Testing of Photo-Multiplier Tubes for the FCAL-II Upgrade at JLab

The Forward electromagnetic Calorimeter (FCAL) in the experimental Hall D at the Jefferson National Laboratory is a state-of-the-art detector initially designed to search for exotic mesons in the GlueX experiment. Recently, this detector has undergone an upgrade to expand its capabilities to detect η particle decays in the JLab Eta Factory (JEF) experiment. The improvement made to the forward calorimeter consists of replacing the central portion of the detector, previously consisting of lead glass blocks, with high resolution, high granularity PbWO₄ crystals. To accomplish this, 1,596 PbWO₄ crystal modules were assembled, visually inspected, tested, and installed in the upgraded FCAL-II calorimeter. One of the critical tasks that I was involved in as an undergraduate student was to inspect and to test each photo-multiplier tube (PMT) before it was installed. In this presentation, I will outline the experimental setup and data analysis methods for the PMT tests, and summarize the results and the impact.