Propagation of vacuum arc plasma beam in a toroidal filter

An analytical solution to the problem of plasma beam transport in a toroidal magnetic filter for unmagnetized ions is derived. A two-fluid model taking into account electromagnetic and pressure forces, electron-ion collisions, magnetic force line curvature, and radial dependence of centrifugal force is used. From comparison with experimental data it is shown that the obtained solution describes well the main properties of plasma beam behavior in the filter, e.g., 1) the relative value of the ion current along the torus decreases exponentially, 2) the deflection of the plasma beam from the center of the torus correlates with the centrifugal drift of the plasma beam across a magnetic field, and 3) experiment and theory agree well on the weak correlation between magnetic field strength and filter efficiency.