1 / 19

Polarized 3 He Relaxation Studies @ Low T

Polarized 3 He Relaxation Studies @ Low T. Q. Ye, D. Dutta, H. Gao, K. Kramer, X. Qian, X. Zong (Duke) R.D. McKeown, L. Hannelius, B. Heyburn, S. Singer (Caltech) R. Golub, E. Korobkina (NC State). Outline. Double-cell system d-TPB coated acrylic cell Tests on uncoated cell

yen
Download Presentation

Polarized 3 He Relaxation Studies @ Low T

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Polarized 3He Relaxation Studies @ Low T Q. Ye, D. Dutta, H. Gao, K. Kramer, X. Qian, X. Zong (Duke) R.D. McKeown, L. Hannelius, B. Heyburn, S. Singer(Caltech) R. Golub, E. Korobkina(NC State)

  2. Outline • Double-cell system • d-TPB coated acrylic cell • Tests on uncoated cell • Tests on d-TPB coated acrylic cell • Summary & Future plan

  3. Double-cell system Spin Exchange Optical PumpingNMR system Bottom part of the double cell system Dewar NMR system

  4. Spin Exchange Optical Pumping (SEOP) • 37Rb: • Rb vapor in a weak B field is optically pumped • Spin exchange with 3He gas 1s22s22p63s23p64s23d104p65s1 Rb heated to 1800C, holding field 7G or 21G Buffer gas N2 let the electrons decay without emitting photons

  5. NMR Polarimetry (Adiabatic Fast Passage) • Effective B-field in a framerotating at is • Ramp the holding field from below the resonance to above it • Signal • AFP conditions Resonance B-field <M> is the fitted amplitude3He polarization

  6. Good acrylic cell attached About 1.5mm clearance, should minimize the use of d-TPB. 5.08cm 3.68cm

  7. Tests with acrylic cells • Test with an uncoated acrylic cell (Jul.-Sep.) • Coated the cell with protonated material (trial) • Coated two cells with d-TPB material and tested them - Cell 1 (Oct. – Nov.)- Cell 2 (Nov. – Now)

  8. Results from top glass cell 3He 0.0014mol N2 1.9e-4mol 3He 0.0041mol N2 2.8e-4mol 300K, 21G

  9. Results from uncoated acrylic cell 21G, 2.05K, fix 3He amount, vary 4He amount

  10. Results from uncoated acrylic cell fix 3He: 4He= 0.0014mol:0.081molvary B-field & Temperature

  11. Results from d-TPB coated acrylic cell 21G, 1.9K, fix 4He amount 0.404mol, vary 3He amount

  12. Need more tests to verify Results from d-TPB coated acrylic cell Measured after one month 21G, 1.9K, fix 3He amount 0.0014mol, vary 4He amount

  13. 4He layer calculation • n is the number of layers • α is the van der Waals constantα=20±7K for He on H2(assume the same for d-TPB coating) • p is the actual 4He pressure in the cell • psat is the saturated vapor pressure at the temperature T 4He amount varies from 0.14mol to 1.1 mol n varies from 2 to 3 layers, doesn’t change much [1] M. A. Paalanen and Y. Iye, Phys. Rev. Lett. 55, 1761 (1985) [2] D. Cieslikowski, A. J. Dahm and P. Leiderer, Phys. Rev. Lett. 58, 1751 (1987)

  14. Wall relaxation time, no bottom(a constant Tmax) Diffusion time from the liquid surface to the bottom The top and the side are coated with 4He layers Gas 3He Liquid 4He Discussion of the data • Bob Golub’s model • Assume cell bottom is bad surface • D ~ 1e-4 cm2/s

  15. The top and the side are coated with 4He layers Gas 3He Liquid 4He Discussion of the data • Dipangkar solved the diffusion equation • Assume most of the relaxation comes from the bottom when solving for the liquid 4He part • As more 4He is put in, the further 3He is away from the bottom C1 diffusion constant of the 4He film times the fraction of the surface covered with impuritiesC2 the fraction of area covered with impurities

  16. Need more tests to verify Discussion of the data 4He level from bottom (cm) 4He amount (mol) Assume D is the same for the film and liquidC1 ~ 0.00001 and C2 ~ 0.20+-0.02 (need more data to verify)

  17. Discussion of the data 4He level from bottom (cm) 4He amount (mol) Assume D is the same for the film and liquidFitting all the 8 points, C1 ~ 0.00001 and C2 ~ 0.23+-0.02(need more data to verify)

  18. Summary & Future Plans • uncoated cell, T1 ~ 102 s, not varying much • coated cell, 4He amount seems to have an optimized value, overall T1 is much longer than the uncoated cell. • More tests on varying 4He amount • Temperature dependence tests (have incomplete data set already) • Tests of uncoated cell with more 4He inside

  19. Reference [1] M. A. Paalanen and Y. Iye, Phys. Rev. Lett. 55, 1761 (1985) [2] D. Cieslikowski, A. J. Dahm and P. Leiderer, Phys. Rev. Lett. 58, 1751 (1987) [3] M. Jimbert and J. Dupont-Roc, J. of Low Temp. Phys. 76, 435 (1989)

More Related