Characterization and tests of 39 channels of the JUNO large PMT electronics

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment under construction in South China. It will make use of 20 kton of highly transparent liquid scintillator (Linear Alkyl-Benzene) contained in an acrylic sphere surrounded by 18000 20" PMTs and 25000 3" PMTs, respectively, aiming at an energy resolution better than 3% at 1 MeV. JUNO is expected to resolve the neutrino mass hierarchy, significantly improve accuracy of the solar oscillation parameters and make a significant impact to several other Neutrino Physics topics. The JUNO Padova research unit is responsible for the design and development of the large PMT readout electronics; in order to verify its performances, a small JUNO mock-up system, equipped with 48 small size PMTs reading out the light generated by a 20 liter liquid scintillator detector, has been assembled and setup at the Legnaro INFN National Laboratories (LNL). Within this context, my thesis work concerns the development of a software for the processing and the analysis of the readout data of the test system at LNL and the evaluation of the performances of the full JUNO electronics chain. In particular, the first part of my thesis focuses on the development of a ROOT based program whose main task is reading the binary files produced by the DAQ system and extracting all the information they provide, such as, for example, the event timestamps or the acquired signal waveforms; this information, in addition to some other important characteristics of the acquired signals, such as the baseline contribution or the integrated charge, is then stored in ROOT files for further elaboration. Another important activity of my thesis work concerns the development of several methods for data quality monitoring of the experimental setup; these methods include in particular a study on the stability, over a long period of time, of the trigger rate and of the baseline contribution to the signals. The data quality monitoring is performed by means of some ROOT based programs, which are developed for this purpose and properly optimised using data acquired in several long term acquisition runs. Furthermore, studies on time correlation and synchronization of signals coming from different PMTs are carried out; these signals are acquired in runs with an external trigger on cosmic muons, generated by three external plastic scintillators. These studies are useful in defining a specific procedure for reconstructing the total charge released by these particles in the liquid scintillator; a detailed analysis of the resulting spectrum allows to obtain, after a careful comparison with the expectation based on theoretical calculations and Monte Carlo simulations, some important results on the evaluation of the setup response. Finally, some additional analyses concerning a more detailed calibration of the apparatus are presented and discussed.