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

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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.