Dynamical aperture studies for the CERN LHC: comparison between statistical assignment of magnetic field errors and actual measured field errors

It is customary to evaluate the performance of a circular particle accelerator by computing the dynamical aperture, i.e. the domain in phase space where bounded singleparticle motion occurs. In the case of the LHC the dynamical aperture computation is performed by assuming a statistical distribution of the magnetic field errors of various magnets classes: the numerical computations are repeated for a given set of realisations of the LHC ring. With the progress in the magnet production and allocation of the available positions in the ring, the statistical approach has to be replaced by the computation of one single configuration, namely the actual realisation of the machine. Comparisons between the two approaches are presented and discussed in details.Â