Compact 3He gas polarizers based on metastability-exchange optical pumping.

Abstract

We describe the design, construction, and operation of polarizers able to deliver 3He gas with high nuclear polarization to external volumes in a very flexible way. They combine metastability-exchange optical pumping, the only method that can rapidly polarize 3He nuclei (at pressures in the millibar range) and peristaltic compression, which is used to transfer optically polarized gas to storage volumes or experimental cells. Two experimental polarizing systems are described: a minimal compact portable system and a larger laboratory system fully equipped for gas polarization measurements. Models combining gas flow, diffusion, and nuclear relaxation are derived to evaluate the combined effects of the key processes potentially limiting the performance of generic polarizing systems. They are used to discuss several design parameters of our polarizers and to interpret our experimental observations. Key results obtained with our systems for different applications are reported. Typical 3He gas polarization values M = 0.4-0.6 following initial compression to more than 600 mbar with flow rates up to 5 standard cubic centimeters per minute are demonstrated.