新型二次电子倍增阴极构型设计与动力学过程

提出了一种可由脉冲功率驱动的新型二次电子倍增阴极构型，并对其进行了动力学过程的初步理论研究。首先，针对该二次电子倍增阴极，建立了动力学模型，获得了二次电子的位移和速度方程，讨论了电子初始出射速度对其轨迹、渡越时间和碰撞能量的影响，理论给出了渡越时间和碰撞能量的近似解析表达式。其次，通过动力学方程与Vaughan二次电子产额经验公式的耦合求解，获得了该二次电子倍增阴极的工作区间，并对其进行了细致讨论。结果表明：该新型二次电子倍增阴极二极管概念上是可行的，在涂敷高二次电子产额系数材料的圆柱形介质上施加合适的轴向和径向静电场(MV/m量级)以及轴向静磁场(T量级)，可以达到电子沿阴极表面螺旋行进过程中实现二次电子倍增并最终获得电流沿轴向放大的设计目标。另外，讨论了正电荷沉积引发的二次电子倍增饱和现象，并对阴极发射电流密度进行了理论粗估，结果表明：阴极发射电流密度可达kA/cm2水平，具备强流发射特性；增加外加径向场强幅值可有效提升阴极发射电流密度。

Abstract

In this paper, the configuration design of a novel multipacting cathode driven by pulsed power source is put forward and its dynamic process is theoretically investigated in detail. Firstly, the dynamic model is established for this novel multipacting cathode, the displacement and velocity expressions are obtained by solving the dynamic equation of secondary electrons. The influences of electron with different initial energy emitted from each direction on electron trajectory, velocity, and impact energy are discussed. The approximate expressions of electron transit time and impact energy are obtained and discussed theoretically. Secondly, to find the multipacting cathode working range, the multipacting susceptibility diagram is obtained and discussed in detail by solving electron dynamic equation coupling Vaughan’s empirical formula (secondary electron yield model). Theoretical results demonstrate that the conception of the novel multipacting cathode is feasible. By applying an appropriate electric field (about MV/m) in axial and radial directions and a proper magnetic field (T) in axial direction on a cylindrical dielectric surface coated by high secondary emission yield coefficient material, the electrons move with spiral trajectories along axial direction. Electron number could be increased effectively by each impact with multipacting interaction. This phenomenon could achieve electron current amplification until multipacting comes to saturation. Finally, the deposit phenomenon of positive charges and multipacting saturation are analyzed and discussed. The roughly theoretical estimation indicates that the novel multipacting cathode has the performance of high emission current density, and the emission current density can run up to the level of kA/cm2. Enhancing the magnitude of applied electrostatic field in radial direction can effectively improve the emission current density.

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董烨, 刘庆想, 李相强, 周海京, 董志伟. 新型二次电子倍增阴极构型设计与动力学过程[J]. 强激光与粒子束, 2018, 30(3): 033001. Dong Ye, Liu Qingxiang, Li Xiangqiang, Zhou Haijing, Dong Zhiwei. Configuration design and dynamic process study of novel multipacting cathode[J]. High Power Laser and Particle Beams, 2018, 30(3): 033001.

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