利用3维高频软件设计了一种用于S波段大间隙速调管的膜片加载大间隙单重入输出腔, 建立了带大耦合孔的输出腔3维全结构模型, 采用3维PIC程序对输出腔的提取效果进行了粒子模拟。研究结果表明：膜片加载的大间隙单重入输出腔开大耦合孔后, 其所有谐振频点的场分布都不再是TM011模式, 因此,在设计此类输出腔时不能以工作频点是否谐振为优化目标。提出了大间隙输出腔设计原则, 根据设计原则优化后的输出腔可稳定提取1.07 GW的平均功率, 提取效率约35.7%。

High frequency characteristics analysis is presented on a washer loaded wide-gap reentrant output cavity for the S-band relativistic wide-gap klystron amplifier(WKA). At resonant frequency points, the electric field modes of the wide-gap output cavity with large coupling hole are not TM011 anymore. To avoid these unwanted modes and their influences on cavity gap field distribution, a large enough distance between designed working frequency and resonant frequency is required. At the same time, an effort to reduce the output cavity external quality factor is also necessary. The output cavity power extraction effect was simulated by using a three-dimension fully electromagnetic particle-in-cell(PIC) code. At beam voltage of 600 kV, cathode current of 5 kA and current modulation depth of 94%, the average output power of an optimized washer loaded wide-gap reentrant cavity is 1.07 GW at 3.6 GHz, with an average power efficiency of about 35.7%.