An issue of the cavity-like structure inside the insertion device at the TPS storage ring

摘要

The first cryogenic permanent-magnet undulator installed at National Synchrotron Radiation Research Center (NSRRC) suffered in the first year from an issue of a high operating temperature. Two bulged transition tapers were identified as possible sources for the large heat load. The profile modeling of the upstream transition taper enabled an estimate of the parasitic heating power, and indicated the cause of the large heat load. Simultaneously, one longitudinal instability was observed when the stored beam current of the TPS storage ring was 500 mA. A corresponding study of the longitudinal coupled-bunch instability induced by the resonance mode of the bulged transition tapers has been undertaken. The simulation results indicated that the longitudinal coupled-bunch instability would become damped by the radiation damping of the accelerator. The newly constructed transition tapers with a new design of the tapers significantly decrease the parasitic heating power. This study focuses on the impacts on beam dynamics of the electron storage ring resulting from the cavity-like structure.