Electrostatic Ion-Cyclotron Oscillations Induced by an Emissive Disc Plate Floating in a Plasma

Measurements have been performed on ion cyclotron oscillations induced by a small emissive disc plate floating in a magnetized collisionless plasma column. The oscillations are observed when the emission is so large that the disc potential is higher than the plasma potential. This means that the oscillations are generated even in the absence of dc electric current passing through the plasma column if the disc potential is positive with respect to the plasma potential. The situation is in contrast with the case of applying positive potentials to a small cold disc plate to generate the ion cyclotron oscillations, where a dc electric current is induced along the plasma column. Main features of the oscillations are consistent with the “potential-driven” model for the generation of ion cyclotron oscillations.