One-dimensional model of the plasma flow in a Hall thruster

A macroscopic model which accounts for the complex interactions between ele ctrostatic, thermal, and kinetic effects in a Hall thruster is presented. T he analysis establishes the one-dimensional steady structure of the flow as consisting of an anode sheath, a long electron free-diffusion region, with reverse ion flow, a thin ionization layer, and the acceleration region, wh ich extends into the plume. The ion flow presents a forward sonic point aro und the exit of the ionization layer, which can be either internal, with a smooth sonic transition, or localized at the channel exit. The supersonic p lume is included via a simple expansion model, allowing closure of the form ulation and calculation of thruster performance. The results indicate good agreement with experimental data for the case of an internal sonic point, a nd they delineate the existence and nonexistence regions in the space of ex ternally controllable parameters. They also unveil the importance of the el ectron pressure, the reverse flow of ions, and the ionization rate in shapi ng the plasma structure, whereas, contrary to common perception, the detail s of the magnetic field profile influence weakly that structure. (C) 2001 A merican Institute of Physics.