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World's Biggest Particle Smasher Springs a Leak
19 September 2008 (All day)
Efforts to get the world's new highest energy atom smasher up and colliding particles hit an unexpected snag today--just 9 days after physicists circulated the first particles through the $5.5 billion Large Hadron Collider (LHC) with astonishing ease. At least one of the LHC's more than 1700 superconducting magnets failed, springing a leak and spewing helium gas into the subterranean tunnel that houses the collider, report officials at the European particle physics laboratory, CERN, near Geneva, Switzerland. Researchers do not yet know the extent of the damage, but some of the machine's parts probably will have to be replaced, a process that could take weeks.
On 10 September, physicists at CERN scored a jaw-dropping success when they turned on the LHC in as little time as it might take the average person to get a new computer out of the box and running (ScienceNOW, 10 September). In just a few hours, researchers had protons whizzing all the way around both of the machine's countercirculating rings. Their success raised the prospect that in as little as a month the enormous collider, which lurks in a 27-kilometer tunnel below the French-Swiss border, might start smashing protons together at unprecedented energies to produce new types of subatomic particles or even probe new dimensions of space.
But even then, researchers warned that setbacks were likely as they bring the most complex scientific device ever built online. Indeed, only a day after the official start-up, a transformer failed and kept the machine from running again until late this week. Technicians solved that problem by simply replacing the transformer, which was handily above ground. Today's setback is likely to be more serious.
At least one of the LHC's magnets, which guide the protons around the ring, abruptly overheated in an event called a "quench." Such a sudden temperature spike occurs when part of a magnet's superconducting wire, which carries electricity without resistance at temperatures near absolute zero, warms up and starts acting like an ordinary wire. With thousands of amps of current running through it, the warm part becomes a ferocious electric heater that can instantly heat the rest of the magnet and boil the frigid liquid helium that keeps the magnet cold. Friday's quench apparently ruptured the plumbing for the helium within the magnets, says CERN spokesperson James Gillies. It heated at least one of the 15-meter-long, 35-metric-ton magnets from 2 kelvin to above 100 kelvin.
Researchers do not yet know how many magnets were involved or whether they will have to replace any of them, Gillies says, "but the fact that there is helium in the tunnel suggest that we will." How long that takes will depend in part on how much of the LHC must be warmed to room temperature for servicing. If it's only a short section, the repair could be relatively quick. But the machine is built in octants, and if workers have to heat and cool an entire octant, then the cooling alone would take several weeks.
For their part, the experimenters waiting for collisions to begin are unfazed by the turn of fortune. Such problems are to be expected, says Peter Jenni, a particle physicist at CERN and spokesperson for the 2500 member collaboration working with the massive ATLAS particle detector. "As I always try to explain, it's certainly not just hitting a button and the thing goes," Jenni says. Judy Jackson, spokesperson for Fermi National Accelerator Laboratory in Batavia, Illinois, recalls that when that lab started its Tevatron Collider in the early 1980s, "it was quenches to the left, quenches to the right." CERN officials hope to have a better appraisal of the damage and any potential delays on Monday.