1 The 3 He Injection Test for the nEDM Experiment 10/2008 Xiaofeng Zhu D. Dutta, H. Gao, M. Busch, Q. Ye, T. Mestler, X. Qian, W. Zheng Duke University nEDM collaboration

2 Outline Introduction Experimental setup Experimental procedure – 3 He injection/collection – Polarization measurement Summary

3 Neutron EDM A permanent EDM d n The current upper limit : d n <2.9x e cm Phys. Rev. Lett. 97, (2006) Improve sensitivity by 2 orders of magnitude – A mixture of ultra-cold neutrons in superfluid 4 He, and polarized 3 He Physics Report 237, 1 (1994) + - s = 1/2 dE T and CP violation Physics beyond SM Baryon Asymmetry of Universe

4 Why Polarized 3 He? Extract n precession frequency using spin dependant nuclear reaction Co-magnetometer d n dipole moment d 3He =0 + - EB EB s = 1/2 n 3 He

5 R&D Efforts on 3 He at TUNL 3 He T 1 measurement in d-TPB coated acrylic cell filled with superfluid 4 He H. Gao, R. Golub, P. Huffman, Q. Ye, and others at TUNL Preparation for injection test – Collect polarized 3 He in a pyrex cell filled with superfluid 4 He – Demonstrate polarization loss is acceptable

6 Setup for 3 He Injection Test Atomic Beam Source: ~100% polarized 3 He atoms/s Cryostat With 4K 50K shield Dilution Refrigerator Liquid He tank at 4K Tri-coil magnet Solenoid magnet

7 Injection/Collection Collection volume pre-filled with superfluid 4 He – 4 He Temp. at 0.3~0.5K – 4 He Volume~27cc 3 He flux from ABS – Intensity:10 14 atoms/s, – Velocity~100m/s After ~100s, ~ He atoms are expected in superfluid 4 He

8 Dilution refrigerator tricoil Helium bath vessel Helium gas Filling pipe To ABS at room temp. 50K 4k Film burner Pyrex cell Heat exchanger 1.3k 0.7k 0.24k

9 Cool the pyrex cell to 0.35K Thermal Link : OFHC copper foil – DR cooling power: 13.8mW with mixing chamber at 0.24K Measurement Copper foil to cool the cell DR MX at 0.24K To ABS DR 1K pot Cs ring Filling pipe for L-He

10 superfluid film suppression Active method – Film burner Passive method (optional) – Cs ring Non wetting of He on Cs surface Safety issues 23 September 2015nEDM collaboration meeting

11 Spin Rotation During injection, 3 He travel through a curved magnetic field. – At ABS exit, 3 He spins parallel to B field – Solenoid coil (20G) Axial field along ABS axis – Tri-coil system (20G) Vertically down direction – Due to space limitation During injection, spins rotate by 45 deg. Tri-coil Solenoid coil 4545 o

12 Spin Rotation: Polarization Loss Negligible Spin follows the field direction – AFP condition: Monte-carlo simulation: – Average spin rotation ~ 3.35±0.30 deg – Polarization ~98.8% Low vapor density to suppress collisions 3 He trajectory AFPNon AFP

13 Polarization Measurement with He/cc Measurement at high field ~1kG to increase signal size Pulsed NMR with a single transceiver coil – Less sensitive to thermal displacement – Smaller RF power – Better signal/noise ratio expected than that of AFP

14 Field Homogeneity for pNMR T * 2 related to longitudinal field gradient: The block time of pNMR is ~20μs Transverse spin relaxation time T * 2 >200 μs – Averaged within 4 He liquid ( R<2.5cm,|z|<2cm) At 1.2kG, Field homogeneity needs to be < 27.5 ppm/cm (30mG/cm) Phy. Rev. A,

15 Tri-coil Design and Test Starting with improved Helmholtz coils – 2 nd and 4 th order cancellation: I 2 /I 1 = ; H/R= – By B. Filippone, Caltech TOSCA Optimization – By S. Balascuta, ASU Numerical and analytical calculation – T * 2 ~2.59ms Average over the liquid He volume, by T.Mestler, Yale – T * 2 ~0.430ms Consider wire geometry, by W. Zheng, Duke Tri-coil built, axial field uniformity is ~16ppm (<27.5ppm) I2I2 I1I1 I1I1 R H Rev. Sci. Instr. V73, 2175

16 pNMR for Injection Test pNMR setup at Duke – An existing magnet modified for this test: 1kG Uniformity ~ 80mG/cm – Tank circuit tuned ~ 3.89MHz – Proton FID signal is observed at room temperature Comparable to 3 He density during injection test ~1X10 14 polarized protons/cc magnet Tank circuit magnet Tecmag Apollo console Tank circuit

17 Trying to improve S/N on 1 H Spin tipping angle at room temp. – RF duration time Spin echo signal – For calibration purpose Cryogenic pre- amplifer, RF shielding, etc FID signal T 2 measurement on water sample

18 Cryogenic pNMR system Faraday cage – Two tunable capacitor – Resonant coil – Copper Semi-rigid coax – Center: Ag coated BeCu – Dielectric: teflon – Sheath: BeCu From D. G. Crabb, UVA Faraday cage

19 Summary Magnets are ready, to be assembled with cryostat pNMR system under optimization Injection test will be carried out at LANL

20 Acknowledgement Los Alamos National Laboratory U.S. Department of Energy under contract # DE-FG02-03ER41231 Collaborating institutions – ASU, BU, Caltech, Duke, LANL, MIT, MSU, NCSU

21 Backup slides

22 Cryogenics Heat load to DR mix:~ 5mW – 13.8mW cooling – By T. Ito – ~2.5mW from film burner – By G. Seidel – 0.5mW pNMR and support – 1.1mW gas introduction tube Cs ring to slow down superfluid flow rate – Torch to chase Cs vapor – Dry ice to condense Cs effectively – CsN3 test will continue Sealing test undergoing – Pyrex to copper adapter 15 thermal cycles – After fail and try, kapton gasket seals well with copper flange Kapton gasket Epoxy 2850GT Cs ring Made by dry ice

23 Safety II: boil off of LHe within Tricoil can Siphon pipe to fill LHe into tricoil can Pipe for safety venting – Heat rate: 2 kW/m 2 – Pressure drop: 5.5 psi Gas – By J. Long Venting velocity: 97m/s ” ID, 45 ” length Reynold number: 5.7x10 5 resistant coefficient: 0.49 – Rupture Avoiding Taconis resonance Siphon pipe Vacuum vent pipe

24 23 September 2015 nEDM collaboration meeting 24 Injection test cell cooling power DR Mixing Chamber Injection test collection volume 4He ~36~22~111~15

25 23 September 2015nEDM collaboration meeting25 Injection test vs nEDM injection ParameterInjection TestnEDM Injection Mechanical Scale0.5 – He Collection volume 25 cc50 – 400 cc Injection volume outletNMR measurement volumeOutlet valve to IV1 Injection port from ABS Requires film burner with ID 1.05” aperture Requires film burner with ID 1.55” aperture Material requirementsCs coated Pyrex cell, no magnetic materials in magnetic field area identical Heat load~0.5mW, conduction cooled from DR mixing chamber via 0.83 m long OFHC Copper foils Similar heat load, ~1.2 m away from DR mixing chamber Measurement technique pNMRSQUIDS