Build-up Factors for High Energy Gamma Rays Normally Incident on Slabs of Lead, Iron, Concrete and Water

Build-up factors and albedos for high energy gamma rays incident normally on slabs of finite thickness have been calculated by a Monte Carlo photon transport code incorporating a detailed bremsstrahlung model based on thick target bremsstrahlung yields and the continuous slowing down approximation for electrons. Build up factors and albedos are presented for photon source energies from 10 to 100 MeV and for slab thicknesses from 1 to 10 mean free paths. Total albedos are also reported for thick slabs