The effects of including linear polarization and Doppler broadening of the Compton-scattered photon energy, i.e., the Compton profile, in a calculation of the exposure buildup factors for plane normal gamma-ray sources are investigated by using an improved electron gamma shower Monte Carlo code, EGS4, for water, iron, and lead in the 40- to 250-keV range for penetration depths of up to 16 mean free paths (mfp). The effects of including the bound Compton total cross section (&sigmabC) and the bound Compton-scattered photon angular distribution by using the incoherent-scattering function [S(x, Z)] were also evaluated. The “pseudo” exposure buildup factors were calculated to determine these effects combined with the effects of Rayleigh and/or Compton scattering. The pseudo exposure buildup factor increases at points farther than a few mfp’s and decreases in the neighborhood of the source upon including linear polarization. It decreases upon including Doppler broadening. The degree of each effect varies with the atomic number of the material. The effect of linear polarization is large for materials of small atomic number; that of the Doppler broadening is large for materials of medium and large atomic number.
