First results from production testing of 64-channel MaPMT R13742 (1 in) and R13743 (2 in) for the LHCb RICH Upgrade

During 2019/20 LHCb Upgrade of the Ring Imaging Cherenkov (RICH) system the current Hybrid Photon Detectors (HPDs), with embedded 1 MHz readout electronics, will be replaced with Multi-anode Photomultiplier Tubes (MaPMTs) with new external 40 MHz readout electronics. Two sizes of Hamamatsu 64-channel MaPMT have been selected as the photon detectors: the 1-inch R13742 and the 2-inch R13743 MaPMTs, custom modifications of the models R11625 and R12699. Including spares, 3100 R13742 and 450 R13743 are purchased. The campaign to characterise all units, to ensure compliance with minimum specifications and to allow for selection of units with similar operational parameters is ongoing. The key characteristics comprise the average gain, the spread of the gain (uniformity), the peak-to-valley ratio, the dark count rate as well as the dependency of the gain on the high voltage (k-factor). So far 474 and 45 units have been tested, respectively. The test results will be presented. Additional measurements and studies, made with subsets of MaPMT, round the picture: the Quantum Efficiency, the loss of photon detection efficiency in magnetic fields and minimal mu-metal shield configurations to effectively shield them up to 3 mT.