Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade

The proposed Advanced Photon Source (APS) multibend achromat (MBA) lattice includes a passive bunchlengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system aects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.