Design of broadband relativistic klystron amplifier

With the electromagnetic code, the buncher and output section of an S-band broadband relativistic klystron amplifier (RKA) are designed and calculated. Three stagger-tuned bunching cavities are used to modulate the electron beam to achieve a bandwidth of 11% when the depth of the fundamental harmonic current is not less than 80%. In order to enhance the bandwidth of the output circuit for RKA, the overlapped mode double-gap output cavity is modeled and simulated. The two modes are overlapped when the structure parameters of the output cavity are appropriate. And the output circuit bandwidth reaches 15% at 80% depth of the fundamental harmonic current. A maximum output power of 1.58 GW and a 10% working bandwidth of 3 dB are obtained by adjusting the frequency and the power of the driven microwave in the particle-in-cell simulation with the designed structure of the whole broadband relativistic klystron amplifier, and the power in the bandwidth is not less than 1 GW.