Calculation of the Water to Graphite Perturbation Factor Ratios for the NACP Type02 Ionisation Chamber Using Monte Carlo Techniques

摘要

Calculations have been made of the water to graphite perturbation factor for theNACP type 02 ionization chamber at energies of 4, 8, 12, and 19 MeV. Within the uncertainties of the calculation, the ratio of the perturbation due to the cavity effect was found to be unity at all energies, whilst the ratio of the perturbation due to the wall effect was found to be unity at 19 MeV, decreasing to 0.99 at 4 MeV. It is likely that the wall effect results have a significant systematic uncertainty due to the poor back-scatter modelling of the EGS code used to perform the calculations.