Polarized 3He Relaxation Studies

@ Low TQ. 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 PumpingNMR system

Bottom part of the double cell system

Dewar NMR system

Spin Exchange Optical Pumping (SEOP) 37Rb:

Rb vapor in a weak B field is optically pumped

Spin exchange with 3He gas

Buffer gas N2 let the electrons decay without emitting photons

)55(1 2/12/1 PSD

1s22s22p63s23p6

4s23d104p65s1

Rb heated to 1800C, holding field 7G or 21G

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

xBzBBeff ˆˆ)( 10

Resonance B-field

CtBmBtB

BMtS nmrHe

)(

)/)(()( 02

12

0

13

<M> is the fitted amplitude 3He polarization

)(1,11

21

0

1

FastTTdt

dBB

)(11

0

1

AdiabaticBdtdB

B

Good acrylic cell attachedAbout 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 test

ed them - Cell 1 (Oct. – Nov.)- Cell 2 (Nov. – Now)

Results from top glass cell

300K, 21G

3He 0.0014mol N2 1.9e-4mol 3He 0.0041mol

N2 2.8e-4mol

Results from uncoated acrylic cell

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

Results from uncoated acrylic cell

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

Results from d-TPB coated acrylic cell

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

Results from d-TPB coated acrylic cell

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

Need more tests to verify

Measured after one month

4He layer calculation n is the number of layers α is the van der Waals constant

α=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 temperatu

re T

]2[],1[3 ln

satpp

Tn

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)

Discussion of the data

Liquid 4He

Gas 3HeThe top and the side are coated with 4He layers

l

L

R

Bob Golub’s model

Assume cell bottom is bad surface

D ~ 1e-4 cm2/s

211

111

T

Diffusion time from the liquid surface to the bottom

Wall relaxation time, no bottom(a constant Tma

x)

sTlDT

TT

Dl

1602632~

1

max

2max

max1

2

1

Discussion of the data Dipangkar solved the diffusi

on 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

)coth()(

2)()(

1 2211

1 l

l

DlC

lLlDC

RC

lLC

lT

bottomT1

sideT1

topT1C1 diffusion constant of the 4He film times the fraction

of the surface covered with impuritiesC2 the fraction of area covered with impurities

Liquid 4He

Gas 3HeThe top and the side are coated with 4He layers

l

L

R

VSConst

T

xMTx

xMDtxM

liquidfilm

f

)/(

2

2

1

)(1)()(

Discussion of the data

Assume D is the same for the film and liquidC1 ~ 0.00001 and C2 ~ 0.20+-0.02 (need more data to verify)

Need more tests to verify

4He amount (mol)

4He level from bottom (cm)

Discussion of the data

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)

4He amount (mol)

4He level from bottom (cm)

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

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)