Relaxation of spin polarized 3He in mixtures of 3He and 4He below the 4He lambda point

We report a first study of the depolarization behavior of spin polarized 3He in a mixture of 3He-4He at a temperature below the 4He lambda point in a deuterated tetraphenyl butadiene-doped deuterated polystyrene (dTPB-dPS) coated acrylic cell. In our experiment the measured 3He relaxation time is due to the convolution of the 3He longitudinal relaxation time, T1, and the diffusion time constant of 3He in superfluid 4He since depolarization takes place on the walls. We have obtained a 3He relaxation time of ~3000 s at a temperature around 1.9 K. We have shown that it is possible to achieve values of wall depolarization probability on the order of (1–2)×10^−7 for polarized 3He in the superfluid 4He from a dTPB-dPS coated acrylic surface.