Fluid and Thermal Dynamical Analysis of Three-Dimensional Spin-Exchange Optical Pumping Cells

TL;DR

This paper uses finite-element analysis to study fluid, thermal, and alkali diffusion dynamics in optical pumping cells, revealing effects like laser run-away and depolarization risks related to temperature and alkali distribution.

Contribution

First simulation of laser run-away effects and detailed analysis of alkali and thermal dynamics in optical pumping cells.

Findings

High-temperature outlet gases cause depolarization.

Alkali density distribution depends on cell geometry.

Laser run-away can be predicted by the model.

Abstract

We present a finite-element analysis of the fluid dynamics, thermal dynamics, and alkali diffusion in a common cell geometry used for spin-exchange optical pumping of $^{129}$Xe using a flow-through polarizer design. The analysis is the first to simulate aspects of the laser run-away effect observed in some optical pumping cells. The analysis further suggests that high-temperature gas in the outlet tube may give rise to rapid depolarization due to high concentrations of alkali vapor. Finally, the analysis indicates that the alkali number density distribution and the specifics of the dynamics are highly dependent upon the the distribution of the alkali metal in the optical pumping portion and outlet tube of the cell.