Development and deployment of a radioxenon injection system for use in underground transport experiments

As part of the Physics Experiment 1 (PE1) subsurface experiment series, a novel radioxenon injection system was developed to transfer radioactive xenon gas from a shipping cask to the experiment location through a sealed section of tunnel. The system consists of a combination of manual and pneumatic valves and is controlled and logged via a single board computer. The effectiveness of the injection system was demonstrated in the leadup to the PE1-A experiment in October 2023, where 55 GBq of 127 Xe was safely and successfully injected into the experiment chamber. This process involved a combination of manual and remote management of pressures and flow rates to minimize radiation exposure and ensure the integrity of the experiment. The results underscore the system's viability for future subsurface transport experiments to better understand radioxenon migration mechanisms following underground nuclear explosions. • Novel system for injection of high activities of radioxenon into an underground experiment • Reusable system allows for injection, quantification, and subsampling of high activity radioactive gas • Injection rates and system pressures controlled remotely and logged for later processing • System efficacy demonstrated in a 55 GBq injection of 127 Xe into the PE1-A experiment