Electron Flux Spectra in Aluminum; Analysis for LET Spectra and Excitation and Ionization Yields

Abstract

Measurements were made of the electron flux generated in effectively infinite aluminum media by uniformly distributed sources of198 Au and ${}^{64}{\rm Cu}$ . Above 100 keV the shapes of the flux spectra are determined by the integral primary beta spectrum. Between 100 keV and 5 keV the flux is constant. Between 5 keV and 100 eV the flux rises as 1/E, and below 100 eV it rises as about $1/E^{3}$ . On an absolute basis the experiment is in agreement with the Spencer-Fano theory above 10 keV but exceeds the theory by as much as a factor of 4 at 400 eV. The results were analyzed to obtain LET spectra as well as K-shell and L-shell ionization, volume plasmon excitation, and electron-electron interaction yields. The conclusions drawn from the analysis were that electrons with energies less than 55 eV contribute as much to the flux in LET space as do electrons with energies greater than 55 eV, that electrons are nearly mono-LET particles, and that volume plasmon excitatio...