A worker inside the Large Hadron Collider tunnel in 2006.

A worker inside the Large Hadron Collider tunnel in 2006.

Maximilien Brice/Claudia Marcelloni/CERN

Large Hadron Collider restart hits a snag

A tiny particle of metal dust is delaying the restart of the world's largest particle accelerator. Physicists at the European particle physics lab CERN on the French-Swiss border had hoped to begin circulating particles in Large Hadron Collider (LHC) this week, after 2 years of downtime to prepare the machine to run at higher energy. But an electrical short discovered over the weekend, apparently caused by a metal particle, has put a snag in those plans. Rectifying the issue could cause a delay of a few days to a few weeks, CERN Director-General Rolf Heuer told ScienceInsider today at an event in Washington, D.C.

"It's unfortunate, it's at the end, almost when we are ready to inject beam, but this is part of the process" says CERN’s director for accelerators, Frédérick Bordry.

Electrical shorts are not uncommon during the process of ramping up the LHC, but because the machine is already cooled down to its very low operating temperature, fixing the problem is now more difficult. If the machine must be warmed up to fix the problem, the work could drag out for weeks.

Luckily, Bordry says, the problem is not with any of the LHCs magnets, so they won't need to remove a magnet, just "this bloody piece of metal." Scientists think they may be able to solve the problem by burning the metal off, or by blowing away the metal fragment with gaseous helium.

Tomorrow, CERN scientists plan to use x-ray imaging to better understand the issue. More specifics on the schedule will be available then.

Heuer is confident that the delay will be minor. And after 2 years without a particle beam, a delay of a few weeks is worth waiting for, he says. Once they inject the beam, it will be another 2 months before they will be ready for the first collisions.

"We are not concerned," Heuer says. “If that's all that happens then we are very happy."