What is the significance of Decay Time?

Scintillation light pulses (flashes) are usually characterized by a fast increase of the intensity in time (pulse rise time) followed by an exponential decrease. The decay time of a scintillator is defined by the time after which the intensity of the light pulse has returned to 1/e of its maximum value. Most scintillators are characterized by more than one decay time and usually, the effective average decay time is mentioned. The decay time is of importance for fast counting and/or timing applications.