Numerical models of Hall thruster ionization oscillations

Abstract

In this thesis, low frequency ionization oscillations in Hall thrusters resembling the breathing mode are studied through computational simulation. The relationship between wall erosion and discharge current oscillations is analyzed using particle-in-cell simulation, and a series of parametric simulations is used to determine the effects of macro-particle size, floating body potential, electron injection region, ion time step size, grid refinement, heavy particle mass reduction, and an artificial permittivity factor. These studies help to determine the parameters that will produce accurate simulations in the future, and identify the parts of the model that need improvement. One-dimensional steady and unsteady Hall thruster models, as well as a generalized sheath model are then developed, and the effects of the parameters that determine stability on the thruster's operating conditions are determined.