Photomultipliers (PMTs) play a critical role in detecting liquid xenon scintillation light for the planned XENON1T experiment, while also having to meet high standards, especially regarding quantum efficiency and intrinsic radioactivity levels. To meet those standards, the R11410-21 PMT series has been developed by Hamamatsu Photonics in cooperation with the XENON collaboration. During the course of this bachelor thesis, various tests of PMTs of this series have been made at the Max-Planck-Institut für Kernphysik, Heidelberg, in order to determine parameters relevant for the experiment, like gain, dark count rate, transit time spread and afterpulse-to-main-pulse ratio and to verify specifications given by the
producer. Because the PMTs will operate in XENON1T at approximately −100 ℃, a specifically designed cool down setup has been used along with a room temperature setup, which has previously been used to test PMTs for the Double Chooz experiment. This allowed testing at room temperature as well as at cryogenic temperatures. Results have verified most of the values given by Hamamatsu and give a positive outlook for usage of the PMT series in XENON1T.