EXPERIMENTAL INVESTIGATION OF COHERENT ELECTRON-TEMPERATURE FLUCTUATIONS ACCOMPANYING A DRIFT-LIKE MODE

A highly coherent drift-like instability in cylindrical plasma geometr y is experimentally investigated using Langmuir probes. Phase-sensitiv e recorded probe characteristics permit the simultaneous measurement o f all relevant plasma parameters (potential, density and electron temp erature). Strong electron temperature fluctuations are observable when ever a significant radial electron temperature gradient is present. Th ese temperature fluctuations are not damped by axial electron heat flu xes, since the axial wavelength is very large. A thorough investigatio n of the axial fluctuation structure and of the effects of the radial electric field on the instability suggest a drift-like instability as an interpretation of the observed fluctuations. The radial fluctuation -induced heat and particle fluxes can be determined from the temporal evolution of the plasma parameters.