Earth’s field effect on magnetic performance of horizontally and vertically polarizing undulators

Abstract

Effects of the interaction of the Earth’s magnetic field with different types of insertion devices (IDs) were studied at the Advanced Photon Source (APS) at Argonne National Laboratory (Argonne) according to the improvement of high-precision field measurements and field correction techniques that should meet the tight requirements for next-generation x-ray sources. The magnetic measurements of two Advanced Photon Source hybrid-type IDs with periods of 33 and 27 mm have been performed. The impact of different design elements was considered. It was demonstrated that the specified limits for IDs can be exceeded if the effect of the Earth’s field is not taken into account for various orientations of the IDs in the storage ring. Numerical simulations were done to better interpret experimental results for both devices and to estimate the effect for novel ID with the horizontal main field, which is now under development.