The wakefield effects of pulsed crab cavities at the Advanced Photon Source for short-x-ray pulse generation

In recent years we have explored the application to the Advanced Photon Source (APS) of Zholents' crab-cavity- based scheme for production of short x-ray pulses [1]. As a near-term project, the APS has elected to pursue a pulsed system using room-temperature cavities [2]. The cavity design has been optimized to heavily damp parasitic modes while maintaining large shunt impedance for the deflecting dipole mode [3]. We evaluated a system consisting of three crab cavities as an impedance source and determined their effect on the single- and multi-bunch instabilities. In the single-bunch instability we used the APS impedance model as the reference system in order to predict the overall performance of the ring when the crab cavities are installed in the future. For multi-bunch instabilities we used a realistic fill pattern, including hybrid-fill, and tracked multiple bunches where each bunch was treated as soft in distribution.