Acoustic neutrino detection in sea water: Technical aspects

Abstract

Abstract. The acoustic neutrino detection technique is a promising approach for future large-scale detectors with the aim of measuring the small expected flux of ultra-high-energy cosmogenic neutrinos. This article focuses on the technical aspects of the application of this technique in water. Though the technique is intriguingly simple, challenges arise from e.g. anisotropic sound propagation, ambient noise or transient background in a natural environment. We present major technical aspects of acoustic neutrino detection based on experience gained with different acoustic test arrays. Before aiming for a largescale acoustic or hybrid (opto-acoustic) detector, the acoustic detection technique needs to be investigated further in the next generation of Cherenkov neutrino telescopes that are currently prepared. We discuss the technical implementation into those large optical detectors, primarily focussing on the KM3NeT project.

Fiber laser design and measurements for fiber optical hydrophones in their application for ultra-high energy neutrino detecti

“…Ultra-high energy (UHE) neutrinos, at an energy of > 10 18 eV may crucial information on the underlying principles of the GZK [1] cut-off mechanism, but also on distant astrophysical sources [2]. Since only very few UHE neutrinos reach earth, their detection require a telescope with a detector volume of circa 100 km 3 . When an ultra high energy (UHE) neutrino interacts with a proton in water a cascade of secondary particles will be produced.…”

“…The sudden heating of the water will cause a pressure wave results in a bipolar signal with a frequency between a few and 50 kHz. A cascade from a 10 18 eV neutrino will cause an sound pressure level of 10 mPa or 5 mPa at a distance of 200 m and 500 m, respectively [3]. To fully reconstruct the direction and energy of a cosmic ray event an array of hydrophones will be used.…”

Acoustic System Development for Neutrino Underwater Detectors

“…In most test setups, the acoustic sensors are grouped to clusters or acoustic antennae, each with a volume in the range of a cubic metre and four to six sensors (Graf 2013). The data of all sensors is digitised individually but the proximity of sensors is utilised in the processing strategies for the data (Richardt et al 2014).…”

“…One of the most challenging issues in the acoustic neutrino detection field is developing an algorithm able to analyse the acoustic data recorded by the underwater array hydrophone that is able to detect the acoustic signal produced by the shower induced by neutrino interaction in water (Graf 2013). The complexity of this task is large; small signals have to be found in the ambient noise at a signal-to-noise ratio near or even below unity, and also neutrino-induced signals have to be distinguished from neutrino-like background signals.…”