Bremsstrahlung and Electron Scattering Cross Sections in Au for 247-Mev Electrons and Positrons

Abstract

The absolute cross sections for gold for the top 40 percent of the bremsstrahlung spectrum have been measured for electrons and positrons of 247-Mev mean energy. A magnetic could chamber containing two Au foils was used. The foils were positioned to intercept an electron or alternately a positron beam provided by a magnetic field analysis of the electron-positron pair members produced in a Pb foil situated in the x-ray beam of the 300-Mev betatron. With the possible exception of the top 2 percent of the spectrum, electron and positron bremsstrahlung were the same. For quantum energies in the interval 0.604 to 0.927 of maximum, the Bethe-Heitler spectrum is 8.7\ifmmode\pm\else\textpm\fi{}2.3 percent above the experimental spectrum. In the same interval the Maximon-Bethe-Davies theory agrees with experiment. Scattering by electrons was also observed as a function of energy of the struck or lowest energy electron. For these particles having energies between 20 and 130 Mev, the scattering cross section ratios of experiment to theory are 0.96\ifmmode\pm\else\textpm\fi{}0.06 and 1.06\ifmmode\pm\else\textpm\fi{}0.08 for incident electrons and positrons, respectively. The cross section ratio of electrons to positrons in the same energy interval is 1.31\ifmmode\pm\else\textpm\fi{}0.13 for experiment and 1.46 for theory. All errors are probable errors.