Dynamic Aperture Studies for the LHC Separation Dipoles

This note reports results concerning the impact of the cold separation dipoles. The algorithm used to set the strength of the nonlinear correctors located in the insertion regions is presented and discussed in detail. The algorithm is crucial for reducing the impact of the nonlinear magnetic field errors of the triplet quadrupoles, and the cold separation dipoles, and thus improving machine performance. Various optical configurations are considered: injection optics, collision optics for protons, and collision optics for ions. The influence of the whole set of cold separation dipoles, i.e. D1s in IR2, IR8, D2s in IR1, IR2, IR5, IR8, and D3s and D4s in IR4, is analysed for the Injection optics. In collision, only the cold D1s and D2s are considered due to the peculiar optical configurations at the IPs, making their contribution dominant with respect to the other classes of cold separation dipoles. The field errors of the warm D1 magnets in IR1 and IR5 are assumed to be small and are neglected.