Computational Study of the Effects of Cathode Placement, Electron Energy, and Magnetic Field Strength on the Confinement of Electrons

Abstract

Recently a number of papers have been published by the Wright State Ion Engine group that have computationally studied the confinement of electrons in the discharge chamber of an ion engine. These studies have investigated the ability of a magnetic field produced by permanent magnets in a ring-cusp configuration to keep electrons from being lost to the anode biased walls of the discharge chamber. Magnet separation, magnet orientation, and magnet number were studied in significant detail. Three parameters that were not studied were the cathode placement, the electron energy, and the magnetic strength. In this work these three parameters are studied computationally. From this work it was found that the ability of a given magnetic field to confine electrons is only weakly dependent on the position of the cathode, somewhat dependent on electron energy, and dependent on the strength of the ring-cusp magnets up to a point, after which the dependence is weaker. The strength of the magnetic field is changed by altering the thickness of the magnet between the north and south poles. Addition results are shown for the effect of changing the magnetic field strength by altering the number of rings of magnets. Also given in this paper are comments on rules-of-thumb for magnetic circuit design.