A category of oscillation identified with the inhomogeneous energy-density driven instability has been experimentally verified. This mode exploits the free energy available from shear in the E×B flow velocity. This shear is produced experimentally by applying different voltages to a segmented disk electrode located on axis at the end of a Q machine plasma column. As plasma conditions are varied between the two parameter regimes that, according to theory, correspond to the current-driven and shear-driven waves, the expected transition in mode characteristics is observed.

• Received 7 January 1994

DOI:https://doi.org/10.1103/PhysRevLett.72.3355