Speaker
Rachael Marie McDermott
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1065.pdf
Insight into turbulent transport via measurements of the plasma flow
R. M. McDermott1, A. Lebschy1,2, C. Angioni1, I. Erofeev1, E. Fable1, W. Hornsby1, A.
Medvedeva1,2, D. Prisiazhniuk1,2, U. Stroth1,2, E. Viezzer3 and the ADEX Upgrade Team
[1] Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
[2] Physik-Department E28, Technische Universität München, Garching, Germany
[3]Dept. of Atomic, Molecular and Nuclear Physics, University of Seville
The core charge exchange recombination spectroscopy (CXRS) systems on ASDEX
Upgrade (AUG) now provide a very high accuracy measurement of the impurity (B, N)
poloidal rotation in the plasma core (upol,Z). This diagnostic has been used to assemble a
database of upol,Z measurements that covers a wide range of plasma parameters. In the edge
(ρϕ>0.7) upol,Z is electron-diamagnetic directed, consistent with neoclassical (NC) theory.
However, in the plasma core (0.2 0.8). Second, the core intrinsic toroidal rotation reverses
concomitant with the peaking of the electron density, which is indicative of trapped electron
modes (TEM) also in the plasma core. Next, at the point of both maximum rotation reversal
and density peaking, ion-directed turbulent phase velocities are observed in the plasma edge
supporting the idea that the turbulence change from TEM to ITG occurs first in this region
and then propagates inward. Lastly, the core toroidal rotation reverses again as the electron
density profile flattens, indicating ITG turbulence also in the core.
These experimental observations show a connection between the dominant residual
stress mechanisms and the electron density profile. This is inline with the results of new, non-
linear, radially global, turbulence simulations of AUG Ohmic plasmas, which quantitatively
reproduce the measured, hollow, rotation gradients and show that the shape of the simulated
residual stress and intrinsic flow is strongly determined by the second derivative of the
density profile.
