Performance of a radon sensor based on a BJT detector on high-resistivity silicon

An autonomous Radon sensor with wireless connectivity has been developed, using a BJT detector on high-resistivity silicon as alpha-particle detector. Charged Radon daughters are collected on the detector surface electrostatically. Thanks to the BJT internal amplification, real-time alpha particle detection is made possible using a very simple readout electronics which records alpha-particle arrival time and charge. Functional tests at known Radon concentrations demonstrated a sensitivity up to 4.9 cph/(100 Bq/m³), which translates into the capability of detecting a Radon concentration of 200±20 Bq/m³ and 500±50 Bq/m³ after 10 and 4 h, respectively. The count rate at nominally-zero Radon concentration was 0.05 cph.