Comparative study of PP0275C hybrid photodetector and XP2020Q photomultiplier in scintillation detection

The properties of a hybrid photodetector (HPD), type PP0275C, produced by Delft Electronic Products B.V., for scintillation detection and spectrometry were studied and compared to a standard XP2020Q photomultiplier. The study was performed for several scintillators, such as NaI(Tl), CsI(Tl) and LSO(Ce) of different dimensions. The excellent capability of the HPD to resolve single photoelectron events was fully confirmed. However, the study of the HPD with the scintillators showed a dramatically reduced number of photoelectrons and a further deterioration of energy resolution, depending on the size (diameter or length) of the crystals. For a 10 mm diameter NaI(Tl) a number of 5000±250 photoelectrons/MeV was measured, which corresponds to about 56% of that observed with the XP2020Q with comparable quantum efficiency. An energy resolution of 9.2% for 662 keV γ-rays from a 137 Cs source as measured with the HPD light readout indicated on a serious degradation, larger than that arising from the statistics of photoelectrons. In conclusion, the study showed that this HPD is optimized for single photon detection but its application to scintillation detection is very limited.