The increasing demands for electron beams with high quality and low timing jitter for accelerator-based applications such as ultrafast electron microscopy (UEM) and ultrafast electron diffraction (UED) have stimulated active efforts to develop suitable injectors for these accelerators. One promising direction in this regard is using of a bimodal rf gun operating in fundamental mode and a phase-locked harmonically-related higher mode. Work reported in this paper is on analysis and design of a bimodal rf gun operating in S-band as the fundamental and C-band as the second-harmonic modes. The rf design for such an rf gun includes the new design like directional coupler and rectangular mode launcher, which presented good transmission, low reflective cross-talk, and allowed multiple iterations of the modification. Compared to the fundamental mode, the new design achieved reduction in rf emittance and energy spread for MeV UEM initial distribution, and reduction in slope of flight time as function of injection phase for MeV UED applications.

中文翻译：

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一次和二次谐波光电阴极双峰枪的仿真研究

对于基于加速器的应用（例如超快电子显微镜（UEM）和超快电子衍射（UED））对高质量和低定时抖动的电子束的不断增长的需求，激发了为这些加速器开发合适的注射器的积极努力。在这方面一个有希望的方向是使用以基本模式和锁相谐波相关的更高模式工作的双峰射频枪。本文报道的工作是分析和设计一种以S波段为基本频率，C波段为第二谐波模式的双峰射频枪。这种RF枪的RF设计包括定向耦合器和矩形模式发射器之类的新设计，具有良好的透射率，低反射串扰，并允许多次修改。与基本模式相比，