Cutting Edge

A silicon detector being installed in the Large Hadron Collider in December 2007.

(Credit: Michael Hoch/CERN)

The world's biggest particle accelerator, the Large Hadron Collider, is in full operation after a year of repairs.

The European Organization for Nuclear Research, CERN, said in a statement on Friday that particle beams are once again circulating in the LHC, and that a clockwise circulating beam was established at 10 p.m. in Geneva.

According to the CERN Twitter feed, an anticlockwise beam was also successfully injected, and both beams have completed many thousands of turns of the LHC.

Read more of "Large Hadron Collider up and running again" at ZDNet UK.

The Large Hadron Collider, currently undergoing repairs, will change its schedule and run through the winter to make sure the experiment provides workable results.

The European Centre for Nuclear Research (CERN) flagship particle accelerator has been out of action since September, when an electrical fault called a halt to an experiment to understand the fundamental physics of matter. It is scheduled to restart in September 2009.

Click image for gallery on the Large Hadron Collider.

(Credit: Maximilien Brice for CERN)

On Wednesday, James Gillies, head of communications at CERN, said the LHC could carry on running over the subsequent months. Normally, CERN particle-acceleration operations cease in November for the winter, because energy costs throughout the winter months are prohibitively high.

"The schedule is fairly tight," Gillies told ZDNet UK. "Instead of shutting down for the winter, this year, we will start up in September, October, or later, and run continually until we have enough data in the can. We will run straight through the winter if necessary."

CERN is able to cover the energy cost of running the LHC during outside its schedule because it had had less expenditure while the experiment was halted, Gilles said. "We're getting the money from the standard CERN budget," he said. "If we hadn't had the incident last year, we would be running the LHC."

Gillies added that CERN would continue to be supplied by EDF on the French side and EOS on the Swiss side, and that EOS would provide energy through the cold season.

The energy demands of the LHC are high. The particle beams are designed to run at a maximum of 7 TeV, and have run at around 5 TeV. There is 350MJ stored in each beam, which CERN scientists estimate has enough energy to drill a 30m hole in copper.

The LHC experiment, designed to smash beams of nuclear particles into each other, was brought to a halt nine days after it was started. A fault in a copper bus-bar caused a resistive zone, which then prevented the normal operation of a quench. This caused an electrical arc, which punctured the cavity containing liquid helium used to supercool both the experiment and the magnets which direct and focus the particle beams.

The fault was the result of an insufficiently welded joint between two of the bus-bars, which are used to carry the superconducting cable. CERN beams department scientist Jorg Wenninger said in a presentation (PDF) on Monday that all the approximately 1,700 joints had been inspected. Many were found to have bad soldering or reduced electrical contact, the same problem that caused the initial incident.

A new quench-monitoring and protection system has been implemented that will give an early warning if any part of the superconducting coils or bus-bars develops high resistance, Gilles noted. He also said that more helium safety valves with a higher capacity were being installed.

Tom Espiner of ZDNet UK reported from London.