A mathematical model of photon scattering in matter for problems of calculation and optimization of radiation shielding in X-ray inspection systems

This article describes the mathematical apparatus of original software that was developed by the authors for calculations of the radiation shielding and the fields of bremsstrahlung and scattered radiation of linear electron accelerators, which is adapted to a wide range of applications. The proposed program is based on the Monte Carlo method; this allows one to carry out a statistical calculation of the bremsstrahlung photon flux and to choose the trajectories of bremsstrahlung photons using a random number generator. The program is intended for the design of beam collimation systems, the calculation of complex radiation shielding profiles with labyrinths and tunnels, the optimization of the size of shielding barriers, assessment of the expected detection system response, and the prediction of the dose distribution in a cross section of a protected object. For verification of the reliability of calculations that are carried out by using this original software, the results of numerical experiments with the proposed code were compared to the results that were obtained using the Monte Carlo code MCNP version 4C3 for backscattered photons and forward transmitted bremsstrahlung photons with a boundary energy of 24 MeV for a number of materials and various thicknesses.