液态金属离子源发射系统的仿真分析

Simulation of Liquid Metal Ion Source

液态金属离子源的发射系统是源设计当中一个十分重要的因素,它的性能的优劣将直接影响到整个离子源的发射特性,进而影响整个聚焦离子束设备的工作性能。因而,在离子源的设计过程中,人们希望通过仿真手段得到影响源发射特性的源几何尺寸参量,以便在液态金属离子源设计时抓住主要参量进行优化设计,从而提高源的发射性能。本文首先用模拟电荷法计算了发射系统的电场,然后用蒙特卡罗方法在模拟发射离子的初始位置和初始速度的基础上,计算了离子轨迹。并通过对大量离子轨迹的统计计算,得出能散、角电流密度和虚源尺寸的特性曲线,从而为分析离子源性能以及设计离子源提供了一个有效的辅助工具。

The liquid metal ion source was simulated with Taylor cone model. The simulation consists of three steps：first, the spatial electric-field distributions of the ion emitter were calculated by charge simulation; next,the trajectories of the emitted ions were estimated by Mont Carlo simulation, based on the calculated initial positions and velocities of the emitted ions;and finally, the characteristics of the liquid metal ion souree,including its angular current density,its energy spread,and its virtual source size, were statistically evaluated.