Linear Imperfections and Operational Aspects Induced by the D1 Multipole Errors for the LHC Upgrade Phase I

In addition to the dynamic aperture as a general machine parameter that has to be optimized in the LHC upgrade machine, strong lower order multipoles will lead to a series of problems for the operation of the machine. A direct influence on the linear beam optics (beta beating, tune shift and coupling) from the a2, b2 multipoles is evident. Equally important however are the multipole coefficients of the next higher order n=3 via the feed down effect. The foreseen half crossing angle of about 205 µrad at the IP creates large offsets in the D1 magnet that finally lead again to a strong a2, b2 errors. The estimates presented in this paper show a distortion in the order of several percent for the beta beat and a considerable shift of the working point. Even after compensation of these effects an influence on the machine performance is expected during machine operation and a further reduction of the multipole coefficients, especially in the case of the D1 magnet, might be needed.