Development of Beam Position Feedback Control System in KU-FEL

The feedback system has been developed in KU-FEL linac to stabilize the FEL power fluctuation. The system consists of six 4-button type BPMs and the signal processing system. As the first step, the beam displacement information at the RF-gun section was used for the feedback control to stabilize the electron energy and the vertical beam position at the RF-gun section. As the result the FEL power fluctuation was largely improved from 40% to 20%, factor 2.