Energy Loss and Straggling of 150-Mev Electrons in Li, Be, C, and Al

Abstract

The most probable energy loss and the straggling distribution for 150-Mev electrons in thin targets (\ensuremath{\sim}2.5 g/${\mathrm{cm}}^{2}$) of Li, Be, C, and Al have been measured utilizing the electron beam of the Stanford Mark III linear electron accelerator. The primary beam energy spectrum had a full width at half-height of 0.20 Mev. The data for the most probable energy loss agree with the theory of Landau when corrected for the density effect according to Sternheimer. A recent recalculation of this density effect on the basis of new values for the mean excitation potentials after Caldwell noticeably improves agreement between theory and experiment for carbon. Comparison is made with previous calculations using Bakker and Segr\`e potentials. The half-widths of the straggling distributions are between 7 and 15% wider than the Landau theory predicts, in qualitative agreement with a recent comment by Hines.