Speaker
Description
Hyper-Kamiokande is a large water Cherenkov detector in Japan to
explore various neutrino physics and discover a nucleon decay. Its
construction started in 2020 and the mass production of a large
aperture photo-detector is planned from the end of 2020. We developed
a photomultiplier tube (PMT) with a 50 cm diameter, R12860 by
Hamamatsu Photonics K.K. and installed over a hundred of them into
Super-Kamiokande. A hundred PMTs were evaluated in Super-Kamiokande
and compared with an R3600 PMT for Super-Kamiokande. It was confirmed
that the resolutions and detection efficiency are doubly improved. A
noise reduction of the PMT was also achieved with suppressing
radioactive contaminations in the glass. In addition, another large
aperture photodetector using a micro channel plate was developed. A
part of the detection wall with the optical acrylic window and several
designs of a shockwave prevention cover are constructed for a test to
demonstrate a coming construction work. A PMT calibration facility is
also under preparation. We present the recent development and improved
performance of the large-aperture photo-detectors.
