Beautiful fish-eye-lens photographs of the insides of Japan's Super-Kamiokande neutrino detector have decorated innumerable magazine pages. The images displayed row upon perfect row of photomultiplier tubes like huge glittering crystal eyeballs, the total structure dwarfing any human in the picture. For five years, those "eyeballs" watched for telltale flashes of light signaling a rare neutrino interaction within the detector volume, and the scientific results made headlines. But on November 12, 2001, a disastrous accident--seemingly a chain reaction of implosions that ripped through the array--reduced 7,000 of the 11,000 phototubes to a pile of shards and rubble.

No one knows what started the incident. For the first time since operations began in 1996, the detector had been emptied of its 50,000 tons of ultrapure water for maintenance and replacement of a few hundred phototubes. During the refilling process, with the tank about 80 percent full, the terrible sound of imploding photomultipliers broke out. "It was as if blasting [in the Kamioka mine] was happening underneath me," says Masayuki Nakahata of Tokyo University, who was in the control room atop Super-K at the time.

This article was originally published with the title Setback for Super-K.

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