Hefei Light Source-by-bunch Measurement And Analog Feedback System

Brightness and stability are key specifications of synchrotron radiation light source. Continual endeavor is directed to acquire high current, high brightness and favorable stability. Whereas the knowledge of coupling impedance (by which we mean the interaction between a beam and the surrounding vacuum chamber) indicates that the probability of improving performance of storage ring is limited by complicated beam surroundings. What caused the beam unstable, and how to cure the beam instabilities are the key questions, which all the accelerator researchers around the world need to face.We would like to provide a solution in this paper.First, we build a high speed, wide-bandwidth measurement system to record the horizontal and vertical rigid oscillation, longitudinal oscillation, and beam current of each bunch. We develop software by using Hilbert transform, time-frequency analysis, phase space reconstruction and self-adjust frequency window. The software is able to analyze beam oscillation amplitude, mode and phase, such transient performance, as well as statistical performance of different bunches. It's a great progress in both time domain resolving and frequency domain resolving.Second, we accomplish an analog transverse feedback system based in this measurement system. The feedback system will work for improving instability threshold, damping high-amp oscillation, and restraining coherent bunch instability during the injection and the operation period of HLS (Hefei Light Source). Especially we have some experiments to replace the sextuple by the feedback system. We are satisfied and also little bit surprised by the experiments results.At last, based this feedback system, we have further improvement. We develop a high speed programmable test platform to restrain, disturb or kick-out any specified bunch or cluster of bunches during several nanoseconds to 999 seconds. It will be used for further beam character research.We discuss the beam behavior base on multibunch theory; introduce the simulation and signal processing methods; analyze feedback principle; show the detail of BxB (Bunch-by-Bunch) system by different function units; set out the measurement, signal processing and feedback results; anticipate the further result by our new high speed programmable test platform.