Study on the scintillation pulse rise time dependence in crystal CsI upon activator concentration and ionization density

An experimental facility for investigating the dependence of a scintillation pulse rise time in CsI crystals upon activator concentration and ionization density is described. The facility incorporates two photomultipliers, fibrous light guides, and a time-to-amplitude converter. The time resolution is 2 ns. An analysis of the obtained results permits to conclude that high activator concentrations, the rise time of the scintillation pulse is determined by the initial distribution of electrons and holes in the crystal, which is dependent on ionization density; at lower activator concentrations, the rise time is determined by the mean distance between the activator centres. The investigation results of the scintillation process in CsI crystals may be used for interpreting the data obtained on other inorganic scintillators