Relaxation of Spin Polarized $^3$He in Mixtures of $^3$He and $^4$He at $\sim$330 mK

TL;DR

This paper reports on the measurement of extremely low depolarization probabilities of polarized helium-3 in a specialized cell at very low temperatures, relevant for precision experiments like neutron EDM searches.

Contribution

The study demonstrates a novel surface coating achieving a depolarization probability of about 1.0×10⁻⁷, significantly improving helium-3 polarization retention at cryogenic temperatures.

Findings

Depolarization probability of ~1.0×10⁻⁷ achieved

Cell coated with deuterated tetraphenyl butadiene-doped polystyrene

Applicable to neutron electric dipole moment experiments

Abstract

We report the measurements of depolarization probabilities of polarized $^3$He in a rectangular acrylic cell with a deuterated tetraphenyl butadiene-doped deuterated polystyrene coating filled with superfluid $^4$He at $\sim$330 mk with a magnetic holding field of $\sim$7.3 G. We achieve a wall depolarization probability of $\sim1.0\times10^{-7}$. Such a surface will find application in a new experiment searching for the neutron electric dipole moment and other applications.