The ANTARES optical beacon system

Abstract

ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It consists of a three-dimensional array of photomultiplier tubes that can detect the Cherenkov light induced by charged particles produced in the interactions of neutrinos with the surrounding medium. High angular resolution can be achieved, in particular, when a muon is produced, provided that the Cherenkov photons are detected with sufficient timing precision. Considerations of the intrinsic time uncertainties stemming from the transit time spread in the photomultiplier tubes and the mechanism of transmission of light in sea water lead to the conclusion that a relative time accuracy of the order of 0.5 ns is desirable. Accordingly, different time calibration systems have been developed for the ANTARES telescope. In this article, a system based on Optical Beacons, a set of external and well-controlled pulsed light sources located throughout the detector, is described. This calibration system takes into account the optical properties of sea water, which is used as the detection volume of the ANTARES telescope. The design, tests, construction and first results of the two types of beacons, LED and laser-based, are presented. (C) 2007 Elsevier B.V. All rights reserved

Measurement of the atmospheric muon flux with a 4GeV threshold in the ANTARES neutrino telescope

“…The rate of genuine coincidences is given by the integral under the peak and can be extracted from the distribution by subtracting the flat background of random coincidences. The positions of the peaks of the time distributions for different pairs of PMTs in the same storey are consistent with zero and are used to cross-check the time offsets computed by the time calibration system [12].…”

Measurement of the group velocity of light in sea water at the ANTARES site

“…This system was primarily designed to perform time calibration in situ [7,8]. There are two types of optical beacons, the LED optical beacons and the laser beacons.…”

Long-term monitoring of the ANTARES optical module efficiencies using $$^{40}\mathrm{{K}}$$ 40 K decays in sea water

“…Two systems of external light sources are used: LED beacons located on four storeys on each detector line, and laser beacons located on the base, at the bottom of several detection lines. They allow to perform both inter-line and inter-storey time calibrations [24]. Reconstructions of tracks from downward going muons created in cosmic-ray interactions in the atmosphere are used as well to determine inter-line and inter-storey time calibrations [25].…”