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P: Fachverband Plasmaphysik
P 16: Poster Session 3
P 16.14: Poster
Mittwoch, 11. März 2020, 16:30–18:30, Empore Lichthof
The Edge Density Profile in Tokamaks — •Christian Schuster1,2, Elisabeth Wolfrum1, Ulrich Stroth1,2, and ASDEX Upgrade Team1 — 1MPI für Plasmaphysik, Garching — 2Physik-Department E28, Technische Universität München
To obtain sufficient fusion power in a future reactor, the plasma in the core has to be hot and dense. Combined with the low plasma density at the wall of current tokamaks, this necessitates maintaining a density gradient. In H-mode the increase in density occurs mainly at the edge of the plasma, in a region known as the pedestal. But also in L-mode there is a steep increase in density at the same position. To extrapolate to future reactors, knowledge about the underlying processes that determine the shape of the density profile is needed.
There are several effects that are responsible for this large density gradient at the edge. We approximate all transport processes in the plasma with an effective diffusivity and mean flow. In H-mode the diffusivity is lowered drastically in the pedestal compared to the core, but the presence of a mean radial flow, called pinch, is unclear [M Willensdorfer, NF 2013]. On the other hand, it was shown that the density profile at the edge often also depends strongly on the source, i.e. neutral atoms entering the edge region [RJ Groebner, PoP 2002].
In steady state it is not possible to disentangle these effects. Modulation experiments were used previously for the analysis of transport in the plasma core. In this contribution we prepare the extension of this technique to the pedestal region, using new diagnostic possibilities and modeling of the tokamak edge.