Combined Opto-Acoustical Sensor Modules for KM3NeT

TL;DR

This paper presents a combined opto-acoustical sensor module for KM3NeT, integrating acoustic receivers with photosensors to improve positional accuracy and reduce complexity in underwater neutrino detection modules.

Contribution

It introduces a novel integrated sensor module combining acoustic and optical sensors, simplifying the design and deployment of detection units in KM3NeT.

Findings

Reduced underwater connectors and module complexity.

Achieved positional accuracy below 20 cm.

Enhanced integration of auxiliary devices.

Abstract

KM3NeT is a future multi-cubic-kilometre water Cherenkov neutrino telescope currently entering a first construction phase. It will be located in the Mediterranean Sea and comprise about 600 vertical structures called detection units. Each of these detection units has a length of several hundred metres and is anchored to the sea bed on one side and held taut by a buoy on the other side. The detection units are thus subject to permanent movement due to sea currents. Modules holding photosensors and additional equipment are equally distributed along the detection units. The relative positions of the photosensors has to be known with an uncertainty below $20\,$cm in order to achieve the necessary precision for neutrino astronomy. These positions can be determined with an acoustic positioning system: dedicated acoustic emitters located at known positions and acoustic receivers along each detection unit. This article describes the approach to combine an acoustic receiver with the photosensors inside one detection module using a common power supply and data readout. The advantage of this approach lies in a reduction of underwater connectors and module configurations as well as in the compactification of the detection units integrating the auxiliary devices necessary for their successful operation.