Next-generation multi-PMT Optical Modules and Data Acquisition for IceCube-Gen2

A new in-ice optical sensor is under development for IceCube-Gen2, the proposed expansion to the IceCube South Pole Neutrino Observatory. With 4 times the sensitivity of the current Digital Optical Modules (DOMs), the “Gen2-DOM” encloses multiple 4-inch Photomultiplier Tubes (PMTs) in a borosilicate glass pressure vessel, distributed homogeneously to guarantee full angular coverage. Challenges arise for the mechanical design from the requirement to minimize the size of each module, which requires close packing of the PMTs and associated electronics. An internal support structure has been designed to enable precise alignment and coupling of the PMTs to the pressure vessel using moulded optical gel ‘pads’. Modular electronics have been custom-designed to fit into the available space and to minimize cost and power requirements for the ~10000 modules to be installed. As IceCube-Gen2 aims to increase sensitivity to PeV-scale neutrino events,the electronics have been designed for a high linear dynamic range by adding a second channel dynode readout on each PMT. An in-module memory buffering system has been implemented, enabling a multi-level trigger design that focuses data transmission on the most interesting events. Prototype modules will be installed in the upcoming IceCube Upgrade.