[Zurück]

E. Wolfrum, M. Faitsch, G. Fuchert, L. Barrera Orte, M. Bernert, G. Birkenmeier, D. Carralero, T. Eich, Y. Gao, B. Kurzan, F. Laggner, H. Mueller, S. Potzel, M. Rack, B. Sieglin, H. Sun, W. Suttrop, M. Willensdorfer, -. EUROfusion MST1 Team, . ASDEX Upgrade Team:
"Effect of magnetic perturbations on pedestal, SOL and divertor in high collisionality plasmas at ASDEX Upgrade";
in: "Proc. 42nd EPS Conference on Plasma Physics, Europhys. Conf. Abstracts", Vol. 39E; EPS Conference on Plasma Physics, 2015, ISBN: 2-914771-98-3, S. 11151 - 11154.

Edge localized modes (ELMs) appear in plasmas with steep pressure gradients in the edge transport
barrier. These ELMs lead to high heat loads onto the divertor. Magnetic perturbations (MPs) are
applied in order to achieve a reduction in the ELM energy fluence to the target. At the same time
MPs affect radial transport in the scrape-off layer due to the additional magnetic field component in
radial direction. In high collisionality discharges at ASDEX Upgrade application of MPs lead to the
disappearance of large type-I ELMs as soon as a critical density is achieved [1]. The critical density
is higher in plasmas with high heating power, indicating a dependence on collisionality [2]. New
experiments were carried out with n=2 MPs in discharges with three different plasma currents, 600
kA, 800 kA and 1 MA, in which the density was raised continuously to span Greenwald fractions
(f_GW) from 0.5 to 0.75. While at the lower densities both ELM types, large type-I and small ones,
are found simultaneously, the large ELMs disappear at high f_GW. The influence of the density
ramp on ELM behaviour, the structure of the midplane kinetic profiles from the pedestal top into
the scrape-off layer (SOL), the thermographic footprint in the divertor as well as on the fluctuations
in the SOL are presented exemplarily for the 600 kA case.