The Optical Beacon Calibration System of the ANTARES Neutrino Telescope

The ANTARES collaboration is about to finish the construction of an underwater neutrino telescope at 2500 m depth in the Mediterranean Sea. The aim of the ANTARES telescope is the detection of high-energy cosmic neutrinos using a 3-dimensional array of 900 photomultipliers distributed in 12 lines. These photomultipliers collect the Cherenkov light induced by the muon produced in the neutrino interaction with the surrounding matter. In order to achieve a good angular resolution, the detector requires a relative time calibration of the order of ~ 0.5 ns. Intending to calibrate the detector at subnanosecond level, a set of pulsed light emitters called Optical Beacons has been designed. They consist of a source of light (LED or laser) with a well- known time emission. The design of these devices and the results obtained with this system will be presented.