Variation of alpha-particle track diameter in CR-39 as a function of residual energy and etching conditions

摘要

It has often been proposed that track diameter in etched detectors can be used for energy spectrometry. To test this proposition, the relationship between track diameter and energy of alpha particles, in the range 0.1-5.5 MeV, incident on CR-39 was studied. Two sets of detectors were irradiated by a collimated normally-incident beam of alpha-particles of different energies, using an Am-241 source. Different foils of the first set were etched for variable lengths of time in such a way that, in each case, the etchant reached the end of the latent track. Foils in the second set were etched for a fixed "short" time of 2 h, for all alpha-energies. The linear rate of energy loss as well as the residual range of alpha-particles was determined by using Henke and Benton's computer program. It is found that, for "short" etching times, the track diameter mimics the "Bragg curve", i.e., at first it rises with falling energy, and then declines, after the peak, at lower energies. If, however, the track is always etched to the end of the alpha-range, it is seen that the larger the alpha-energy the larger is the diameter. In other words, in all cases the integrated area under the Bragg curve, covering the etched portion, is a good indicator of the alpha-track diameter. (C) 1999 Elsevier Science Ltd. All rights reserved. [References: 6]