Off-resonance heating of mirror confined plasmas

Abstract

Experiments are described in which microwave power above or below the electroncyclotron frequency is applied to mirror codned plasmas. Above resonance, a finite heating rate is measured. Below resonance, the plasmas are expelled. The upper off-resonance heating rate and the lower off-resonance power required to expel the plasma agree with the predictions of a proposed theoretical model in which the spatial variation of the microwave electric field of the multimode cavity randomizes the electron motion.

Observation of Plasma Heating Due to Parametric Instabilities at the Upper Hybrid and at the Cyclotron Harmonic Frequencies

“…1 (Runaway electrons do not appear to cause the instability. 3 ) When the q = 2 singular surface is moved toward the plasma surface by lowering q(a) or by causing the current channel to shrink by increasing pressure as evidenced by a constriction of the electron temperature profile, 1 Low-frequency oscillations, which can lead into the violent disruptive instability which sets the q (current) limit of tokamak operation, are investigated with a heavy-ion beam probe. Direct measurements of the space potential and the perturbation of the electron density inside the hot tokamak plasma resolve the electric field contribution to the mode rotation and the spatial structure of the mode.…”