trino detectors, several groups began to build a new generation of such dual-purpose detectors. The largest one in the world was again built in the Kamioka mine and was called Super-Kamiokande, and with good reason. This mammoth fifty-thousand-ton tank of water, surrounded by ir.,800 phototubes, was o

t two large experiments were commissioned and built to do just this, one deep underground next to Lake Erie in a salt mine, and one in a mine near Kamioka, Japan. The mines were necessary to screen out incom- ing cosmic rays that would otherwise produce a background that would swamp any proton decay si