Development of the ultra-high sensitivity radon monitor based on electrostatic collection method

Abstract The radioactive decay of radon (Rn-222) and its progenies are significant background sources in an extremely low background environment, interfering with investigation like detecting dark matter and observing neutrinos. In this paper, a 1000 L ultra-high sensitivity radon monitor for China Jinping Underground Laboratory (CJPL) based on electrostatic collection and Au-Si surface barrier detector was developed. The monitor is capable of distinguishing Rn-220 from the energy spectrum and effectively eliminating any interference caused by Rn-220. At an absolute air humidity of 0.02 g/m3, the scale factor of the monitor is: 17.35 ± 0.88 (counts/day)/(mBq/m3). Moreover, it achieves a remarkable lower limit of detection of 0.17 mBq/m3 in a single-day measurement. These findings demonstrate the suitability of the ultra-high sensitivity radon monitor for diverse scenarios demanding stringent background requirements.