Non-Resonant Dynamic Stabilization of the m = 1 Diocotron Mode

The m = 1 diocotron mode of a nonneutral plasma column confined in a Malmberg-Penning trap, i.e. the rotation of the plasma center-of-charge around the longitudinal symmetry axis, is experimentally found to be unstable. We have investigated in the ELTRAP device a control mechanism of the radial drift of the column based on a Radio Frequency drive applied on an azimuthally sectored electrode of the trap. Systematic experiments show the characteristic features of the mechanism, namely the presence of amplitude and frequency thresholds as well as the non-resonant behavior, whose interpretation invokes the concept of dynamic stabilization.