Performance Studies of the Acoustic Module for the IceCube Upgrade

The IceCube Upgrade will augment the existing IceCube Neutrino Observatory by deploying 700 additional optical sensor modules and calibration devices within its center at a depth of 1.5 to 2.5 km in the Antarctic ice. One goal of the Upgrade is to improve the positioning calibration of the optical sensors to increase the angular resolution for neutrino directional reconstruction. An acoustic calibration system will be deployed to explore the capability of achieving this using trilateration of propagation times of acoustic signals. Ten Acoustic Modules (AM) capable of sending and receiving acoustic signals with frequencies from 5 to 30 kHz will be installed within the detector volume. Additionally, compact acoustic sensors inside 15 optical sensor modules will complement the acoustic calibration system. With this system, we aim for an accuracy of a few tens of cm to localize the Acoustic Modules and sensors. Due to the longer attenuation length of sound compared to light within the ice, acoustic position calibration is especially interesting for the upcoming IceCube-Gen2 detector, which will have a string spacing of around 240 m. In this contribution we present an overview of the technical design of the Acoustic Module as well as results of performance tests with a first complete prototype.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC2023). See arXiv:2307.13048 for all IceCube-Gen2 contribution

The Surface Array planned for IceCube-Gen2

IceCube-Gen2, the extension of the IceCube Neutrino Observatory, will feature three main components: an optical array in the deep ice, a large-scale radio array in the shallow ice and firn, and a surface detector above the optical array. Thus, IceCube-Gen2 will not only be an excellent detector for PeV neutrinos, but also constitutes a unique setup for the measurement of cosmic-ray air showers, where the electromagnetic component and low-energy muons are measured at the surface and high-energy muons are measured in the ice. As for ongoing enhancement of IceCube’s current surface array, IceTop, we foresee a combination of elevated scintillation and radio detectors for the Gen2 surface array, aiming at high measurement accuracy for air showers. The science goals are manifold: The in-situ measurement of the cosmic-ray flux and mass composition, as well as more thorough tests of hadronic interaction models, will improve the understanding of muons and atmospheric neutrinos detected in the ice, in particular, regarding prompt muons. Moreover, the surface array provides a cosmic-ray veto for the in-ice detector and contributes to the calibration of the optical and radio arrays. Last but not least, the surface array will make major contributions to cosmic-ray science in the energy range of the transition from Galactic to extragalactic sources. The increased sensitivities for photons and for cosmic-ray anisotropies at multi-PeV energies provide a chance to solve the puzzle of the origin of the most energetic Galactic cosmic rays and will serve IceCube’s multimessenger mission

Mechanical design of the optical modules intended for IceCube-Gen2

IceCube-Gen2 is an expansion of the IceCube neutrino observatory at the South Pole that aims to increase the sensitivity to high-energy neutrinos by an order of magnitude. To this end, about 10,000 new optical modules will be installed, instrumenting a fiducial volume of about 8 km3. Two newly developed optical module types increase IceCube’s current sensitivity per module by a factor of three by integrating 16 and 18 newly developed four-inch PMTs in specially designed 12.5-inch diameter pressure vessels. Both designs use conical silicone gel pads to optically couple the PMTs to the pressure vessel to increase photon collection efficiency. The outside portion of gel pads are pre-cast onto each PMT prior to integration, while the interiors are filled and cast after the PMT assemblies are installed in the pressure vessel via a pushing mechanism. This paper presents both the mechanical design, as well as the performance of prototype modules at high pressure (70 MPa) and low temperature (−40∘C), characteristic of the environment inside the South Pole ice