[OA074] Fano theory validation of the MCNP6.0 Monte Carlo code for medical applications. (August 2018) - Teles, Pedro
Abstract : Purpose: Fano theory states that charged particle fluence through a medium should be independent of mass density. Therefore, the validity of a Monte Carlo code depends on whether the transport of charged particles complies with this theory. In this work, in the framework of the EMPIR funded RTNORM project, the validity of the Fano theory in the Monte Carlo code MCNP6.0 is tested in a cavity. Methods: The methodology used is based on the one performed for the code PENELOPE. Two concentrical cylinders of graphite are created, with the inner one having a density equal to the density of air, and the outer one with the natural density of graphite. A linear source of electrons with energy E 0 is created and the dose in the inner cylinder is determined. The width of the outer cylinder is equal to 1.4* R CSDA . In this setup, the value of: Q = Dose per particle E 0 1 + 2 ρ wall Δ z wall ρ gas Δ z gas should be equal to 1. Dose per particle is determined by means of the tally F6 of the MCNP6.0 code. Default as well as modified physics parameters are used to ascertain limits of the validity. Parameters such as EFAC, ESTEP are changed to verify the changes in the value of Q . Results: Results show that if using default physics parameters in the MCNP6.0 code the Fano theory is not verified in the E 0 electron range of 50–200 keV. Conclusions: MCNP6.0 has difficulty in tallying energy deposition accurately in a cavity if default physics parameters are used. In this energy range MCNP6.0 presents crossing-boundary artifacts that could probably be due to the use of the condensed-history electron transport Energy Indexing Algorithm (ITS algorithm).