A neutrino observatory is a device for detecting neutrinos. Due to the very weak interaction of neutrinos with matter, these devices must be very large to detect a significant number. Such observatories are often built underground, to isolate the detector from cosmic rays and other background radiation.
Many detection methods have been invented. At the Super-Kamiokande, a large volume of water, surrounded by photomultipliers that monitor the Vavilov-Cherenkov effect, which occurs when a neutrino creates an electron or a muon on entering water. The Sudbury Neutrino Observatory is similar, but uses heavy water.
Other detectors use large amounts of chlorine or gallium, in which we look respectively for argon or germanium created during the interaction with neutrinos.
MINOS uses a solid plastic scintillator monitored by phototubes. Borexino uses a liquid scintillator. The future NOνA detector will use a liquid scintillator, monitored by an avalanche photodiode.
Neutrino telescopes are a special category of neutrino observatories used for doing neutrino astronomy. Examples include the DUMAND, Baïkal, NESTOR, NEMO, AMANDA, IceCube, ANTARES experiments and its future successor KM3NeT.
Neutrino observatories sometimes use the Earth to filter out background noise generated by the interaction of cosmic rays with the Earth's atmosphere. Indeed, these interactions generate many muons, some of which are picked up by the detector, even several kilometers underground. This background noise is often much larger than the expected signal for neutrinos.
Notes and references
Ring imaging Cherenkov detector Physics Portal Astronomy Portal