Characterization of the hamamatsu r11265 multi-anode photomultiplier tube with single photon signals

In view of the upgrade of the LHCb RICH detectors, multi-anode photomultiplier tubes (Ma- PMTs) were chosen as the baseline devices. The most promising models were tested, the latest being the Hamamatsu R11265. This tube is arranged in a 8×8 matrix of 2.9×2.9 mm2 pixels with a very small inactive border near the sides of the device. The total active area coverage is more than 75%. The device is being tested for single photon response with a commercial LED as the source of single photons. Current-feedback operational amplifiers are used as fast charge sensitive amplifiers. The outputs of the operational amplifiers are acquired with a fast oscilloscope. The very high readout speed simulates the fast readout which is foreseen in the upgraded LHCb, and provides excellent time resolution which helps in resolving the single photon events.