Radon Registration with an Electret Diffusion Chamber

A passive detector for the measurement of environmental radon activity concentration is presented. It consists of a diffusion chamber containing an integrating solid state nuclear track detector. Opposite to the detector foil a negatively charged electret is positioned. The radon gas enters the chamber volume by diffusion through a filter which retains radon daughters. The positively charged decay products inside the chamber are collected on the electret surface and thus plateout on the inside of the chamber wall is reduced. The a active decay products on the electret surface irradiate the track detector in a defined manner and thus increase the track density for a given time. The sensitivity of the diffusion chamber for radon registration is thus enhanced by a factor of 3. Using such a chamber the exposure time for environmental radon monitoring can essentially be reduced.