The study of active geomagnetic shielding coils system for JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator (LS) detector for neutrino mass ordering and other physics research. uses large-size $20$ inches photomultiplier tubes to detect photons from scintillator. PMTs are sensitive easily affected such that the detection efficiency loses about 60$\%$ under geomagnetic field intensity ($\sim$500 mG). It has significantly negative effect on performance, compensation system necessary shielding. As permalloys rusted in water, better way shielding apply an active coils system. simulations show set of 32 circular can meet experiment requirement. residual magnetic less than 0.05 G Central Detector Photomultiplier Tube (CD-PMT) region (38.5-39.5 m diameter). A prototype coil with 1.2 was built validate simulation design. measured data results consistent each other, effectively reduced by coils, verifying design JUNO. This study expected provide practical guidance PMT future large-scale designs.