Results of Preliminary Tests of PAR Bunch Cleaning

A particle accumulator ring (PAR) is used at the Advanced Photon Source (APS) to collect multiple linac bunches and compress them into a 0.3-ns single bunch for booster injection. A 9.77-MHz fundamental and a 117.3-MHz harmonic rf system (RF12) are employed for initial beam capture and bunch-length compression, respectively. Satellite bunches with very low charge form when the phase or loading of the rf systems drift. These satellites cause bunch purity deterioration in the storage ring. Storage ring and booster bunch cleaning has been tried but proved to be difficult due to top-up mode of operation in the storage ring and tune drift in the booster synchrotron. Recently we implemented a PAR bunch cleaning system with tune-modulated harmonic rf knockout. The results showed that the cleaning method is feasible and can achieve the goal of bunch purity better than 10-8. This report describes the system configuration, test results, and system performance.