Wake Field Effect from the Undulator Vacuum Chamber in PAL-XFEL

Wake field effect on the electron beam from the undulator chamber in PAL-XFEL is analyzed. The wake field takeover some energy from the electron beam which will increase the energy spread of the electron beam. This will cause the degradation of the radiation power in PAL-XFEL. To decrease the effect, the surface of the undulator vacuum chamber should be fabricated with 200 nm surface roughness and 5 nm oxidation layer. In this presentation, the numerical calculation of the wake will be shown. Simulation results of the radiation generation in PAL-XFEL also will be presented.