Calculation of Ionization Frequency Distributions in Small Sites

Ionization frequency distributions for 1- to 4-MeV protons have been calculated using Monte Carlo techniques for an absorber site having an effective diameter of 250 nm (unit density materials) and results compared with experiment. For proton tracks passing through the absorber site, the calculated frequency distributions, mean ionization, and relative variance agree very well with experiment. The results suggest that the Monte Carlo method, employing sophisticated source terms, can be used effectively to calculate ionization and energy deposition in sites too small for experimental techniques.