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The status of 3 He Relaxation Time Measurement at ~400mK

The status of 3 He Relaxation Time Measurement at ~400mK. Q. Ye, D. Dutta, H. Gao, W. Zheng, X. Zhu Duke University R. Golub, P. Huffman, F. Dubose NC State University May 20, 2008. Outline. Experimental Apparatus 2007 Summer Results Modifications to the MC & acrylic cell

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The status of 3 He Relaxation Time Measurement at ~400mK

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  1. The status of 3He Relaxation Time Measurement at ~400mK Q. Ye, D. Dutta, H. Gao, W. Zheng, X. ZhuDuke University R. Golub, P. Huffman, F. DuboseNC State University May 20, 2008 Duke nEDM Collaboration Meeting

  2. Outline • Experimental Apparatus • 2007 Summer Results • Modifications to the MC & acrylic cell • 2008 April Results • Future plan Duke nEDM Collaboration Meeting

  3. Experimental Schematics Detachable cell Filled with polarized 3He Detachable cell mount MixingChamber Distance between the top polarized 3He cell and the bottom acrylic cell ~ 218.4cm Buffer Volume (copper) 293.4 cm 3He transfer 4He capillary Dilution Refrigerator d-TPB coatedacrylic cell IVC d-TPB coated acrylic cell RF coils pickup coil

  4. Transfer Polarized 3He • Transfer polarized 3He onto top of the DR using portable magnetic field • 90% polarization left

  5. 2007 Results • Cell filled with 1.23mol super-fluid 4He (~63% full), cooled down to 0.530K • Total amount of 3He in the cell was 0.00092 mol (polarization~5%) • 3He relaxation time (~1263 seconds with an AFP loss of 0.5%) at 7.5G holding field • Hard to cool down the cell filled with super-fluid 4He Duke nEDM Collaboration Meeting

  6. After Modification 0.25mm capillary restrict 4He film flow Gold-plated 99.999% copper wires Grooves for copper wires to go thru Duke nEDM Collaboration Meeting

  7. 2008 Results 1/8” copper tubing For the 1.5mm pure copper cooling wire to go through Small copper piece Temperature sensor holder

  8. Leak found at the joint The leak was found around this region. The hole was filled with stycast 1266. Duke nEDM Collaboration Meeting

  9. Heat Input Study • Lowest MC temp. ~ 44mK with the acrylic cell being empty (~15.3 kOhm) Duke nEDM Collaboration Meeting

  10. Condensing 4He into acrylic cellvolume: ~ 54cc (need ~ 5000 torr 7.5 liter 4He to fill) During the filling process, 1Kpot temperature ~ 2.05K (25.8 kOhm) Still pressure ~ 8.5e-2 mBar Still turbo power ~ 200W IVC pressure ~1.2-1.4e-5 mBar Stable operation

  11. 3He Relaxation Time • Wall depolarization probability is deduced 3He relaxation time measurements Duke nEDM Collaboration Meeting

  12. nEDM experimental cell • The neutron EDM experimental cell ~ 7.6cm × 10.2cm × 50.0cm (S/V ~ 0.5) • Scaled 3He relaxation time ~4260s (S/V=1.284) or 4910s (S/V = 1.48). Duke nEDM Collaboration Meeting

  13. Next steps • Depolarization probability comparable (slightly worse) to that from 1.9K (~2e-7, Q. Ye et al. to appear in PRA) • Improve 3He relaxation time, how? • Better coating? How do we quantify coating, using atomic force microscope (AFM)? • Put on gradient coils along z-axis to study geometric phase effect under nEDM experimental conditions Duke nEDM Collaboration Meeting

  14. Thank you! Duke nEDM Collaboration Meeting

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