Anomalous gain drop effects in Hamamatsu 3998-01 photomultiplier

Currently, in our IdentiFINDER LGH instruments, commercially available 30S30_B380 (LaBr3) detectors, purchased from Saint-Gobain Crystals, are deployed. They are equipped with R3998-01 photomultipliers from Hamamatsu Photonics. With this type of photomultiplier, we recently encountered a new issue in our devices related to a unprecedented gain drop/recovery, occurring at a certain temperature and count rate. The experiments will be outlined and the results presented.