Polarized 3 He Relaxation 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 Tests on d-TPB coated acrylic cell Summary & Future plan

Double-cell system Spin Exchange Optical Pumping NMR system Bottom part of the double cell system Dewar NMR system

Spin Exchange Optical Pumping (SEOP) 37 Rb: Rb vapor in a weak B field is optically pumped Spin exchange with 3 He gas Buffer gas N 2 let the electrons decay without emitting photons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 Rb heated to C, holding field 7G or 21G

NMR Polarimetry (Adiabatic Fast Passage) Effective B-field in a frame rotating at is Ramp the holding field from below the resonance to above it Signal AFP conditions Resonance B-field is the fitted amplitude 3 He polarization

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

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)

Results from top glass cell 300K, 21G 3 He mol N 2 1.9e-4mol 3 He mol N 2 2.8e-4mol

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

Results from uncoated acrylic cell fix 3 He: 4 He= mol:0.081mol vary B-field & Temperature

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

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

4 He layer calculation n is the number of layers α is the van der Waals constant α=20±7K for He on H 2 (assume the same for d-TPB coating) p is the actual 4 He pressure in the cell p sat is the saturated vapor pressure at the temperature T 4 He 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)

Discussion of the data Liquid 4 He Gas 3 He The top and the side are coated with 4 He layers Bob Golub’s model Assume cell bottom is bad surface D ~ 1e-4 cm 2 /s Diffusion time from the liquid surface to the bottom Wall relaxation time, no bottom (a constant T max )

Discussion of the data Dipangkar solved the diffusion equation Assume most of the relaxation comes from the bottom when solving for the liquid 4 He part As more 4 He is put in, the further 3 He is away from the bottom C 1 diffusion constant of the 4 He film times the fraction of the surface covered with impurities C 2 the fraction of area covered with impurities Liquid 4 He Gas 3 He The top and the side are coated with 4 He layers

Discussion of the data Assume D is the same for the film and liquid C 1 ~ and C 2 ~ (need more data to verify) Need more tests to verify 4 He amount (mol) 4He level from bottom (cm)

Discussion of the data Assume D is the same for the film and liquid Fitting all the 8 points, C 1 ~ and C 2 ~ (need more data to verify) 4 He amount (mol) 4He level from bottom (cm)

Summary & Future Plans uncoated cell, T 1 ~ 10 2 s, not varying much coated cell, 4 He amount seems to have an optimized value, overall T 1 is much longer than the uncoated cell. More tests on varying 4 He amount Temperature dependence tests (have incomplete data set already) Tests of uncoated cell with more 4 He inside

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)