Shop-vacs to the rescue
In creating neutrinos for the MINOS experiment at Fermilab, the NuMI focusing horn delivers batches of protons using intense magnetic fields generated by 200,000-ampere pulses of electric current. The pulses deliver enormous amounts of heat. Without 36 gallons per minute of low-conductivity (or de-ionized) water for cooling, the horn would burn itself up. At 4:40 p.m. on Friday, June 30, the worst happened: there was no water flowing to the horn's cooling nozzles.
About a gallon of tiny, leak-clogging resin beads, each each one fiftieth of an inch (half a millimeter) thick, had moved the wrong way through the de-ionized water system loop due to a failed check valve. They clogged the nozzles completely. Unclogging took more than three weeks of 20-hour days for the repair crews.
Sticky when wet, the beads blow away like grains of sand when completely dry. Using two vacuum cleaners on prototype components in another location, crews were able to suction out the beads. Kris Anderson, the engineer directing the cleanup, told some crew members go out and buy industrial-size vacuum cleaners. With 50 nozzles cooling the horn's inner conductor, and 19 in the outer conductor, 69 nozzles had to be cleared. The horn was finally "buttoned up" on July 26, some 27 straight days of work later including the July 4 holiday and weekends.
Anderson can't say enough about the dedication of the crews, some of whom worked near-80-hour weeks. Even the vacuum cleaners rated special mention. "They came right off the shelf, and they weren't expensive," Anderson says. "We ran those things 20 hours a day for three weeks, and none of them burned out. Whoever makes those things has a pretty good product."
Mike Perricone
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