Effects of Fringe Fields and Insertion Devices Revealed Through Experimental Frequency Map Analysis

Following the pioneering work at the ALS [1] frequency map analysis (FMA) was performed at BESSY. With 7 families of sextupole magnets available in the storage ring, amplitude dependent tune shifts can be made rather small. Therefore, the impact of fringe fields of dipoles and quadrupoles as well as systematic octupole and decapole field components of these magnets are visible in the maps. At BESSY, the FMA is used in preparation of the storage ring for topping-up operation. Insertion devices (IDs) with their dynamic and static field integrals distort the frequency maps (FM) and reduce the horizontal dynamic aperture significantly. Shimming can recover the aperture which is important for efficient injection. The current status of the experiments as well as the results of the theoretical modeling will be presented.