The main task of the Top Tracker detector of the neutrino reactor experiment Jiangmen Underground Neutrino Observatory (JUNO) is to reconstruct and extrapolate atmospheric muon tracks down to the central detector. This muon tracker will help to evaluate the contribution of the cosmogenic background to the signal. The Top Tracker is located above JUNO's water Cherenkov Detector and Central Detector, covering about 60% of the surface above them. The JUNO Top Tracker is constituted by the decommissioned OPERA experiment Target Tracker modules. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multianode photomultiplier tubes. Compared to the OPERA Target Tracker, the JUNO Top Tracker uses new electronics able to cope with the high rate produced by the high rock radioactivity compared to the one in Gran Sasso underground laboratory. This paper will present the new electronics and mechanical structure developed for the Top Tracker of JUNO along with its expected performance based on the current detector simulation.
The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino medium baseline experiment under construction in southern China. The experiment has been proposed with the main goals of determining the neutrino mass ordering and measuring the oscillation parameters with sub-percent precision. To reach these goals, JUNO is located about 53 km from two nuclear power plants and will detect electron antineutrinos from reactors through inverse beta decay. Furthermore, an unprecedented energy resolution of 3 % at 1 MeV is required. The JUNO detector consists of 20 kt of liquid scintillator (LS) contained in a 17.7 m radius acrylic vessel, which is instrumented with a system of 17 612 20-inch Large-PMTs and 25 600 3-inch Small-PMTs, with a total photo-coverage greater than 75 %. Additionally, 2400 Large-PMTs are installed in the instrumented Water Pool detector. The signal from the Large-PMTs is processed by the JUNO electronics system, which can be divided into two main parts: the front-end electronics, placed underwater, consisting of a Global Control Unit (GCU); and the back-end electronics, outside water, consisting of DAQ and trigger. Each GCU reads three Large-PMTs and has the main tasks of performing the analog-to-digital conversion of the signals, generating a local trigger to be sent to the global trigger, reconstructing the charge, tagging events with a timestamp, and temporarily storing data in the local FPGA memory before transferring it to DAQ upon a global trigger request. The poster will mainly focus on the description of the underwater electronics for the Large-PMTs. Results from tests on a small setup with 13 GCUs at Laboratori Nazionali di Legnaro, Italy, will also be presented.
The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino medium baseline experiment under construction in Southern China, expecting to begin data taking in 2023. JUNO is a liquid-scintillator-based detector with an active target mass of 20 kt and aims to detect and study electron antineutrinos from reactors to improve the knowledge in the field of neutrino oscillations. The scintillation light emitted by the interaction of an antineutrino in the detector is detected by a system of 17 612 20-inch Large-PMTs and 25 600 3-inch small-PMTs. The signal from the Large-PMTs is processed by the JUNO Large-PMT readout electronics, which consists of several hardware components and is partly placed underwater. Given the ambitious physics goals of JUNO, the electronic system has to meet specific requirements, and a thorough characterization is required. After describing the readout electronics, tests and results performed with a small-scale integration test facility at Laboratori Nazioni di Legnaro, Italy, are here presented and discussed.
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