FPGA implementation of a highly efficient pulse discrimination trigger algorithm for the JUNO large PMTs readout electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino physics experiment located in China. A 20 kton multipurpose underground Liquid Scintillator (LS) will allow the determination of the neutrino mass hierarchy by measuring the nuclear antineutrino energy spectrum. An excellent energy resolution and a large detector fiducial volume are key ingredients for addressing many important topics in neutrino and astroparticle physics. The LS detector is instrumented by 18000 20 inches PhotoMultiplier Tubes (PMT) which corresponds to about 75% of coverage. The Front-End readout electronics focuses on the Global Control Unit (GCU) board which, thanks to the on-board Field Programmable Gate Array (FPGA), is able to do an online processing of the PMTs waveform, providing first-level trigger requests as well as timing synchronization and data forwarding to the Data Acquisition (DAQ) system. The JUNO experiment requires an evaluation of single photoelectron signals originated by the PMTs and, in this conditions, the signal amplitude is comparable to the electronics background noise. Therefore, the paper aims to describe a new kind of trigger algorithm, featuring a high discrimination power. After having defined its architecture, the test section compares the pulse detection efficiency in low Signal-to-Noise Ratio (SNR) scenarios, with a simple leading-edge trigger.