| The Hall-effect thruster, or Hall plasma accelerator; uses its applied magnetic field to restrict electron motion, and shape its accelerating electrostatic potential. Unfortunately, the Hall thruster exhibits anomalous electron transport. As a result, it is difficult to predict the Hall thruster's axial electron current; and optimize its magnetic field for improved thrust efficiency. This thesis examines anomalous electron transport processes in the Hall-effect thruster, and adds to understanding in this field. A non-intrusive diagnostic is used to investigate self-induction in the Hall thruster, and provide a check on intrusive plasma property measurements. The results suggest intrusive measurements could obscure features important to ionization and acceleration in the Hall thruster, and self-induction (though small) could impact thruster performance. The non-intrusive diagnostic is then used to examine whether plasma property fluctuations could affect cross-field diffusion in the Hall thruster. The results demonstrate a correlation between fluctuations and the discharge current, and suggest oscillations could be responsible for axial transport. This thesis then considers the implications of E x B shear in magnetized plasma transport. Shear is found to modify classical and fluctuation-induced transport processes, and provide an explanation for the transport barrier near the exit of the Hall thruster. Lastly, approaches are considered to circumvent disadvantages in the conventional Hall thruster's design. A new magnetic field topology is developed, and a "wall less" Hall thruster is built. The new thruster exhibits external acceleration, and wall-effects are reduced. It is concluded significant improvements can still be made in Hall thruster physics if anomalous transport, processes are designed for. |
