Jiangmen Underground Neutrino Observatory
22°07′06″N 112°31′07″E / 22.11827°N 112.51867°E
The Jiangmen Underground Neutrino Observatory (JUNO) is a medium baseline reactor neutrino experiment currently operating at Kaiping, Jiangmen in Guangdong province in Southern China. It aims to determine the neutrino mass hierarchy and perform precision measurements of the Pontecorvo–Maki–Nakagawa–Sakata matrix elements. It will build on the mixing parameter results of many previous experiments.
The collaboration was formed in July 2014 and construction began January 10, 2015. Funding is provided by a collaboration of international institutions. Originally scheduled to begin taking data in 2023, , the US$376 million JUNO facility was completed and the experiment started on 26 August 2025. JUNO is the world's largest transparent spherical detector.
Planned as a follow-on to the Daya Bay Reactor Neutrino Experiment, it was originally to be sited in the same area, but the construction of a third nuclear reactor (the Lufeng Nuclear Power Plant) in that region would disrupt the experiment, which depends on maintaining a fixed distance to nearby nuclear reactors. Instead it was moved west to a site (Jingji town, Kaiping, Jiangmen) located 52.5 km from both of the Yangjiang and Taishan nuclear power plants.