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Polarized 3 He Relaxation Studies @ Low T

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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)

- Double-cell system
- d-TPB coated acrylic cell
- Tests on uncoated cell
- Tests on d-TPB coated acrylic cell
- Summary & Future plan

Spin Exchange Optical PumpingNMR system

Bottom part of the double cell system

Dewar NMR system

- 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

- 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

About 1.5mm clearance, should minimize the use of d-TPB.

5.08cm

3.68cm

- 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)

3He 0.0014mol N2 1.9e-4mol

3He 0.0041mol N2 2.8e-4mol

300K, 21G

21G, 2.05K, fix 3He amount, vary 4He amount

fix 3He: 4He= 0.0014mol:0.081molvary B-field & Temperature

21G, 1.9K, fix 4He amount 0.404mol, vary 3He amount

Need more tests to verify

Measured after one month

21G, 1.9K, fix 3He amount 0.0014mol, vary 4He amount

- 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)

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

- Bob Golub’s model
- Assume cell bottom is bad surface
- D ~ 1e-4 cm2/s

The top and the side are coated with 4He layers

Gas 3He

Liquid 4He

- 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

Need more tests to verify

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)

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)

- 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

[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)