VARIATION OF THE CRITICAL REGISTRATION ANGLE OF ALPHA-PARTICLES IN CR-39 - IMPLICATIONS FOR RADON DOSIMETRY

This paper describes a methodology to characterize the response of a detector to alpha particles of different incidences and energies using an experimental irradiation system and an etching model. Implications for radon dosimetry are discussed. For each incident energy there is a particular angle above which alpha particles no longer induce an observable etched track. This angle also depends on the etching and on the conditions of observation of the detector. It is necessary to known the variation of that critical angle with incident alpha particle energy for given etching and observation conditions in order to determine the theoritical detection efficiency of a radon detector. This variation was studied for a CR39 detector (Tastrack, G.B.) over the energy range of the alpha particles emitted by radon (5,5 MeV) and its two short-life daughters: Po218 (6 MeV) and Po214 (7,7 MeV).