Y. Abreu

GAMOS: An easy and flexible way to use GEANT4

The wide range of physics models available in GEANT4, as well as its outstanding geometry and visualization tools, has made it gain widespread use in several fields of physics, like high energy, medical, space, etc. Nevertheless the use of GEANT4 often requires a long learning-curve, which implies a good knowledge of C++ and the GEANT4 code itself. GAMOS facilitates the use of GEANT4 by avoiding the need to use C++, providing instead a set of user commands. One of the novelties of GAMOS with respect to similar simulation codes lies in its flexibility, which makes it appropriate for simulation in many physics fields. This flexibility is sustained by the wide range of geometrical configurations, primary generators and physics lists supported and by the comprehensive set of tools that help the user in extracting detailed information from the simulation through user commands. The use of the plug-in technology contributes to this flexibility, as it facilitates the extension of the framework to include extra functionality not foreseen by the framework authors. GAMOS counts already with several hundreds registered users in the five continents; while it is more frequently used in the medical physics field, its use has also been extended to other fields, like high energy physics, space physics, neutron shielding, etc.

Monte Carlo assisted classical method for the calculation of dpa distributions in solids materials

In the present work the extended Monte Carlo assisted Classical Method (MCCM) is presented. The method consists on a calculation procedure for the determination of the displacements per atom (dpa) distribution in solid materials, which allows studying the gamma irradiation damage in different materials. The same one is based on the electrons elastic scattering classic theories and makes use of the Monte Carlo simulation of physical processes involved in the radiation interactions with substance. Recently, the contribution from positrons to dpa distributions has been also included. This method has been applied to different materials: metals (iron), semiconductors (Si and CZT) and high temperature superconductors like YBCO. Among other things, this procedure has allowed to study the dpa cross sections and the in-depth dpa distributions in a wide range of incident gamma energies. Also in compound materials, the contribution from each atomic species is possible to be evaluated.

MCSAD: Monte Carlo simulations of atom displacements induced by fast electrons in solids

Present contribution deals with Monte Carlo simulation of atom displacements rates resulting in solids based on a calculation algorithm supporting the description of the conditions favouring the occurrence of single fast electron elastic scattering in solids, leading to the displacement of atoms from their crystalline sites. Firstly, a McKinley-Feshbach differential cross-section renormalization is introduced by considering single elastic scattering events with scattering angles only within the interval [θl, π], where θl is the limiting angle, under which multiple scattering events with relative low scattering angles prevails over the single ones. On this basis, a Monte Carlo simulation code (MCSAD) of atom displacements induced by electrons and photons was implemented. In particular, total atom displacements produced along an electron travelling path were sampled in different solids matrix and compared with Oen-Holmes-Cahn theory predictions at different electron initial energies. As a result, it was concluded that Oen-Holmes-Cahn calculations overestimate normalized atom displacements rates in comparison with present MCSAD ones in a range up to between 10 to 73% rate, where maximum deviation were observed in YBCO for heaviest atom. It was also found that Oen-Holmes-Cahn absolute atom displacements distributions overestimated in about 30 to 40 times at the maximum of the AD rate simulated by MCSAD code.

Theoretical foundations of atom displacements induced by fast electron elastic scattering in solids

Present contribution deals with the theoretical description of the conditions favoring the occurrence of single fast electron elastic scattering in solids, leading to the displacement of atoms from their crystalline sites.

Radiation damage evaluation on LYSO and LuYAP materials through dpa calculation assisted by Monte Carlo method

The aim of the present work is to study the radiation damage induced in LYSO and LuYAP crystals by the gamma radiation and the secondary electrons/positrons generated. The displacements per atom (dpa) distributions inside each material were calculated following the Monte Carlo assisted Classical Method (MCCM) introduced by the authors. As gamma sources were used Sc-44, Na-22 and V-48. Also the energy of gammas from the annihilation processes (511 keV) was included in the study. This procedure allowed studying the in-depth dpa distributions inside each crystal for all four sources. It was also possible to obtain the separate contribution from each atom to the total dpa. The LYSO crystals were found to receive more damage, mainly provoked by the displacements of silicon and oxygen atoms.

Multiscale modeling of radiation damage and annealing in Si samples implanted with 57-Mn radioactive ions

The radiation damage created in silicon materials by 57Mn→57Fe ion implantation has been studied and characterized by Mössbauer spectroscopy showing four main lines, assigned to: substitutional, interstitial and damaged configuration sites of the implanted ions. Nevertheless, the Mössbauer spectrum of 57Fe in this materials remains with some ambiguous identification regarding the implantation configurations before and after annealing, specially the damaged configurations and its evolution. In the present work some possible implantation configurations are suggested and evaluated using a multiscale approach by Monte Carlo ion transport and electronic structure calculations within DFT. The proposed implantation environments were evaluated in terms of stability and the 57Fe hyperfine parameters were calculated to establish the connections with the experimental observations. Good agreement was found between the experimental and the calculated hyperfine parameters for some configurations; suggesting which ones could be the implantation environments before and after sample annealing.