Photon-produced electron fluence calculated with photoelectron angular distribution of Sauter expression

Sauter expression is often used for photoelectron angular distribution in photon/electron transport codes. The expression is known to show too forward peak for high-Z materials. Monte-Carlo simulations of electron transmission and reflection to 662-keV photons for lead revealed that Sauter expression overestimated electron transmission and underestimate electron reflection. The effect was due to the photoelectrons produced directly from the source photons and those from the scattered photons; the influence of the latter increased with lead thickness.