Longitudinal and Transverse Feedback Systems for Pls Storage Ring*

The Pohang Light Source (PLS) storage ring uses two bunch-by-bunch feedback systems a longitudinal feedback system (LFS) and a transverse feedback system (TFS) to cure the coupled bunch instabilities due to higher order modes of RF cavities and resistive wall impedance. The LFS employs the digital electronics developed for ALS and PEPII and uses a cavity-type kicker, and it was successfully commissioned in 1999 with the aid of SLAC. The TFS uses analog two-tap coax notch filters for closed orbit offset signal rejection. The TFS is now in upgrade to use one kicker per transverse plane to improve efficiency over the previous system with a kicker combining both planes in a single structure. This paper will describe the achieved results of curing the coupled bunch instabilities by using the LFS and TFS together with current status.