Microwave reflectometry for turbulence studies on ASDEX Upgrade

We study the evolution of turbulence at several radial plasma locations in the Axially Symmetric Divertor Experiment (ASDEX) Upgrade tokamak, using mi crowave reflectometry. We analyze two types of scenarios: H-mode plasmas wi th improved performance and plasmas with electron cyclotron resonance heati ng modulation. Profound modifications of the turbulence spectra, occurring at specific plasma regions, have been found in both cases, indicating the r elation between turbulence changes and confinement. The results demonstrate the ability of the reflectometry system on ASDEX Upgrade to make localized measurements. Mapping the radial distribution of turbulence can help us to understand the links between plasma rotation, shear, ExB flows, and the pl asma turbulence behavior. (C) 2001 American Institute of Physics.