采用TE34, 10-模式开展了140 GHz兆瓦级圆柱回旋管腔体的设计和优化, 并分析了工作模的模式竞争情况.由于两个邻近模式TE33, 10-和TE31, 11+的竞争TE34, 10-未能在高效率区稳定振荡, 使得输出功率显著降低.为了抑制模式竞争计算了工作模和两个竞争模的滞回曲线, 结果表明, TE34, 10-能够在磁场由其低功率振荡区下降时对竞争模形成抑制, 而在磁场由低到高时则由于竞争模的率先起振反而被竞争模所抑制.基于此设计了由5. 59 T下降至5. 51 T的时变磁场曲线, 在此磁场下开展了包含42个模式在内的多模时域计算, 结果表明竞争模式被有效抑制, 工作模在此磁场曲线下能够稳定获得0. 96 MW的稳定输出功率, 对应的电子效率为36. 7％, 频率为140 GHz.%A cylindrical gyrotron cavity is designed and optimized with a high order mode TE34, 10-to deliver an output power of megawatts level at 140 GHz. Analysis on mode competition indicates that the two adjacent modes TE33, 10-and TE31, 11 +involve in competition and cause significant decreasing of output power of TE34, 10-. To suppress the competition hysteresis loops of TE31, 11 +and TE33, 10-with TE34, 10-are calculated, which indicates TE34, 10-can inhibit growth of the other two modes with decreasing magnetic field from its lowefficiency single mode oscillation zone, while it turned out just the opposite with increasing magnetic field due to the earlier oscillation of the competitors. Based on the results, a multimode time-dependent calculation including 42 modes is carried out with magnetic field dropping from 5. 59 T to 5. 51 T, the results showthat mode competition is successfully suppressed, the operation mode TE34, 10-realizes stable single mode oscillation with an output power of 0. 96 MW and an electron efficiency of 36. 7％ at 140 GHz.
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