Stabilizing effect of a nonresonant radio frequency drive on the m=1 diocotron instability

It has been experimentally shown that the rotation radius of a non-neutral plasma column around the longitudinal axis of a Malmberg–Penning trap experiences a growth in amplitude (m = 1 diocotron instability), leading to the loss of the plasma on the surface of the confining electrodes. A new stabilization mechanism has been investigated with the help of systematic experiments in the ELTRAP (ELectron TRAP) device where a high-frequency, low-amplitude drive has been applied on an azimuthally sectored electrode. An effective confining force is created, which reduces the offset of the column from the center. This interpretation and its theoretical analysis show a qualitative agreement with the experimental findings, where a net confinement effect is present for a wide range of drive amplitudes and frequencies.