One-dimensional flow structure in Hall thrusters

Summary form only given. Hall thrusters are gridless annular electrostatic ion accelerators, in which thrust is transmitted to the structure via the azimuthal electron drift Hall current. Ionization and acceleration occur in, or at the exit of an open-ended annular channel, with a radial magnetic field acting to retard electron flow to the upstream anode. The lack of a grid structure to define the plasma potentials and separate the ionization and acceleration regions makes it difficult to predict a-priori the spatial structure of the plasma, which is of prime importance in determining wall erosion. Complex two-dimensional PIC simulations exist, but a need remains for a clear delineation of the non-linear interactions between flow, chemistry and electrodynamics which produces the self-consistent plasma properties distribution. This paper attempts to fill this need by using a simplified 1-D formulation, but pursuing the consequences of the various mathematical singularities which arise in it. It is shown in particular that two ion-sonic points usually occur in the flow, one at the anodic inlet (with ion flow directed upstream), and one either at the open exit plane, or at an intermediate point in the channel.