Stopping powers of 200-3000 keV He-4 and 550-1750 keV H-1 ions in Vyns

Stopping powers for Vyns (vinylchloride-vinylacetate copolymer) were measured both for He-4 ions in the range 200-3000 keV and for H-1 ions in the range 550-1750 keV using the transmission technique. A detector model is used for the energy calibration to improve the accuracy of the stopping power curve for He-4 ions in the low energy region. The estimated uncertainty in the stopping power values is similar to 1.5% for He-4 ions and similar to 2% for H-1 ions. A comparison is made between a parametrization of the present data and several parametrizations of the stopping power found in the literature. The stopping power values closest to the present experimental data for He-4 ions are obtained by adding elemental stopping powers using Bragg's rule. For this the experimental values for the C1 stopping power reported earlier should be used. The charge state scaling, sometimes used to take account for phase-state effects, is not appropriate for Vyns. For H-1 ions, the parametrization closest to our data is that of Janni from 1982.