Detalhes do Artigo
[306286] Monte Carlo Study of the External Environment Influence on the Energy Deposited in a Cavity Ionization Chamber
Autores: Carlos Alberto Lucas Suplino Filho, Pedro Pacheco de Queiróz Filho, Cosme Norival Mello da Silva
Resumo: The LNMRI is developing an ionometric determination of the absorbed dose to water for primary standardization in the 60Co beam. For the characterization of the primary standard ionization chamber, it is necessary to carry out experimental measurements and simulations with sufficient statistics to reach the appropriate uncertainty levels. To optimize the CPU time of these simulations, a computational study was carried out with the PENELOPE code on the contribution to the energy deposited in the cavity, coming from the electrons generated in the air outside an ionization chamber. These electrons were discriminated to evaluate their contribution to the energy deposited in the cavity. As a result of the transport of electrons in the air outside of the chamber, a 0.015% change in the energy deposited in the cavity was obtained by an “Recommended simulation”, through many simulations, all of them with 2×109 events.
Considering the irrelevance of the influence of charged particles external to the cavity, three simulations were compared. The “detailed simulation”, with consumes huge CPU time; the “recommended simulation”, that uses the transport parameters recommended in the PENELOPE manual, and the “Optimized simulation”, that disregards external electrons. The impact on CPU time was significant. The estimated CPU times for 109 events were 80, 3 and 1.5 hours, for the detailed, recommended and optimized simulations, respectively.