Radon monitoring using long-range alpha detector-based technology

Long-range alpha detector (LRAD) technology is being studied for monitoring radon gas concentrations. LRAD-based instruments collect and measure the ionization produced in air by alpha decays. These ions can be moved to a collection grid via electrostatic attraction or air currents. LRAD-based instruments using an electrostatic ion-transport design collected approximately 95% of the radon produced ions, while instruments using an airflow transport design collected from 44% to 77% of these ions, depending on detector geometry. The current produced by collecting this ionization is linear with respect to ²²²Rn concentration over the available test range of 0.07 to 820 pCi/L. In the absence of statistical limitations due to low radon concentrations, the speed of response of LRAD-based instruments is determined by the air exchange rate, and therefore changes in radon concentration can be detected in just a few seconds. Recent tests show that at radon concentrations below 20 pCi/L current pulses produced by individual alpha decays can be counted, thus improving detector sensitivity and stability even further. Because these detectors are simple, rugged, and do not consume much power, they are natural candidates for portable, battery operation