SPECTROSCOPIC ANALYSIS OF PROTON-INDUCED FLUORESCENCE FROM YTTRIUM AND GADOLINIUM OXYSULFIDE PHOSPHORS

We have determined the effect of proton-induced damage on relative scintillation efficiency of various inorganic phosphors. This is the first study of proton-induced degradation of phosphors such as Y2O2S:Eu, Gd2O2S:Pr, and Gd2O2S:Tb. Materials were selected for high efficiency, fast prompt fluorescence response, and minimal delayed fluorescence. Phosphors were exposed to a 3 MeV proton beam at ambient temperatures to control heating damage. Real time, in situ measurements of the fluorescence spectra permitted observation of the spectral characteristics for the deterioration of scintillation yield due to particle induced damage. The light spectra emitted were nearly identical to those excited by electrons, indicating a common excitation process. Rare earth oxysulfides give intense emissions but the corresponding light intensity drops rapidly with dose. Light intensity decreases with dose, following the Birks and Black model where damage sites compete for excitons with light producing sites. Decay of broadband and spectral peak intensity follow similar patterns. The Birks and Black deterioration relation is fitted to each spectral line with empirical decay parameters.