Three-dimensional model of electron beam generated plasma

Abstract

A three-dimensional model for magnetized electron beam generated plasma is described, which includes a coupled fluid simulation of the bulk plasma and a Monte Carlo model for beam electrons. A modified form of the classical expressions for magnetized-plasma electron transport coefficients is used in the fluid plasma model. The plasma model is calibrated and validated using Langmuir probe measurements in a cylindrical electron beam generated plasma, where the beam is launched parallel to the magnetic field. The electron density (ne) and temperature (Te) are measured along and across the beam for several gas pressures and magnetic fields in Ar. The validated plasma model is then used to examine a three-dimensional electron beam generated plasma system. Generally, plasma densities are on the order of 1016 m−3 and, since there is no externally applied electric field in the plasma region, Te is below 1.25 eV in Ar. The chamber in the simulation is slightly asymmetric perpendicular to the axis of the electron beam and the magnetic field. This asymmetry combined with the E × B drift produce non-uniformities in the plasma even if the magnetic field is spatially uniform in the chamber. However, the cross-field plasma uniformity can be controlled by tailoring the magnetic field profile to enhance or reduce plasma production near the periphery of the chamber.