Proton decay experiment to determine the ultimate stability of matter..Physics: Proton Decay. Ohio, Morton Salt Mine (1985). Proton decay detector located 600 meters underground in the Morton salt mine near Cleveland, Ohio.which consists of a massive tank containing 21 cubic meters of ultra pure water, its walls lined with photomultiplier tubes, which detect faint flashes of Cerenkov light emitted by the passage of charged particles