e型电子枪中非均匀磁场偏转系统的聚焦特性研究

利用永磁铁结构的偏转聚焦系统产生的非均匀磁场,改进了目前e型电子枪电子束偏转聚焦特性,同时缩小了枪体体积,减小了功耗.采用边界元法与等效磁荷法,模拟了偏转聚焦系统的非均匀磁场,再利用龙格一库塔法模拟出电子在该系统中的运动轨迹.为获得良好的聚焦特性,电子发射速度和发射位置应进行优化选择,同时电子束保持水平出射.研究结果表明:电子枪阳极板端点与阴极灯丝中心点保持水平可满足电子水平出射;非均匀分布的磁场对e型电子枪中电子束具有良好的聚焦作用;所设计的偏转聚焦系统在电子束流为50～100 mA时,束斑小于3 mm.

The Focusing and Deflecting Characters of e-Type Electron in Heterogeneous Magnetic Field

The focusing and deflecting system is formed by heterogeneous magnetic field struc-ture,which improves the focusing and deflecting characters of e-type electrons.The electron traj-ectory in the deflection system of electron gun is calculated by using the boundary element method and the Runge-Kutta method.Then the focusing and deflection characteristics of electron gun are studied.The good characteristics of the deflection system of electron gun can be obtained by opti-mizing the velocity and the location of emitting electron beam and by the aclinie emission of the electron beam,that can be achieved by making the end of the anode and the middle part of the cathode level.A new type of deflection system of electron gun is designed,and results with the new svstem show that non-unifornl magnetic field makes the beam of e-type eletron gun focus well,and the electronic beam diameter is less 3 mm when the emitting current is 50 to 100mA.