Application of the EGS4 Monte Carlo Code to a Study of Multilayer Gamma-Ray Exposure Buildup Factors of up to 40 mfp

Abstract

Multilayer γ-ray exposure buildup factors of up to 40 mfp were calculated using an electron-photon cascade Monte Carlo code, EGS4, as a point isotropic source. A kind of splitting technique was used in the EGS4 calculations in order to obtain reasonable results at very deep penetration problems, such as 40 mfp.The double-layer γ-ray exposure buildup factors were calculated for combinations of water, iron and lead for 0.1, 0.3, 0.6, 1.0, 3.0, 6.0 and 10MeV γ-rays. The thickness of the first medium was set to 1, 5, 10 or 20 mfp. As typical triple-layered shields, the calculations were performed for 4 different configurations of water, iron and lead.The behavior of multilayer buildup factors for deep penetration problems was studied using the obtained results. Buildup factors after the bounday show the tendency to vary largely depending on the material combination and the source energy of γ-rays.