Status of the 20-in. PMT Instrumentation for the JUNO Experiment
The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment currently under construction. The primary goal of this experiment is to determine the neutrino mass hierarchy and precisely measure the oscillation parameters by detecting reactor anti-neutrinos. The JUNO experiment will be equipped with about 20000 large photo-cathode PMTs (20-in.): 15000 MCP PMTs from NNVT and 5000 Dynode PMTs from Hamamatsu. To achieve a 3% energy resolution, the PMTs are required to have high detection efficiency as well as very high optical coverage in the central detector. The JUNO PMT instrumentation includes PMT characterization, base (voltage-divider), waterproof potting, implosion protection, and finally assembly and installation to the detector. An extensive and complete test program has been developed and is carried on to verify the critical PMT parameters. Moreover, since the PMTs are required to work for 20 years in high-purity water with a depth of 44 m, and the voltage-divider, high voltage unit and the readout electronics will be placed close to the PMTs in the water pool, it is very important to design a highly reliable waterproof potting. Finally, since to achieve a large optical coverage (75%), the PMTs have to be closely packed with clearances of few mm, the protection from possible chain implosions and the installation are very challenging tasks.
KeywordsJUNO PMT Potting Implosion protection Assembly Installation
PACS29.20.Ej 52.59.-f 29.25.-t
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