Stabilization of Drift Instabilities of an Inhomogeneous Plasma by Means of an RF Electric Field

The possibility of stabilizing effects that an rf electric field imposes on drift instabilities in an inhomogeneous plasma is investigated. A two-species, nonisothermal plasma, situated in an externally applied static magnetic field is considered with the rf electric field applied in the same direction as the dc magnetic field. The plasma is "mildly" inhomogeneous in density, with a density gradient perpendicular to the confining magnetic field. Using a hydrodynamic model for the plasma it is found that under certain conditions an increase in the frequency of the drift oscillations is obtained as the result of the application of the rf electric field. The increase in the frequency of the drift oscillations results in an increase in the magnitude of the stabilizing term associated with Landau damping which in turn yields a smaller growth rate for the drift instability. Discussions of the state of the plasma for different values of the frequency of the applied electric field are presented and the feasible ranges of values of the above quantity required for stabilization are determined. It is concluded that the resulting stabilization is significant only in a very narrow rf band. Therefore, the application of this technique appears to be a difficult experimental undertaking.