考虑电子注发射度的圆孔膜片透镜焦距  

Modification of Focal-Length Formula of Thin-Film Circular Aperture for Emittance-Dominated Electron Beam

作　　者：曾鹏[1] 王光强[1] 李爽[1,2] 王东阳[1] 滕雁[1] 

机构地区：[1]西北核技术研究所高功率微波技术重点实验室,西安710024 [2]西安交通大学电子与信息工程学院,西安710049

出　　处：《真空科学与技术学报》2016年第5期556-561,共6页Chinese Journal of Vacuum Science and Technology

摘　　要：随着真空电子器件及所用电子注尺寸的减小,发射度效应成为器件设计过程中需要考虑的重要因素之一。圆孔膜片透镜是组成真空电子器件的一种基本元件,本文通过理论推导获得了考虑电子注发射度效应的圆孔膜片透镜焦距公式。首先基于圆孔膜片透镜电位分布,对透镜厚度进行了界定。随后利用透镜区电子注边缘电子的径向动力学方程推导了电子的傍轴轨迹方程,通过对该方程的数学变换获得了考虑电子注发射度效应的圆孔膜片透镜焦距公式。最后以平行圆柱流Pierce枪阳孔为例,分析了典型强流细束电子注不同导流系数、发射度和半径下透镜焦距的变化,与经验修正结果符合较好。The focal-length formula,previously formulated by Davisson-Calbick and Birdsall,of thin-film circular-aperture lens of emittance-dominated electron beam was modified to widen its applications in advanced vacuum electronic devices. First,the film thickness was determined in terms of the potential distribution around the lens.Next,the impact of the beam＇s emittance on the focal-length was mathematically modeled and theoretically analyzed by deriving the paraxial trajectory equation,obtained via manipulating the radial dynamics equation of the electrons on the beam＇s outer edge in the lens region,to modify the focal-length formula by mathematical transformation. And finally,the newly-modified focal-length fomula was applied to a parallel cylindrical flow Pierce-gun with thermionic cathode. The predicted results show that the perveance,emittance,and beam radius significntly reduce the focallength of the narrow,high current density electron beam. The predicted and empirically modified results were found to be in good agreement.

关 键 词：发射度 圆孔膜片透镜 阳孔透镜 焦距 

分 类 号：TN122[电子电信—物理电子学]