基于螺旋慢波加热机制的电子回旋共振离子源电磁计算分析

Electromagnetic Calculation Analysis of Electron

关键词:  ECR离子源  螺旋天线  螺旋慢波  电子获能指标

Key words:  ECR ion source  Helix antenna  Helix slow wave  Electronic energy absorbing index

摘要:

为提高电子回旋共振离子推力器(ECRIT)的推力，扩展其应用领域，从制约离子源电离度的电子加热机制出发，研究螺旋慢波条件下ECR离子源的电子加热机制，并与传统耦合天线的加热机制进行对比，得到了螺旋慢波的加热特点。基于螺旋天线的色散方程，采用有限元方法，计算并分析不同结构参数下离子源放电室内静磁场、微波电场和ECR区电子获能指标的分布规律，最终获得螺旋慢波加热的新型ECR离子源结构。计算结果表明，螺旋慢波条件下，电子加热范围得到显著拓宽，更有利于离子源电离度的提高。在输出频率4.2GHz、输出微波功率30W和给定离子源腔体结构条件下，以最宽电子加热范围为目标，计算得到离子源最佳的螺旋慢波耦合天线和磁路结构，此时螺旋角为7°，磁环位置为a=10mm，b=20mm。

Abstract:

In order to improve the thrust performance of electron cyclotron resonance ion thruster (ECRIT) and extend its application，the electronic heating mechanism of ECR ion source under helix slow wave condition was researched，and the heating characteristics of helix slow wave were obtained by comparing the resonant heating conditions of traditional coupling antenna. Based on dispersion equations of the helical antenna and with different candidate structures in discharge chamber，the static magnetic field，microwave electromagnetic field and electronic energy absorbing index in ECR region was computed by using finite element method，and finally an entirely new structure of ECR ion source with helix slow wave heating mechanism was obtained. The calculation results show that the heating effect is greatly improved and is more beneficial to the improvement of the degree of ionization in ion source by the helix slow wave heating condition. Aimed at the wide range of electronic heating and with calculation microwave conditions of 30W power and 4.2GHz frequency，the optimal spiral angle of helix slow wave coupling antenna is 7°，and the optimal magnetic circuit structure is the size combination of a=10mm，b=20mm.