On June 28, 2025, a special tour of the construction site for the Hyper-Kamiokande project was held in Hida City, Gifu Prefecture, Japan. Hyper-Kamiokande is a next-generation international scientific research facility scheduled to begin operations in 2028. Approximately 70 participants attended the event, including representatives from the University of Tokyo, Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT), Gifu Prefecture, and construction-related companies.
From left to right: Shoichi Ogio, Director of the Institute for Cosmic Ray Research (ICRR), The University of Tokyo; Teruo Fujii, President of The University of Tokyo; Mizue Shiomi, Director of the Research Promotion Bureau, MEXT; Yasuhiro Kubo, President of Tokyo Electric Power Services Corporation; Yoshikazu Oshimi, Chairman and Executive Director of Kajima Corporation; Nobutaka Tanabe, Executive Director of Kamioka Mining and Smelting Corporation; Yoshihide Ezaki, Governor of Gifu Prefecture; Shoji Asai, Director-General of the High Energy Accelerator Research Organization (KEK); Masato Shiozawa, Director of the Kamioka Observatory, ICRR, The University of Tokyo; Shigetaka Moriyama, Deputy Director of ICRR, The University of Tokyo.
The Hyper-Kamiokande detector is designed to have a fiducial mass eight times greater than its predecessor, Super-Kamiokande, and will be equipped with newly developed, high-sensitivity photosensors. The project aims to advance our understanding of the Grand Unified Theory and the evolutionary history of the universe by investigating phenomena such as proton decay, CP violation (the asymmetry between neutrinos and antineutrinos), and observing neutrinos from supernova explosions. The construction budget was officially approved by the Japanese Diet in February 2020, marking the formal launch of the project. Excavation of the main cavern began in November 2022, following the completion of both the approach and access tunnels. The main dome, measuring 69 meters in diameter and 21 meters in height, was completed in October 2023, and excavation of the vertical cavern for the main detector has been ongoing since then.
Now nearing completion, the vertical cavern—located 600 meters underground—is one of the largest underground spaces in the world. It will house Hyper-Kamiokande’s enormous water tank, which will be fitted with approximately 20,000 newly developed photosensors and around 1,000 multi-photosensor modules designed to detect the faint light produced by neutrino interactions.
The ceremony, presided over by ICRR Associate Professor Yoichi Asaoka, was held at the underground site designated for the future installation of Hyper-Kamiokande’s water purification systems. Following opening remarks by Shoichi Ogio, Director of ICRR, key figures involved in the project—University of Tokyo President Teruo Fujii, KEK Director-General Shoji Asai, and Masato Shiozawa, Director of the ICRR Kamioka Observatory—delivered their comments. This was followed by congratulatory speeches from distinguished guests: Mizue Shiomi, Director of the Research Promotion Bureau at MEXT; Yoshihide Ezaki, Governor of Gifu Prefecture; Yoshikazu Oshimi, Chairman and Executive Director of Kajima Corporation; and Nobutaka Tanabe, Executive Director of Kamioka Mining and Smelting Corporation.
As part of the ceremony, President Fujii presented certificates of gratitude to the construction companies—Kajima Corporation, Tokyo Electric Power Services Corporation, and Kamioka Mining and Smelting Corporation—in recognition of their contributions. The event concluded with closing remarks by Shigetaka Moriyama, Deputy Director of ICRR.
Visit the following UTokyo website for further details.
