Time-dependent axial fluid model of the Hall thruster discharge and its plume

Abstract

Abstract One-dimensional axial models of a Hall thruster give a good qualitative picture of the main physical phenomena in the discharge with small computational effort. Time-dependent models, in particular, are widely used for the analysis of low-frequency axial oscillations (i.e. the breathing mode). The standard time-dependent three-fluid model found in the literature is here enhanced by extending the physical domain beyond the cathodic surface into the far plume, and improving the modeling of some physical phenomena. A suite of five models is presented in this work with an increasing complexity of added physics; the most complete version accounting for ion and neutral energy evolution equations along with the partial inclusion of electron inertia. The added physics has a non negligible impact on both the dynamics of the breathing mode and the time-averaged response of the plasma. In particular, it is found that the onset of the instability is sensitive to both the level of modeled physics and the operational parameters. In some cases, the strong breathing mode oscillations can result in a weak plasma attachment to the anode, leading to the collapse of the normal anode sheath and to the subsequent failure of the model.