Bunch-by-bunch measurement system of HLS

This paper presents a newly implemented wideband(100 MHz) bunch oscillation measurement system, which is in nature different from the narrow-band (<5 MHz) facilities employed before. Basic formalism and implementation details of the system are introduced to illustrate the function of observing coupled bunch instabilities in time and frequency domain. The designed function includes detecting of transverse oscillation, synchrotron phase oscillation, as well as bunch filling pattern. Some diagnostics results of machine instabilities and application of this system are also discussed, which well depict bunch filling mechanism, instability coupling between transverse and longitudinal directions, inherent machine damping time, as well as dominant oscillation modes.