The Backscattering of Positrons and Electrons

Beta-rays from a point source, backscattered by materials of various atomic numbers $Z$ have been collected over a $2\pi$ solid angle and also over narrow solid angles at various obliquities. In all cases electrons are backscattered to a greater extent than positrons. The number and energy spectrum of the backscattered beta-rays depend strongly on the direction of emergence and on $Z$. In spite of the use of hetero-energetic sources, the results can be interpreted qualitatively on the basis of multiple scattering, in terms of a "sidescattered" and a "diffused" component.