Evaluation of hamamatsu H8500 new series MA-PMTs for readout of high-resolution LaBr3:Ce scintillation crystal

In this work we report on the performance of the MA-PMT prototype, Hamamatsu H8500C-100 MOD 8, with reduced dynode stages (eight) and super bialkali photocathode (38% Q.E. @ 380 nm). This tube represents the latest technological advancement to improve energy and spatial resolution of gamma imagers. It is particularly suitable for applications involving new high light yield scintillators. To evaluate the performances of this tube, we compared the energy and spatial resolution response with the analogous ones obtained from a standard H8500 MA-PMT coupled to a LaBr₃:Ce scintillation crystal with the same identity. All measurements were performed with a 64 channel electronic readout. An improvement of about 10% in energy and spatial resolution was found, not properly in agreement with the increased value of quantum efficiency. However, this detector configuration permits to obtain 0.92 mm value of the intrinsic spatial resolution and 7.4% of energy resolution which represent the best results obtained with 4.0 mm thickness continuous LaBr3:Ce crystal.