The JUNO double calorimetry system

The Jiangmen Underground Neutrino Observatory (JUNO) detector was designed to achieve 3% energy resolution which required 18,000 high quantum efficiency 20-inch PMTs (LPMTs) closely packed around the liquid scintillator (LS) target ball. Besides this, 25,000 3-inch PMTs (SPMTs) were also designed to be installed between the LPMTs gaps forming a double calorimetry system to improve and extend JUNO physics reach, with a better energy resolution, muon reconstruction, supernova neutrino detection and so on. The LPMTs have been produced by the Chinese NNVT (15,000 PMTs) and by the Japanese Hamamatsu Photonics company; the 3” PMTs are made by the HZC company. Until recently more than 15,000 LPMTs and SPMTs have been produced, respectively. Performance test data so far indicate that both LPMTs and SPMTs perform as expected. Both system’s high voltage divider, potting, cabling, connector are in the production phase. The electronics and underwater box are all making good progress.