通过分析广义传输线理论中的模式耦合系数, 优化设计了一支94 GHz光滑缓变结构回旋管, 当电子注电压50 kV, 电流6 A, 横纵速度比1.4, 工作磁场3.548 5 T时, 在频率94.099 GHz处得到了41%互作用效率, 约120 kW的功率输出; 与折变结构回旋管相比, 缓变结构回旋管中的工作模式纯度提高约27 dB, 注波互作用效率提高约7%。基于自洽非线性理论计算的互作用效率与PIC模拟结果有较好的一致性。

Through analysing the coupling coefficient of the generalised telegraphist’s equations, an optimized 94 GHz gyrotron with gradually tapered cavity is designed. An output power of about 120 kW, corresponding to 41% efficiency, and an oscillation frequency of 94.099 GHz are achieved with a 50 kV, 6 A helical electron beam with a pitch angle of 1.4 at a guiding magnetic field of 3.548 5 T. Compared with the line-joint cavity, the purity of the operating mode is enhanced above 27 dB and the efficiency increases about 7% in the gyrotron with gradually tapered cavity. The efficiency of the beam-wave interaction calculated by the code based on the self-consistent nonlinear theory is in well accord with that simulated by PIC.