Particle physicists seeking to uncover the secrets of the universe will have a little longer to wait after the CERN laboratory in Switzerland confirmed a delay in the start-up of the Large Hadron Collider (LHC) - the world’s most powerful particle accelerator.

The LHC is a 27-kilometre circular tunnel 100 metres below the French-Swiss border near Geneva, in which protons will collide at close to the speed of light. CERN says it will now start operations next spring, not in November as originally planned.

"The start-up at full level was always scheduled for spring 2008, but we had planned to test the machine for two weeks before Christmas, which will not now take place," said James Gillies, a spokesman for the laboratory.

The delay is due to an accumulation of minor setbacks, Gillies added. Earlier this year, a support structure for one of the accelerator’s superconducting magnets broke during tests. “We identified a design fault and this is now being repaired,” he said.

The superconducting magnets have also taken longer than expected to cool to their 1.9-Kelvin operating temperature. “We’re learning how to cool 38000 tonnes of equipment to a temperature lower than outer space. It’s a very complex machine,” says Gillies.

"Ambitious undertaking"

The LHC has been assembled over 15 years in a project involving more than 10000 physicists, and 500 research bodies and firms around the world. The machine was originally planned to start operating in 2002, but funding problems delayed the launch until 2007.

The project "could be the most ambitious scientific undertaking ever", and its results "will probably change our fundamental knowledge of the universe", its organisers say.

Scientists plan to smash together high-energy protons in two counter-rotating beams in the tunnel to look for signatures of supersymmetry, dark matter and the origins of mass.

The beams will be made up of billions of protons, which will be injected into the accelerator in bunchesand kept circulating for hours, guided by thousands of powerful superconducting magnets. Each proton will go around the 27-km ring over 11,000 times a second.