This stitched photo shows the central detector of the Jiangmen Underground Neutrino Observatory under construction in Jiangmen, South China’s Guangdong Province on October 9, 2024. Photo: Xinhua
The Jiangmen Underground Neutrino Observatory (JUNO) completed the filling of 20,000 tons of liquid scintillator on Tuesday, commencing official operation and data collection, the state broadcaster CCTV News reported.
Following more than 10 years’ preparation and construction, JUNO has become the world’s first operational ultra-large-scale and ultra-high-precision neutrino-dedicated large scientific facility.
During its trial operation, the first batch of data acquired by JUNO comprehensively reached or even exceeded the design metrics. This milestone enables the facility to address one of the most significant challenges in particle physics – determining neutrino mass ordering – while empowering scientists to conduct cutting-edge research on neutrinos originating from the sun, supernovae, atmospheres, and earth, unlocking new frontiers in the exploration of unknown physics, according to the report.
The core of JUNO is a liquid scintillator detector immersed in a 44-meter-deep cylindrical pool in the underground hall buried deep in a granite layer of a hill in Kaiping, Jiangmen city, South China’s Guangdong Province. The detector is supported by a stainless steel mesh shell with a diameter of 41.1 meters, which holds an acrylic sphere with a diameter of 35.4 meters that is filled with 20,000 tons of liquid scintillator.
The detector is equipped with 20,000 photomultiplier tubes of 20 inches and 25,000 photomultiplier tubes of three inches, as well as cables, magnetic shielding coils, light baffles and other components.
JUNO is capable of detecting neutrinos produced by the Taishan and Yangjiang nuclear power plants about 53 kilometers away, while achieving unprecedented precision in measuring the energy spectra.
The challenging project was launched jointly by the Chinese Academy of Sciences (CAS) and the Guangdong government in 2015. It is built by a large international team with nearly 700 members from 74 research institutions across 17 countries and regions.
As one of the world’s most powerful experiments to uncover neutrino mystery, JUNO is expected to operate for at least 30 years.
The completion of JUNO’s filling process and the commencement of data collection mark a groundbreaking progress. This marks the world’s first operational ultra-large-scale and ultra-high-precision neutrino-dedicated large scientific facility, enabling scientists to address fundamental questions about the nature of matter and the universe,” said Wang Yifang, spokesperson of the JUNO team, according to CCTV.
Neutrinos, the smallest and lightest among the 12 elementary particles that make up the material world, are electrically neutral and can travel at a speed close to light. Since the Big Bang time, they have permeated the entire universe and generated various phenomena, such as nuclear reactions inside stars, supernova explosions, the operation of nuclear reactors, and the radioactive decay of substances in rocks.