Measuring the scintillation decay time for different energy depositions in NaI:Tl, LSO:Ce and CeBr3 scintillators

This study presents a simple experimental setup for precise inspection of scintillation decay characteristics as a function of the energy deposited in scintillators. The results are discussed for NaI:Tl, LSO:Ce and CeBr3 crystals. The tested samples were coupled to a fast response R5320 photomultiplier from Hamamatsu. The decay time constants were measured by fitting the anode pulses of the PMT registered directly with a TDS5054B digital oscilloscope from Tektronix. Simple analog electronics composed of timing single channel analyzers, gate generators and coincidence/logic unit was used for selection of the deposited energy converted into light within the scintillator, and for triggering the scope to register relevant scintillation pulses. High precision of the experimental setup allowed for registration of non-proportionality curves for all samples. Moreover, non-proportionality was measured for fast and slow decay mode of NaI:Tl separately. The measurement was also used for inspection of possible differences in the pulse shapes originating from Compton scattering events and photoabsorption.