The Large Hadron Collider (LHC) tunnel at Cern. Photograph: Martial Trezzini/AP
Scientists at the Large Hadron Collider at Cern near Geneva are celebrating a major milestone after the machine broke energy records overnight to become the most powerful particle accelerator in the world.
At 12.44am this morning, the LHC accelerated beams of subatomic particles to higher energies than any achieved before in a collider.
The machine, which occupies a 27km circular tunnel that straddles the French-Swiss border, was restarted 10 days ago after being shut down for more than a year while engineers repaired damage caused by a helium leak when it was first switched on in September last year.
"The machine is working like a dream," Lyn Evans, project manager of the LHC, told the Guardian. "It's brilliant. By the end of the week we should be really moving."
Inside the particle accelerator, two counter-rotating beams of hydrogen nuclei are whipped up to more than 99.99% the speed of light. At four points around the machine the beams are crossed, steering the particles into high-energy smash-ups. The collisions recreate in microcosm the conditions that existed moments after the big bang.
According to Einstein's famous equation E = mc2, the energy released by the collisions can create matter in the form of particles that appear in the collider's detectors.
Scientists hope that when they sift through the subatomic debris they will find particles that are new to physics, such as the Higgs boson, which gives mass to elementary particles, and possibly particles of dark matter, an elusive substance that clusters around galaxies and accounts for most of the mass in the universe.
At 9.48pm last night, engineers at Cern accelerated one beam of particles to 1.05 trillion electronvolts. Three hours later, both beams were hurtling around the machine, each with an energy of 1.18 trillion electronvolts. The energies are greater than any achieved at what is now the second most powerful collider in the world, the Tevatron at Fermilab on the outskirts of Chicago.
"For me, it's not so much the energy record that matters, it's that we've got through the start of the acceleration process where things are changing rapidly," Evans said. As the beams are accelerated, eddy currents build up in the enormous superconducting magnets inside the machine and produce erratic magnetic fields that affect how the beams behave.
In the next few days, Cern managers will decide whether to start colliding particles at even greater energy, or run for a short time at lower energies. Scientists will use the first collisions to calibrate their detectors, ensuring they pick up any particles that might be produced under the known laws of physics.
"We're about to move into a new energy regime, and when we do that, we can start to see new things," Evans said.
"We are still coming to terms with just how smoothly the LHC commissioning is going. It is fantastic," said Rolf Heuer, Cern's director general. "We are continuing to take it step by step, and there is still a lot to do before we start physics in 2010. I'm keeping my champagne on ice until then."
Over the next week, engineers will increase the beam intensity to a level that is expected, before Christmas, to reveal new physics at work. The first extended series of high-energy collisions is expected to start in January or February next year, when each beam will be accelerated to 3.5 trillion electronvolts.
"I was here 20 years ago when we switched on Cern's last major particle accelerator, LEP," said Steve Myers, Cern's director of accelerators and technology, referring to the Large Electron Positron collider, which smashed electrons into their antimatter counterparts, positrons.
"I thought that was a great machine to operate, but this is something else. What took us days or weeks with LEP we're doing in hours with the LHC. So far, it all augurs well for a great research programme."
guardian.co.uk © Guardian News and Media Limited 2009
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