Improvement of Microwave Discharge Ion Engine with Antenna for Uniform and High dense Plasma Generation

本研究的目的是与日本宇宙航空研究开发机构合作，开发一种新型的微波放电离子推进器，产生均匀的等离子体和高推力密度，并进行数值模拟，以优化发动机配置，以开发两种尺寸的离子发动机。我们发展了一种耦合质点网格(PIC)和时域有限差分(FDTD)方法的程序。得出了以下结论：1)对于微波传播，证明了天线结构与微波传播效率的相关性，从而得出了最佳天线结构。2)对于放电室中的等离子体产生，存在于线圈之间的电子来自ECR和天线附近的高强度电场，3)为了有效地产生等离子体，天线需要靠近ECR区。应用数值分析中的设计规律，研制了新型100 mm级离子发动机，并测量了其推力性能。在质量流量为0.24 mg/S、入射微波功率为32W的条件下，该发动机的推进器性能、推进剂利用率和离子束生产成本分别为0.62、276 W/A。在质量流量为0.020 mg/S、入射微波功率为10W时，微型离子发动机的推进器性能、推进剂利用率、离子束生产成本、估算推力、估算比冲和估算推力效率分别为0.92、590W/A、0.80mN、4180s和0.58.

The aim of this study is developing a novel microwave discharge ion thruster, uniform plasma generation and high thrust density in cooperation with Japan Aerospace Exploration Agency.Numerical simulation was done in order to optimize the engine configurations for developing two size ion engines. We have developed a code coupling particle-in-cell (PIC) method and finite difference time domain (FDTD) one. Adopting these methods has advantages in that PIC method can treat collision process and distribution function while FDTD method can analyze absorption of microwave in plasma.The following conclusions were obtained.1) With respect to microwaves propagation, the dependence of antenna configuration on microwave propagation efficiency was proved, this led the optimum antenna configuration.2) With respect to the plasma production in the discharge chamber, electrons existing between the yokes are energized from the ECR and the electric field of high strength near the antenna, and the plasma is maintained by ionization collisions of the energized electrons.3) the antenna needs to be close to the ECR region for the effective plasma production.Applying the design law from numerical analysis, novel 100 mm class ion engine was developed and the thrust performance of it was measured. The thruster performance of this engine, propellant utilization, ion beam production cost, are 0.62,276 W/A, respectively, at mass flow rate =0.24 mg/s, and incident microwave power = 32 W.On the basis of numerical simulation results and experimental results of 100 mm class ion engine, a miniature microwave discharge ion engine was developed. The thruster performance of the miniature ion engine, propellant utilization, ion beam production cost, estimated thrust, estimated specific impulse and estimated thrust efficiency are 0.92,590 W/A,0.80 mN,4,180 sec and 0.58,respectively, at mass flow rate =0.020 mg/s, and incident microwave power = 10 W.