The Hyper-Kamiokande (Hyper-K) detector is to be located 650m underground in the Kamioka mine, Hida city, Gifu prefecture, Japan. The detector design consists of a cylindrical tank with outer dimensions of 60m height × 74m diameter; this is filled with 260,000 metric tons of ultrapure water to form a ‘water Cherenkov detector’. The detector fiducial volume of Hyper-K is planned to be 10 times larger than that of Super-Kamiokande, which will make it thr world’s largest underground water tank.
We have been developing the world’s largest photosensors, which exhibit a 50% higher photodetection efficiency than that of the Super- Kamiokande photosensors. These new photosensors are able to measure light intensity and its detection time with a much higher precision.