Gamma ray attenuation measurements

The good resolution of a Ge(Li) detector was used to measure gamma ray attenuation coefficients in narrow beam geometry. The effect of multiple scattering on the pulse height distribution of the transmitted gamma rays and on the measured attenuation coefficients was studied and shown to be small up to three mean free paths. Values of attenuation coefficients were determined in the case of lead for 0.662 MeV, 1.116 MeV, 1.17 MeV and 1.33 MeV gamma rays, and in the case of tantalum and molybdenum for 0.662 MeV and 1.116 MeV gamma rays. The experimental values are in fair agreement with the calculated ones. (Auth.)