Calculated yields and slowing-down spectra for electrons in liquid water: implications for electron and photon RBE

Abstract

Detailed Monte Carlo calculations have been carried out of slowing-down spectra and yields for a number of end-points for electrons in liquid water. These investigations were made to study the differences in physical effects of different low-LET radiations and implications for RBE. Initial electron energies from 1 keV to 1 MeV were used, and all secondary electrons were following in the computations until their energies fell below 10 eV. Though there are substantial differences in the slowing-down spectra at energies near and above the K-shell ionisation potential of oxygen, the energy spectrum of electrons at lower energies is found to be essentially independent of the initial energy of the primary electron. The number of events per unit energy deposited is also essentially independent of the primary electron energy.