绝缘毛细管对高电荷态离子导向的自洽场模拟分析

Transmission of highly charged ions through insulating capillaries provides insights on the processes of ion-surface collisions. Meanwhile, it also has very broad application prospects and research value such as in fabricating beam deflection elements or producing micro/nanometer-sized beams. .Lots of the experimental results that the highly charged ions through the insulating capillaries with the initial charge state and energy, are mainly due to the repulsive electric field produced by the self-organized formation of deposited charges. Therefore, a Self-Consistent Field approximation for calculating the deposited potential at the capillary inner wall is employed to simulate the highly charged ions guided through the insulating capillaries. It can clearly show the guiding behavior of the transmitted ions. Comparing with the Classical Trajectory Monte Carlo Simulation and the Charge Drift Model, the factors influencing the guiding effect such as the bulk resistivity, the surface resistivity, the length and the diameter of the capillary, the incident energy and current density of the projectiles, especially boundary conditions, are considered systematically in the simulation. So, the Self-Consistent Field approximation has more advantages than other simulation models, to provide the theoretical prediction and guidance for the experiments of the transmission of highly charged ions through insulating capillaries. In this project, we will simulate the highly charged ions guided through the insulating capillaries with different shapes and with the different boundary conditions, to obtain the exact mathematical relationship of the experimental parameters of the guide effect, and to explain how to the deposited charges transport at the capillary wall.

绝缘毛细管对高电荷态离子的导向效应是研究高电荷态离子与固体表面相互作用的重要手段之一，同时为制作离子偏转元件、获取离子微束提供了新的途径，具有重要的研究价值和应用前景。.基于众多高电荷态离子在绝缘毛细管中保持原有的电荷态和能量出射的导向实验，离子在毛细管中主要是受到了管壁沉积电荷产生的导向场的作用。自洽场理论模型采用管壁沉积电势的自洽场近似法，可以还原离子在毛细管中的导向行为。相对于经典轨道输运模型和电荷迁移模型，自洽场理论可以系统地分析毛细管的体电阻率、面电阻率、规格以及离子的能量、流强密度等，尤其是边界条件对导向行为的影响。因此，自洽场模拟具有很大的优越性，对导向实验可以提供更多地理论预测和指导。本项目将对高电荷态离子在不同边界条件下的不同形状绝缘毛细管中的导向行为进行自洽场模拟，以获取实验参数与导向效应的精确数学关系，以及毛细管壁沉积电荷的迁移、扩散对导向的影响。

绝缘毛细管对离子束的导向机制是研究掠入射条件下电荷态离子与固体表面相互作用的重要手段之一，也是确保获取精准离子微束的必备条件和制作离子偏转元件的前提基础。.本项目构建了离子束通过电荷沉积抬升平行板、倾斜板表面电势形成静电场，静电场又偏转离子的运动方向从而影响电荷沉积过程的数学模型。基于自洽场理论近似法，本项目推导了束流在导向毛细管内的运动学方程组，并采用C++语言编写了计算程序。目前，该计算程序可以模拟一定条件下离子束在二维平行板通道、二维倾斜板通道中的导向行为，能够大体重现离子束能量、流密度、束流入射倾角、平行板长度、板间距、电阻率等对离子束导向行为的影响；可以给出沉积电荷、沉积电势在二维板内壁上的分布情况等；以及可以研究不同边界条件下各个模拟参数对离子束导向效应的影响。.由于实验发现光滑的导向板表面存在放电不稳定性，本项目还设计加工了带有沟槽的高纯石英、PEEK、尼龙、聚四氟乙烯、赛钢板（聚甲醛板）等平行板，并组建了对称和非对称平行板毛细管。在中国科学院近代物理研究所EBIS超低能重离子综合研究平台上开展的导向实验，采用4.2—18.2 keV Ar2+离子轰击不同边界条件下不同材质的平行板毛细管，观察到了更加稳定的导向离子束，为制作小型离子偏转装置的制作提供了思路。