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P: Fachverband Plasmaphysik
P 1: Helmholtz Graduate School for Plasma Physices I
P 1.2: Fachvortrag
Montag, 29. Februar 2016, 11:25–11:50, b302
Study of TEM-ITG turbulence transitions using Poloidal Correlation Reflectometry at AUG — •Dmitrii Prisiazhniuk1,2, Andreas Krämer-Flecken3, Garrard Conway1, Peter Manz1, Tim Happel1, Ulrich Stroth1,2, and The ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany — 2Physik-Department E28, Technische Universität München, 85748 Garching,Germany — 3Institut für Energieforschung - Plasmaphysik,Forschungszentrum Jülich, Association EURATOM-FZJ, 52425 Jülich, Germany
In several tokamaks a linear increase of the energy confinement time of Ohmic plasmas with the line averaged electron density has been reported. However, above a critical density the energy confinement time saturates. The corresponding regimes are named LOC and SOC, respectively. One hypothesis for the transition from LOC to SOC is a change in the dominant drive of the turbulence, from the trapped electron mode (TEM) to the ion temperature gradient (ITG). The main plasma parameters responsible for the change of the transport behaviour are still not identified. The recently upgraded Poloidal Correlation Reflectometer system in ASDEX Upgrade has been used to study the TEM-ITG transition. The system allows the study of turbulence characteristics (perpendicular & radial correlation length as well as the decorrelation time) and its interaction with the mean flow for a wide range of densities. The change of these parameters during the transition from TEM to ITG turbulence will be presented and the role of quasi-coherent structures will be discussed.