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静电四级透镜具有优越的电子光学聚焦成像性能,单一静电四极透镜可实现电子束线聚焦,组合静电四极透镜系统拥有点聚焦的能力。文中对实现点聚焦的双静电四极透镜系统相关参数进行了计算,利用电子光学软件SIMION仿真发现,静电四极透镜之间的畸变场与两端的边缘场引起的像差会严重影响系统聚焦成像质量。仿真分析了系统像差与发射电子初动能的关系。结果表明:系统在保证点聚焦的情况下,增加电子发射初动能可以有效减小系统像差;当电子初动能增加至1×105 e V时,最大发散角为2°的电子束在聚焦平面上的弥散斑减小至3.2μm×28μm。
The electrostatic quadruple lens has superior electron-optical focusing imaging performance, a single electrostatic quadrupole lens enables focusing of the electron beam line and the ability of the electrostatic quadrupole system to have point focusing. In this paper, the parameters of the double electrostatic quadrupole lens system for point focusing are calculated. By using the simulation software SIMION, it is found that the aberration caused by the electrostatic quadrupole lens and the fringe field at both ends will seriously affect the system focus imaging quality. The relationship between the system aberrations and the initial kinetic energy of the emitted electrons is analyzed. The results show that the system can reduce the system aberration effectively by increasing the initial kinetic energy of electron emission under the condition of ensuring the focal point. When the initial kinetic energy increases to 1 × 105 eV, the maximum divergence angle is 2 °, Dispersion on the reduced to 3.2μm × 28μm.