The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton liquid scintillator detector
with primary physics goal of neutrino mass hierarchy determination and precise measurement of
the neutrino oscillation parameters, as well as the measurement of solar neutrinos, geo-neutrinos,
supernova neutrinos and the diffuse supernova neutrinos. The detector will be built in a 700
m deep underground laboratory. A multi-veto system will be built for cosmic muon detection
and background reduction. The central detector will be submerged in the ultra pure water pool
instrumented with about 2000 MCP-PMTs (20 inches) to serve as an active water Cherenkov
detector for muon tagging. Both the pool walls and the central detector external surface will
be coated with Tyvek reflector to increase the light collection efficiency. The muon detection
efficiency will be > 95% for water Cherenkov detector. With this veto system, the cosmic muon
induced fast neutron background can be reduced to the level of ~0.1 /day