A Compact Array Transducer for Full Calibration of Underwater Acoustic Detection Neutrino Telescopes

[EN] KM3NeT, the underwater neutrino telescope in the Mediterranean Sea, is a detector under construction. KM3NeT uses Digital Optical Modules (DOMs) to detect neutrinos but there will be a study about the viability to acoustic detection of neutrinos using mainly the acoustic sensors the telescope has for positioning purposes. For this, it is necessary to calibrate and test the acoustic response of the receivers in the detector to determine the sensitivity to detect the neutrino acoustic signal and discriminate it from the environmental background. In this work, the strategy for the calibration of the sensor system using a compact array using three steps (frequency, directivity and neutrino signal-like) is described. Moreover, some R&D activities and results about the second step (long parametric directive signals) are shown.Financial support of the Spanish Plan Estatal de Investigación, ref. PGC2018-096663-B-C43 (MICINN/FEDER)Ardid Ramírez, M.; Tortosa, DD.; Martínez Mora, JA. (2019). A Compact Array Transducer for Full Calibration of Underwater Acoustic Detection Neutrino Telescopes. IEEE. 591-595. https://doi.org/10.1109/IOTSMS48152.2019.8939244S59159

Development of a trigger for acoustic neutrino candidates in KM3NeT

The KM3NeT Collaboration is constructing two large neutrino detectors in the Mediterranean Sea: ARCA, located near Sicily and aiming at neutrino astronomy, and ORCA located near Toulon and designed for the study of intrinsic neutrino properties. The two detectors together will have hundreds of Detection Units with Digital Optical Modules kept vertically by buoyancy forming a large 3D optical array for detecting the Cherenkov light produced after the neutrino interactions. To properly reconstruct the direction of the incoming neutrino, the position of the DOMs, which are not static due to the sea currents, must be monitored. For this purpose, the detector is equipped with an Acoustic Positioning System, which is composed of fixed acoustic emitters on the sea bottom, a hydrophone in each DU base, and a piezoceramic sensor in each DOM, as acoustic receivers. This network of acoustic sensors can be used not only for positioning, but also for acoustic monitoring studies such as bioacoustics, ship noise monitoring, environmental noise control, and acoustic neutrinos detection. This work explores the possibility of creating a trigger for saving the data for ultra-high-energy neutrino candidates detected acoustically by the hydrophones. The acoustic signal caused by the neutrino interaction in a fluid is a short-time duration Bipolar Pulse extremely directive and with a Fourier transform extending over a wide range of frequencies. A study of signal detection, has been done by simulating BP produced by the interaction of a UHE neutrino at 1 km from the detector at zero-degree incidence added to the experimental real acoustic data. Finally, a trigger proposal has been developed in order to record candidates of BPs and it has been tested. The number of candidates per second, precision, and recall have been monitored according to the cuts applied and parameters calculated by the algorithm.Comment: 9th International Workshop on Acoustic and Radio EeV Neutrino Detection Activities - ARENA202

Underwater Acoustic Positioning System for the Monitoring of KM3NeT Optical Modules

[EN] KM3NeT, the underwater neutrino telescope in the Mediterranean Sea, is a detector under construction. KM3NeT uses Digital Optical Modules (DOMs) to detect neutrinos by detecting the Cherenkov light of relativistic particles produced in the interaction. To reconstruct the neutrino event and the coming direction, it is necessary to monitor the position of each DOM, which is not fixed since it is mounted in flexible string lines, held close to vertical by buoys but sensitive to sea currents. A piezo-ceramic transducer is installed inside of each DOM. Using some emitters anchored in the sea floor it is possible to calculate the position of the DOMs by triangulation of distances obtained from the determination of the time of flight of the acoustic wave. In this work, the acoustic model used for the simulation of the system is described and the results presented.[ES] KM3NeT, el detector submarino que se encuentra en construcción en el Mar Mediterráneo, usa Módulos Digitales Ópticos (DOMs) para localizar neutrinos, a través de la detección de la luz de Cherenkov producida por partículas relativistas durante la interacción con el agua. Para reconstruir el camino seguido por el neutrino, es necesario saber la posición de cada DOM, el cuál no se encuentra fijo ya que está sujeto a unos cables anclados que se mantienen en vertical gracias a una boya en el final de la línea, lo cual la hace sensible al movimiento de las corrientes marinas. Cada DOM contiene instalada una cerámica piezoeléctrica, como receptor acústico, y usando unos emisores anclados en el fondo del mar se puede estimar la posición de cada DOM triangulando las distancias entre ellos, las cuales se saben por el tiempo de vuelo de la señal acústica. En este trabajo, se presenta una simulación del sistema y se describe el modelo acústico usado.Ardid Ramírez, M.; Bou Cabo, M.; D. Tortosa, D.; Martínez Mora, JA.; Poirè, C. (2019). Underwater Acoustic Positioning System for the Monitoring of KM3NeT Optical Modules. Revista de Acústica. 50(3-4):24-33. http://hdl.handle.net/10251/160009S2433503-

