Monte Carlo Analysis of Gamma Scattering in Silicon and Germanium

Calculations have been made of the number and energy spectrum of primary electrons generated in silicon and germanium volumes by incident gamma photons of energy 300 kcV to 3 Mev. Direct calculations were used for small silicon samples, and Monte Carlo methods for larger germanium samples where multiple gamma scattering wqas significant. Primary electron populations generated within silicon by the same exposure dose from cesium-137, cobalt-60, sodium-24 and fission gamma sources are compared. The simulation of primary electron spectra generated within the sample, rather than the incident gamma spectrum is considered as an applied radiation effects technique. The multiple scattering calculations show that as sample volume increases, the density of ionization increases for a fixed gamma exposure, and that the flux of electrons with sufficient energy to cause displacements decreases for a fixed absorbed gamma energy dose.