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AbstractThe empirical formula of gamma-ray buildup factors by a geometric-progression (G-P) method was modified by presenting the K parameter as a function of the penetrating distance from the source. The values of the parameters are given for the modified G-P method fitted to the exposure and absorbed dose buildup factor data for air, water, concrete, and iron calculated by a moments method code. The results from the present method are in good agreement with the basic data, for the 0.015- to 15-MeV energy range and for the 0.5- to 40-mfp distance range.The five parameters used in the formula for the modified G-P method change smoothly with the source energy. Therefore, the buildup factor for any arbitrary energy can easily be estimated by the interpolation of the parameters with respect to the energy. Moreover, this formula fits the buildup factor for lead, including bremsstrahlung, calculated by the discrete ordinates code PALLAS.
Yoshiko Harima (Tue,) studied this question.