Photomultiplier tubes (PMTs) are often used in low-background particle physics experiments, which rely on an excellent response to single-photon signals and stable long-term operation. In particular, the Hamamatsu R11410 model is the light sensor of choice for liquid xenon dark matter experiments, including XENONnT. The same PMT model was also used for the predecessor, XENON1T, where issues affecting its long-term operation were observed. Here, we report on an improved PMT testing procedure which ensures optimal performance in XENONnT. Using both new and upgraded facilities, we tested 368 new PMTs in a cryogenic xenon environment. We developed new tests targeted at the detection of light emission and the degradation of the PMT vacuum through small leaks, which can lead to spurious signals known as afterpulses, both of which were observed in XENON1T. We exclude the use of 26 of the 368 tested PMTs and categorise the remainder according to their performance. Given that we have improved the testing procedure, yet we rejected fewer PMTs, we expect significantly better PMT performance in XENONnT.

光电倍增管 (PMT) 常用于低背景粒子物理实验，它依赖于对单光子信号的出色响应和稳定的长期运行。特别是，Hamamatsu R11410 型号是液体氙暗物质实验（包括 XENONnT）的首选光传感器。相同的 PMT 模型也用于前身 XENON1T，观察到影响其长期运行的问题。在这里，我们报告了一种改进的 PMT 测试程序，该程序可确保 XENONnT 中的最佳性能。我们使用新的和升级的设施，在低温氙气环境中测试了 368 个新的 PMT。我们开发了新的测试，旨在通过小泄漏检测光发射和 PMT 真空的退化，这可能导致称为后脉冲的虚假信号，两者都在 XENON1T 中观察到。我们排除了 368 个测试 PMT 中的 26 个的使用，并根据其性能对其余部分进行分类。鉴于我们改进了测试程序，但我们拒绝了更少的 PMT，我们预计 XENONnT 中的 PMT 性能会显着提高。