The Calculation of Proportional Counter Energy-Deposition Spectra from Experimental Data

Experimental energy-deposition frequency distributions, measured by means of a proportional counter, have been transformed to those of other pathlengths, under a compound Poisson process, and the results have been compared with the corresponding experimental spectra. The computational technique, in the form of a computer program, was written by Kellerer. The input distributions were produced by ∼45 MeV and 600 MeV protons passing through tissue-equivalent gas mixtures whose areal densities are on the order of$1\times 10^{-4}\ {\rm g}/{\rm cm}^{2}$. For transformations which produce calculated spectra whose mean energies lie sufficiently close to those of the input spectra (shift factors of ∼0.75), reliable predictions of experimental energy-deposition spectra can be made. Calculations of this type potentially could reduce considerably the experimental work which must be done to define distributions needed for the folding of such distributions into those corresponding to volumes of interest.