Real-time position control of free-electron laser beams: theory and experiments

This paper addresses the feedback control of electron-beam positions in Duke University Free-Electron Laser Facility. The input-output relationship for this system is algebraic and the system is subject to noise and disturbance inputs. The information about beam position is obtained by sensory devices, called beam position monitors, distributed throughout the storage ring. In contrast, the beam position profile is controlled by passing currents through the coils of correction magnets distributed around the ring. A desired control objective is to move the stored electron-beam to specific locations in the vacuum chamber and to stabilize the orbit in the presence of disturbances. The technical details of implementing the data acquisition and control scheme and their integration with the existing control system modules are presented along with the experimental results.