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The general term Cherenkov detector indicates an instrument or set of instruments to detect relativistic particles through the Cherenkov radiation they produce.
Astronomy uses these to detect energetic cosmic rays descending through Earth atmosphere, and also uses them to detect descending gamma-ray photons, which produce particle interactions with the atmosphere such as pair production. The incoming high energy photons or cosmic-ray particles generate more photons and particles, which can, in turn, each have enough energy that this process repeats, the flights of the resulting in particles and photons forming a downward cone-shaped volume within the medium, the whole process termed an air shower when it occurs in the atmosphere. From the theory of Cherenkov-radiation production, data from a number of such sensors, including timing, yields information regarding characteristics of the photon or particle that triggered it. Some terms used for these are Cherenkov telescope or Cherenkov gamma-ray telescope. The term imaging atmospheric Cherenkov telescope (IACT), further-implies that enough particles are collected to create an image, e.g., an gamma-ray image. The ground detectors may be somewhat-ordinary telescopes for some spectral band.
Another type of cherenkov detector consists of a tank or tanks of some fluid chosen for its practical ability to produce detectable Cherenkov radiation (in some cases, water), surrounded by sensors such as photomultiplier tubes. For cosmic rays and neutrinos, natural bodies of water have also been used. Also, some crystals have been used for relatively-small such detectors.
Examples of Cherenkov telescopes:
Among other Cherenkov detectors are neutrino observatories, such as IceCube, which detections cherenkov radiation within a large volume of ice.