Otimização do crescimento de cristais cintiladores inorgânicos em matriz CsI dopada com lítio para uso como detectores de radiação

Abstract

TOMAZ, L. F. Optimization of growth of the inorganic scintillators crystals in CsI matrix doped with lithium for use as radiation detectors. 2019. 100 p. Dissertação (Mestrado em Tecnologia Nuclear)-Instituto de Pesquisas Energéticas e Nucleares-IPEN-CNEN/SP. São Paulo. Scintillators are solid, liquid or gaseous materials capable of efficiently converting high energy radiation into radiation in the ultraviolet or visible spectrum, by partially or totally absorbing the incident radiation. Regarding the investigation of scintillating crystals, the inorganics occupy considerable space in the group of scintillators used in the areas of work with radiation and they are applied as detectors. The objective of this work was to develop inorganic scintillation crystals in the CsI matrix using the lithium ion (Li +) as a doping element, in concentrations of 10-1 M, 10-2 M, 10-3 M and 10-4 M, by means of the Bridgman technique. The behavior of the crystals was studied by exciting them with different energy levels of alpha radiation, gamma radiation and also, with neutron radiation and the results were compared to the pure CsI matrix. The crystals were excited with gamma radiation in the energy range of 59 keV to 1333 keV, alpha radiation with energy 5.54 MeV and neutron radiation with energy of 1 MeV to 12 MeV. The CsI:Li crystals were, also, subjected to physical and chemical characterization, such as: optical transmittance, emission of luminescence, distribution of Li dopant along the growth axis and confirmation of the crystal structure. Lithium doped crystals showed better response to alpha radiation when compared to pure CsI crystal and sensitivity increases as the dopant Li concentration also increased, crystals CsI:Li with concentrations of 10-2 M and 10-3 M presented the best pulse height for gamma radiation. CsI: Li crystals showed sensitivity to neutron detection, with counts volume significantly higher than pure CsI crystal. The CsI:Li 10-3 M and 10-2 M crystals showed better neutron radiation detection in the Li doping concentration range studied. Addition of Li to the CsI matrix resulted in crystals with promising results for use as detectors, when excited with gamma, alpha and neutron radiation.