Using the GEANT4 Monte Carlo simulation software, the efficiency of the HPGe extended range detector of the Environmental Radiological Surveillance Laboratory of CIMAV was modeled. A 137Cs certified point source was employed to determine the experimental gamma efficiency in the desired geometry for the energy of 662 keV. The resulting value was compared with the theoretical efficiency obtained by the Monte Carlo simulation. The results of the simulation were consistent with the experimental one. The same method was applied to calculate the theoretical efficiency in the same detector for borosilicate filters in an extended geometry. The energy then was 477 keV, of the gamma quanta from 7Be, to determine its concentration in air. This efficiency value was applied for air sampling in the city of Chihuahua.

This work presents the results of a simulation by the Monte Carlo method, performed through the GEANT4 code, of the irradiation and energy deposition by high flux X-rays on the piezoelectric ceramic Bismuth-Sodium Titanate doped with Barium. X-rays energies were around the Ti-K absorption edge emulating a transmission experiment, and the irradiation with 5300 eV X-rays for a fluorescence experiment. The method consists of introducing the data that describes a characteristic R3c structure of the polarized ceramic, reported in the literature. The absorption coefficients for the energies of interest, as well as the energy deposited in the form of radiation doses, are calculated. Intensity changes for specific energy lines in the micro-fluorescence spectra, which suggest the presence of vacancies in the crystal structure, are verified via simulation. The vacancy density produced by a typical photon flux of a fourth-generation synchrotron beam is calculated through the threshold displacement energy for vacancy production. Consequently, the simulation is carried out for a structure with appropriate Bi and O vacancies, and the ability to detect the radiation damage is verified by comparison with micro-XRF and XAFS experimental results. The simulation predicts a maximum dose of 1.21-1.27x105 Gy irradiating 107 photons for the given energy and a maximum vacancy density of 1.10x108 / micron3 for oxygen atoms and 6.90x107 /micron3 for bismuth atoms.