The Large Hadron Collider, a 27-kilometre accelerator, is due to start operation in July 2008
CERN's new machine still aiming for 2008 debut.
Rumours of construction delays at the world's largest particle accelerator have exaggerated the size of the problem, according to the project's head. "There have been no show stoppers," wrote Robert Aymar, director-general of CERN, the particle physics lab near Geneva, Switzerland, in the 8 October issue of the lab's CERN Bulletin. "We can all look forward to the LHC producing its first physics in 2008."
His reassuring announcement came after gossip on physics blogs of new problems that could set the lab's Large Hadron Collider (LHC) even further behind its already delayed start date. But for all the reassurance, the LHC schedule remains tight, says project leader Lyn Evans. Relatively small mishaps could push the opening back beyond July 2008, when the LHC is supposed to start doing physics.
The machine is a CHF10-billion (US$8.4-billion) accelerator designed to slam protons into each other at energies of up to 14 teraelectronvolts - 7 times the current record. Detectors will comb through the debris from the collisions for evidence of the Higgs mechanism, which is believed to endow all other particles with mass, and for signs of physics beyond the 'standard model', the current theoretical framework of particle physics.
LHC construction has already faced a number of setbacks and delays. For example, in March, a support holding a superconducting magnet in one section of the machine failed, leaving engineers scrambling for a fix (see Nature doi:10.1038/news070402-3 ; 2007).
The latest round of speculation was sparked in September when engineers found that several pieces of tubing between magnets had crumpled as the machine was being prepared for servicing. Just six out of 424 sections collapsed, according to Raymond Veness, who leads the LHC's vacuum engineering team. But the failures blocked the beam line, along which particles will eventually travel. "This is a potentially nasty problem," Veness says.
For the time being, engineers have improvised a solution. Using compressed air, they are firing a small plastic ball equipped with a radio-transmitter through the line. By detecting where the ball comes to a halt, they have been able to spot collapsed sections in a matter of minutes. But changing the defective sections, a half-day task, adds to an already full maintenance schedule. "Everyone is stretched in all directions," adds Veness.
"I don't think anyone sees it as an insurmountable problem," says Peter Limon, a high-energy physicist at Fermilab in Batavia, Illinois, the only other lab currently working with very high-energy protons. But whether the July date can be met will depend on how the magnet systems behave in additional tests this winter, says Evans. A magnet or other component failure in a section of the ring cooled to liquid helium temperatures for testing could set things back by months because of the time needed to warm the section up for repairs and cool it back down.
"The next three months are going to be pretty critical," says Evans. "If something unforeseen comes up between now and then, it will slip. There's no doubt."
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