Analysis of energy distribution by depth dose curves and its application to the dosimetry of fast electrons

The spectral distribution of electrons at any depth in a phantom is of great interest in dosimetry. A method for analysing the spectral distribution has been developed. The energy analysis is made by separating the measured depth dose curve into depth dose curves of monoenergetic electrons. For each monoenergetic beam the energy and the relative yield are determined. As an example, the method is applied to analyse the scatter effect of the applicator on the energy distribution of an electron beam. The energy distribution is found to be a function of the position inside the applicator and of the applicator size. The results of the energy analysis are compared with other well known methods of energy determination. The mean energy derived from the energy analysis is much less than the most probable energy derived from the practical range and much less than the mean energy derived from the 50% range. The application of this method of energy analysis to electron dosimetry is discussed. (author). 16 refs, 7 figs