Series testing and characterization of 1100 Hamamatsu H12700 Multianode Photomultiplier tubes

Both the future CBM-RICH and the recently upgraded HADES-RICH use Hamamatsu H12700 Multi-Anode Photomultipliers (MAPMTs) as their photon detectors. To test the MAPMTs thoroughly before using them in the detectors, the photon sensors were qualified well in advance and a test bench was built to efficiently characterize each MAPMT. The test bench measures the single photoelectron gain, dark rate, relative efficiency, and afterpulse probability of each channel. This article describes the operating principle of the test bench and discusses the distributions of each measured quantity over 1100 MAPMTs. Additionally, the long-term aging effects of the H12700 MAPMT are investigated based on repeated measurements of individual MAPMTs.