The Specific Primary Ionization and Energy Loss of Fast Electrons in Matter

Abstract

By utilizing the dependence of the efficiency of a Geiger-Mueller counter upon the primary ionization of a counted particle, the primary ionization by electrons in hydrogen has been determined for energies in the range 0.2 Mev to 9.0 Mev. The relative stopping powers of carbon and ${\mathrm{H}}_2$O have also been investigated, the results yielding evidence for the existence of a polarization effect which reduces the energy loss of fast particles in condensed matter. Experimental results are compared with those of the Bethe-Bloch theory and the Halpern-Hall theory which takes into account the polarization properties of the medium.