Charged particles generated by high-energy events, such as neutrino interactions or proton decay, emit Cherenkov light when they pass through the water. Photosensors attached to the wall of the Hyper-Kamiokande tank are used to collect this Cherenkov light. The light collected is then used to identify the type of each particle and to measure their energy and position.
We have developed a new model of high-performance photosensor to improve the efficiency and the precision of the measurements. Basic properties of the new photosensors such as the detection efficiency, counting resolution, and timing resolution have been successfully improved by a factor of two compared to the photosensors currently used in Super-Kamiokande.
The mass production of the photosensors for Hyper-Kamiokande has started. The first photosensors arrived at ICRR in December 2020. We will check the delivered sensors to confirm that they satisfy the performance requirements and measure their individual properties.
The mass production will be completed within six years, ready to start the experiment in 2027.