Characteristics changes of unsealed Nal(Tl) detector under atmospheric moisture effect

Abstract

The light yield and energy resolution impairment of Nal(Tl) crystals being stored unsealed is associated with changes in the scintillation efficiency, q, and the light collec- tion coefficient, r. It is just the depletion of the crystal in activator that is responsible for the 11 deterioration in the near-surface "dead" scintillator layer while changes in t are due to the surface enrichment in thallium, no matter what is the detector size. A simple test is proposed to detect the initial stages of the crystal moistening influenced on the Nal(Tl) crystal properties