Abstract
Following the first observation of an astrophysical high-energy neutrino flux with the IceCube Neutrino Observatory in 2013, planning for an upgrade of the detector is progressing, which will expand the capabilities of the detector both at low and high neutrino energies. A substantial contribution to the improved performance is anticipated to be achieved by the application of advanced optical module technology. The multi-PMT optical module, mDOM, consists of 24 3-inch PMTs which provide, amongst others, a large, homogeneous photosensitive area and sensitivity to the incident direction of photons. After an introduction, the current status of the mDOM development is presented with emphasis on the characterization of the photomultipliers under consideration.
Highlights
Photomultiplier performancePMT testing was carried out with slightly different setups in Erlangen (Hamamatsu PMT) and Madison (HZC PMT). 66 Hamamatsu PMTs were tested while the HZC batch consisted of three tubes
Following the first observation of an astrophysical high-energy neutrino flux with the IceCube Neutrino Observatory in 2013, planning for an upgrade of the detector is progressing, which will expand the capabilities of the detector both at low and high neutrino energies
The gain g was derived from a single photoelectron (SPE) charge spectrum as g = ∆Q/e, where ∆Q is the position of the single-photoelectron charge peak relative to the pedestal determined from a fit of the distribution based on [6], and e is the electron charge
Summary
PMT testing was carried out with slightly different setups in Erlangen (Hamamatsu PMT) and Madison (HZC PMT). 66 Hamamatsu PMTs were tested while the HZC batch consisted of three tubes. The gain g was derived from a single photoelectron (SPE) charge spectrum (illustrated in Fig. 3) as g = ∆Q/e, where ∆Q is the position of the single-photoelectron charge peak relative to the pedestal determined from a fit of the distribution based on [6], and e is the electron charge. For both PMT models the gain was determined in relation to the PMT supply voltage ( known as gain slope). The Hamamatsu PMT is slightly superior to the HZC model This difference is expected to become more pronounced if both PMTs are operated at identical gain. The data allowed to derive an effective diameter for the PMT under investigation (integration of the area weighted by the relative signal strength) which was found to be 77 mm to 78 mm, exceeding the more conservative statement of 72 mm by the manufacturer
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