Development of the micro-channel plate photomultiplier for the Belle II time-of-propagation counter

The time-of-propagation counter for the Belle II experiment is a new particle identification device using ring imaging Cherenkov technique. In order to detect each Cherenkov photon with a timing precision of 30-40 ps in a 1.5 T magnetic field, a micro-channel plate photomultiplier tube is a suitable device for the TOP counter. By introducing an atomic layer deposition technique on the micro-channel plate surface, the tube lifetime was improved by a factor of 3-10 relative to more conventional devices. A total of 530 tubes have been produced. To ensure appropriate tube performance, the quantum efficiency, gain and transit time spread have been measured for all units. The results from each measurement are discussed. Results from a beamtest with a 2 GeV/c positron beam are also reported and demonstrate the good tube performance.