Development of an aerosol chamber for calibration of ²²⁰Rn progeny detectors

This paper describes an aerosol chamber system that can be used for calibrations and performance experiments of passive (220)Rn progeny detectors. For the purpose of this study, an aerosol generation system using carnauba wax as the aerosol material was mounted into the (220)Rn chamber. We used the chamber to measure characteristics of the equilibrium factor (F) of (220)Rn and unattached fraction (f(p)) of (220)Rn progeny, which are important parameters for dose estimation. The first experiment showed that continuous and stable generation of the unattached and aerosol-attached (220)Rn progeny concentrations was obtained. We observed that the spatial distributions in the chamber of the vertical profiles of the unattached and aerosol-attached (220)Rn progeny concentrations were homogeneous, as were the particle number concentration and count median diameter. The values of F and f(p) and their characteristics observed in this study were in the same range as the values reported from indoor measurements. We found that the characteristics of F and f(p) were dependent on the aerosol conditions (particle diameter and particle number concentration).