双静电四极透镜点聚焦特性分析与仿真

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1105 eV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3.2m28m。

Analysis and simulation of point-focusing property of a quadrupole lens pair

A pair of quadrupole lens has excellent imaging performance, electrostatic quadrupole lens can focus the electron beam into a line, quadrupole lens pairs have the ability to focus the electron beam into a point. The point-focusing property of a quadrupole lens pair was investigated in this paper, using the electron ray tracing simulation program SIMION. The simulation of electron distribution quantitatively showed that the fringing field at both ends and the aberration in the crossover image caused an electron beam blur. The aberration of a quadrupole lens pair as a function of the electron initial kinetic energy was discussed, and the result indicated that the aberration would be effectively reduced if the kinetic energy of electrons increased. 10 000 electrons were flown in a SIMION simulation and the entry angle 0 is randomly varied so that -101, the size of diffuse spot at the focal plane reduced to 3.2 m28 m as the kinetic energy of electrons increased to 1105 eV.