Collective Effects in the TLS Storage Ring after the Installation of Superconducting RF Cavity

A superconducting (SC) rf cavity designed by Cornell University [1] was installed in the storage ring at Taiwan Light Source (TLS) in December of 2004. The purpose of rf system upgrade is to increase the stored beam current without collective instabilities caused by higher-order-modes (HOM) of rf cavity. Beam measurements related to collective effects are performed. Results are compared with those measured prior to the rf system upgrade. Theoretical studies on collective effects after the rf upgrade are also presented.