The Jiangmen Underground Neutrino Observatory (JUNO) is a medium baseline[2][3] reactor neutrino experiment under construction at Kaiping, Jiangmen in Southern China. It aims to determine the neutrino mass hierarchy and perform precision measurements of the Pontecorvo–Maki–Nakagawa–Sakata matrix elements. It will build on the mixing parameter results of many previous experiments. The collaboration was formed in July 2014[4] and construction began January 10, 2015.[5] The schedule aims to begin taking data in 2023.[6] Funding is provided by the Chinese Academy of Sciences, but the collaboration is international.
"JUNO" redirects here. For other uses, see Juno.
Planned as a follow-on to the Daya Bay Reactor Neutrino Experiment, it was originally planned for the same location, but the construction of a third nuclear reactor (the planned Lufeng Nuclear Power Plant) in that area would disrupt the experiment, which depends on maintaining a fixed distance to nearby nuclear reactors.[7]:9 Instead it was moved to a location 53km from both of the planned Yangjiang and Taishan nuclear power plants.[7]:4
Detector
The main detector consists of a 35.4m (116ft) diameter transparent acrylic glass sphere containing 20,000tonnes of linear alkylbenzene liquid scintillator, surrounded by a stainless steel truss supporting approximately 53,000 photomultiplier tubes (17,000 large 20-inch (51cm) diameter tubes, and 36,000 3-inch (7.6cm) tubes filling in the gaps between them), immersed in a water pool instrumented with 2000 additional photomultiplier tubes as a muon veto.[8] As of 2022, construction of the detector is well underway.[9] Deploying this 700m (2,300ft) underground will detect neutrinos with excellent energy resolution.[3] The overburden includes 270m of granite mountain, which will reduce cosmic muon background.[10]
The much larger distance to the reactors (compared to less than 2km 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
Predicted oscillation probability of electron neutrinos (black) oscillating to muon (blue) or tau (red) neutrinos, as a function of distance from source. Existing short-baseline experiments measure the first small dip in the black curve at 500km/GeV; JUNO will observe the large dip at 16000km/GeV. For reactor neutrinos with an energy of ≈3MeV, the distances are ≈1.5km and ≈50km, respectively. This plot is based on assumed mixing parameters; the measured shape will differ and allow the actual parameters to be computed.
The main approach of the JUNO Detector in measuring neutrino oscillations is the observation of electron-antineutrinos ( ν e) coming from two future nuclear power plants at approximately 53km distance.[10] Since the expected rate of neutrinos reaching the detector is known from processes in the power plants, the absence of a certain neutrino flavor can give an indication of transition processes.[10]
Although not the primary goal, the detector is sensitive to atmospheric neutrinos, geoneutrinos and neutrinos from supernovae as well.
Expected sensitivity
Daya Bay and RENO 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%.[11]
Li, Yu-Feng (25 Feb 2014). "Overview of the Jiangmen Underground Neutrino Observatory (JUNO)". International Journal of Modern Physics: Conference Series. 31: 1460300. arXiv:1402.6143. Bibcode:2014IJMPS..3160300L. doi:10.1142/S2010194514603007. S2CID118556513.
Другой контент может иметь иную лицензию. Перед использованием материалов сайта WikiSort.org внимательно изучите правила лицензирования конкретных элементов наполнения сайта.
2019-2025 WikiSort.org - проект по пересортировке и дополнению контента Википедии