Abstract

Photon buildup factors for soft tissue, water, and dosimetric materials have been computed in the energy range of 0.2 to 2 MeV using geometric progression (GP) fitting approximation. The results for soft tissue and water have been compared with the values obtained through Monte Carlo code MCNP4C. Data obtained from GP fitting method quite well obey a semi empirical relation which is a function of penetration depth, Compton scattering and energy absorption cross section. With the help of this semi-empirical approximation, buildup factors for gamma and X-rays in soft tissue, water, and dosimetric materials consisting of elements Hydrogen (H), Carbon (C), Nitrogen (N) and Oxygen (O), can be easily estimated in the energy range of 0.2 to 2 MeV up to penetration depths of 10 mfp.   

Key words: Buildup factor, geometric progression (GP) fitting method, Monte Carlo method, radiation shielding.