Influence of strongly curved large-bore superconducting bending magnets on the optics of storage rings

Abstract

At present, small storage rings featuring strongly curved large-bore superconducting bending magnets are being studied or are under construction at several places in the world. As shown previously, the optics of small rings can be strongly influenced by nonlinear effects [1]. In addition, it is expected that particle trajectories will be influenced more strongly by end fields in the case of large-bore superconducting bending magnets than in the case of small-aperture iron magnets. In order to account for these effects, a computer code has been written to produce the orbit transfer map through third order for bending magnets. This transfer map can then be used in the nonlinear optics and tracking code MARYLIE. The transfer map is computed for the case of an arbitrary magnetic field with mid-plane symmetry. The magnetic field data must be provided separately, e.g. by a magnetic field code, measurements, or by analytic formulae. These tools are applied to the proposed lithography storage ring at Karlsruhe. It is shown how the end fields affect tunes, chromaticities, and stability limits.