Experimental investigation of coherent electron temperature fluctuations accompanying a drift-like mode

A highly coherent drift-like instability in cylindrical plasma geometry is experimentally investigated using Langmuir probes. Phase-sensitive recorded probe characteristics permit the simultaneous measurement of all relevant plasma parameters (potential, density and electron temperature). Strong electron temperature fluctuations are observable whenever a significant radial electron temperature gradient is present. These temperature fluctuations are not damped by axial electron heat fluxes, since the axial wavelength is very large. A thorough investigation 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.