Integral measurements of plural and multiple scattering of electrons with energies between 10 and 100 keV for 6 ≤ Z ≤ 83: I. Thin and intermediate-thickness targets

Abstract

Angle-integrated plural- and multiple-scattering distributions have been measured for electrons impinging with kinetic energies from 10 to 100 keV on targets with atomic numbers between those of C and Bi and mass thicknesses ranging from to 300 2. The thinnest targets, to 20 2, are not self-supporting and have been deposited on C backings with areal densities around 10 2. The intermediate-thickness ones are made of a single element and have mass thicknesses of to 300 2. The electrons scattered at frontal angles are collected with a Faraday cup covering the polar angles below 12.0°. In addition, to supplement this information, an aluminium ring spanning a polar angle interval of has been installed around the entrance of the Faraday cup and the charge deposited on it has also been recorded. The electrical current in the scattering chamber is measured as well so as to provide an accurate normalisation. Corrections for the fraction of impinging electrons backscattered by both the Faraday cup and the ring are applied to the data. The measurements are compared with the predictions of a Monte Carlo code that simulates each individual elastic collision. For targets made of a single element, the analytical Goudsmit–Saunderson and Lewis theories are tested as well. In all cases, the single-scattering angular differential cross sections, obtained by partial-wave solution of the Dirac equation in a self-consistent central potential, are taken from the ICRU Report 77. Good agreement is found within the uncertainties of the data. An analytical formula for the angular integration of the Goudsmit–Saunderson distribution is presented in an Appendix.