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Tuesday, September 23, 2008

Trouble in the LHC: fried wiring and leaking helium to blame

By Tim De Chant

The Large Hadron Collider (LHC) that straddles the Switzerland-France border was beset by an unfortunate equipment failure Friday, September 19—just nine short days after it first hurled particles around its 16.6 mile (27km) track. Scientists with the European Center for Nuclear Research, popularly known as CERN, acknowledged the severity of the damage will delay research at the particle accelerator for a minimum of two months.

LHC operators were putting the most recently installed electrical circuits through their final paces late Friday morning when they noticed a helium leak between the Alice and CMS detectors. Liquid helium supercools the accelerator's magnets to 1.9 degrees Kelvin, a temperature just above absolute zero. Lacking coolant, about 100 magnets warmed by 100 K, prompting scientists to shut down the LHC. The leak also compromised the vacuum within the collider's tubes. The costly damage may also prevent scientists from completing any high-energy collisions this year as the facility shuts down for the winter to save power.

Physicists hope the LHC will help them find the Higgs boson, a particle thought to give mass to matter. They see the Higgs as a missing link, the only particle predicted by the Standard Model that has not been discovered.

Repairs to the damaged sector are still a ways off, as scientists will have to warm the equipment well above operating temperatures—a controlled process that will take weeks. Likewise, after the damage is mended, the affected sector has to be cooled over many weeks.

CERN says faulty wiring is likely the cause of the damage. The tremendous current normally used by the accelerator likely melted a bad connection between two magnets, sparking subsequent failures.

This isn’t the LHC's first setback. Over the weekend of September 13 and 14, workers replaced a malfunctioning 30-ton electrical transformer. To perform the transplant, scientists warmed the tunnel, and then spent most of the following week cooling it down again.

Such mishaps, CERN says, are part-and-parcel of firing up the largest particle accelerator in the world. The LHC is seven times more powerful than the reigning champion, Fermilab's Tevatron outside Chicago. While the first tests at the LHC were low power loops, scientists had planned on completing high-energy collisions as early as October of this year. This most recent incident may push the first exciting experiments into next year.

Yet while the LHC is down, physicists at Fermilab will have more time to continue their quest for information about the Higgs boson particle. Even though the Tevatron is likely not powerful enough to find the Higgs, the Fermilab accelerator is still in the race, with physicists looking to end its storied career with a bang before its 2010 decommissioning.

Original here

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