Coupled-bunch instabilities in the APS ring

A study of coupled bunch instabilities for the APS storage ring is presented. The instabilities are driven by the higher-order modes of the fifteen 352-MHz single-cell RF cavities. These modes are modeled using the 2-D cavity program URMEL. The program ZAP is then used to estimate the growth time of the instabilities for an equally spaced bunch pattern. The cavity modes most responsible for the instabilities is singled out for damping.<>