MEOP based 3He polarization and injection system for experiments below 1 K

TL;DR

This paper presents a MEOP-based system for producing highly polarized helium-3 gas at room temperature, designed for injection into ultra-cold environments for neutron EDM experiments, with minimal polarization loss.

Contribution

The paper introduces a specialized helium-3 polarization and injection system optimized for ultra-cold neutron experiments, achieving high polarization with low loss during transfer.

Findings

Achieved 80% helium-3 polarization at room temperature.

Designed injection system minimizes polarization loss to approximately 0.72%.

Enables precise delivery of polarized helium-3 into superfluid helium at 400 mK.

Abstract

Metastability exchange optical pumping (MEOP) is a widely used technique for producing polarized $^{3}$He. In connection with an experiment to search for the electric dipole moment of the neutron (nEDM) we have built a MEOP based $^{3}$He polarization and injection system to prepare 80 % polarized $^{3}$He at room temperature which will be injected into a ~400 mK measurement cell filled with superfluid $^{4}$He. We describe the polarization and injection system, which is designed to allow for final concentrations of $10^{-8}-10^{-10}$ of 80 % polarized $^{3}$He in the superfluid filled measurement cell. Only $\approx0.72\%$ polarization loss due to gradients is expected during injection