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Update of the injection test

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. Outline. Magnets system collection reservoir Pyrex Cell design Cs coating monitoring 3 He- 4 He mixture

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Update of the injection test

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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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