Science Daily published a report on the newest neutrino detector now operating in China:
"Deep beneath southern China, JUNO has launched one of the most ambitious neutrino experiments in history. With its massive 20,000-ton liquid scintillator detector now operational, it's poised to answer one of particle physics' greatest mysteries: the true ordering of neutrino masses. Built over more than a decade and involving hundreds of scientists worldwide, JUNO not only promises to resolve questions about the building blocks of matter but also to open entirely new frontiers—from exploring signals of supernovae to hunting for evidence of exotic physics."
The Jiangmen Underground Neutrino Observatory (JUNO) has successfully completed filling its 20,000-tons liquid scintillator detector and begun data taking on Aug. 26.
After more than a decade of preparation and construction, JUNO is the first of a new generation of very large neutrino experiments to reach this stage. Initial trial operation and data taking show that key performance indicators met or exceeded design expectations, enabling JUNO to tackle one of this decade's major open questions in particle physics: the ordering of neutrino masses -- whether the third mass state (ν₃) is heavier than the second (ν2).
Located 700 meters underground near Jiangmen city in the Guangdong Province, JUNO detects antineutrinos produced 53 kilometers away by the Taishan and Yangjiang nuclear power plants and measures their energy spectrum with record precision. Unlike other approaches, JUNO's determination of the mass ordering is independent of matter effects in the Earth and largely free of parameter degeneracies. JUNO will also deliver order-of-magnitude improvements in the precision of several neutrino-oscillation parameters and enable cutting-edge studies of neutrinos from the Sun, supernovae, the atmosphere, and the Earth. It will also open new windows to explore unknown physics, including searches for sterile neutrinos and proton decay.
JUNO is designed for a scientific lifetime of up to 30 years, with a credible upgrade path toward a world-leading search for neutrinoless double-beta decay. Such an upgrade would probe the absolute neutrino mass scale and test whether neutrinos are Majorana particles, addressing fundamental questions spanning particle physics, astrophysics, and cosmology, and profoundly shaping our understanding of the universe.
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China turns on giant neutrino detector:
See Here.
More than a decade after construction began, China has commenced operation of what it claims is the world's most sensitive neutrino detector.
Neutrinos are subatomic particles that have no charge and therefore pass through most matter without leaving any sign of their passing. Physics can't fully explain neutrinos, so scientists are interested in observing them more often to learn more about how they behave.
The Jiangmen Underground Neutrino Experiment (JUNO) is buried 700 meters under a mountain and features a 20,000-tonne "liquid scintillator detector" that China's Academy of Science says is "housed at the center of a 44-meter-deep water pool." There's also a 35.4-meter-diameter acrylic sphere supported by a 41.1-meter-diameter stainless steel truss. All that stuff is surrounded by more than 45,000 photo-multiplier tubes (PMTs).
The latter devices are super-sensitive light detectors. A liquid scintillator is a fluid that, when exposed to ionizing radiation, produces light. At JUNO, the liquid is 99.7 percent alkylbenzene, an ingredient found in detergents and refrigerants.
JUNO's designers hope that any neutrinos that pass through its giant tank bonk a hydrogen atom and produce just enough light that the detector array of PMTs can record their passing, producing data scientists can use to learn more about the particles.
The answer lies in the facility's location – a few tens of kilometers away from two nuclear power plants that produce neutrinos.
The Chinese Academy of Science's Journal of High Energy Physics says [source in Chinese] trials of JUNO succeeded, suggesting it will be able to help scientists understand why some neutrinos are heavier than others so we can begin to classify the different types of the particle – a key goal for the facility. The Journal also reports that scientists from Japan, the United States, Europe, India, and South Korea, are either already using JUNO or plan experiments at the facility.
China likes to share some of its scientific achievements. When it retrieved moon rocks, it made sure to show them off and allow some foreign labs to examine them. It looks like Beijing is keen to ensure the world appreciates JUNO's efforts to help us all appreciate neutrinos.
(Score: 4, Informative) by PiMuNu on Wednesday September 03 2025, @06:55AM
This is a nice experiment to get at the mass hierarchy in neutrinos.
US and Japanese programmes coming online will be able to check for matter antimatter asymmetry (which we already see in quarks), and complete the basic measurement of neutrino parameters.
Nb: neutrino oscillation and gravity are the only physics that do not fit into the standard model of particle physics; gravity is very hard to chase down, so if you want to understand "what is matter" chasing neutrino oscillations is really important.
(Score: 4, Interesting) by ls671 on Wednesday September 03 2025, @10:31AM (1 child)
I am reposting the same as I posted in the "dupe" version which was posted soon after just in case the "dupe" version goes away...
Canada's one wasn't bad, 9600 photomultiplier vs 43,200 photomultiplier for the Chinese one. I don't recall why they closed it. Is a bigger neutrino detector that relevant anyway for scientific findings? I guess a bigger one will just probably get more neutrinos but is it that important? Canada's one was more than twice deeper into the ground so better filtering from other particles as well so less "interference". Quality might be important too although I would think the water might play a role in the filtering as well.
https://sno.phy.queensu.ca/ [queensu.ca]
https://astro-canada.ca/l_observatoire_de_neutrinos_de_sudbury-the_sudbury_neutrino_observatory-eng [astro-canada.ca]
In short I'd be curious to see a side by side comparison of the two but I couldn't find anything, just "biggest" and Japan wants to build a bigger one. Is it just like a bragging contest or bigger necessarily means better?
For the ones not familiar with the topic, a neutrino can potentially go all the way through planet Earth without hitting anything and continue his trajectory after that. American have used neutrinos to send secret messages to their submarines in the past but as far as I know they gave up on that because the submarines would have to be in one very precise location to catch the directional beam and it proved to be unreliable because of that.
Everything I write is lies, including this sentence.
(Score: 2) by PiMuNu on Thursday September 04 2025, @07:19AM
I put a reply in the dupe as that seemed to be generating more discussion.