W波段三次谐波回旋振荡管的模拟与设计

研究了影响毫米波谐波回旋管互作用效率的多个因素,通过采用三次谐波工作,94 GHz回旋管的工作磁场降低到了1.185 T,使采用永磁体取代超导磁体成为可能.利用自洽非线性计算和粒子模拟研究了回旋振荡管的注-波互作用过程,发现了腔体品质因数与互作用效率的内在联系,研究了工作电压和电子注横纵速率比对耦合强度的影响,考虑了磁场渐变及电子注速度离散对互作用效率的影响,通过选择合理的工作模式和系统参数,当工作电压为40 kV、工作电流为12 A、电子注横向速度离散为3%时获得了95 kW的输出功率及19.7%的效率.当采用单级降压收集极后,效率可以进一步提高到39.2%.

Simulation and design of a W-band third-harmonic gyrotron oscillator

Some key issues associated with the interaction efficiency of a harmonic gyrotron oscillator operating in the millimeter wave regions were studied. Operating at the third-harmonic, the required magnetic field was reduced to 1.185 T for a 94GHz gyrotron oscillator, which makes it possible to replace the superconducting magnet by a permanent magnet. A self-consistent code and a particle-in-cell(PIC) software were used to investigate the harmonic beam-wave interaction. The interplay between the cavity quality factor and interaction efficiency was revealed, and the dependence of both beam voltage and electron beam pitch factor on the coupling coefficient was also studied. Through carefully choosing operating mode, optimizing system parameters, and using linearly increased axial magnetic field, the output power of 95kW and efficiency of 19.7% was achieved under accelerating voltage of 40kV, beam current of 12 A, and transverse velocity spread of 3%. The efficiency can be further increased to 39. 2% by utilizing a single stage depressed collector(SDC).