CERN Restarts Large Hadron Collider
After more than a year of repairs, the Large Hadron Collider, the world's largest machine, restarts in Geneva.The European Organization for Nuclear Research, the Geneva-based particle physics laboratory, announced the Large Hadron Collider is operating once again. Following more than a year of repairs, CERN researchers said the particle accelerator, which cost $10 billion to construct, successfully circulated beams of protons in opposite directions at the same time. The project was brought to halt soon after the first tests began in September 2008 after a fault was discovered between two superconducting bending magnets. "It's great to see beam circulating in the LHC again," said CERN director general Rolf Heuer. "We've still got some way to go before physics can begin, but with this milestone we're well on the way."
Recommissioning the LHC began in the summer, and successive milestones have regularly been passed since then, CERN announced. The LHC reached its operating temperature of 1.9 Kelvin, or about -271 Celsius, on October 8. Particles were injected on October 23, but not circulated. A beam was steered through three octants of the machine on November 7, and circulating beams have now been re-established.
In their normal superconducting state, there is negligible electrical resistance across these connections, but in a small number of cases abnormally high resistances have been found in the superconductor. These have since been repaired, CERN announced in August. However, there remained a number of cases where the resistance in the copper stabilizer connections is higher than it should be for running at full energy, leading to the decision to run the LHC at an energy of 3.5 TeV per beam when it started.
CERN said the LHC will run at 3.5 TeV per beam until a significant data sample has been collected and the operations team has gained experience in running the machine. Thereafter, with the benefit of that experience, the energy will be taken towards 5 TeV per beam. At the end of 2010, the LHC will be run with lead ions for the first time. After that, the LHC will shut down and work will begin on moving the machine towards 7 TeV per beam.