Angular distribution of electrons behind barriers comparable to the extrapolated range

Abstract

A study is reported of the angular distribution of monoenergetic electrons from a betatron which have traversed barriers of Al, Cu, and Pb with thicknesses reaching the extrapolated range. The initial electron energy is in the range 3–8 MeV. The experimental results agree well with Monte Carlo calculations carried out for identical calculations and with the results of earlier work for smaller barriers. The half-width of the electron angular distribution, increasing with increasing barrier thickness, reaches a nearly constant value, while the distribution itself corresponds to the laws of complete diffusion, i. e., converts into a distribution similar to cos²Θ. As the thickness of the absorbers is increased further, the half-width decreases and the distribution becomes narrower, due to the penetration far into the absorbers of electrons which have been scattered predominantly in the forward direction.