Status and first results of the acoustic detection test system AMADEUS

The AMADEUS system is integrated in the ANTARES neutrino telescope in the Mediterranean Sea and aims for the investigation of acoustic particle detection techniques in the deep sea. Installed at a depth of more than 2000 m, the acoustic sensors of AMADEUS are using piezo-ceramic elements for the broad-band recording of acoustic signals with frequencies ranging up to 125 kHz. AMADEUS consists of six clusters, each one comprising six acoustic sensors that are arranged at distances of roughly 1 m from each other. Three acoustic clusters are installed along a vertical mechanical structure (a so-called Line) of ANTARES with spacings of about 15 and 110 m, respectively. The remaining three clusters are installed with vertical spacings of 15 m on a further Line of the ANTARES detector. The horizontal distance between the two lines is 240 m. Each acoustic cluster allows for the suppression of random noise by requiring local coincidences and the reconstruction of the arrival direction of acoustic waves. Source positions can then be reconstructed using the precise time correlations between the clusters provided by the ANTARES clock system. AMADEUS thus allows for extensive acoustic background studies including signal correlations on several length scales as well as source localisation. The system is therefore excellently suited for feasibility studies for a potential future large-scale acoustic neutrino telescope in sea water. Since the start of data taking on December 5th, 2007, a wealth of data has been recorded. The AMADEUS system will be described and some first results will be presented.