The LHC A unique tool Why do we need the LHC? LHC operations Technical challenges A unique tool The Large Hadron Collider (LHC) is a particle accelerator which is being built at CERN, the European Organization for Nuclear Research, the world's largest particle physics laboratory. When it will switch on in 2007, it will be the most powerful instrument ever built to investigate on particles proprieties. The LHC will take the place of CERN's Large Electron Positron (LEP) collider, and will sit in its 27 Km long tunnel, about 100m underground. It will accelerate 2 separate beams of protons up to an energy of 7 TeV , and then bring them into head-on collisions (from here the name "collider"). The protons collision energy will then be of 14 TeV. But the LHC will not be limited to the study of proton-proton collisions as it can also collide heavy ions, such as lead, with a collision energy of 1148 TeV. A view of the LHC Before being injected into the LHC, proton beams will be prepared by CERN's existing "accelerator complex". This is a succession of machines with increasingly higher energies, injecting the beam each time into the next one, which takes over to bring the beam to an even higher energy. The CERN accelerator complex To bend the 7 TeV protons around the ring, the LHC dipoles must be able to produce magnetic fields of 8.36 Tesla, a value which is made possible by the use of "superconductivity". This is the ability of certain materials, usually at very low temperatures, to conduct electric current without resistance and power losses, and therefore produce high magnetic fields. The LHC will operate at about 300 degrees below room temperature (even colder than outer space!) and use the most advanced superconducting magnet and accelerator technologies ever employed. 1,296 superconducting dipoles and more than 2,500 other magnets will guide and collide the LHC beams. They range from small, normally conducting bending magnets to large, superconducting focusing quadrupoles. When completed, the accelerator will be the largest superconducting installation in the world. Five experiments, with huge detectors, will study what happens when the LHC's beams collide. They will handle as much information as the entire European telecommunications network does today!