Development, Installation and Operation of a Container-based Mass Testing System for 20-inch Photomultiplier Tubes for JUNO

Abstract

One of the big unanswered questions in neutrino physics is the ordering of the neutrino masses. This will be addressed by the Jiangmen Underground Neutrino Observatory (JUNO), a large liquid-scintillator neutrino oscillation experiment currently under construction in China. To reach its primary goal of determining the neutrino mass ordering (as part of a broad physics program), JUNO requires an unprecedented energy resolution of at least 3%/sqrt(E_vis[MeV]), which is realized i.e. by a high optical coverage consisting of about 18’000 20-inch photomultiplier tubes (PMTs). All parts deployed in the JUNO experiment further need to fulfill dedicated quality criteria; this is relevant in particular for the 20-inch PMTs regarding several key characteristics (such as dark rate, photo-detection efficiency, charge and timing resolution etc.). Consequently, each of the 20-inch PMTs needs to be tested and characterized separately before being mounted into the detector.In the scope of this thesis, a specially designed multi-channel PMT mass testing facility within four commercial shipping containers has been developed and assembled in collaboration with colleagues from University of Hamburg. These four container systems include a dedicated light system, commercial read-out electronics and a custom-made data acquisition software for fully automated control of the PMT characterization. This PMT mass testing facility aims to measurement several key characteristics in a stable and comparable way and assessed according to the requirements of JUNO. The system has been set up close to the JUNO site and has been running successfully for almost three years now.This thesis presents design and setup of the mass testing facility, including measurements investigating the performance, accuracies and systematics of the developed systems as well as an exemplary data analysis of more than one thousand 20-inch PMTs, proving the capability of the facility. This work is supported by the Deutsche Forschungsgemeinschaft.