Erosion characteristics analysis of molybdenum grid in ion thrusters based on optical emission spectroscopy method and actinometry

Abstract

Optical emission spectroscopy (OES) method is a powerful technique to identify the components of species in the plasma and obtain density based on actinometry. The key component of high-precision and long lifetime aerospace device, such as the grid of ion thruster, is usually made up by erosion-resistant materials, resulting in an extremely low density of erosion product. But the information on these erosion processes is indispensable to optimize the design of those components. The traditional method used to evaluate the erosion process mainly depends on measuring the depth of erosion, while it is a process that necessitates the accumulation of at least hundreds of hours. So, the traditional way is incapable of measuring in multiple working condition and cannot provide online monitoring. Considering this dilemma, this work demonstrates an advanced actinometry based on OES method to analyze the Mo atoms generated during the working process of ion thruster, with more specific atomic emission lines of working gas and product used than the traditional method. The result of this work indicates that the Mo atoms at trace level can be detected successfully, and the concentration of Mo atoms can also be determined based on the advanced actinometry. The result obtained in this work also reveals more intricate relationship between erosion characteristics and various operational parameters, indicating that OES method and advanced actinometry can be used for evaluating the erosion characteristics of aerospace device in different working conditions in a real-time and efficient way, which plays a vital role in deep space exploration and gravitational wave detection by contributing lifetime optimization designs of those devices.