THEORETICAL-MODEL FOR RESPONSE CALCULATION OF ELECTRET IONIZATION CHAMBERS FOR RADON DOSIMETRY

The application of electret chambers for radon measurements requires t he exact determination of their response. Therefore, a theoretical mod el has been established in order to calculate the radon response for a ny electret ionisation chamber and to quantify the physical processes responsible for the decrease of response at lower electret voltages. M oreover, a deeper understanding of the processes inside the chamber is helpful for the discussion of possible uncertainties of measurements. The model is based on a numerical calculation of the electric field i nside the chamber and in the electret reader arrangement. It is shown that the main reasons for the decrease of the radon response with decr easing electret voltage are the growing recombination loss due to a lo wer field strength and the influence of changes in the electret surfac e charge distribution on the reader characteristics. The results of th e calculation are compared with experimental data.