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 d etector 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 obse rvable etched track. This angle also depends on the etching and on the conditions of observation of the detector. It is necessary to known t he variation of that critical angle with incident alpha particle energ y for given etching and observation conditions in order to determine t he theoritical detection efficiency of a radon detector. This variatio n was studied for a CR39 detector (Tastrack, G.B.) over the energy ran ge of the alpha particles emitted by radon (5,5 MeV) and its two short -life daughters: Po218 (6 MeV) and Po214 (7,7 MeV).