Performance evaluation of the large-aperture Hybrid Photo-Detector

We have been developing a 20-inch high quantum efficiency Hybrid Photo-Detector (HPD) as a candidate photosensor for the Hyper-Kamiokande detector. As a first step of R&D, we have developed a prototype of 8-inch HPD. Compared with the photomultiplier tube used in Super-Kamiokande, the 8-inch HPD has a lower dark rate of 2 kHz at 0.5 photoelectron threshold, a better single photoelectron transit time spread of 1.2 ns in sigma and a better single photoelectron resolution of 12%.