Plasma lens and plume divergence in the Hall thruster

The effect of magnetic field curvature on the plume divergence in the Hall thruster is analyzed. The two-dimensional plasma flow and electric field are determined self-consistently within the paraxial approximation in this plasma lens, a nearly axial electric field perpendicular to the curved magnetic field lines. The ion radial velocity along the thruster is described analytically. The authors suggest positioning the ionization layer near the zero of the magnetic field in a reversing-direction field configuration for a minimal beam divergence. They also show that an additional emitting electrode can reduce plume divergence.