LHC accelerating science

The first beam in the Large Hadron Collider at CERN was steered around the full 27 km of the world's most powerful particle accelerator on September 10, 2008, in Geneva. Beams of protons circulating in opposite directions are to be brought into collision and the resulting spray of particles will be analysed. High-field superconducting magnets are required to guide and focus the beams. This implies high electrical currents, which can only be accommodated by superconducting windings offering no resistance to electricity, and therefore no dissipation. To maintain the magnet windings in the superconducting state under high currents and high fields, they must be cooled down to -271.3°C, just 1.9°C above absolute zero by sub-cooled helium (See IIR Newsletter No. 29). Unfortunately, on September 19, during commissioning (without beam) of the final LHC sector at high current, an incident occurred resulting in a large helium leak (about 2 tonnes) into the tunnel. According to CERN, the most likely cause of the incident is a faulty electrical connection between two of the accelerator's magnets. The time necessary to achieve room temperature, inspection and repairs precludes a restart before CERN's obligatory winter maintenance period, bringing the date for restart of the accelerator complex to early spring 2009. CERN specified that "Particle accelerators such as the LHC are unique machines, built at the cutting edge of technology. Each is its own prototype, and teething troubles at the start-up phase are therefore always possible." In spite of this delay, CERN remains optimistic and the official inauguration is still scheduled on October 21, 2008. The aim of the LHC experiments is to "allow physicists to complete a journey that started with Newton's description of gravity. Gravity acts on mass, but so far science is unable to explain the mechanism that generates mass". LHC experiments will also "investigate the reason for nature's preference for matter over antimatter, and they will probe matter as it existed at the very beginning of time."Information provided by Philippe Lebrun, Head of the IIR's Section A and from CERN press releases: http://press.web.cern.ch/press/PressReleases/List.html The photo shows where the cryogenic systems of the superconducting dipole magnets were testedbefore being installed in the LHC tunnel