rf Stabilization of an Axisymmetric Tandem Mirror

Plasma with significant central-cell beta can be sustained in a tandem mirror composed of three axisymmetric simple mirror cells by the use of ion-cyclotron resonant heating. Radial ponderomotive force due to the rf electric field opposes the centrifugal force due to the field-line curvature to ensure interchange stability. This is indicated by the sensitive dependence of the plasma stability on the sign of the difference between the rf frequency and the ion-cyclotron frequency.