Characterization of the Hamamatsu 8-inch R14688-100 PMT

Large-scale optical neutrino and dark-matter detectors rely on large-areaphotomultiplier tubes (PMTs) for cost-effective light detection. The newR14688-100 8-inch PMT developed by Hamamatsu provides state-of-the-art timingresolution of around 1 ns (FWHM), which can help improve vertex reconstructionand enable Cherenkov and scintillation light separation in scintillation-baseddetectors. This PMT also provides excellent charge resolution, allowing forprecision photoelectron counting and improved energy reconstruction. The Eosexperiment is the first large-scale optical detector to utilize these PMTs. Inthis manuscript we present a characterization of the R14688-100 singlephotoelectron response, such as the transit-time spreads, the dark-rates, andthe afterpulsing. The single photoelectron response measurements are performedfor the 206 PMTs that will be used in Eos.