Abstract
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, acoustic sensor networks are being deployed in deep seas to detect this phenomenon as a first step toward building a neutrino telescope. In order to study the feasibility of the method, it is critical to have a calibrator that is able to mimic the neutrino signature. In previous works the possibility of using the acoustic parametric technique for this aim was proven. In this study, the array is operated at a high frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated mimicking the UHE neutrino acoustic pulse. To this end, the development of the transducer to be used in the parametric array is described in all its phases. The transducer design process, the characterization tests for the bare piezoelectric ceramic, and the addition of backing and matching layers are presented. The efficiencies and directivity patterns obtained for both primary and parametric beams confirm that the design of the proposed calibrator meets all the requirements for the emitter.
Highlights
Astrophysical neutrino detection is based on Cherenkov light measurement induced by secondary leptons, like muons, which are produced by neutrino interactions with matter while passing across the Earth
Besides IceCube, the existing neutrino telescopes currently in use are the NT200+ in Lake Baikal [2], ANTARES [3] and a new optical-based deep-sea neutrino telescope under construction, the KM3NeT
The objective of the acoustic array calibrator is the emission of bipolar pulse signals with similar characteristics to the signal produced by a 1020 eV neutrino interacting in water at a distance of 1 km, which would be detected with an amplitude of about 10 mPa in the low-ultrasonic frequency range with an opening angle of about 1 ̋
Summary
Astrophysical neutrino detection is based on Cherenkov light measurement induced by secondary leptons, like muons, which are produced by neutrino interactions with matter while passing across the Earth. An emitter able to imitate the bipolar pulse signal generated by the neutrino in water will be extremely useful For this purpose, an acoustic array calibrator is being designed. The emissions from the emitter calibrator, which will be time controlled, will allow the sensors to be trained for neutrino detection It will improve the classification and identification of the acoustic neutrino signals, telling them apart from noise or other transient background signals [13]. The objective of the acoustic array calibrator is the emission of bipolar pulse signals with similar characteristics to the signal produced by a 1020 eV neutrino interacting in water at a distance of 1 km, which would be detected with an amplitude of about 10 mPa in the low-ultrasonic frequency range (maximum amplitude between 5 kHz and 20 kHz) with an opening angle of about 1 ̋. The emission of the low-frequency (tens of kHz) acoustic bipolar pulse is generated by using the parametric emission technique at a high frequency (hundreds of kHz)
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