Provided by Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo
A massive cavern measuring 69 meters in diameter and 94 meters in height has been created 600 meters underground in the mountains of Hida City, Gifu Prefecture. This space is designed for installing the next-generation particle detector "Hyper-Kamiokande." An international team led by the University of Tokyo and the High Energy Accelerator Research Organization plans to begin observations in 2028 to unravel the origins of the universe and matter.
Hyper-Kamiokande is a third-generation particle detector that follows Kamiokande (1983-1996) and Super-Kamiokande (1996-present). Kamiokande led to the late Masatoshi Koshiba's Nobel Prize in Physics (2002) for the world's first observation of elementary particle neutrinos from a supernova explosion. Super-Kamiokande led to Takaaki Kajita's Nobel Prize in Physics (2015) for the discovery of neutrino oscillation demonstrating that neutrinos have mass.
Starting in May 2021, a tunnel was excavated toward the construction site, first excavating the dome portion of the ceiling, then digging down the cylindrical section from October 2023 onward. Work proceeded while removing rock and soil generated by excavation through a vertical shaft in the center. The cavern completed after excavation ended on July 31 measures approximately 330,000 cubic meters and is said to be one of the world's largest artificial caverns created in bedrock.
Hyper-Kamiokande will be completed when a cylindrical ultra-large water tank is installed in this underground cavern, over 20,000 ultra-sensitive photosensors measuring 50 centimeters are mounted on the walls, and the tank is filled with 260,000 tons of ultrapure water. The effective volume capable of collecting data is approximately eight times that of Super-Kamiokande. The plan is to unravel the origins of the universe and matter by observing "Cherenkov light," the faint ring-shaped light that appears in water, to elucidate the properties of elementary particle neutrinos and to attempt discovery of "proton decay," which is said to be Nobel Prize-worthy research.
Original article was provided by the Science Portal and has been translated by Science Japan.