Electret ion chamber parametric studies for high sensitivity radon monitoring

Abstract

An electret ion chamber (EIC) is a passive integrated ion chamber that has been widely used for indoor and outdoor radon monitoring. The EIC consists of a thin layer of charged Polytetrafluoroethylene (PTFE) electret film inside an electrically conductive chamber. The PTFE electret film provides a quasi-permanent electric field capable of collecting ions and acts as a quantitative sensor. Radon gas diffuses into the EIC through the embedded filtered areas, and alpha particles emitted from radon and its decay products ionize the air inside the chamber. The collection of ions via an electret film of opposite signs results in a surface potential reduction proportional to the radon exposure, exposure duration, and EIC sensitivity. To accommodate the differing requirements for radon monitoring, EICs of different volumes (210, 500, and 1000 cm³) have been designed, constructed and studied by employing PTFE electret films of varying thicknesses. The sensitivity of EICs was found to be dependent on the EIC volume, thickness, area, and polarity of PTFE electret film. So, by considering such parameters, EICs can be developed to meet the sensitivity requirements for short-, mid-, and long-term indoor and outdoor radon monitoring applications.