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Zen, H.

Paper Title Page
TUPC113 Beam Energy Compensation by RF Amplitude Control for Thermionic RF Gun and Linac Based Mid-infrared FEL 1329
 
  • H. Zen, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki, S. Sasaki, T. Shiiyama
    Kyoto IAE, Kyoto
 
  Institute of Advanced Energy, Kyoto University has constructed a mid-infrared FEL facility which consists of a thermionic RF gun, a traveling-wave type accelerating tube and a halbach type undulator. The electron beam quality is critical for lasing FEL. However, we found that the beam energy after the accelerator tube decreased from 25 to 23.5 MeV (around 6%) during macro-pulse duration (~4μsec), because.the beam current increases from 65 to 120 mA during the macro-pulse due to the backbombardment effect in the RF gun. To compensate the energy drop and to minimize the energy spread over the macro-pulse, the amplitude of RF power fed to the tube was controlled. Since a precise micro-bunch interval required to build up the FEL, the RF phase was also controlled. As the result, the energy spread of the electron beam was greatly reduced from 6 to 0.8% in FWHM which was same with micro-pulse energy spread (~0.8%). The phase stability during macro-pulse was also improved from 10 to less than 2 degree.