The JUNO experiment

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector aiming at the measurement of anti-neutrinos issued from nuclear reactors at a 53km distance, having as primary goal the determination of the neutrino mass hierarhcy. The detector will be located 1800m. w. e. underground and consists of a 20 kiloton liquid scintillator contained in a 35.4m diameter acrylic sphere, instrumented by more than 17000 20 inch PMTs ensuring a 77% photocatode coverage. The required energy resolution to discriminate between the hierarchies at the 3-4 sigma C. L. in about 6 years of data taking is 3% at 1 MeV. To achieve such a precision, severe constraints on the detector components quality are set: the PMTs need a quantum efficiency of more than 27% and the attenuation length of the liquid has to be better than 20m (at 430 nm). The precise measurement of the anti-neutrino spectrum will allow to reduce the uncertainty below 1% on solar oscillation parameters. The international collaboration of JUNO was established in 2014, the civil construction started in 2015 and the R&D of the detectors is ongoing. The expected start of data taking is set for 2020.