The main goal of the JUNO experiment is the determination of the neutrino mass ordering. To achieve this, an extraordinary energy resolution of at least 3 % at 1 MeV is required for which all parts of the JUNO detector need to meet certain quality criteria. This is relevant in particular for those which are related to the energy resolution of the detector, such as the photomultiplier tubes (PMTs) to be deployed in JUNO. This paper presents the setup and performance of a dedicated PMT mass testing facility to examine and characterize the performance of the 20-inch JUNO PMTs. Its quasi-industrial size and operation level allows to test all 20000 PMTs intended to be used in the JUNO experiment. With this PMT mass testing system, several key characteristics like dark count rate, peak-to-valley ratio, photon detection efficiency, and timing resolution have been determined at an operating gain of 1 × 107 and assessed with respect to the requirements of JUNO. Measurement conditions and modes for the PMTs as well as estimated accuracies for the determination of the individual PMT parameters with the system are presented as well.
Micro-Raman temperature study and X-ray fluorescence (XRF) spectroscopy were used for characterization of the blue glaze on Saint Johnthe Baptist -majolica terracotta relief attributed to Andrea Della Robbia and Saint Johnthe Baptist withCross -majolica terracotta statue attributed to Giovanni Della Robbia. Both objects are on permanent exhibition in the John and Mable Ringling Museum of Art in Sarasota, FL. This study proves that the detection of the 548 cm −1 Raman band alone cannot serve as evidence for presence of lazurite crystallites in the pigment in the glaze. It was established that the famous Della Robbia blue is due to the combined effect of Co-Ni-Cu-Zn atoms and S 3 − ions embedded in a lead silicate matrix. It is proposed that the Della Robbia family used Co-containing sulfide ores as a source for manufacturing their blue pigments.
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