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Design and performance of the multi-PMT optical module for IceCube Upgrade

Abstract:

Located deep in the ancient glacial ice of Antarctica, IceCube [1] is the neutrino telescope with the largest instrumented volume worldwide. IceCube’s initial energy range, optimized for the investigation of the neutrino sky at the TeV to PeV energy scale and beyond, was extended down to∼ 10 GeV by DeepCore [2], enabling world-class measurements of neutrino oscillation parameters [3, 4]. The IceCube Upgrade [5] will further enhance IceCube’s capabilities through the installation of 693 new optical modules distributed along seven vertical strings, mainly located in the DeepCore region. The Upgrade will reduce IceCube’s energy threshold to a few GeV which will significantly enhance the precision of oscillation measurements. It will also provide a platform for improved calibration of the existing detector. The enhanced understanding of the optical properties of the deep ice will reduce the main systematic errors that contribute to the directional uncertainty of astrophysical neutrinos allowing us to re-analyze more than ten years of archival IceCube data. The optical module is the basic building block of a large-volume neutrino telescope. In firstgeneration detectors it features a single large PMT measuring the amount of incoming photons (derived from the signal charge) as well as their arrival times. Novel optical sensors will play a key role in the expected performance enhancements of the IceCube Upgrade. A large fraction will be multi-PMT Digital Optical Modules (mDOMs) featuring 24 relatively small PMTs (see Sec. 2.1). This multi-PMT approach, introduced to deep-sea detectors by the KM3NeT Collaboration [6], results in attractive advantages …