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3 He Relaxation below 1 K

3 He Relaxation below 1 K. Jacob Yoder UIUC October 6 th , 2006. Outline. Goals Proposed method of measurement Status / To do. Goals. Measure relaxation time of 3 He on dTPB coated acrylic at temperatures between 0.3 K and 1.0 K

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3 He Relaxation below 1 K

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  1. 3He Relaxation below 1 K Jacob Yoder UIUC October 6th, 2006

  2. Outline • Goals • Proposed method of measurement • Status / To do

  3. Goals • Measure relaxation time of 3He on dTPB coated acrylic at temperatures between 0.3 K and 1.0 K • Measure relaxation time of 3He in the presence of other materials

  4. Proposed method RT pumping cell • Polarized 3He produced by MEOP • Double cell: 3He polarized at room temp, T1 measured in cold cell V1 Manifold V2 Cold Cell

  5. 3He cycling RT pumping cell 1) V1openV2open; Evacuate cells 2) V1openV2closed; Fill with 3He 3) V1closedV2closed; Pump 3He 4) V1closedV2open; 3He pulled into cold cell as pressure equalizes 5) V1closedV2closed; Measure T1 Repeat V1 Manifold V2 Cold Cell

  6. Status as of last meeting • Cryostat reached 0.3 K unloaded • Magnet built • ~ 1h relaxation time seen in valve-less pyrex cells

  7. Cool down with dummy cell • Glass dummy cell cooled to ~1 K • Anchors did not uniformly cool the cell • Anchors will need to cover large fraction of the glass surface area

  8. Magnet and NMR setup in place • Magnet placed around cryostat • Laser, valve-less double cell, coils put in place

  9. Polarization measured in “cold” cell • FID amplitude in the cold cell 3.3 mV in old location, 2.1 mV in cryostat • T1 of 2500 s before, now T1 ~ 100 s • T2 in each cell dropped by approximately ½ • Losses are likely due to nearby magnetic materials, which need to be moved away

  10. Relationship between gradients and Relaxation times Mismatch between implied gradients likely due to highly localized gradient. Wilson seal or ball valve probably the culprit.

  11. Nearby Magnetic Materials Wilson Seal Ball Valve

  12. Valve/O-Ring issues • Contamination of the MEOP discharge • Contamination becomes problematic approximately 2 weeks after filling. This is much longer than the expected fill measurement cycle • Depolarization of 3He as it passes through the valve • The valve did not reduce the polarization in the “cold” cell in RT test • “Real” valved double cell built

  13. To Do • Reduce background gradients by removing magnetic materials and possibly relocating cryostat +redo room temp test (2 wks) • Put fill/pumpout manifold in place and test (3 wks) • Relaxation measurement with pure 3He gas in pyrex cell below 1 K (3 wks) • 4He wall coating? (2 wks) • Construct/borrow dTPB (?) coated cell and perform relaxation measurement at working temperature (8-12 wks) • Test other materials

  14. Costs (to be assumed by Illinois) • Upgrades to manifold -$500 • Glassware -$1000 • Materials for new cells 4X -$1200 • LHe for tests (6 tests, 250 l/test) -$5265 • Contingency (20%) -$1600 • Total -$9600

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