Plasma Dynamical Processes and Turbulence Studies using Advanced Microwave Diagnostics
Turbulence / flow interaction (TS, AUG, TCV)
Background: A key question in plasma transport is the interaction of small scale turbulence structures and mesoscale plasma ExB zonal flow (ZF) structures. Both correlation (TEXTOR) and Doppler reflectometry (ASDEX Upgrade) systems - which directly measure Er fluctuations with high resolution - have been particularly successful.
Recent ASDEX Upgrade results reveal the importance of ZF fluctuations (geodesic acoustic modes - GAMs) in the L-H confinement mode transition. The interaction of turbulence driven ZFs, mean equilibrium driven flows and the turbulence itself is also considered to play an important role in determining fluctuation levels (and hence anomalous transport) as well as impacting on the dynamics and form of the wave number spectrum.
Goal: Many parameter dependencies, however, remain to be studied. TCV - with its wide flexibility in plasma triangularity and elongation - will allow the influence of plasma shaping on ZF generation and damping to be studied in detail. Also, Resonant Magnetic Perturbations (RMPs) - which are known to mitigate edge localized modes (ELMs) - have also been shown on TEXTOR to moderate GAMs due to the 3D structure of magnetic field perturbations generated at the plasma edge. These experiments need to be repeated on divertor plasmas on ASDEX Upgrade and TCV.
For this programme the transportable reflectometer system from TEXTOR will be valuable. Similarly, one of the Tore Supra/LPP reflectometers is being adapted to be portable to AUG and TCV.
Project lead by IPP & LPP Patrick Simon (PhD- IPP) Alexander Storelli (PhD - LPP) Dr. Garrard Conway Dr. Pascale Hennequin Dr. Laure Vermare Prof. Uli Stroth