Discharge characteristics and increased electron current during azimuthally nonuniform propellant supply in an anode layer Hall thruster

Abstract

Discharge current components, such as electron, ion beam, and lost-to-wall currents, are obtained as functions of azimuthal propellant inhomogeneity in a Hall thruster. Discharge characteristics are discussed based on discharge current oscillation and radial–azimuthal discharge photography. A highly oscillative operation regime is found to be accompanied by radially enlarged expansion of discharge under limited electron currents. Further increases in neutral inhomogeneity lead to quiescent discharge combined with enhanced electron currents and an azimuthally separated ionization region. An axial one-dimensional classical view of electron flow is found to explain the observed electron current evolution only until moderate propellant inhomogeneity occurs. Through discharge image analysis, it is shown that plasma inhomogeneity increases linearly with respect to the input neutral particle inhomogeneity. The evolution of the inhomogeneity does not capture a stepwise increase in the electron current during discharge mode changes; however, the monotonic increase featured in each discharge regime shows that the azimuthal gradient of plasma properties can contribute to increased electron current. Lastly, the weakened magnetic barrier to electron flow resulting from axial–azimuthal variation in plasma structures is presented as another possible cause of increased electron current in nonuniform propellant operations.

Two-dimensional hybrid model of gradient drift instability and enhanced electron transport in a Hall thruster

“…putational load of the hybrid model. Further, the entire circumference simulation may enable in-depth analyses of longwavelength rotating spokes 26,47 and thruster operations with artificial inhomogeneities 38,48 .…”

Evolution of electron cross-field transport induced by an equilibrium azimuthal electric field in an $\mathrm{E}\times\mathrm{B}$ Hall thruster discharge under an azimuthally inhomogeneous neutral supply

“…The changes in these parameters are explained using the force balance on electrons. It is noteworthy that the present work is distinguished from our past works where the focus was made on resolving the plasma structure and identifying electron flux by E θ , 16 and characterizing discharge behavior depending on the input neutral inhomogeneity level 17 .…”

“…E × B plasmas is reported in a number of numerical [10][11][12][13] and experimental studies [14][15][16][17] of E × B plasma. Similar transport effects by an induced (fluctuating) field is often discussed in the magnetically confined fusion machines 18 .…”