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IMB, the Irvine-Michigan-Brookhaven detector, was a nucleon decay experiment and neutrino observatory located in a Morton Salt company's Fairport mine on the shore of Lake Erie in the United States 600 meters underground. It was a joint venture of the University of California, Irvine, the University of Michigan, and the Brookhaven National Laboratory.[1] 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, particularly those from Supernova SN 1987A.[2]
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.[3] 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, IMB was able to estimate the initial direction of neutrinos.
History

Ground was broken at the salt mine in 1979; the water tank for the detector itself was finished in 1981. The project was delayed by funding problems and leaks in the water tank, but by the end of summer 1982 the detector was operating at full capacity. The first results were published in 1982.[4] In 1987, it gained fame for detecting 8 of the roughly 1058 neutrinos emitted by Supernova 1987A. This discovery was completely unexpected; supernovas as near as 1987a are extremely rare and virtually unpredictable. The detector collected data until 1991.[5]

This volume of water contains on the order of 1031 protons. In one year of observation no proton decay event was recorded. This put the half-life of a proton at or above 1031 years.
References

The Underground Search for Clues to an Unstable Universe, Popular Science, Vol. 219, No. 8 (December, 1981); pages 64-67.
John C. Vander Velde's IMB page, accessed 11 April 2008.
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 Detector: The First 30-Days." D. Sinclair et al. 1982. Los Alamos 1982, Proceedings, Science Underground, pg. 138-142.

Russell J. Clark's IMB page Archived 2004-12-14 at the Wayback Machine, accessed 5 July 2006.

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Neutrino detectors, experiments, and facilities
Discoveries

Cowan–Reines ( ν e) Lederman–Schwartz–Steinberger ( ν μ) DONUT ( ν τ) Neutrino oscillation SN 1987 neutrino burst

Operating
(divided by
primary
neutrino
source)
Astronomical

ANITA ANTARES ASD BDUNT Borexino BUST HALO IceCube LVD NEVOD SAGE Super-Kamiokande SNEWS

Reactor

Daya Bay Double Chooz KamLAND RENO STEREO

Accelerator

ANNIE ICARUS (Fermilab) MicroBooNE MINERνA MiniBooNE NA61/SHINE NOνA NuMI T2K

0νββ

AMoRE COBRA CUORE EXO GERDA KamLAND-Zen MAJORANA NEXT PandaX SNO+ XMASS

Other

KATRIN WITCH

Construction

ARA ARIANNA Baikal-GVD BEST DUNE Hyper-Kamiokande JUNO KM3NeT SuperNEMO FASERν

Retired

AMANDA CDHS Chooz CNGS Cuoricino DONUT ERPM GALLEX Gargamelle GNO Heidelberg-Moscow Homestake ICARUS IGEX IMB K2K Kamiokande KARMEN KGF LSND MACRO MINOS MINOS+ NARC NEMO OPERA RICE SciBooNE SNO Soudan 2 Utah

Proposed

CUPID GRAND INO LAGUNA LEGEND LENA Neutrino Factory nEXO Nucifer SBND UNO JEM-EUSO WATCHMAN

Cancelled

DUMAND Project Long Baseline Neutrino Experiment NEMO Project NESTOR Project SOX BOREX

See also

BNO (Baksan or Baxan Neutrino Observatory) Kamioka Observatory LNGS SNOLAB List of neutrino experiments

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Proton decay experiments
Operating

Super-Kamiokande

Retired

Frejus Homestake HPW IMB Kamiokande KGF NUSEX Soudan 1 Soudan 2

Proposed

ANNIE Hyper-Kamiokande LAGUNA

See also

B − L Grand Unified Theory Georgi–Glashow model

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