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 heating in a magnetized collisionless plasma column. The oscillations are observed when the emission is so l arge that the disc potential is higher than the plasma potential. This means that the oscillations are generated even in the absence of de e lectric current passing through the plasma column if the disc potentia l is positive with respect to the plasma potential. The situation is i n contrast with the case of applying positive potentials to a small co ld disc plate to generate the ion cyclotron oscillations, where a de e lectric current is induced along the plasma column. Main features of t he oscillations are consistent with the ''potential-driven'' model for the generation of ion cyclotron oscillations.