Acoustic parametric techniques for neutrino telescopes

[EN] In this work, we present a compact transmitter array based on the parametric acoustic sources effect able to reproduce the acoustic signature of an Ultra-High Energy neutrino interaction in water. We also propose to use directive transducers using the parametric technique for the characterization of piezo-ceramic sensors contained in the KM3NeT DOMs. This technique can minimize the need for an anechoic tank.Ardid Ramírez, M.; Tortosa, DD.; Llorens Alvarez, CD.; Martínez Mora, JA.; Saldaña-Coscollar, M. (2019). Acoustic parametric techniques for neutrino telescopes. EPJ Web of Conferences (Online). 216:1-3. https://doi.org/10.1051/epjconf/201921604001S13216Saldana M., PhD Thesis, Acoustic System Development for Neutrino Underwater Detectors. Gandia: Universitat Politecnica de Valencia (2017)Buis E.J.; et al. Characterization of the KM3NeT hydrophone. ARENA2018 this issue

Underwater Communication Using Acoustic Parametric Arrays

[EN] This paper presents a study of different types of parametric signals with application to submarine acoustic telecommunications. In all of them, the carrier frequency is 200 kHz, which corresponds to that resonation of the transducer under study, while they differ by the different modulations they present. In this sense, we study modulations with sweeps (4 to 40 kHz), in which represent binary codes (zeros and ones), getting closer to the application in acoustic telecommunications. The different properties of the transmitting signals in terms of communication speed, directivity, efficiency and power needed are discussed as well.We acknowledge the financial support of Plan Estatal de Investigación, ref. FPA2015-65150-C3-2-P (MINECO/FEDER), and of the Generalitat Valenciana, Grant PrometeoII/2014/079.Ardid Ramírez, M.; Campo-Valera, MM.; Tortosa, DD.; Felis-Enguix, I.; Llorens Alvarez, CD.; Martínez Mora, JA. (2018). Underwater Communication Using Acoustic Parametric Arrays. Proceedings. 2(139):1-7. https://doi.org/10.3390/ecsa-4-04907S17213

KM3NeT Detection Unit Line Fit reconstruction using positioning sensors data

[EN] The KM3NeT collaboration is constructing two large neutrino detectors in the Mediterranean Sea: ARCA, located near Sicily and aiming at neutrino astronomy, and ORCA, located near Toulon and designed for neutrino oscillation studies. The two detectors, together, will have hundreds of Detection Units (DUs) with 18 Digital Optical Modules (DOMs) maintained vertical by buoyancy, forming a large 3D optical array for detecting the Cherenkov light produced after the neutrino interactions. To properly reconstruct the direction of the incoming neutrino, the position of the DOMs must be known precisely with an accuracy of less than 10 cm. For this purpose, there are acoustic and orientation sensors inside the DOMs. An Attitude Heading Reference System (AHRS) chip provides the components values of the Acceleration and Magnetic field in the DOM, from which it is possible to calculate Yaw, Pitch and Roll for each floor of the line. A piezo sensor detects the signals from fixed acoustic emitters on the sea floor, so as to position it by trilateration. Data from these sensors are used as an input to reconstruct the shape of the entire line based on a DU Line Fit mechanical model. This proceeding presents an overview of the KM3NeT monitoring system, as well as the line fit model and a selection of results.Tortosa, DD.; Poirè, C. (2021). KM3NeT Detection Unit Line Fit reconstruction using positioning sensors data. Journal of Instrumentation. 16(9):1-7. https://doi.org/10.1088/1748-0221/16/09/C090231716

Acoustic Parametric Signal Generation for Underwater Communication

This paper presents a study of different types of parametric signals with application to underwater acoustic communications. In all the signals, the carrier frequency is 200 kHz, which corresponds to the resonance frequency of the transducer under study and different modulations are presented and compared. In this sense, we study modulations with parametric sine sweeps (4 to 40 kHz) that represent binary codes (zeros and ones), getting closer to the application in acoustic communications. The different properties of the transmitting signals in terms of bit rate reconstruction, directivity, efficiency, and power needed are discussed as well