On electron drift current in hall plasma devices with inhomogeneous and anisotropic plasmas

摘要

Summary form only given. Operation of a number of plasma devices such as Hall thrusters for electric propulsion and magnetrons for plasma processing rely on ExB drift of electrons in crossed electric and magnetic fields. The closed drift of electrons supports plasma ionization. The magnetic field constrains electron motion in perpendicular direction, while ions can be freely accelerated and extracted by the electric field from the discharge and used for various purposes such as thrust for electric propulsion, material deposition and modification for plasma processing. The electron current is also a source of free energy resulting in a number of discharge instabilities. In all, it is important to accurately predict the electron drift velocity and electron current. Large fraction of the electron current is due to the ExB drift. In a plasma with finite temperature the contribution of diamagnetic velocity due to inhomogeneous plasma pressure becomes important and comparable (for typical parameters) to the ExB drift. The magnetic gradient and curvature drifts existing in guiding center theory do not contribute additional current unless the plasma pressure is anisotropic. The structure and various contributions to the total electron current in inhomogeneous plasma and inhomogeneous magnetic field are discussed for some typical parameters of Hall devices.