Ionoluminescence investigation of ambient humidity effects on CsI:Na scintillator crystal

Effects of ambient humidity on the ionoluminescence spectra of synthesized CsI:Na crystals were investigated for a time period of more than 500 days. Regarding the typical penetration depth of the applied ion beams in the ionoluminescence technique, it is suitable for investigating the humidity effects which are detectable at the outer surface of the scintillators. Three luminescence bands were observed for the samples, including CsI intrinsic luminescence and Na related bands, at ~ 310, 420 and 487 nm. It is shown that the relative intensity of the Na-related band, located at ~ 420 nm, significantly decreases over exposition time to humidity and exhibits considerable redshift. Since this band is the dominant one for detection purposes, its alteration leads to a decrease in the efficiency of CsI:Na scintillator. It was also observed that the relative intensity of this band for the sample which was grown in presence of trivial amount of humidity in the crucible, was initially much weaker and reacted less to the ambient humidity. The results of the present work demonstrate the capabilities of ionoluminescence as a suitable technique for scintillators’ characterization.