- Irvine-Michigan-Brookhaven (detector)
IMB, the Irvine-Michigan-Brookhaven detector, was a
nucleon decay experiment andneutrino observatory located in a salt mine on the shore ofLake Erie in theUnited States . It was a joint venture of theUniversity of California, Irvine , theUniversity of Michigan , and theBrookhaven National Laboratory . Like several other particle detectors (seeKamiokande II ), it was built primarily with the goal of observingproton decay , but it achieved greater fame through neutrino observation.Design
IMB consisted of a roughly cubical tank about 17 × 17.5 × 23
meter s, filled with 2.5 million gallons ofultrapure water which was surrounded by 2,048photomultiplier tubes [ [http://lss.fnal.gov/archive/test-proposal/0000/fermilab-proposal-0805.pdf A Proposal for a Long Baseline Oscillation Experiment Using A High Intensity Neutrino Beam from the Fermilab Main Injector to the IMB Water Cerenkov Detector; FNAL P805.] ] . IMB detected fast moving particles such as those produced by proton decay or neutrino interactions by picking up theCerenkov radiation generated when such a particle moves faster than the speed of light in water. Since directional information was available from the phototubes, it was able to estimate the initial direction of neutrinos.History
IMB was built in the early 1980s and announced its first results in 1982 ["IMB Detector: The First 30-Days." D. Sinclair et al. 1982. Los Alamos 1982, Proceedings, Science Underground, pg. 138-142.] . In 1987, it gained fame for detecting 8 of the roughly neutrinos emitted by
Supernova 1987a . It collected data until 1991. [ [http://www-meg.phys.cmu.edu/~clark/imb.html Russell J. Clark's IMB page] , accessed 5 July 2006.]This volume of water contains on the order of
proton s. In one year of observation no proton decay event was recorded. This put the lifetime of a proton at or above years.References
[ [http://www-personal.umich.edu/~jcv/imb/imb.html John C. Vander Velde's IMB page] , accessed 11 April 2008.]
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