Energy Resolution and Slow Components in Undoped CsI Crystals

According to the present knowledge, the non-proportionality of the light yield of scintillators appears to be the fundamental limitation of energy resolution. However, several observations collected in the last 15 years on the influence of slow components of the light pulses on energy resolution suggest more complex processes in the scintillators. The presented study of undoped CsI crystals shows a large deterioration of the intrinsic resolution of the crystal, when most of the light, including slow component was integrated. Moreover, it was confirmed by a large difference of the non-proportionality characteristics measured at short peaking time, corresponding to the integration of the fast intrinsic emission of the CsI, and that observed with a long peaking time, when the slow component was integrated.