IMB

IMB (for Irvine-Michigan-Brookhaven detector) was an neutrino detector located in a mine in Ohio operating 1981 through 1991, a Cherenkov detector consisting of a tank of pure water surrounded by photomultiplier tubes. Among the detectors accomplishments was detection of a neutrino burst coincident with the EMR of SN 1987A reaching Earth.

Though it functioned as a working neutrino observatory, its original aim was to detect proton decay within the water tank, and finding none over the course of a year implied a proton half-life on the order of 10³¹ years or more.