Effect of elastic collisions on energy deposition by electrons in water

Monte Carlo simulation methods have been used to evaluate the effects of elastic collisions on the transport of 0.1, 1, 10, and 100 keV energy electrons in water. The simulations show that transport-related phenomena in the direction axial (parallel) to the initial direction of travel are more dependent on elastic processes than those in the radial (perpendicular) direction. A decrease in the total elastic cross section to 10% of its gas phase value increases the mean axial penetration depths and the maximum of the axial energy deposition gradients by as much as a factor of 2. The most pronounced effects are observed for electrons of 100 eV energy where even the mean radial penetrations are doubled. Except for these low energies, the mean radial penetrations and the radial energy deposition gradients are relatively unaffected by elastic processes, implying that these parameters are mainly determined by inelastic collisions.