Study on relative collection efficiency of PMTs with spotlight

BackgroundPhoton detection efficiency is a key parameter of PMTs in high-precision neutrino and dark matter experiments, while normally the quantum efficiency is used with a normalization factor and angular response as the detection efficiency, where it is always coupled with detector response from the calibration normalization. Here, the absolute photon detection efficiency of 20'' PMTs in photon-counting level is further considered rather than the combination of quantum efficiency and normalization factors.
Purpose and methodIn order to have a good understanding of photon detection efficiency of the large-area PMT, we conduct a detailed comparison of relative collection efficiencies of a series of PMTs with spotlight. This study is based on the tests of relative quantum efficiency and relative detection efficiency, checked with several light intensities.
ConclusionAll the results are consistent in relative QE and DE measurement with different light intensities, and the error of each parameter is coupled in our studies. Based on the measurements, Hamamatsu R12860 shows the maximum collection efficiency with spotlight at PMT center, and Hamamatsu R12199, R1355 and HZC XP72B22 have the same level of CE within the uncertainty.
DiscussionFollowing the configuration on incident light and DE definition, we can further define the DE of a large-area PMT with similar algorithms, which will also be used for detector simulation in JUNO.