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Cylindrical diffusion chamber with solid state nuclear track detector placed at the bottom of the chamber is frequently used device for measuring radon concentration in dwellings. In this work, the diffusion chamber with CR-39 detector was modeled to determine track distribution on the lateral (cylinder) wall of the chamber and compare track density between cylinder wall and bottom. Model is based on the diffusion, deposition and decay of radon and its progeny in diffusion chamber. Equations for criteria of track visibility and track density were derived. Along with theoretical model, measurements were performed to verify the theoretical results. Three different chambers with CR-39 detectors slabs attached along the cylinder wall were investigated. It was found that alpha track density on cylinder wall is not uniform and depends on the shape and size of the chamber. Deviation of track density along cylinder wall was up to 30% for chambers used in this work. Sensitivity of the cylinder wall was found to be almost the same as the sensitivity of the bottom. In comparison with the experiment, theoretical results give good predictions. Along with previous results of the authors where bottom track density was modeled, presented model can be used for calibration and optimization of the diffusion chambers used for radon measurements. • Distribution of alpha particle tracks on lateral wall of diffusion chamber is theoretically modeled and experimentally measured. • Track density distribution exhibits complex dependence on chamber dimensions and is not uniform. • Detector response functions and critical angle are verified. • Theoretical model for calibration of cylinder diffusion chamber is developed. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate spatial distribution of alpha particle tracks produced by radon and its progeny in radon diffusion chambers. Three cylindrical chambers equipped with CR-39 detectors were used in the experiment. Radon concentration was estimated using RAD7 device. Distribution of alpha particle tracks on detector surface was found to be nonuniform; track density close to the chamber walls was up to 30% lower than in the centre. The results were compared with the predictions of analytical method applied to the same chamber dimensions. Critical angle of detection was expressed in relation to particle incident energy, using TRACK_VISION computer software. It was shown that the shape of track density distribution highly depends on the chamber size, as well as on the critical angle of particle detection. Sources of track density variation were investigated by analyzing partial contributions from volumetric and deposited fractions of radon and its progeny. Side-wall contribution increases while volumetric and plateout contributions decrease with increasing radial distance from detector centre. Changing chamber dimensions affects the relative influences of these partial contributions, resulting in different distributions of visible tracks on detector surface. Experimental results were compared to the values obtained using previously developed software based on Monte Carlo method. Five different expressions of detector response function (V) were applied in the study; two of them significantly underestimated the experimental results. • Distribution of alpha particle tracks on detector surface is not uniform. • Track density distribution exhibits complex dependence on chamber dimensions. • Partial contributions from volumetric and deposited fractions were analysed. • Critical detection angle was expressed in relation to particle incident energy. [ABSTRACT FROM AUTHOR]