Design of bunch-by-bunch measuring and transverse feedback system at HLS

In order to cure and suppress beam instabilities caused by the high order modes (HOM) in the RF cavity and the resistive wall impedance of the vacuum chamber, a bunch by bunch measuring and transverse feedback system of broad band with two BPM is under development now. It can detect and analyze the coupled-bunch(CB) instabilities in time and frequency domain, bunch filling pattern in injection and injection ratio, and suppress CB instability for advanced machine performance. The design concepts and detailed development of the system are presented in this paper. The high frequency of HLS is 204 MHz, which requires the bandwidth of the feedback system wider than 100 MHz. The primary ideas to choose the broad-band components and the system parameters are also expounded.