Intrinsic energy resolution of CsI(Tl) scintillation detectors

Early experiments for the determination of intrinsic energy resolution as a measure of the dispersion of photons created in scintillation detectors were strongly influenced by poor statistics due to low photoelectric yield of PMTs. CsI(Tl) is among the scintillators for which the scintillation photon to e-h pair conversion efficiency with Si photodiodes (PDs) is practically unity, thus providing much better statistics. Contrary to PMTs, however, the limiting factor in this combination is the much higher electrical noise, which should therefore be taken into correction for the determination of the true intrinsic resolution. (K.A.)