Status analysis on sputtering and erosion evaluation methods of ion optic systems

In the past few decades, ion engines have been widely used in deep-space propulsion and satellite station-keeping. The aim of extending the thruster lifetime is still one of the most important parts during the design stage of ion engine. As one of the core components of ion engine, the grid assembly of ion optic systems may experience long-term ion sputtering in extreme electro-thermal environments, which will eventually lead to its structural and electron-backstreaming failures. In this paper, the current studies of the grid assembly erosion process are systematically analyzed from the aspects of sputtering damage process of grid materials, numerical simulations, and measurements of erosion characteristics of grid assembly. The advantages and disadvantages of various erosion prediction models are highlighted, and the key factors and processes affecting the prediction accuracy of grid assembly erosion patterns are analyzed. Three different types of experimental methods of grid assembly erosion patterns are compared. The analysis in this paper is of great importance for selecting the sputter-resistant grid materials, as well as establishing the erosion models and measurement methods to accurately determine the erosion rate and failure modes of grid assembly. Consequently, the working conditions and structure parameters of ion optic systems could be optimized based on erosion models to promote the ion engine lifetime.