Investigations of multiple backscattering and albedos of 1.12 MeV gamma photons in elements and alloys

The energy and intensity distributions of multiple backscattering of 1.12 MeV gamma photons emerging from targets of elements and alloys are observed as a function of thickness and atomic number (Z) of the target. The numbers of these multiply backscattered events show an increase with increase in target thickness, and then saturate for a particular thickness of the target called saturation thickness (depth). The saturation thickness decreases with increasing atomic number and varies as e−Z. The multiple backscattering, an interfering background noise in Compton profile, has been successfully used to assign the ‘‘effective atomic number’’ to alloys. Monte Carlo calculations also support the present experimental results. The number, energy and dose albedos are also found to be saturating for the same thickness where the numbers of multiply backscattered events saturate.