Recent progress on a radon detector with electrostatic collection

In the field of particle physics, various experiments have been designed in order to search for rare physics processes beyond the standard model. The radioactive noble gas radon is one of the major background sources below the MeV region in rare-event search experiments. To precisely monitor the radon concentration in purified gases, radon detectors with electrostatic collection are widely used. To extend the application of the Rn detector, we have constructed a calibration system in the Kamioka underground laboratory and evaluated the detector performance by filling the Rn detector with various gases, such as purified air, argon, xenon, and tetrafluoromethane. In these proceedings, we overview the recent progress of the Rn detector development, its performance with various gases, and a Rn removal test using activated carbon fibers.