Electron Cross-Field Transport in a Miniaturized Cylindrical Hall Thruster

Summary form only given. Conventional annular Hall thrusters become inefficient when scaled to low power. Their lifetime decreases significantly due to the channel wall erosion. Cylindrical Hall thrusters that have lower surface-to-volume ratio and, thus, seem to be more promising for scaling down, exhibit performance comparable with conventional annular Hall thrusters of the similar size. Efficiency of a Hall thruster decreases with increasing electron current. Understanding of the mechanisms of electron transport in the discharge is, therefore, essential for the development of higher efficiency thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. It is shown that in order to explain the observed discharge current, the electron anomalous collision frequency nu_B has to be on the order of the Bohm value, nu_Bapomega_o/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant