Temperature dependence of the photostimulated luminescence in KCl:Eu ²⁺

The goal of this work is to understand the physical mechanism behind the signal stabilization process in KCl:Eu²⁺, a storage phosphor material that has generated renewed interest due to its potential in radiation therapy dosimetry application. The temperature dependency of the photostimulated luminescence (PSL) spectra and intensity vs. time post X-ray irradiation was measured. Commercial BaFBr:Eu²⁺ materials were included in this study for comparison. Unlike BaFBr:Eu²⁺, broadening of the F(Cl ^-) stimulation band and red-shift of the peak were observed for KCl:Eu²⁺ with increasing temperature. For irradiations at temperatures lower than 200 K, PSL intensity of KCl:Eu²⁺ showed recuperation behavior in the first 2 h post-irradiation and stayed almost constant with time thereafter. Moreover, spatially-correlated storage centers increased from 24% for irradiation at 50 K to 31% at 195 K and almost 100% at room temperature. The data suggest that certain types of charge storage-centers were mobile and contribute to the fast fading in PSL.