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Advancements in nEDM Injection Test: Superconducting Magnets and Pulsed NMR System Updates

This update details significant improvements in the nEDM injection test developed by Duke University and collaborating institutions. Key enhancements include the design of a pulsed NMR system featuring tri-coils and solenoid coils, optimized Cs coating for reduced wall depolarization effects, and an innovative collection reservoir design. The cooling system employs advanced superconducting magnets and new power supplies, achieving cost reductions while maximizing performance. The update outlines testing schedules, design innovations, and instrumentation aimed at improving measurement accuracy in the nEDM experiment.

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Advancements in nEDM Injection Test: Superconducting Magnets and Pulsed NMR System Updates

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  1. Update of the injection test 06/2007 nEDM H. Gao, M. Busch, Q.Ye,T. Mestler, X. Qian, W. Zheng, X. Zhu Duke University And others in nEDM collaboration

  2. Outline • Magnets system • collection reservoir • Pyrex Cell design • Cs coating • monitoring 3He-4He mixture • Design of Pulsed NMR system

  3. Superconducting Magnets • Tri-coils and solenoid coils • 20G,spin rotation of 45 deg. • 1.2KG, holding field for NMR • Tri-coil • A bath of liquid He • Cooling can built by MIT • June, by Cryomagnetics • Solenoid coil (Cu:NbTi) • Conductive cooled by Al6061 mandrel • June, by AMI Solenoid coil Tri-coil --Caltech

  4. Power supply for superconducting solenoid • A Kepco Power supply with quench protection • Cost reduced by a factor of 10 • Power supply from Superconducting magnet company is an overkill, too expensive • Pure inductive load, • ~1400V spike voltage at quenching

  5. New design of collection reservoir • Glass to metal adaptor • Glass joint with kapton O-ring is hard to seal • A separated bottom cell • Closer to final test. • Solenoid coil for pNMR is applicable • Instead of side coil • Smaller sample size • Longer T2: ~5.5ms pre-filled 4He NMR solenoid Probe coil Bottem cell forpNMR

  6. Cell inner Surface treatment at room temperature • Cs coating reduces wall depolarization effect • Cs Azide Rod moves down into top/bottom cell • heating Cs Azide (CsN3) rod • Cs moves straightly in vacuum • No shadow area Cs Azide rod

  7. 3He-4He mixture • temperature and pressure measurements provide valuable information • 3He vapor concentration X : • 3He liquid concentration Xliq , W/k=1.54 Kelvin • Applicable at equilibrium state P.J. Nacher, J low Temp. Phys V97, p417,1994 • ~10 temperature sensors will be installed • Ruthenium Oxide RTDs from Lakeshore

  8. Polarization measurmnet • Plused NMR • Resonance frequency at 3.89MHz • Very low density of 3He: 1014atoms/cc • Very good signal to noise ratio • Must Push what is possible for pNMR • Most helpful to have squids detector • Will squids work without magnetic shielding?

  9. Schematic of pNMR probe Apollo console from NCSU • Signal in the probe coil • >160V during RF transmitter • ~1uV NMR signal of FID RF amp Inside dewar

  10. pNMR : tank circuit • Tank circuit: • Probe Coil at resonance • Inductance: 32uH with 40 turns • Tunable capacitor • non magnetic • low temperature • High voltage • piston trimmer

  11. Resonance tuning inside dewar • Piston trimmer close to probe coil • Very small signal: 1nV/loop • the circulating current does not need to go through the coax • Piston trimmer capacitor ordered • 5~120pF C (pF) Number of turns

  12. Probe of pNMR close to our design Rev. of Sci. Instr. 68, 2132 (1997).

  13. COAX connects the tank circuit • High-Q Coax cable: • inner: Ag plated BeCu • outer: CuNi • insulated with Teflon • good electric conductivity • Poor thermal conductivity Courtesy by Dr. William Halperin, NWU

  14. Inhomogeneous B1 field for single solenoid probe coil 2cm Spins rotate by 90 deg. RF pulse duration time: ~100uS B1 field: 7.6G 2cm A separate Helmholtz coil for RF power transmitting is under design

  15. pNMR: RF amplifier • From Tomco • Linear amplifier type: AB • Blanking time ~1us • 1dBm=0.22V • RF noise:~ 0.2uV

  16. lumped circuit Works as a duplexer Block pre-amp during RF transmitting Conducting for FID RF Amplifier From Tomco Blanking time ~1us 1dBm=0.22V RF noise:~ 0.2uV pNMR: lumped circuit and RF Amplifier Zi Zo = Z2= 1/ω2c2

  17. Other studies on cryogenic pNMR • Low noise high impedance Pre-amp • Q-spoils circuit to shorten the recovery time • Ground loop • Ultrasonic noise

  18. Schedule • Test and install the magnet system • in June , July and August • Start pyrex cell fabrication • June and July • Optimize pNMR system • To see glycerol signal with Apollo console at low field • Improve the signal/noise ratio at room temperature • Cool the sample and tank circuit • improve signal at low temperature • June , July and August

  19. Thanks!

  20. Design of Feed through and trimmer handle BNC-SMA Hermetically sealed SMA bulkhead SMA-coax adaptor Courtesy by Dr. William Halperin, NWU

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