The Effect Of Pre-ionization On Low Frequency Oscillation And Wall Corrosion In Hall Thruster

Hall thruster, a type of electric propulsion with long lifetime, is an ideal low thrust device for long missions such as satellite station keeping and deep space exploration. Because of its good overall performance, such as high specific impulse, high propulsion efficiency and long lifetime, Hall thruster has been widely used for space explore missions of various spacecraft. Recently, the lifetime challenge of Hall thruster has been raised by the requirement of applying the thruster to more complex propulsion tasks. It was found through the experiments made with an Aton-type Hall thruster that some of the propellant was ionized in the buffer chamber by “quick electrons.” This ionization is called“preionization” to discriminate it from the ionization in the discharge channel. The effect of preionization on low frequency oscillation was experimentally studied by changing the electric field intensity in the buffer chamber.In this study, a two-dimensional axisymmetric fully kinetic Particle-In-Cell and Monte Carlo Collision model is developed to to study the physical process of the Hall thruster in this paper. The distribution of the particles is tracked by the fully-kinetic PIC-MCC method. A sample sheath model with different scaling rate is ported into the simulation to investigate the effect of scaling laws on the parameters in steady state of the hall thruster.The relationship between low frequency oscillation and preionization ratio was investigated through numerical simulation. The results obtained indicate that the amplitude of low frequency oscillation decreases as the preionization ratio increases. It was found through the analysis and numerical simulation of the physical process of low frequency oscillation that the positive feedback of electron density was the main cause of low frequency oscillation. The increase of preionization ratio decreases the amplitude of the feedback variation thereby reducing the amplitude of low frequency oscillation.The effect of pre-ionization on erosion of the channel wall of Hall thruster is studied in the paper. The erosion model is established based on the sputtering model of the wall, and the erosion rate is calculating using the distribution of ions and tabulated data of the sputter yield of the wall material. The results obtained indicate that the erosion of the channel wall increases and the amplitude of low frequency oscillation decrease as the pre-ionization ratio increases. Thus, in the designing of the new generation Hall thruster, more aspects must be considered to achieve better performance and longer life of the thruster.