Ultra-sensitive radon assay for low background liquid xenon detectors

Radon contamination is a significant challenge for rare event searches such as neutrinoless double beta decay (0νββ) and Weakly Interacting Massive Particle (WIMP) detection. These experiments employ highly sensitive radon assay techniques to identify and select low-emission materials to meet background requirements. This work presents the development of ultra-sensitive electrostatic chamber (ESC) instruments designed to measure the radon emanation of materials in a recirculating gas loop. In contrast to traditional methods that separate emanation and detection steps, these systems allow continuous radon transport and detection due to a custom-built recirculation pump. These devices are powerful tools for screening materials in the development of low-background liquid xenon detectors, enabling statistically-limited minimal detectable activities of 20 μBq.