Simulation of irradiation uniformity for polyethylene and polypropylene in various high energy fields

When material samples are subjected to an irradiation field, the radiation energy may distribute unevenly at different depths, which greatly influences the irradiation induced modification. In this study, a novel method to improve the radiation uniformity is proposed. The dose distribution inside polyethylene and polypropylene in γ-ray and electron beam irradiation fields are simulated using the software GEANT4 by Monte Carlo method. Based on the simulation results, it is found that the addition of auxiliary aluminum layer after the sample can improve the radiation uniformity under γ-ray irradiation because of the contribution of the secondary electrons emitted from the aluminum layer. Furthermore, the uniformity of energy deposition using electron beams is better when the beam energy is higher. The energy deposition distributions inside the samples are simulated, and the most uniform ranges where the deviations are less than 2%, 3%, and 5% for polyethylene and polypropylene are suggested. This work may serve as a reference of irradiation uniformity for certain materials.