The Jiangmen Underground Neutrino Observatory (JUNO) is a medium baseline reactor

neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

experiment under construction at

Kaiping Kaiping (), postal map romanization, alternately romanization of Chinese, romanized in Cantonese as Hoiping, is a county-level city in Guangdong provinces of China, Province, China. It is located ín the western section of the Pearl River Delt ...

Jiangmen Jiangmen (), alternately romanized in Cantonese as Kongmoon, is a prefecture-level city in Guangdong Province in southern China. As of the 2020 census, its three urban districts, plus Heshan City being conurbated, with 2,657,662 inhabitants ar ...

Guangdong Guangdong (, ), alternatively romanized as Canton or Kwangtung, is a coastal province in South China on the north shore of the South China Sea. The capital of the province is Guangzhou. With a population of 126.01 million (as of 2020) ...

province in Southern

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. It aims to determine the neutrino mass hierarchy and perform precision measurements of the

Pontecorvo–Maki–Nakagawa–Sakata matrix In particle physics, the Pontecorvo–Maki–Nakagawa–Sakata matrix (PMNS matrix), Maki–Nakagawa–Sakata matrix (MNS matrix), lepton mixing matrix, or neutrino mixing matrix is a unitary mixing matrix which contains information on the misma ...

elements. It will build on the mixing parameter results of many previous experiments. The collaboration was formed in July 2014 and construction began January 10, 2015. The schedule aims to begin taking data in 2023. Funding is provided by the Chinese Academy of Sciences, but the collaboration is international. Planned as a follow-on to the

Daya Bay Reactor Neutrino Experiment The Daya Bay Reactor Neutrino Experiment is a China-based multinational particle physics project studying neutrinos. The multinational collaboration includes researchers from China, Chile, the United States, Taiwan (Republic of China), Russia, ...

, it was originally to be sited in the same area, but the construction of a third nuclear reactor (the Lufeng Nuclear Power Plant) in that region would disrupt the experiment, which depends on maintaining a fixed distance to nearby nuclear reactors. Instead it was moved west to a site (Jingji town, Kaiping, Jiangmen) located 53 km from both of the

Yangjiang Yangjiang (, ), alternately romanized as Yeungkong, is a prefecture-level city in southwestern Guangdong Province in the People's Republic of China. It borders Maoming to the west, Yunfu to the north, Jiangmen to the east, and looks out to the ...

and

Taishan nuclear power plant The Taishan Nuclear Power Plant () is a nuclear power plant in Taishan, Guangdong province, China. The plant features two operational EPR reactors. The first unit, Taishan 1, entered commercial service in December 2018, but was shut down from J ...

Detector

The main detector consists of a diameter transparent

acrylic glass Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylite, ...

sphere containing 20,000 tonnes of

linear alkylbenzene Linear alkylbenzenes (sometimes also known as LABs) are a family of organic compounds with the formula C6H5CnH2n+1. Typically, ''n'' lies between 10 and 16, although generally supplied as a tighter cut, such as C12-C15, C12-C13 and C10-C13, for de ...

liquid

scintillator A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed ...

, surrounded by a

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

truss supporting approximately 53,000

photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sho ...

tubes (17,000 large diameter tubes, and 36,000 tubes filling in the gaps between them), immersed in a water pool instrumented with 2000 additional photomultiplier tubes as a muon veto. As of 2022, construction of the detector is well underway. Deploying this underground will detect neutrinos with excellent energy resolution. The overburden includes 270 m of granite mountain, which will reduce cosmic muon background. The much larger distance to the reactors (compared to less than 2 km for the Daya Bay far detector) makes the experiment better able to distinguish neutrino oscillations, but requires a much larger, and better-shielded, detector to detect a sufficient number of reactor neutrinos.

Physics

The main approach of the JUNO Detector in measuring neutrino oscillations is the observation of electron-antineutrinos () coming from two

nuclear power plant A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a electric generator, generato ...

s at approximately 53 km distance. Since the expected rate of neutrinos reaching the detector is known from processes in the power plants, the absence of a certain neutrino

flavor Flavor or flavour is either the sensory perception of taste or smell, or a flavoring in food that produces such perception. Flavor or flavour may also refer to: Science *Flavors (programming language), an early object-oriented extension to Lis ...

can give an indication of transition processes. Although not the primary goal, the detector is sensitive to atmospheric neutrinos,

geoneutrinos A geoneutrino is a neutrino or antineutrino emitted in decay of radionuclide naturally occurring in the Earth. Neutrinos, the lightest of the known subatomic particles, lack measurable electromagnetic properties and interact only via the weak nucle ...

and

neutrinos A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is ...

from

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

e as well.

Expected sensitivity

Daya Bay and

RENO Reno ( ) is a city in the northwest section of the U.S. state of Nevada, along the Nevada-California border, about north from Lake Tahoe, known as "The Biggest Little City in the World". Known for its casino and tourism industry, Reno is the c ...

measured θ₁₃ and determined it has a large non-zero value. Daya Bay will be able to measure the value to ≈4% precision and RENO ≈7% after several years. JUNO is designed to improve uncertainty in several neutrino parameters to less than 1%.

References

External links

Jiangmen Underground Neutrino Observatory
web site
JUNO at Shanghai Jiao Tong University

JUNO documents
at

INFN The Istituto Nazionale di Fisica Nucleare (INFN; "National Institute for Nuclear Physics") is the coordinating institution for nuclear, particle, theoretical and astroparticle physics in Italy. History INFN was founded on 8 August 1951, to furt ...

* {{Neutrino detectors Physics experiments Underground laboratories Neutrino observatories Science and technology in China

Detector

Physics

Expected sensitivity

See also

References

External links