Values of Bethe-Bloch stopping power parameters for Vyns (vinylchloride-vinylacetate copolymer) extracted from stopping power measurements with 0.55-1.75 MeV protons and 1.03-3.22 MeV alpha particles

Recent transmission-type measurements of the stopping powers of Vyns (a vinylchloride-vinylacetate copolymer) for 0.55-1.75 MeV protons and 1.03-3.22 MeV alpha particles have been analyzed in terms of modified Bethe-Bloch stopping power theory in order to extract values of the parameters known as the mean excitation energy (I) and Barkas-effect parameter (b). The weighted average value of I thus established, 110.8 eV, exceeds the prediction based on linear additivity by some 3%, and the weighted average of b, 1.54, agrees very well with expectations. The results of this analysis are compared with those from a previous similar study of another material having essentially the same average atomic number and atomic weight but quite different atomic composition, called Kapton. (C) 1999 Elsevier Science B.V. All rights reserved.