Radon progeny distributions inside a diffusion chamber and their contributions to track density in SSNT detectors

Diffusion of alpha emitter radon progeny inside a cylindrical diffusion chamber was simulated. In the simulation of atomic movements, we took into account the random nature of the diffusion direction and the decay process. The alpha emitter distributions in volume, lateral wall and top cover of a 6.0 cm height diffusion chamber for different diameters were determined. Results show non-uniform distribution of radon progeny. As chamber diameter increases, the tendency of radon progeny is to accumulate in central regions of the chamber volume (218Po) and inner wall (218Po and 214Po). Depending on chamber diameter and detector size, non-uniform distribution of radon progeny deposited on SSNTs surface can be achieved if the detector is horizontally located at the bottom. The fraction of surface where 222Rn progeny are deposited diminishes as chamber diameter increases. Due to the relatively short 218Po half-life, for diameters larger than the assumed height its subsequent atoms decay in air before their deposition on chamber wall. The form in which radon progeny is distributed in volume and walls of chamber can affect the quantity and distribution of tracks in detector.