Transmission of Gamma Rays Through Large Thickness of Heavy Materials

The purpose of the present investigation has been a study of the feasibility of straightforward numerical determinations of the transmission of gamma rays through large thicknesses of materials containing heavy elements. The limitation of the discussion to heavy elements makes possible some simplifications essentially because of the large probability of absorption by the photoelectric effect of photons which are degraded to low energy. The present approach to the gamma ray transmission problem is based on the notion that one need consider only those transmitted gamma rays which have suffered relatively few scatterings even for thicknesses of materials of approximately 20 mean free paths. The validity of this view is demonstrated by the results which are presented in the following sections. Specific calculations have been made of the attenuation of gamna rays with incident energy 10 mc2 through thicknesses of uranium up to 20cm. These calculations are adjusted to give the attenuation through thicknesses of lead up to 35 em.