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Yoshikawa, K.

Paper Title Page
MOPAN043 Beam Charge Feedback System for Thermionic Cathode RF-Gun 254
  • H. Ohgaki, T. Kii, K. Masuda, T. Yamazaki, K. Yoshikawa, H. Zen
    Kyoto IAE, Kyoto
  A beam current feedback system to stabilize the long-time operation of thermionic cathode RF-Gun has been developed in Kyoto University FEL facility where a 4.5-cell thermionic cathode RF-gun provides electron beam to drive a mid-infrared free electron laser. However, the back-bomberdment effect seriously increases the temperature of the cathode surface, and thus the stable operation was quit difficult without continuous control of the cathode temperature or the beam current. We have tried to stabilize the beam current by using a feedback system. The beam current was monitored with current transformer, which was located at the exit of the gun or at the downstream of the energy analyzer, was read by oscilloscope. The total charge was calculated in a PC and the LabView PID-unit controlled the cathode heater current. As a result, the long term stability of the beam current dramatically improved.