Construction of Jiangmen Underground Neutrino Observatory's main body completed

After more than nine years of construction, the main body of the Jiangmen Underground Neutrino Observatory (JUNO) was completed on Wednesday and is scheduled to be put into operation next year. 

The observatory, located in Jiangmen City, south China's Guangdong Province, is the world's largest transparent spherical detector 700 meters underground to capture elusive neutrinos, often dubbed "ghost particles," to unravel the secrets of the infinitesimally small and the infinitely vast in the universe.

A 44-meter-deep tank 700 meters underground is where the JUNO is located. It has a stainless steel mesh shell with a diameter of 41 meters, an organic glass ball 35.4 meters in diameter, 45,000 photomultiplier tubes, and other key components. After the mesh shell and the glass ball were put together, the installation of the photomultiplier tube modules were completed Wednesday afternoon.

The JUNO is a multipurpose neutrino experiment whose priority is to determine neutrino mass hierarchy. When neutrinos go through the detector, a very small part of them interact with the liquid scintillator, producing scintillation light, which can be seen by the surrounding photomultiplier tubes.

(Cover: The Jiangmen Underground Neutrino Observatory in Jiangmen City, Guangdong Province, south China. /CMG)