Sensitivity of LR115 detector in diffusion chamber to 222Rn in the presence of 220Rn

Determination has been made of the sensitivity of LR115 type 2-track detectors (in units of m) to 222Rn, measured in the presence of 220Rn. Measurements have been made by means of a widely used diffusion chamber while Monte Carlo simulations have also been conducted. The experimentally derived sensitivities for 222Rn and 220Rn were found to be 0.470±0.022 and 0.486±0.042 m, respectively. For Monte Carlo simulations, the sensitivities to 222Rn gas were found to range from 0.618×10–2 m (assuming that all 218Po progeny decay before deposition onto the internal walls of the diffusion chamber) to 0.405×10–2 m (assuming that all 218Po progeny are deposited on the internal walls of the same containment vessel before decaying). The sensitivity to 220Rn gas of 0.465×10–2 m found from Monte Carlo simulations agrees to within uncertainty with experimental findings. The experimentally derived sensitivity value for 222Rn indicates that 30% of the 218Po progeny decay before deposition onto the internal walls of the diffusion chamber.