The Jiangmen Underground Neutrino Observatory (JUNO) has efficiently accomplished filling its 20,000-tons liquid scintillator detector and begun information taking up Aug. 26. After greater than a decade of preparation and development, JUNO is the primary of a brand new technology of very massive neutrino experiments to succeed in this stage. Preliminary trial operation and information taking present that key efficiency indicators met or exceeded design expectations, enabling JUNO to deal with one in all this decade’s main open questions in particle physics: the ordering of neutrino plenty — whether or not the third mass state (ν₃) is heavier than the second (ν2).
Prof. Yifang Wang, a researcher on the Institute of Excessive Power Physics (IHEP) of the Chinese language Academy of Sciences and JUNO spokesperson, stated: “Finishing the filling of the JUNO detector and beginning information taking marks a historic milestone. For the primary time, we’ve got in operation a detector of this scale and precision devoted to neutrinos. JUNO will enable us to reply basic questions concerning the nature of matter and the universe.”
Positioned 700 meters underground close to Jiangmen metropolis within the Guangdong Province, JUNO detects antineutrinos produced 53 kilometers away by the Taishan and Yangjiang nuclear energy vegetation and measures their power spectrum with report precision. Not like different approaches, JUNO’s dedication of the mass ordering is impartial of matter results within the Earth and largely freed from parameter degeneracies. JUNO may also ship order-of-magnitude enhancements within the precision of a number of neutrino-oscillation parameters and allow cutting-edge research of neutrinos from the Solar, supernovae, the ambiance, and the Earth. It should additionally open new home windows to discover unknown physics, together with searches for sterile neutrinos and proton decay.
Proposed in 2008 and permitted by the Chinese language Academy of Sciences and Guangdong Province in 2013, JUNO started underground development in 2015. Detector set up began in December 2021 and was accomplished in December 2024, adopted by a phased filling marketing campaign. Inside 45 days, the workforce crammed 60,000 tons of ultra-pure water, retaining the liquid-level distinction between the inside and outer acrylic spheres inside centimeters and sustaining a flow-rate uncertainty under 0.5%, safeguarding structural integrity. Over the following six months, 20,000 tons of liquid scintillator had been crammed into the 35.4-meter-diameter acrylic sphere whereas displacing the water. All through, stringent necessities on ultra-high purity, optical transparency, and very low radioactivity had been achieved. In parallel, the collaboration performed detector debugging, commissioning, and optimization, enabling a seamless transition to full operations on the completion of filling.
On the coronary heart of JUNO is a central liquid-scintillator detector with an unprecedentedly massive efficient mass of 20,000 tons, housed on the heart of a 44-meter-deep water pool. A 41.1-meter-diameter stainless-steel truss helps the 35.4-meter acrylic sphere, the scintillator, 20,000 20-inch photomultiplier tubes (PMTs), 25,600 3-inch PMTs, front-end electronics, cabling, anti-magnetic compensation coils, and optical panels. All PMTs function concurrently to seize scintillation mild from neutrino interactions and convert it to electrical alerts.
Prof. MA Xiaoyan, JUNO Chief Engineer, remarked: “Constructing JUNO has been a journey of extraordinary challenges. It demanded not solely new concepts and applied sciences, but additionally years of cautious planning, testing, and perseverance. Assembly the stringent necessities of purity, stability, and security known as for the dedication of a whole bunch of engineers and technicians. Their teamwork and integrity turned a daring design right into a functioning detector, prepared now to open a brand new window on the neutrino world.”
JUNO is hosted by the IHEP and includes greater than 700 researchers from 74 establishments throughout 17 international locations and areas. “The landmark achievement that we announce immediately can also be a results of the fruitful worldwide cooperation ensured by many analysis teams exterior China, bringing to JUNO their experience from earlier liquid scintillator set-ups. The worldwide liquid scintillator neighborhood has pushed the know-how to its final frontier, opening the trail in the direction of the formidable physics objectives of the experiment,” commented Prof. Gioacchino Ranucci, Deputy spokesperson of JUNO and a Professor on the College of Milano and INFN-Milano.
JUNO is designed for a scientific lifetime of as much as 30 years, with a reputable improve path towards a world-leading seek for neutrinoless double-beta decay. Such an improve would probe absolutely the neutrino mass scale and take a look at whether or not neutrinos are Majorana particles, addressing basic questions spanning particle physics, astrophysics, and cosmology, and profoundly shaping our understanding of the universe.