Azimuthal Current-Neutralization of a Rotational Light Ion Beam by a Plasma

The rotational motion of a light ion beam and a plasma immersed in a uniform magnetic field is investigated within the framework of the macroscopic fluid equations including force terms due to radial pressure variations. Drift motion caused by the radial electric and magnetic forces rotates the beam fluid element and the plasma electron fluid element in the same azimuthal direction. The motion leads to the over-neutralization of the azimuthal beam current by the plasma electron current. It is found that the ion beam is compact and never hollowed out in over-neutralized states. The radial density profiles of the beam are obtained and the condition for radially confined equilibria in those over-neutralized states is examined.