Irvine-Michigan-Brookhaven (detector)

IMB, the Irvine-Michigan-Brookhaven detector, was a nucleon decay experiment and neutrino observatory located in a salt mine on the shore of Lake Erie in the United States. It was a joint venture of the University of California, Irvine, the University of Michigan, and the Brookhaven National Laboratory. Like several other particle detectors (see Kamiokande II), it was built primarily with the goal of observing proton decay, but it achieved greater fame through neutrino observation.

Design

IMB consisted of a roughly cubical tank about 17 × 17.5 × 23 meters, filled with 2.5 million gallons of ultrapure water which was surrounded by 2,048 photomultiplier 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 the Cerenkov 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 $10^\{58\}$ 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 $10^\{31\}$ protons. In one year of observation no proton decay event was recorded. This put the lifetime of a proton at or above $10^\{31\}$ years.

References

[ [http://www-personal.umich.edu/~jcv/imb/imb.html John C. Vander Velde's IMB page] , accessed 11 April 2008.]