Measurement of microwave spectra from a high-density toroidal discharge with current-driven turbulence

Microwave radiation measurements in the region ωsub(pi)<<ω<ωsub(ce) in a high-density (ωsub(pe)>>ωsub(ce)) tokamak with turbulent skin heating show evidence of a Cerenkov beam-plasma instability during the first few microseconds of the heating pulse. It is proposed that the instability is caused by the interaction of populations of freely accelerated electrons with the bulk of the plasma, and corresponds to the unstable propagation of oblique whistlers along group-velocity resonance cones. Measured microwave spectra and their interpretation are presented. (Auth.)