Direct excitation of high-amplitude chirped bucket-BGK modes.

For the first time, high amplitude (Deltan/n approximately 40%), high Q (up to 100 000) Bernstein, Greene, and Kruskal modes have been controllably excited in a plasma. The modes are created by sweeping an excitation voltage downwards in frequency, thereby dragging a phase space "bucket" of low density into the bulk of the plasma velocity distribution. The modes have no linear limit and differ markedly from plasma waves and Trivelpiece-Gould modes.