After starting with a bang, which promptly turned into a whimper, scientists quietly powered up the Large Hadron Collider for a second time.
The preliminary run was low key compared with the ill-fated switch-on in September last year, but CERN scientists said the first beams suggested that the £3.6 billion experiment in Switzerland was finally under way again. “It’s the beginning of a very well-planned and cautious switch-on,” Brian Foster, a particle physicist from the University of Oxford, said.
On Friday proton beams and lead ions were sent at a relatively low energy around a section of the ring containing the “A Large Ion Collider Experiment” (Alice) detector. Protons were also sent through the LHCb detector, which is designed to investigate why the Universe is made up almost entirely of matter and hardly any antimatter. The beams travelled through a quarter of the ring in total.
“The acid test of any accelerator is when you put the beam in,” said Steve Myers, director of accelerators and technology at CERN. “We were holding our breath a little bit, but it worked incredibly well.”
The accelerator was switched off last year after only nine days because of a faulty electrical connection between two magnets. The flaw resulted in more than a tonne of liquid helium coolant leaking from magnets, causing them to warm up by as much as 100C. Since then the magnets have been cooled back down to just 1.9 degrees above absolute zero (-273C).
When the accelerator is fully functioning, protons and heavy ions, such as lead, will be accelerated to almost the speed of light around the machine’s 27km (17-mile) underground ring. By smashing them together in high-speed collisions, scientists hope to re-create conditions similar to those of the early Universe.
The collisions could provide the first experimental evidence to prove the existence of the Higgs boson, which many scientists believe explains the origin of mass. Other researchers are looking for evidence of supersymmetry, the idea that every particle in the Universe has a “companion” particle.
Last week Holger Bech Nielsen, of the Niels Bohr Institute in Copenhagen, and Masao Ninomiya, of the Yukawa Institute for Theoretical Physics in Kyoto, suggested that the breakdowns at the collider could have been caused by the Higgs boson itself.