一种低能量远焦距电子枪技术

Research on a Low Energy Tele-focus Electron Gun

针对可移动非接触式月球表面电位探测器的电位无扰动测量单元对低能远焦电子束的需求,设计了低能远焦电子枪。以平板二极管电子枪为电子源,匹配两个静电聚焦透镜,将电子源引出的发散电子束聚焦为需要的形状,并加速至所需能量。优化电子枪的几何参数以及施加在电极上的电位,电子枪引出的电子束能量在5~500 eV内,并且具有良好的电子光路特性。电子束能量为5 eV时,初始半径r为5 mm,束腰至电子枪出口的距离p约为133 mm。随着能量增加,r逐渐减小至500 eV时的3 mm左右,p逐渐减小至105 mm。电子束经月球表面电场反射被电子收集平极接收,仿真数据和理论分析结果均表明,电子枪的工作距离为400~600 mm,平板接收的电子占发射电子比例在96%以上。电子枪结构质量仅408 g,满足探测器对电子枪的质量需求。

A low energy tele-focus electron gun is designed based on a subsystem of movable non-contact lunar surface potential detector. The electron gun consists of a diode extraction source and two three-element electrostatic lenses. The source produces a divergent beam which is then accelerated to energy Ke by lenses, and is focused into the shape of interest. By optimizing the geometric parameters of electron gun and the voltage applied to electrode, the electron beam has good optical characteristics and the electron energy is adjustable from 5 eV to 500 eV continuously. The initial radius r equals to 5 mm,and the distance p from the output electrode to the beam waist equals to 133 mm when the beam energy is 5 eV. As the beam energy increases to 500 eV, initial radius r decreases to 3 mm, and the distance p decreases to 105 mm. The electron beam reflected by lunar electric field is received by the collector plate. When working length H is between 400 mm and 600 mm, the electrons received by plate account for more than 96% of the beam electrons. The mass of the electron gun is only 408 g, which can meet the requirements of electron guns for lunar exploration.