Dynamic effects and their control at the LHC

Tune, chromaticity and orbit of the LHC beams have to be precisely controlled by synchronising the magnetic field of quadrupole, sextupole and corrector magnets. This is a challenging task for an accelerator using superconducting magnets, whose field and field errors will have large dynamic effects. The accelerator physics requirements are tight due to the limited dynamic aperture and the large energy stored in the beams. The power converters need to be programmed in order to generate the magnetic functions with defined tolerances. During the injection process and the energy ramp the magnetic performance cannot be predicted with sufficient accuracy, and therefore real-time feedback systems based on magnetic measurements and beam observations are proposed. Beam measurements are used to determine a correction factor for some of the power converters. From magnetic measurements the excitation of small magnets to compensate the sextupolar (b/sub 3/) and decapolar (b/sub 5/) field components in the dipole magnets will be derived. To meet these requirements a deterministic control system is envisaged.