The Jiangmen Underground Neutrino Observatory (JUNO) has efficiently accomplished filling its 20,000-tons liquid scintillator detector and begun knowledge taking up Aug. 26. After greater than a decade of preparation and development, JUNO is the primary of a brand new technology of very giant neutrino experiments to succeed in this stage. Preliminary trial operation and knowledge taking present that key efficiency indicators met or exceeded design expectations, enabling JUNO to sort out one among 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 Vitality Physics (IHEP) of the Chinese language Academy of Sciences and JUNO spokesperson, mentioned: “Finishing the filling of the JUNO detector and beginning knowledge taking marks a historic milestone. For the primary time, we’ve in operation a detector of this scale and precision devoted to neutrinos. JUNO will permit us to reply elementary questions concerning the nature of matter and the universe.”
Situated 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 crops and measures their power spectrum with file precision. Not like different approaches, JUNO’s willpower of the mass ordering is impartial of matter results within the Earth and largely freed from parameter degeneracies. JUNO can even 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 environment, and the Earth. It can 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 group 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 have 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 intensely low radioactivity have been achieved. In parallel, the collaboration carried out 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 giant efficient mass of 20,000 tons, housed on the heart of a 44-meter-deep water pool. A 41.1-meter-diameter chrome 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 indicators.
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 in addition years of cautious planning, testing, and perseverance. Assembly the stringent necessities of purity, stability, and security referred to as for the dedication of a whole lot 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 as we speak can also be a results of the fruitful worldwide cooperation ensured by many analysis teams outdoors 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 elementary questions spanning particle physics, astrophysics, and cosmology, and profoundly shaping our understanding of the universe.
