Validation and integration tests of the JUNO 20-inch PMT readout electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a large neutrino detector currently under construction in China. JUNO aims to determine the neutrino mass ordering and to perform leading measurements detecting terrestrial and astrophysical neutrinos over a wide energy range, spanning from 200 keV to several GeV. Given the ambitious physics goals of JUNO, its readout electronics has to meet specific requirements, which motivated the thorough characterization described in this manuscript. The time synchronization among the electronics modules was found to exceed by few ns the theoretical expectation, as a consequence of the non-optimal data taking conditions. However, the system showed an excellent stability over long data taking periods, ensuring that any time offset could be calibrated out at the beginning of the data taking. The maximal deviation from a linear charge response was found to be 1.1% for the high gain ADC and 0.8% for the low gain ADC. In a JUNO-like environment, i.e 40 m underwater, the recorded FPGA temperature complied with the reliability standards of JUNO.