# Enhanced Polarization of Low Pressure $^3$He through Metastability-Exchange Optical Pumping at High Field

## TL;DR

This paper demonstrates high nuclear polarization of low-pressure helium-3 gas using metastability-exchange optical pumping at magnetic fields above 2 Tesla, enabling potential applications in polarized ion sources for collider facilities.

## Contribution

It introduces a method to achieve high polarization of helium-3 at high magnetic fields and pressures, advancing the development of polarized ion sources for collider experiments.

## Key findings

- Achieved over 80% polarization at 2, 3, and 4 T
- Reached 89% polarization at 3 T with 664 s relaxation time
- Successfully polarized 1 torr helium-3 sealed cells in high magnetic fields

## Abstract

We report high steady-state nuclear polarization of 1 torr $^3$He gas nuclei via metastability-exchange optical pumping at magnetic fields above 2 T. The introduction of highly polarized $^3$He gas into Brookhaven's Electron Beam Ion Source would enable a new, polarized $^3$He ion source for use at the Relativistic Heavy Ion Collider and a future Electron-Ion Collider facility. By adapting recent developments in high field metastability-exchange optical pumping for higher pressure gas, we have successfully polarized 1 torr $^3$He sealed cells in the EBIS solenoid. Through careful manipulation of the RF discharge parameters, polarizations above 80% were attained at 2, 3 and 4 T, with 89% being reached at 3 T with a 664 s relaxation time.