Correction of the Long-Range Beam-Beam Effect in LHC using Electro-Magnetic Lenses

The beams in LHC collide head-on in at most four experimental points. Due to the small bunch spacing, the beams experience more than one hundred 'near-misses' on either side of the collision points. The transverse beam separation at these places, limited by the quadrupole aperture, is in the range of 7 to 13 sigma. The non-linear part of these 'long-range' interactions appears to be the dominant mechanism for beam blow-up or beam loss in simulation. A simple non-linear model of the long-range interactions can be devised. It shows that the latter may be locally corrected with good accuracy using wires as correcting lenses. The non-linearity measured by the tune footprint is reduced by one order of magnitude. Pulsing the correcting lenses cancels the so-called PACMAN effect.