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

Abstract

The IceCube Upgrade is the first step towards the next-generation neutrino observatory at the South Pole, IceCube-Gen2, and will be installed in the central region of the existing array. The Upgrade will consist of 693 newly developed, densely spaced optical sensors and 50 standalone calibration devices, which will enhance IceCube's capabilities both at low and high neutrino energies. Of the new sensors, 402 will be multi-PMT Digital Optical Modules (mDOMs). Consisting of 24 small photomultipliers arranged inside a pressure vessel, the mDOM features a large sensitive area distributed nearly homogeneously over the full solid angle. The use of multiple, individually read-out PMTs allows directional information to be obtained for the registered photons and enables the use of multiplicity triggering within a single module, e.g., for background suppression. The challenges driving the mDOM development included tight restrictions on module size, data-transfer rate, and power consumption as well as the harsh environment in the deep ice at the South Pole. In this contribution we present the final mDOM design that meets these challenges.

Design and Performance of the mDOM Mainboard for the IceCube Upgrade

“…IceCube Upgrade will comprise about 700 optical sensors on seven strings. Among these sensors, 402 are mDOMs (multi-PMT Digital Optical Modules) [2]. Each mDOM features 24 3-inch photomultiplier tubes (PMTs), read out individually with a 120 MSPS 12-bit ADC.…”

A multi-PMT optical sensor for IceCube-Gen2

“…The photons are collected by Digital Optical Modules (DOMs), installed in boreholes drilled into the ice at depths ranging between 1450 m and 2450 m. The IceCube Upgrade will consist of nearly 800 new optical modules on 7 strings. There are two main optical module designs for the Upgrade: the mDOM [2] (figure 1), featuring 24 Photomultiplier Tubes (PMTs) of 3 diameter, yielding an almost homogeneous angular coverage, and the DEgg [3] (figure 1), with two 8 PMTs opposite each other. The Long Optical Module (LOM), developed from the multi-PMT Upgrade modules, has a reduced diameter (12 ) to enable the module to fit in a narrower hole, saving time and fuel costs for drilling.…”