Monte Carlo simulation of electron beam transport in graphite for composite application from MeV down to eV

摘要

A Monte Carlo method. based on the treatment of the individual interactions and using the null collision technique to reduce the computation time, has been developed for the simulation of electron-matter interactions and validated for the case of graphite. Results describing the electron energy behaviour (energy deposition, energy distribution, electron density, etc) have been obtained for various initial energies (1 MeV, 500 keV, 100 keV, 10 keV and 1.6 keV) of the electron beam down to several lower limit or cutoff energies (100 keV, 25 keV, 5 keV and 10 eV). The specificity of the present simulation is, therefore, to cover quite a wide energy range (e.g. from 1 MeV down to 10 eV) during the electron transport in graphite. The electron-matter collision cross sections needed for the Simulation over such an energy range (from 10 eV up to 1 MeV) are given. At higher energies, the elastic and inner-shell inelastic collision cross sections take into account the relativistic effects, and the photons resulting from the bremsstrahlung processes are considered as electron sources when they undergo Compton and photoelectric processes. At intermediate and low energy ranges, the inelastic collision cross sections for the conduction band excitations are obtained from a classical dielectric function model. The significant effect of the lowering of the cutoff energy on the deposited energy is emphasized, while the contribution to the deposited energy of the photon interactions is shown to be quite low in the case of the present initial beam energies.