London, Dec 5 : An internal report sent to physicists working on the Large Hadron Collider (LHC) at the CERN laboratory near Geneva in Switzerland, has instructed them to restart the giant machine by end of July 2009.
The LHC, also called the 'giant particle smasher', is the world's largest and highest energy particle accelerator complex, intended to collide opposing beams of protons with very high kinetic energy. It circulated its first particle beams on September 10, 2008, but a few days later had to suspend operations due to equipment failure.
The accident that forced the LHC to shut down, less than 10 days after it started operation, highlighted weaknesses in the collider's design.
The problem arose when an electrical fault punched a hole in the enclosure containing cryogenic liquid helium, causing it to vaporise.
Because the gas could not escape fast enough, this led to an explosive burst of pressure that damaged neighbouring sections of the machine.
Engineers plan to address this problem by improving the pressure relief system, which includes increasing the number of valves.
The decision now is whether to install this upgrade all round the LHC's 27-kilometre ring, or in stages.
To upgrade the whole ring, it would all have to be warmed up, effectively ruling out any chance of running the machine next year.
Alternatively, the pressure relief system could be upgraded in the three sectors that are already warm, leaving any further improvements to the scheduled shutdown a year from now.
LHC project leader Lyn Evans told New Scientist that the quicker option is the only one on the table.
"The priority for 2009 is to get beams in the LHC and data for the experiments," he said. "We will be doing this as soon as possible, but no sooner," he added.
According to Jorg Wenninger, a member of the operations team, "The people who want to be really careful would say we have to do all the upgrades and there are others that say, with all the measurements we have now, we feel extremely confident that we are taking no risks next year."
Evans remains confident that the LHC will be running again next year.
Interim improvement to the pressure relief system in the cold sectors will be "totally adequate" for the low-energy beams planned for 2009, according to him.