The effects of insertion devices on beam dynamics in the ALS

Abstract

It is shown that introducing undulators into the ALS (Advanced Light Source) causes a significant reduction in dynamic aperture. However, the effect is similar to that which is expected from the storage ring when realistic magnetic imperfections, magnet misalignments, and a corrected closed orbit are included. Moreover, when undulators are added into the imperfect machine there is little further degradation of the dynamic aperture. In all cases the machine acceptance will be determined by the physical (vacuum aperture), rather than the diminished, dynamic aperture. Thus, the insertion devices are not expected to impact the elastic gas scattering lifetime of the ALS. The momentum acceptance of the storage ring is seriously affected by the undulators; this will impact the Touschek lifetime of the ALS. However, at the levels predicted by the present study, the resulting overall beam lifetimes are still acceptable. >