Optimized design of stop-flow polarizer for hyperpolarized 129Xe MRI

Motivation: In the Spin Exchange Optical Pump (SEOP) technique, the spare space between pump cell and gas manifold, called dead space, might impact polarization through dilution and dark rubidium depolarization. Goal(s): This study aims to improve the design of the stop-flow polarizer to minimize dead gas and thus increase the polarization efficiency. Approach: A magnetic-compatible actuator was designed for automatic control of cell stem valves opening/closing in our homemade polarizer, with good adaptability of main pumping field, Class I laser regulation and mechanical deviation. Results: Results show that under the same temperature, the polarization levels with actuator were always better than the control group. Impact: The application of actuator in stop-flow polarizer shows the feasibility of improving polarization through minimizing dead space. It can be quite useful when acquiring small amount of HP gas but with higher requirement on polarization.