新型二次电子倍增阴极的蒙特卡罗模拟研究

提出了一种新型二次电子倍增阴极强流二极管，并对其进行了动力学理论简化模型和蒙特卡罗数值模拟的对比验证研究。首先，基于设计结构原型，根据二次电子发射特性进行合理简化，建立了动力学模型，获得了电子速度、位移以及渡越时间的解析结果，并结合Vaughan的二次电子产额模型，确定了该新型二次电子倍增阴极强流二极管的理论工作区间；其次，理论分析了施加径向电场的重要意义，并给出了二次电子运动特征参数(最大位移、渡越时间、碰撞能量等)的理论预估结果；最后，对该新型二次电子倍增阴极强流二极管进行了蒙特卡罗模拟研究，获得了电子的运动轨迹、碰撞能量以及二次电子倍增工作区间等物理图像，并将蒙特卡罗数值模拟结果与理论结果进行了比对，两者吻合程度较好，对可能的误差来源进行了分析讨论。理论和模拟结果表明:新型二次电子倍增阴极强流二极管概念可行，工作区间内通过调整施加电场与磁场幅值，可有效达到电子运动状态可控的目标。另外，理论粗估了二次电子倍增饱和条件下的阴极发射电流密度，结果表明: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发射电流密度。最后，对该新型二次电子倍增阴极设计步骤和依据进行了讨论。

Monte Carlo simulation of a novel multipacting cathode

In this paper, a novel high current diode with multipacting cathode is studied and verified by using simplified dynamic theory and Monte Carlo simulation. Firstly, based on the design-prototype and the emission characteristics of secondary electron, the dynamic model is established, the expressions of electron velocity, displacement and transit time are obtained from the simplified dynamic equations. The multipacting cathode's working range (multipacting susceptibility) is obtained, by using dynamic theory and Vaughan's SEY (Secondary Electron Yield) model. Secondly, the importance of the applied electric field in radial direction is discussed, and the characteristics parameters of moving secondary electrons are analyzed theoretically, such as maximum displacement, transit time, and impact energy. Finally, the novel high current diode with multipacting cathode is investigated by using Monte Carlo simulation in detail. The physical images of secondary electron's trajectory, impact energy and the multipacting working range diagram are analyzed and discussed. The theoretical results are verified by Monte Carlo simulation and they agree with the theoretical results. The possible reason of the error between theoretical and simulated results is discussed. Both theoretical and numerical results demonstrate that the concept of the novel high current diode is feasible, by adjusting the magnitude of the applied electric field and magnetic field, the moving status of secondary electrons could be controlled effectively. Under the condition of multipactor saturation, 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. In addition, the design procedure of the multipacting cathode is introduced and discussed in detail.