PROPAGATION OF A MAGNETIZED PLASMA BEAM IN A TOROIDAL FILTER

A two-fluid magneto-hydrodynamic model for the motion of a vacuum-are- produced magnetized plasma beam in a toroidal magnetic filter is prese nted. The model takes into account in a self-consistent way electron-i on collisions and electrical, magnetic, centrifugal and pressure force s. An analytical solution is obtained that describes the distribution of the plasma density, the electron and ion velocities, the electric f ield and the current in the plasma. Analytical expressions for the fil ter efficiency as a function of the toroidal magnetic field are also d erived. The effect of the centrifugal and diamagnetic ion drifts on th e polarization electric field is studied. It is shown that the efficie ncy increases exponentially when the polarization field decreases. A d ecrease of the polarization field can take place when a current path o utside the plasma short-circuits the electrical currents generated by the magnetic field in the plasma. When there is no polarization electr ic field, the filter efficiency eta(c) increases with the magnetic fie ld as eta(c) = (1 + B-c(2)/B-2)(-1) where B-c(2) = m(i) Gamma(o)/(sigm a perpendicular to RR2), m(i) is the ion mass, Gamma(o) is the total i nput ion flux, sigma(perpendicular to) is the transverse plasma conduc tivity and R and R' are the major and minor radii of the torus, respec tively.