Polarized 3 He Relaxation Low T N. Boccabello, D. Dutta, H. Gao, K. Kramer, X.Qian, Q. Ye, X. Zong (Duke) L. Hannelius, B. Heyburn, R.D. McKeown, S. Singer (Caltech) nEDM Collaboration 2 December, 2004 Meeting

Outline Introduction Double Cell System Improvement On the Double Cell System Results 3 He relaxation time T 1 due to the d-TPB coated surface Summary & Future Plan

Introduction Study the relaxation rate of polarized 3 He under actual nEDM experimental conditions: At Duke mK temperature 2. enclosed in a d-TPB coated acrylic cell 3. in a bath of superfluid Helium-4 4. at low 3 He concentrations 5. low B field and high E field 1. relaxation 300K, 4.2K, 2.4K, 2.0K 2. in the presence of d-TPB coated acrylic sticks 3. with various densities of 4 He

Duke Setup

Improvements On the Double Cell System AFP loss has been reduced both in the oven cell and dewar cell Modified Narrow Transport Tubing

Results from “Nicole” 3 He density, 3 He and 4 He ratio ~ 1:1 With d-TPB coated surfaces 31.9% of the glass surface In the oven In the dewar 300K The starting points: dewar cell is better than the oven cell (~ 0.9 hr)*

Results from “Nicole” 3 He density, 4 He density 2.4K, with d-TPB coated 7G

Comparison with Previous Measurements [C. P. Lusher, M. F. Secca, M. G. Richards, Journal of Low Temperature Physics, V72, Nos.1/2, 1988] Spherical sealed cell, radius~1cm, n 3 =3.3*10 17 /cc (10.1 torr), n 4 =7.0*10 16 /cc (1.99torr), n H2 =5.3*10 16 /cc 45KHz, 2.4K, T 1 ~ 600 sec Our double cell system radius~2.5cm n 3 =8.3*10 19 /cc (2350 torr) n 4 =9.0*10 19 /cc ( KHz, 2.4K with d-TPB surface T 1 ~ 510 sec

Comparison with Previous Measurements T 1Ad is the relaxation time in the adsorbed phase (assume the same in two cases) N 3B is the number of 3 He atoms in the bulk N 3Ad is the number of 3 He atoms in the adsorbed phase A is the effective surface area; V is the volume of the cell λ 3 is the 3 He thermal de Broglie wavelength m 3 * is the effective mass of the 3 He adatom ∆W 3 is the adatom-substrate binding energy (~15K for 4 He, and ~13K for 3 He on hydrogen) The double cell system works OK! [C. P. Lusher, M. F. Secca, M. G. Richards, Journal of Low Temperature Physics, V72, Nos.1/2, 1988]

Results from “Nicole” Measure the relaxation 300K, 4.2K, 2.4K with / without the d-TPB coated surface Extract T 1 due to the d-TPB coated surface

Results from “Nicole” 2.4K, with d-TPB surface2.4K, without d-TPB surface Relaxation time = 6.64 mins Corrected R. T. = 9.82 mins Relaxation time= 8.52 mins But the error is pretty big *Due to the deterioration of the double cell system

Results from “Nicole” T 1 due to the d-TPB coated surface at various temperatures Temp(K)B 0 (G)T 1 due to d-TPB (mins)

Results from “Samantha” Contamination sources have been identified Test experiments were done to reduce the deterioration of the cell Procedures of gas filling and pump out have been revised to prevent contamination

Results from “Heather” Due to accidents while chasing Rb to the pumping cell, this double cell system did not provide any useful results The new double cell system is ready and we will be working on it soon

Summary & Future Plan T 1 due to d-TPB coated surface has been extraced for the first 2.4K More measurements are needed to reduce the error in extracting T 1 due to d-TPB coated surface Plan to carry out same measurements below lambda point More 4 He, more d-TPB coated surface will be introduced Estimation of T 1 due to d-TPB coated surface for neutron EDM cell geometry