Study on Effect of Structure and Propellant on Beam of ECR Ion Source

结构和工质对ECR离子源引出束流的影响规律研究

Received: 22 November 2018

Abstract

To increase the ion current from the ion source is an important way to improve the performance of the electron cyclotron resonance ion thruster(ECRIT). The ion migration distance, magnetic topology and propellant have a close influence on the extracting ion beam. This influence is studied through both magnetic circuit structure calculation and experiments, by using an ion source with different gate mounting positions and magnet lengths. Experimental results show that the distribution of the ECR region will be discontinuous when the length of the magnet is too short. This will greatly reduce the performance of the ion source. To increase the length of the magnet is beneficial to the beam emission at high gas flow rate, but it reduces the beam emission at low gas flow rate. The effect of the ion migration distance on the ion beam is related to the plasma density in the ion source. When the gas flow rate is low, a longer gate mounting ring is beneficial to increase the ion current. When the gas flow rate is high, the different magnetic topology will cause the gate mounting ring which influences on the ion current. At low gas flow conditions, xenon gas can significantly improve the discharge stability of the ion source and increase the ion current. However, at high gas flow rate, the concentration effect of the neutral particles is too strong that affects the energy accumulation process of the free electrons. This would cause the decrease in the ion current.

摘要

提高离子源引出束流是提高电子回旋共振离子推力器（ECRIT）性能的重要途径，而离子迁移距离、磁路结构和气体工质等因素对引出束流有着密切的影响。利用具有不同栅极安装位置和磁体长度的离子源，通过实验研究，分析磁路、离子的迁移距离以及工质对引出束流的影响。实验结果表明：磁体长度过短会引起ECR区的不连续分布从而造成离子源性能大幅度下降，增加磁体长度在高流量下有利于提高栅极引出束流，低流量下会使束流降低；栅极安装环长度对引出束流的影响规律与离子源的磁路结构和工作状态有关，在气体流量较低时，更长的安装环有利于提高引出束流，高气体流量条件下，不同的磁路结构会使栅极安装环对引出束流产生不同的影响规律；氙工质可以明显提高低流量条件下离子源的引出束流和放电稳定性，但在高流量下受进气位置影响，中性粒子过于聚集而造成自由电子能量积累受到影响，从而会出现束流下降的现象。