Evaluating the radiation detection of the RbGd 2Br 7:Ce scintillator by Monte Carlo methods

Abstract

The purpose of this study was to investigate the radiation detection efficiency of the recently introduced RbGd 2Br 7:Ce (RGB) scintillator material by a custom developed Monte Carlo simulation code. Considering its fast principal decay constant (45 ns) and its high light yield (56 000 photons/MeV), RbGd 2Br 7:Ce appears to be a quite promising scintillator for applications in nuclear medical imaging systems. In this work, gamma-ray interactions, within the scintillator mass were studied. In addition, the effect of K-characteristic fluorescence radiation emission, re-absorption or escape, as well as the effect of scattering events on the spatial distribution of absorbed energy was examined. Various scintillator crystal thicknesses (5–25 mm), used in positron emission imaging, were considered to be irradiated by 511 keV photons. Similar simulations were performed on the well known Lu 2SiO 5:Ce (LSO) scintillator for comparison purposes. Simulation results allowed the determination of the quantum detection efficiency as well as the fraction of the energy absorbed due to the K-characteristic radiation. Results were obtained as a function of scintillator crystal thickness. The Lu 2SiO 5:Ce scintillator material showed to exhibit better radiation absorption properties in comparison with RbGd 2Br 7:Ce. However, RGB showed to be less affected by the production of K-characteristic radiation. Taking into account its very short decay time and its high light yield, this material could be considered to be employed in positron imaging (PET) detectors.