新型二次电子倍增阴极构型设计与动力学过程

董烨; 刘庆想; 李相强; 周海京; 董志伟

doi:10.11884/HPLPB201830.170328

新型二次电子倍增阴极构型设计与动力学过程

doi: 10.11884/HPLPB201830.170328

董烨^{1, 2,},
刘庆想¹,
李相强¹,
周海京²,
董志伟²

1.
西南交通大学物理科学与技术学院, 成都 610031
2.
北京应用物理与计算数学研究所, 北京 100094

基金项目:

国家自然科学基金项目 11475155

国家自然科学基金项目 11305015

详细信息

作者简介:
董烨(1981－)，男，副研究员，从事脉冲功率及高功率微波技术研究；dongye0682@sina.com

中图分类号: O521.3
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出版历程
- 收稿日期: 2017-08-27
- 修回日期: 2017-11-20
- 刊出日期: 2018-03-15

Configuration design and dynamic process study of novel multipacting cathode

1.
School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China
2.
Institute of Applied Physics and Computational Mathematics, Beijing 100094, China

摘要

摘要: 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。
- 二次电子倍增阴极 /
- 二极管 /
- 动力学方程 /
- 二次电子倍增敏感区间
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.
- multipacting cathode /
- diode /
- dynamic equation /
- multipacting susceptibility boundaries

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图 1 二次电子倍增阴极表面电子运动轨迹示意图

Figure 1. Schematic of trajectories of secondary electrons on surface of multipacting cathode

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图 2 二次电子倍增阴极二极管构型及场形分布模拟结果

Figure 2. Configuration design and electric-field distribution of multipacting cathode for high-current diode

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图 3 二次电子倍增阴极表面坐标变换示意图

Figure 3. Schematic of coordinate transformation of multipacting cathode surface

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图 4 电子运动轨迹(法向出射)

Figure 4. Trajectories of electron (v_x0≠0)

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图 5 电子速度和动能随时间演化关系(法向出射)

Figure 5. Velocity and kinetic energy of electron (v_x0≠0)

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图 6 电子运动轨迹(y方向水平出射)

Figure 6. Trajectories of electron (v_y0≠0)

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图 7 电子速度和动能随时间演化关系(y方向水平出射)

Figure 7. Velocity and kinetic energy of electron (v_y0≠0)

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图 8 电子渡越角

Figure 8. Transit angle of electron

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图 9 电子碰撞能量

Figure 9. Impact energy of electron

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图 10 二次电子倍增阴极工作区间预估(固定法向电场强度幅值)

Figure 10. Working range of multipacting cathode (fixed electric field strength in radial direction)

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图 11 二次电子倍增阴极工作区间预估(固定轴向磁感应强度幅值)

Figure 11. Working range of multipacting cathode (fixed magnetic flux density in axial direction)

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图 12 二次电子倍增阴极工作点的动态演化

Figure 12. Working point evolution of multipacting cathode

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表 1 电子掠入射情况下不同二次电子发射特性材料的碰撞能量上下限

Table 1. E₁ and E₂ of different SEE-materials under grazing incidence

δ_max0	E_max0/eV	E₁/eV	E₂/keV
3	420	29.5	46.5
1.5	420	76.7	6.59
3	210	20.76	23.32

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参考文献(18)

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