  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 2000m, the
acoustic sensors of AMADEUS are using piezo-ceramic elements for the broad-band
recording of acoustic signals with frequencies ranging up to 125kHz. AMADEUS
consists of six clusters, each one comprising six acoustic sensors that are
arranged at distances of roughly 1m from each other. Three acoustic clusters
are installed along a vertical mechanical structure (a so-called Line) of
ANTARES with spacings of about 15m and 110m, respectively. The remaining 3
clusters are installed with vertical spacings of 15m on a further Line of the
ANTARES detector. The horizontal distance between the two lines is 240m. 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.
