- Neutrino telescope
In astronomy, a neutrino telescope is usually a detector consisting of a large mass of
wateror ice, surrounded by an array of sensitive light detectors known as photomultipliertubes. This allows the observation of astronomical objects by detecting the neutrinos they emit, rather than their light (or photons) as in an ordinary telescope. The field of neutrino astronomyis still very much in its infancy: the only confirmed extraterrestrial sources so far are the Sunand supernova SN1987A.
GALLEXexperiment used about 30 tons of galliumas reaction mass. A neutrino is able to react with an atom of gallium-71, converting it into an atom of the unstable isotope germanium-71. The germanium was then chemically extracted and concentrated. Neutrinos were thus detected by measuring the radioactive decay of germanium. This experiment is difficult to scale up due to the prohibitive cost of gallium. Larger experiments have therefore turned to a cheaper reaction mass.
The currently most common detector design consists of a large mass of
wateror ice, surrounded by an array of sensitive light detectors known as photomultipliertubes. This design takes advantage of the fact that particles produced in the interaction of the incoming neutrino with an atomic nucleustypically travel faster than the speed of light in the detector medium (though of course slower than the speed of light in a vacuum). This generates an "optical shockwave" known as Čerenkov radiationwhich can be detected by the photomultiplier tubes.
Super-Kamiokandeneutrino detector uses 50,000 tons of pure water surrounded by 11,000 photomultiplier tubes buried 1 km underground. It is able to detect the incident direction of incoming neutrinos by detecting which photomultipliers fire. Kamiokande, the predecessor of Super-Kamiokande, was able to detect the burst of neutrinos associated with supernova 1987A, and in 1988it was used to directly confirm the production of solar neutrinos.
Antarctic Muon And Neutrino Detector Array(AMANDA) operated from 1996to 2004. This detector used photomultiplier tubes mounted on strings, buried deep (1.5-2km) inside the glacial ice at the South Pole in Antarctica. The ice itself is used as the detector mass. The direction of incident neutrinos is determined by recording the arrival time of individual photons using a three-dimensional array of detector modules containing one photomultiplier tube each. This method allows detection of neutrinos above 50 GeV with a spatial resolution of approximately 2 degrees. AMANDA has been used to generate neutrino maps of the northern sky in order to search for extraterrestrial neutrino sources and in searches for dark matter. AMANDA is currently in the process of being upgraded to the IceCubeobservatory, eventually increasing the volume of the detector array to one cubic kilometer.
In the Mediterranean Sea, the ANTARES telescope is fully operational since May 30th, 2008. This telescope uses the sea water as the detector mass.
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