New design of an acoustic array calibrator for underwater neutrino telescopes

A short bipolar pressure pulse with ‘pancake’ directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, several acoustic sensors are deployed in deep sea trying to detect the phenomena as first step to build a neutrino telescope. In order to study its feasibility, it is critical to have a calibrator able to mimic the neutrino ‘signature’. In previous works we developed  a first compact array calibrator prototype that validated the possibility of using the acoustic parametric technique for this aim, but due to limitations in terms of power efficiency, transducer properties and electronics matching, the application was not fully fulfilled. In this paper, we describe a new proposed design of a compact calibrator composed of an array of piezo ceramic tube transducers emitting in axial direction, and new specific electronics adapted to the transducers to feed it more efficiently. The array is operated at high-frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated permitting to mimic the UHE neutrino acoustic pulse with the required power. All the design processes involved and the results are presented: ceramic characterization, signal processing, simulations, tests, etc.