Hall thruster with externally driven breathing oscillations

Hall thrusters exhibit usually two types of large amplitude low frequency (10-30 kHz) oscillatory modes, so called breathing mode and spoke mode. In our previous works, it was demonstrated that both these modes can be controlled via the external modulations of the discharge voltage applied to the anode or anode segments. Two regimes of the thruster response, linear and nonlinear, have been revealed depending on the modulation amplitude. There was also observed a resonance-kind behavior-the amplitudes of the excited oscillations of the discharge current and the ion current reach their respective maximum as the modulation frequency approaches the frequency of natural oscillations (breathing or spoke). A one-dimensional model explained this result, in part, due to a decrease of the phase between low-frequency oscillations of the plasma density and the electric field. In this paper, we briefly review recent results on a modulated cylindrical Hall thruster. One important practical implication of these results is that the thruster operation with externally driven breathing oscillations may open a new way to implement enhanced thrust-to-power ratio Hall thrusters.