Global correction of magnetic field errors in LHC interaction regions

Global compensation of nonlinear field errors based on the minimization of nonlinearities in a one-turn map was found to be very effective in reducing the detrimental effects of magnetic field errors in the LHC collision latt ice. With a few groups of low-order correctors, nonlinear terms in the one- turn map can be minimized order-by-order and, consequently, the dynamic ape rture is substantially increased and the phase-space region occupied by bea ms becomes much more linear. One advantage of the global correction is the possibility of further optimization of the correction based on a direct mea surement of a one-turn map with beam-dynamics experiments.