Hyper-Kamiokande is a proposed next generation underground water Cherenkov detector capable of observing leptonic CP violation, nucleon decay, supernova neutrino and so on. Because of its large volume, 20(25) times larger than that of Super-Kamiokande for total (fiducial) mass, the total cost of photo-detectors will be expensive. Therefore cost-effective and high performance large-area photo-detectors are required to realize such a large detector. As one of photo-detector candidates, a hybrid photo-detector (HPD), which is made of a phototube and an avalanche diode (AD), is under development. Because of its simple structure, the manufacture cost is expected to be low. And a fast drift time of electron and large bombardment gain bring a good timing resolution and high photoelectron detection efficiency. The HPD with a diameter of 50 cm is expected to have a better performance than the existing photomultiplier tube with the same diameter. However, because of the large photoelectric surface, an AD with a diameter of 20mm is used in 50 cm HPD in order to ensure the collection efficiency. As a result, a new preamplifier for high parasitic capacitance is needed. Moreover, a new kind of HPD with a multi-channel AD is also under development to reduce the parasitic capacitance seen by preamplifier. In this presentation, we will report the development status of 50 cm HPD and the performance of two prototypes: one is the HPD with a single-channel AD and an improved preamplifier, the other one is the HPD with a multi-channel AD.

Kyoto University

The University of Tokyo, Tokyo Institute of Technology, Okayama University, Hamamatsu Photonics K.K.