The dependence of energy absorption buildup factors on energy and effective atomic number in plastic materials

A theoretical method is presented to determine the energy absorption gamma radiation buildup factors in various plastic materials in the energy range of 0.015 to 15.0 MeV, with penetration depths up to 40 mean free path (mfp). The dependence of energy absorption buildup factor on incident photon energy and the effective atomic number (zeff) has also been studied. In a practical situations, the sophisticated Monte Carlo computer techniques would be applied. However a feature of the presented theoretical method is its ability to make the consequences of the physics of the scattering process in plastic materials more apparent. In addition, it can be quickly employed to give a first hand buildup estimate prior to a more detailed computer analysis. (author)