Compensating Parasitic Collisions Using Electromagnetic Lenses

Long-range collisions are important not only for e+e- factories, but they also limit the dynamic aperture of hadron colliders. Their effect can be compensated by a current-fed wire mounted parallel to the beam. A compensation scheme based on this idea has been proposed for the Large Hadron Collider (LHC). First, successful machine experiments with a prototype device in the CERN SPS explored the dependence on the beam-wire distance and on the wire excitation. Various different types of beam signals and monitors were used to gather maximum information about the impact of the wire on beam dynamics. Two additional devices will be installed in 2004, in order to explicitly demonstrate the compensation, to study pertinent tolerances, and, furthermore, to assess the respective merits of different beam-beam crossing schemes for several interaction points.