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

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

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

4. Proposed method Polarized 3 He produced by MEOP Double cell: 3 He polarized at room temp, T 1 measured in cold cell Manifold RT pumping cell Cold Cell V1 V2

5. 3 He cycling 1)V1 open V2 open; Evacuate cells 2)V1 open V2 closed; Fill with 3 He 3)V1 closed V2 closed; Pump 3 He 4)V1 closed V2 open; 3 He pulled into cold cell as pressure equalizes 5)V1 closed V2 closed; Measure T 1 Repeat Manifold RT pumping cell Cold Cell V1 V2

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  V in old location, 2.1  V in cryostat T 1 of 2500 s before, now T 1 ~ 100 s T 2 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 3 He 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 3 He gas in pyrex cell below 1 K (3 wks) 4 He 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