GENEVA The giant particle collider built to reproduce "Big Bang" conditions will now be restarted in September to allow time for repairs, not the summer as planned, the European Organization for Nuclear Research (CERN) said.
In a statement late on Monday, CERN said the first particle collisions would take place in October, following repairs and the installation of new safety features to the Large Hadron Collider (LHC), the biggest and most complex machine ever built.
After another short technical stop at the end of 2009, the collider will run until autumn next year, producing enough data on the smallest building blocks of matter to announce results in 2010, it said.
"The schedule we have now is without a doubt the best for the LHC and for the physicists waiting for data," CERN Director General Rolf Heuer said in the statement.
"It is cautious, ensuring that all the necessary work is done on the LHC before we start up, yet it allows physics research to begin this year," he said.
The new timetable represents a setback of six weeks on the previous schedule, which had foreseen that the LHC's giant tunnels would be cooled down to their operating temperature of just above absolute zero by early July.
CERN had previously said it would restart the collider this spring after shutting it down in September because of an electrical fault and helium leak, only nine days after starting it up to great fanfare.
The collider is designed to recreate conditions just after the Big Bang, believed by most cosmologists to have created the universe 13.7 billion years ago.
It sends beams of sub-atomic particles around a 27-km (17-mile) tunnel under the French-Swiss border outside Geneva to collide with each other at nearly the speed of light.
These collisions will explode in a burst of energy which scientists will monitor for new or previously unseen particles which they predict could help explain the nature of mass and the origins of the universe.
CERN has said the accident last year never posed any danger. When it first started the machine it had to rebuff suggestions that the experiment would create millions of black holes that would suck in the earth.
CERN, whose scientist Tim Berners-Lee is credited with inventing the World Wide Web in 1990, said in December it expected the repairs to cost up to 35 million Swiss francs ($30 million).
The LHC has already cost 10 billion francs ($8.5 billion) to build, supported by CERN's 20 European member states and other countries including the United States and Russia.
(Reporting by Jonathan Lynn; Editing by Nick Vinocur)