Comparative Analysis of Nuclear Cross Sections in Monte Carlo Methods for Medical Physics Applications

The data used in two Monte Carlo (MC) codes, EGSnrc and MCNPX were compared and a majority of the data used in MCNPX was imported into EGSnrc. The effects of merging the data of the two codes were then examined. MCNPX was run using the ITS electron step algorithm and the default data libraries mcplib04 and el03. Two runs are made with EGSnrc. The first simulation uses the default PEGS cross section library. The second simulation utilizes the data imported from MCNPX. All energy threshold values and physics options are made to be identical. A simple case was created in both EGSnrc and MCNPX that calculates the radial depth dose from an isotropically radiating disc in water for various incident, monoenergetic photon and electron energies. Initial results show that much less central processing unit (cpu) time is required by the EGSnrc code for simulations involving large numbers of particles, primarily electrons, when compared to MCNPX. The detailed particle history files - ptrac and iwatch - are investigated to compare the number and types of events being simulated in order to determine the reasons for the run time differences