Abstract
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.
Highlights
: 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
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
The XENONnT PMT testing campaign was improved in several ways compared to that of XENON1T
Summary
Quantum efficiency: the quantum efficiency (QE) of a PMT is defined as the ratio between the number of photoelectrons (PEs) emitted from the photocathode and the number of incident photons. The lower end of the distributions are truncated due to the contractually agreed minimum QE of 28% Both the distributions of all PMTs and the subset of qualified tubes have a mean QE of 34.0%, with a standard deviation of 2.8%. Some PMTs reach exceptionally high QEs of more than 40% These values are very similar to those of the XENON1T PMTs, with a mean and standard deviation of 34.5% and 2.8% [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
