Completion of the main cavern dome section of the Hyper-Kamiokande experiment


On October 3, 2023, the dome section of the main cavity for Hyper-Kamiokande experiment, situated underground in Kamioka-cho, Hida City, Gifu Prefecture, was completed. The dome has a diameter of 69 meters and a height of 21 meters.

The Hyper-Kamiokande project started in 2020 with the tunnel excavation and construction progressing smoothly  since the ground breaking in May 2021. Excavation of the main cavern began in November 2022, gradually expanding the space of the dome section while ensuring the stability of the bedrock. Currently, following completion of the dome section, excavation of the cylindrical section below has begun. The cylindrical section, with a diameter of 69 meters and a height of 73 meters, in combination with the dome section, will constitute the largest artificial underground cavity in the world.

Moving forward, the excavation of the cylindrical water tank section will proceed throughout 2024, and the construction of the water tank liner will be conducted in 2025. In 2026, devices such as photodetectors will be installed inside the water tank, and operations are scheduled to begin in 2027.


The completed main cavern dome section (diameter: 69m, height: 21m)


Overview of Hyper-Kamiokande detector



Hyper-Kamiokande experiment; Excavation of the gigantic underground cavern has finally begun (2023/5/29)