Large Hadron Collider to be started up after fault forced year-long closure

The Large Hadron Collider (LHC) will be started up tomorrow for the first time since a catastrophic fault forced it to be shut down for more than a year.

Engineers at the Cern particle physics laboratory plan to begin injecting protons into the world’s most powerful atom-smasher at around 4pm GMT tomorrow afternoon, after the “big bang machine” was formally handed over to its operations team.

A first beam of particles should be circulating one way around the LHC’s 27km (17-mile) ring by Saturday, and the second beam travelling in the opposite direction should be captured soon afterwards.

The first low-energy collisions could follow within as little as a week, though Cern has yet to decide how to press on once the beam insertion is complete. Engineers also plan to crank its energy up to 1.2 teraelectronvolts (TeV) before Christmas, which would break the world record for a particle accelerator.

High-energy collisions are scheduled for January, after a two-week Christmas break. These will allow physicists to start using the £4 billion machine to search for the Higgs boson — the elusive “God particle” thought to give matter its mass — and other new insights into fundamental physics.

The eagerly awaited restart will end a 14-month hiatus during which the LHC has been mothballed. Just nine days after the machine was first switched on last September, a connection between two magnets failed, tearing a hole in the collider and causing a huge leak of the liquid helium that cools its superconducting magnets.

Engineers took more than a year to investigate and repair the fault, to check the rest of the accelerator for similar problems and replace faulty magnets, and to install new safety devices to prevent a repeat.

Work on the restart was briefly interrupted earlier in the month when a piece of baguette, probably dropped by a bird, caused a short-circuit in an electrical substation.

The repair work was formally finished on Wednesday, when the LHC was handed over to the operations team. “The building work is complete for everything we want to do until the end of the year, so the keys have been handed over,” said James Gillies, Cern’s director of communications.

Steve Myers, Cern's director of accelerators and technology, said: “It’s a big psychological thing to say now we’re ready for operations. When you’re doing the hardware commissioning, people still have the right to go into the tunnels to tinker and fix things. Now they have to think twice before touching anything. It’s an important psychological flip.

“What we’re planning to do is on Friday evening, we will start to try to put beams into the machine, starting around 5pm [Central European Time] if everything goes to plan. On Saturday we will capture the beam and get it around once or twice, then during the weekend we intended to do something for the other beam, so hopefully we will have two beams circulating.

“The mood here is fantastic. Everybody is excited and exhilarated. We’re all looking forward to seeing the machine doing what it’s supposed to do. We’ve spent the last year worrying about joints and splices and repairs. Now we can start worrying about what matters most, and that’s the beam.”

Once the beam has been inserted, the science team will decide whether to stage low-energy collisions at 450 gigaelectronvolts, or to start immediately to ramp the energy up to 1.2 TeV. Either way, some collisions and a 1.2 TeV energy should be achieved by Christmas.

The world’s most powerful existing atom-smasher, the Tevatron at Fermilab near Chicago, operates at a maximum energy of 1 TeV.

In January, high-energy collisions should take place for the first time, and engineers will start readying the accelerator for a further jump in energy, to 3.5 TeV.

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