A High-Power and Broadband G-Band Extended Interaction Klystron Based on Mode Overlap

A G -band multigap extended interaction klystron (EIK) adoptingmode overlapmethod with ladder-type structure is proposed to achieve high power, high efficiency, and broad bandwidth. The gap number is set larger than the conventional EIK to achieve its potential. The high-frequency characteristics of the modes in output cavity are studied. The length ratio of long and short slots is optimized to obtain appropriate mode frequency interval and effective characteristic impedance. In our scheme, the gap number of output cavity is determined as 17 with the mode overlap of pi mode and 15/16 pi mode. The circuit structure andworking conditions are carefully designedand optimized to solve the problem of instability under large gap number. With a beam current of 0.3 A, a voltage of 15.8 kV, and a magnetic field of 0.75 T, the particle-in-cell simulation shows that with the increase of frequency, the output cavity can work with two modes overlap and expand the 3-dB bandwidth to 1.32 GHz, which is more than two times of our previous work. Also, a maximum output power of 870 W, an efficiency of 18.4%, and a gain of 46.4 dB are finally obtained. The numerical simulation results definitely demonstrate the feasibility ofmode overlap and its ability to the expansion of EIK bandwidth in the terahertz band.

Automated summary

This paper proposes a G-band multigap extended interaction klystron (EIK) with a ladder-type structure and mode overlap method, aiming to achieve high power, high efficiency, and broad bandwidth. By optimizing the number of gaps, length ratio of slots, circuit structure, and working conditions, the EIK bandwidth in the terahertz band is successfully expanded.