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The Muon Spectrometer of the ATLAS Experiment at CERN is composed of Thin Gap Chambers (TGC) and Monitoring Drift Tubes (MDT) technologies. TGCs are arranged in 6 Big Wheels and 2 Small Wheels. Gain stability and efficiency are required to be monitored during the Large Hadron Collider (LHC) operation (runs). A Charge monitoring board is identified as a solution to measure gain and efficiency during runs for the forthcoming High Luminosity upgrade. Specifications and topology are proposed with preliminary results as a demonstration of feasibility.

The novel Hamamatsu Multi Pixel Photon Counter Array S12045(X) is an array of 16 individual MPPCs (3×3 [mm2]) (further in the article MPPC array channel) each with 3600 G-APD (Geiger-mode Avalanche Photodiode) pixels (50×50 [μ m2]). Each MPPC in the array works with its individual reverse bias voltage around 70[V]. We studied the main features of each MPPC array channel for 2800 MPPC arrays at different temperatures. Two measurement systems were built to extract Gain, Breakdown Voltage, Photon Detection Efficiency (PDE), Optical Cross-talk and Dark rate for each MPPC array channel. The article describes the characterization process of MPPC arrays used in GlueX experiment (Jefferson Lab, Hall D). The hardware and the performed data analysis are described, which include new analytical expressions to obtain the number of photoelectrons and Optical Cross-Talk. The dynamical behavior of characterization parameters is presented as well.