Dose computation applications of the electron loss model

Abstract

A generalisation of the Fermi-Eyges small angle multiple scattering model for electron penetration in dense media, called the electron loss model, is presented. This generalisation allows electron loss from the penetrating beam with depth, z, in the scattering medium. The probability of loss is assumed to be proportional to the square of the angle of scatter of the electron from its incident direction. The transport equation formulated has exact solutions under Gaussian and pencil beam initial conditions. These solutions have Gaussian features for both the angular and spatial distribution of electrons at a given depth in the scattering medium and also contain a multiplicative factor which describes the fraction of the initial number of electrons remaining in the beam at depth. A constant of proportionality between the 'loss' parameter, tau (z), and the linear scattering power, k(z), is postulated for the absorbing medium.