Computation of the Critical Angle of Track Registration in Alpha-Irradiated CR-39 Detectors on the Basis of Time-Dependent Track Etch Rates

Abstract

The formation of etched tracks by alpha particles has to be characterised quantitatively in order to compute the response of CR-39 detectors for radon or neutron dosimetry. Whether a primary or secondary alpha particle produces a visible etched track depends on its angle of incidence with respect to the critical angle of track registration. The latter quantity can be calculated from the bulk etch rate and the track etch rate varying along the alpha particle trajectory. Consequently, the critical angle depends on the initial alpha energy and the etching time. This relationship was determined taking into account several effects resulting in restrictions on the track development, such as etching delay at large angles of incidence or overetching of tracks within the given etching period.