IIHE Invited seminar: Fiber optic hydrophones for acoustic neutrino detection

Abstract:
The scientific potential for detecting cosmic neutrinos with energies at or above the GZK cut-off—the energy limit for cosmic rays due to interactions with the cosmic microwave background—has been extensively discussed in the literature. The recent observation of a very high-energy event by the KM3NeT telescope has further fueled this discussion, as it may represent the first detection of a GZK neutrino. However, despite this remarkable result, the extremely low expected flux of ultra-high-energy neutrinos (Eν > 1018 eV) clearly indicates that their detection will require a telescope with an effective volume exceeding 100 km3.

Acoustic detection offers a promising approach for observing these ultra-high energy cosmic neutrinos. The sound waves generated by their energy deposition in the deep sea can propagate over many kilometers with little attenuation, making it feasible to instrument a vast volume of water for neutrino detection. Achieving this requires the development of acoustic detection technologies capable of supporting a large-scale, deep-sea sensor network.

Fiber-optic hydrophone technology stands out as a promising candidate for such a network, combining the necessary sensitivity to detect the faint acoustic signals from neutrino interactions with the potential for cost-effective large-scale deployment. Nikhef is actively developing this fiber-optic hydrophone technology to meet the sensitivity and operational requirements of deep-sea environments.

In this presentation, I will report on the progress of the hydrophone development and outline the plans toward a future acoustic neutrino telescope — opening a window to explore the universe beyond the GZK horizon.

Short bio:
Ernst-Jan Buis is a researcher and engineer specializing in technology development and systems engineering. He earned his PhD in 2002 from Nikhef and the University of Amsterdam, where his work focused on the ATLAS detector at CERN. His doctoral research centered on supersymmetry and the ATLAS inner tracker system.
After completing his PhD, Ernst-Jan moved to space instrumentation, contributing to major ESA missions. These include the future space-based gravitational wave observatory LISA, the X-ray observatory Athena, and BepiColombo, the planetary mission to Mercury.
At TNO, the Dutch institute for applied sciences, he led the development of fiber optic hydrophones for acoustic neutrino detection—a critical technology for large-scale, passive underwater sensor networks. For five years, he also played a key role in the KM3NeT experiment as a systems engineer and member of the project steering committee.
Recently, Ernst-Jan joined Nikhef as a staff scientist, where he now focuses entirely on acoustic neutrino detection. In addition to his research, he serves as a lecturer at Delft University of Technology