to afford on large-scale. Larger experiments have therefore turned to a less costly reaction mass. Radiochemical detection methods are only useful for counting neutrinos; they provide almost no information on neutrino energy or direction of travel. Cherenkov detectors "Ring-imaging" Cherenkov detectors take advantage of a phenomenon called Cherenkov light. Cherenkov radiation is produced whenever charged particles such as electrons or muons are moving through a given detector medium somewhat faster than the speed of light in that medium. In a Cherenkov detector, a large volume of clear material such as water or ice is surrounded by light-sensitive photomultiplier tubes. A charged lepton produced with sufficient energy and moving through such a detector does travel somewhat faster than the speed of light in the detector medium (although somewhat slower than the speed of light in vacuum). The charged lepton generates a visible "optical shockwave" of Cherenkov radiation. This radiation is detected by the photomultiplier tubes and shows up as a characteristic ring-like pattern of activity in the array of photomultiplier tubes. As neutrinos can interact with atomic nuclei to produce charged leptons which emit Cherenkov radiation, this pattern can be used to infer direction, energy, and (sometimes) flavor information about incident neutrinos. Two water-filled detectors of this type (Kamiokande and IMB) recorded a neutrino burst from supernova SN 1987A. Scientists detected 19 neutrinos from an explosion of a star inside the Large Magellanic Cloud – only 19 out of the octo-decillion (1057) neutrinos emitted by the supernova. The Kamiokande detector was able to detect the burst of neutrinos associated with this supernova, and in 1988 it was used to directly confirm the production of solar neutrinos. The largest such detector is the water-filled Super-Kamiokande. This detector uses 50,000 tons of pure water surrounded by 11,000 photomultiplier tubes buried 1 km underground. The Sudbury Neutrino Observatory (SNO) uses 1,000 tonnes of ultrapure heavy water contained in a 12 metre-diameter vessel made of acrylic plastic surrounded by a cylinder of ultrapure ordinary water 22 metres in diameter and 34 metres high. In addition to the neutrino interactions visible in a regular water detector, a neutrino can break up the deuterium in heavy water. The resulting free neutron is subsequently captured, releasing a burst of gamma rays that can be detected. All three neutrino flavors participate equally in this dissociation reaction. The MiniBooNE detector employs pure mineral oil as its detection medium. Mineral oil