency sigma_d, which is about 6 for the optimal neutron wavelength range.

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

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

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

PC Asymmetry analysis Wire pair asymmetry – does not include correlations

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 (43.6 ± 6.8) x 10-8 G. Hales, R-matrix theory

PV asymmetry – wire 2

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

n3He 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 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