Scintillation degradation of YAG: Ce under low-energy ion bombardment

Abstract

We have measured the degradation of the scintillation yield of single crystal YAG: Ce under He+ irradiation at low energies between 28 and 58 keV. The scintillator was irradiated at the rare isotope ReAccelerator (ReA) facility at the National Superconducting Cyclotron Laboratory (NSCL). The scintillation emission is attributed to its rapid 5d–4f transition of Ce3+ ions. As the bombardment time increases, an exponential decay of the light output is observed due to the induced radiation damage of the crystal lattice. Color centers formed by the radiation damage are likely to act as exciton capturing centers, leading to a quench of the scintillator yield. It is possible that these color centers are oxygen vacancies with trapped electrons or the formation of Ce4+ and Y2+. The decrease of the experimentally observed light yield as a function of particle fluence is found to be in fair agreement with the Birks model. Analysis indicates that the damage cross section of scintillation centers slightly decreases with the ion energy. The value of the relative exciton capture probability for YAG: Ce is considerably small compared to the magnitude proposed by Birks for anthracene under α-particle irradiation. On the other hand, the half brightness fluence is estimated to be larger at higher energy because the ion particles create less damaged centers per unit of path length and activate more luminescence centers. Therefore, the scintillator degrades slower and exhibits better scintillation efficiency under higher-energy irradiation.