Ultrasonic Transmitter for Positioning of the Large Underwater Neutrino Telescope KM3NeT

Underwater ultrasonic transducers are commonly used for marine applications including communication and positioning systems. In this work, an ultrasonic transmitter transducer developed for the very large underwater neutrino telescope KM3NeT positioning is presented. The telescope infrastructure will have some degree of motion due to sea current; hence a positioning system is needed in order to monitor the position of the optical sensors. For this purpose, a reliable and affordable positioning based on acoustic systems is used. The ultrasound transmitter prototype developed as part of the positioning system is composed of a commercial FFR transducer and specifically designed electronics to optimize the system and fulfil the requirements of the KM3NeT infrastructure. The transmitter is able to generate high-power short signals with arbitrary waveform in a range of 20 kHz - 40 kHz and withstand high pressures. Signal processing techniques such as advanced cross-correlation methods and filtering as well as broad-band ultrasound signals are also applied for optimizing the acoustic emission and position detection. The work done for a precise laboratory testing and optimization of the system is described. The prototype has been integrated in the ANTARES neutrino telescope for testing its accuracy and the reach in situ. The test results obtained are also presented in this communication.