First Experiments of the Digital Global Feedback in SRRC

The digital global feedback system (DGFB) was implemented to suppress orbit drift, low frequency beam motion, and orbit perturbed by insertion devices. Measured response matrix and singular value decomposition (SVD) [1, 2, 3] techniques were applied in this experiment. The feedback controller is based on PID algorithm [5]. Digital filtering techniques were used to removed noise of electron beam position reading, to compensate eddy current effect of vacuum chamber, and to increase bandwidth of orbit feedback loop. The infrastructure of digital feedback system is composed of orbit acquisition system, gigabit fiber links, digital signal processing hardware and software, high precision digital-to-analog converters. The experimental results is presented in this report.