Abstract
Total ionisation produced by 42 MeV oxygen ions when stopped in nitrogen, carbon dioxide, methane and propane, and methane-based tissue-equivalent (TE) gases was measured using a variable pressure ionisation chamber. From these measurements average energy required to form an ion pair (W) for oxygen ions in the above gases was determined. Ionisation produced by oxygen ions in traversing a given path length in the chamber filled with various gases was also measured and used to determine the stopping power (Linfinity ). W and Linfinity for methane-based TE gas was calculated by adding the contributions from constituent gases. Calculated values of Linfinity obtained (a) using the proton stopping power data of Janni (1966) and Andersen and Ziegler (1977) and (b) using Northcliff and Schilling tables (1970) were compared with measured values for various gases. Calculated values were higher than those measured except for nitrogen based on Andersen and Ziegler (1977) data. W-values determined in the present study for oxygen ions in nitrogen and methane-based TE gas were consistent with published values.
Published Version
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