Liquid Crystal Polarimetry for Metastability Exchange Optical Pumping of 3He

TL;DR

This paper presents a compact liquid crystal polarimeter designed to measure nuclear polarization in helium-3 gas during optical pumping, utilizing circular polarization of discharge light under low magnetic field conditions.

Contribution

It introduces a novel liquid crystal-based polarimeter setup for precise polarization measurements in helium-3 optical pumping experiments, including correction methods for systematic errors.

Findings

Successful measurement of circular polarization of dim discharge light.

Identification and correction of systematic errors in polarization measurement.

Potential for improved polarization diagnostics in helium-3 experiments.

Abstract

We detail the design and operation of a compact, discharge light polarimeter for metastability exchange optical pumping of 3He gas near 1 torr under a low magnetic field. The nuclear polarization of 3He can be discerned from its electron polarization, measured via the circular polarization of 668 nm discharge light from an RF excitation. This apparatus measures the circular polarization of this very dim discharge light using a nematic liquid crystal wave retarder (LCR) and a high-gain, transimpedance amplified Si photodiode. We outline corrections required in such a measurement, and discuss contributions to its systematic error.