Stabilization of the diocotron instability in an annular plasma

Abstract

The stabilization of the diocotron instability by an applied radial dc electric field in an annular magnetized pure electron plasma is investigated experimentally. The radial electric field E(r) from the annular plasma gives rise to a radially dependent azimuthal E(r)×Bz drift. The shear in this drift provides the free-energy source for the instability. A sufficiently large bias applied to a central conductor changes the rotation rates of the plasma and stabilizes the instability. The diocotron instability is experimentally identified by its dispersion relation. Its nonlinear saturation is explained in terms of the broadening of its radial extent and trapping of the azimuthally drifting electrons.