Performance study of the new Hamamatsu R9779 & Photonis XP20D0 fast 2" photomultipliers

The focus of this paper is the evaluation of the new fast 51 mm-diameter, 8-stage Hamamatsu R9779 photomultipliers (PMTs) with an acceleration-ring at the front-end and the Photonis XP20D0 PMTs with a screening grid in front of the anode. The following performance characteristics have been measured: timing resolution, anode-scan-uniformity and time resolution uniformity. The unfolded timing resolutions for two R9779 had been measured to be 194 ps and 193 ps with plastic scintillators. The unfolded timing resolutions for two XP20D0 with plastic scintillators are 181 ps and 154 ps, respectively. The variation in time resolution across the windows of the two R9779 is 117 ps and 171 ps and 79 and 73 ps for the two XP20D0 PMTs.