Reliability study for protons transport applied to ultra-thin layers

Author(s): Gabriela Hoff

The use of Monte Carlo general toolkits to different applications, especially the ones that has multiple processes and models available to transport the same particle kind requires, more and more, associate to the application development the transport radiation knowledge and the validation or reliability evaluation, in order to define the best transport process and model evoked by the simulation. When the validation is impossible, due to the lack of experimental data, the reliability evaluation takes an important role. In addition, when multiple transport processes and models are available, it is important to perform a quantitative comparison among the possible options to apply a specifi c study case to guarantee the accuracy of simulation results. The Geant4-DNA is a Monte Carlo simulation toolkit that works in an energy range that makes it impossible, nowadays, to perform a proper microscopic validation of the cross-sections and the dynamic diffusion parameters but allows, very limited, macroscopic validation, especially because it may simulate physics, physical-chemistry and chemistry processes applied to molecular geometries for quantifi cation of damage (such as single-strand, double-strand breaks, base oxidation...). Considering the complexity of the physics, physical-chemistry and chemistry processes simulated it is important to guaranty the accuracy of the beginning of this dynamic process by getting the best model to simulate the radiation transport and energy deposition. This paper presents a reliability evaluation for incident protons beam of 2 MeV on polymers ultra-thin fi lms. Furthermore, comparison among different available physics lists Geant4-DNA (version 10.02.p01) with incident protons beam for different energies (2 to 20 MeV) interacting with homogeneous ultra-thin layers of water (2 to 200 nm) was performed. In general, the standard (DNA) physics list of Geant4-DNA presented the most consistent results and the DNA-Opt1 physics list was more time consuming, presenting the worst results for dosimetry for ultrathin layers.