The Penetration of Gamma-Radiation through Thick Layers I. Plane Geometry, Klein-Nishina Scattering

A rough method is developed for estimating the intensity of gamma-rays which have passed through thick targets. Only Klein-Nishina scattering is considered. The treatment is exact both for those gamma-rays which are unscattered and those which are scattered once. The accuracy of the results for rays which are multiple scattered depends upon the fact that most of the scattering takes place in the forward direction with only small angles of deviation. Numerical calculations are made for energies of 2, 6, and 10m₀c² and all thicknesses of target. If A is the intensity of the initial beam, and I is the intensity after passing through a target of D mean-free-paths measured in terms of the initial unscattered gamma ray, it is found that: initialenergy,=2m₀c²,I/A,=(1+0.478D+0.030D²)e^-D, initialenergy,=6m₀c²,I/A,=(1+0.400D+0.0080D²)e^-D, initialenergy,=10m₀c²,I/A,=(1+0.33D+0.0040D²)e^-D.The contributions to the intensity are given for the gammarays which have been scattered a various number of times. Extensive tables are given which are generally useful for any problems in which only Klein-Nishina scattering is assumed.