Status of the ANTARES Underwater Neutrino Telescope

G. Hallewell

Centre de Physique des Particules de Marseille,
Representing the ANTARES Collaboration

Abstract

The ANTARES Collaboration is constructing a deep underwater neutrino detector for operation at 2400 m off the French Mediterranean coast near Toulon. The detector, which will begin operation in 2004, will contain nine hundred photomultiplier tubes housed in spherical optical modules. The photomultiplier axes will be angled 45 downward toward the seabed to observe the Cerenkov emissions of upward-going muons created by the interactions in or near the detector of very high energy neutrinos traversing the earth. These neutrinos arrive undeviated from a variety of galactic and extragalactic sources of astrophysical interest, and might be produced in the possible annihilation of dark matter neutralinos.

Optical modules will be grouped in triplets at thirty levels on each of ten detection lines, rising from -2300 m to -1950 m. The detector lines will be powered via a single conductor from the shore. Current will return via the seawater, using sea and shore station electrodes. A central titanium junction box will split the power between the detector lines, distribute clock signals and regroup the data signals from the ten detector lines. Light signals from the 25 cm diameter photomultiplier tube in each optical module will be processed by an "analog ring sampler front end ASIC. Digitized pulse heights will be colour multiplexed onto optical fibre up-links to be sent to the shore station via a 40 km multi fibre electro-optic cable (laid October 2001) for on-shore filtering and event building.

Since each line will be suspended between a sea anchor and a submerged buoy subject to movement by deep ocean currents, its curvature and twist will be regularly measured using a system of seabed acoustic transponders and hydrophones. In addition each line is equipped with tilt-meters and compasses so that its movement can be logged. A network of laser and LED beacons will be used to give redundancy in the on-line calibration of photomultiplier timing.

The development of the detector will be discussed. The present status and the installation and commissioning schedule will be outlined. Results from site evaluation and the development of supporting instrumentation will be addressed.