Volumetric erosion rate reduction of Hall thruster channel wall during ion sputtering process

Abstract

The mechanisms of the volumetric erosion rate reduction of the channel wall were studied theoretically and numerically in order to explain the reasons why the volumetric erosion rate of Hall thruster channel decreases over time. The results of the theoretical analysis indicate that the variation of three sputtering conditions results from the increase in the tilt angle and the erosion depth of the channel wall erosion surface during the surface evolution process. The mass loss of the Hall thruster channel wall material is a reduction process due to which the ion flux divergent angle is smaller than the value that corresponds to the sufficient condition of the reduction process. The simulation results of the channel wall erosion process qualitatively agree well with the experimental results, and the numerical analysis of the reduction process shows that the magnitude orders of three sputtering condition variation effects on the volumetric erosion rate reduction are the same, and the reduction rate reaches its maximum value in the initial operation period when the ion radiation angle equals the optimum sputtering rate angle. This work provides theoretical fundamentals of the channel wall erosion reduction process and it can be used for the lifetime prediction and optimum design of the Hall thruster.