ANTARES

ANTARES (Astronomy with a Neutrino Telescope and Abyss environmental RESearch project) is a neutrino detector residing 2.5 km under the Mediterranean Sea off the coast of Toulon, France. It is designed to be used as a directional neutrino telescope to locate and observe neutrino flux from cosmic origins in the direction of the Southern Hemisphere of the Earth, a complement to the South Pole neutrino detector IceCube that detects neutrinos from both hemispheres. The experiment is a recognized CERN experiment (RE6). Other neutrino telescopes designed for use in the nearby area include the Greek NESTOR telescope and the Italian NEMO telescope, which are both in early design stages. The data taking of ANTARES was finished in February 2022, after 16 years of continuous operation. Design The array contains a set of twelve separate vertical strings of photomultiplier tubes. Each one has 75 optical modules and is about 350 meters long. They are anchored at the bottom of the sea at a depth of about 2.5 km, roughly 70 meters apart from each other. When neutrinos enter the southern hemisphere of the earth, they usually continue traveling directly through it. On rare occasions, a few muon neutrinos interact with the water in the Mediterranean Sea. When this happens, they produce a high energy muon. ANTARES works by its photomultiplier tubes detecting the Cherenkov radiation emitted as the muon passes through the water. The detection techniques used discriminate between the signature of "upward-going muons", a muon neutrino that has had interactions with matter below the detector (the Earth), and much higher flux of "downward atmospheric muons". In contrast to the South Pole neutrino telescopes AMANDA and IceCube, ANTARES uses water instead of ice as its Cherenkov medium. As light in water is less scattered than in ice this results in a better resolving power. On the other hand, water contains more sources of background light than ice (radioactive isotopes potassium-40 in the sea salt and bioluminescent organisms), leading to a higher energy thresholds for ANTARES with respect to IceCube and making more sophisticated background-suppression methods necessary. Construction history The construction of ANTARES was completed on May 30, 2008, two years after the first string was deployed. Initial testing began in 2000. Equipment indirectly related to the detector such as a seismometer were deployed in 2005.