Three-dimensional whole-tube simulation of C-band relativistic klystron amplifier

The three-dimensional whole-tube model for a C-band relativistic klystron amplifier is designed. With the integrated model, the high frequency characteristic analysis and optimization of the tube are presented. A three-dimensional full-electromagnetic particle-in-cell(PIC) code is used to simulate the absorption of injected microwave, and to simulate the fundamental harmonic modulated current when electron beams propagate through the input and idler cavity gaps. The simulated result show that the input cavity matches with the input waveguide and most energy of the input microwave is absorbed by electron beams and the resonant cavities. The modulation depths of the fundamental harmonic modulated current are about 11% at 20 cm downstream of the input cavity gap and about 76% at 15 cm downstr