Numerical Simulation of High Specific Impulse Ion Thruster Optics

A high specific impulse ion thruster (HiIsp-IT) operated at a voltage of 10 kV has been studied and the problems of direct ion impingement on the accelerating grid and of production and impingement of charge-exchange ions have been considered. In order to investigate these problems and to facilitate the design of HiIsp-IT grid systems, a three-dimensional particle simulation code (“igx”) that employs an energy compensation method, a simplified pre-sheath definition method, a region sharing method was developed. This code also simulates the production and subsequent motion of charge-exchange ions. Using the code, results obtained quickly using a personal computer are shown to be in good agreement with experimental data associated with: (1) crossover impingement under low-beam-current condition and (2) the star-shaped pattern of the cross section of each beamlet as it passes through the accelerating grid. It argued that the “igx” code simulation is a useful tool for rapid preliminary analysis and design of HiIsp-IT grid systems. This paper also discusses an optimization method for a grid system design represented by many parameters. It is confirmed that a genetic algorithm works efficiently in this optimization application.