Design Study of High Efficiency CW Klystron for CEPC

In order to reduce energy consumption and operating cost for CEPC, the 650MHz/800kW high efficiency klystron has been regarded as a priority key technology to be researched and developed. In this paper, the recent progress of high efficiency CW klystron for CEPC is reviewed briefly. Then the RF section design study of the second stage of high efficiency klystron for CEPC is presented. Several computer codes have been used for klystron simulation. The simulation results with different codes are presented, which are in good agreement. The whole klystron simulation using 3D PIC solver in CST indicated that the klystron efficiency was achieved up to 78% with asymmetry coaxial coupler.