September 28, 2009
New Upgrades For LHC’s November Restart
After a widely publicized helium leak shut down the Large Hadron Collider last year, engineers began installing an early warning system they hope will prevent any similar problems, BBC News reported.
When a "faulty splice" between magnets knocked the LHC offline last September, it delayed the start of science operations by more than a year.
This LHC "ring," which is built inside a circular tunnel straddling the French-Swiss border near Geneva, is split into eight distinct parts, or sectors. Six of these are now at or close to their operating temperature of -456F.
Officials told the BBC that engineers are powering up magnets in three sectors to prepare for the injection of proton beams into the ring and a low-intensity beam could be injected into the LHC by the middle of October.
Only parts of the collider would be involved in this beam test and if all goes to plan, the first beam collisions could start before the end of the year.
A magnet problem called a "quench" caused a ton of liquid helium to leak into the LHC tunnel, forcing engineers to shut the collider down since September 19, 2008.
The cause of the accident was found to be an electrical fault in one of the splices, or "interconnects", linking two of the 1,200 "superconducting" magnets that accelerate particles around the LHC, according to an investigation carried out for the European Organization for Nuclear Research (CERN).
Superconductivity is the property, exhibited by some materials at very low temperatures, to channel electrical current with zero resistance and very little power loss. A quench occurs when part of a magnet heats up, causing its superconducting properties to be lost.
Engineers have had to install hundreds of new detectors around the machine in order to protect against such events.
Experts say the newly upgraded quench protection system is also expected to improve monitoring of the interconnects between magnets.
"It will allow us to constantly monitor the status of the interconnections. If there is any deterioration detected by the system, the powering of the magnets will be automatically stopped, preventing any damage," said Gianluigi Arduini, deputy head of hardware commissioning for the LHC.
James Gillies, CERN's director of communications, told BBC News that would prevent the kind of damage that occurred in 2008.
"We would be looking at downtime of a matter of weeks, rather than a year... we're in a much better place than we were 12 months ago."
However, at the end of the year when the collider finally re-starts, it is expected to do so at about half its intended energy. The machine "“ which normally runs at energies of seven trillion electron volts "“ will clash together protons at energies of just 3.5 trillion electron volts in its first few months of operation.
Gillies said that because the collider has hundreds to thousands of faulty electrical splices between magnets, it limits the amount of current they can safely put in right now.
Rather than repairing all the faulty splices right now, the engineers have been told instead not to exceed a maximum "safe" limit of five trillion electron volts when the collider re-starts in November.
Other tests uncovered concerns about a number of the magnets themselves, since some of them had been trained to their operating current before being lowered into the LHC tunnel.
But once connected underground, some of them were found to have "lost" their training.
Gillies said they couldn't get up to the current necessary for operating at seven trillion electron volts at the first try.
Engineers are hoping to get the LHC up to five trillion electron volts before the machine goes into its planned downtime again in November 2010.
Soon after, the team will attempt to re-train magnets and possibly replace a proportion of the splices to reach the seven trillion electron volts needed to carry out some of science's most anticipated experiments.
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