Diseño y desarrollo de la electrónica de los emisores acústicos para los sistemas de posicionamiento y calibración de telescopios submarinos de neutrinos

Abstract

Neutrino telescopes are a new way of looking at the Universe. For more than a decade these structures are being designed to study the Universe from a new point of view, that is, from the particles generated in the cosmic accelerators of particles. These infrastructures are not only useful to study the Universe, but they can also be used in the field of Particle Physics and even in the study of underwater life. Most of these telescopes are based on the detection of the so-called Cherenkov light using photomultipliers, the difference between them lies in the medium in which they are located (ice or water) and in the infrastructure used. Specifically, European telescopes mount these photomultipliers in an underwater vertical structure anchored at great depth, which is under the influence of sea currents. For this reason they suffer displacements that affect the location of the photomultipliers and it becomes necessary to implement a positioning system for the telescope to be functional. For this, an acoustic system consisting of emitters anchored to the sea floor and receivers located at the different levels of the vertical structure is used. One of the objectives of the present thesis is the development of these acoustic emitters. For this purpose we have developed different laboratory prototypes with different features until obtaining an improved prototype that was installed and tested in ANTARES and NEMO telescopes. This showed that the prototype worked perfectly within the established requirements and then, we proceed to design a final version of the much more powerful and functional emitter, acoustic beacon, to be mounted inside aluminum vessels together with an omnidirectional acoustic transducer, which will be located in anchored positions of the new KM3NeT neutrino telescope. In collaboration with the MSM Company, 18 acoustic beacons were developed for KM3NeT-ARCA being two of them installed in the first marine campaign at the end of 2015, and being able then to verify their correct operation. On the other hand, interaction of ultraenergetic neutrinos with matter also produces a thermoacoustic pulse with bipolar form, axial symmetry and highly directive. The feasibility of the acoustic detection technique and the possibility of implementing it in these telescopes have been under study for years. In order to test and calibrate this technique, it is necessary to have an acoustic emitter system able of generating a signal similar to the neutrino signature. This has been the second objective developed in this thesis. To achieve this objective, a compact and versatile calibrator based on an array of acoustic transducers using parametric generation has been designed. Given the complexity of the pulse to emulate and the novelty of the technique to be used, it has been necessary to carry out different laboratory tests in order to obtain suitable transducers and electronics able of making them to work at the required power and efficiency. The positive results obtained in this line suggest that we will be able to obtain a full functional neutrino acoustic calibrator soon. Finally, I would like to mention that I have participated in the different research and activities described in the thesis, putting especial emphasis in the development of the electronics and the software/firmware of the developed acoustic emitters.