A Comparison of Gamma-Ray Buildup Factors for Low-ZMaterial and for Low Energies Using Discrete Ordinates and Point Monte Carlo Methods

Abstract

This paper discusses the calculation of exposure and absorbed dose buildup factors for a photon point source in infinite beryllium in the low-energy range of 0.03 to 0.3 MeV, for penetration depth up to 40 mfp, using two discrete ordinates codes, PALLAS-PL, SP-Br, and ANISN. Comparisons of both result to values obtained by point Monte Carlo calculations using the electron gamma shower version 4 code show reasonable agreement for two types of sources: normally incident and point isotropic sources. The fitting parameters of a geometric-progression method formula are determined for the resulting buildup factor data. These fitting parameters are in good agreement with the basic data within 5% over a great variation in magnitude.