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W. Suttrop, L. Barrera Orte, A. Herrmann, R. McDermott, T. Eich, R. Fischer, B. Kurzan, P. Lang, A. Mlynek, T. Pütterich, S. Rathgeber, M. Rott, T. Vierle, E. Viezzer, M. Willensdorfer, E. Wolfrum, I. Zammuto, . ASDEX Upgrade Team:
"Studies of edge localized mode mitigation with new active in-vessel saddle coils in ASDEX Upgrade";
Plasma Phys. Control. Fusion, 53 (2011), 1240141 - 1240148.

The ASDEX Upgrade tokamak is currently being enhanced with a set of invessel
saddle coils for non-axisymmetric perturbations aiming at mitigation or
suppression of edge localized modes (ELMs). Results obtained during the first
experimental campaign are reported. With n = 2 magnetic perturbations, it
is observed that type-I ELMs can be replaced by benign small ELM activity
with strongly reduced energy loss from the confined plasma and power load to
the divertor. During these phases with ELM mitigation, no density reduction
(density `pump-out´) is observed. ELM mitigation has, so far, been observed
in plasmas with different shape and different heating mixes and, therefore,
different momentum input. The ELM mitigation regime can be accessed
with resonant and non-resonant perturbation field configurations. The main
threshold requirement appears to be a critical minimum plasma edge density
which depends on plasma current. So far it is not possible to distinguish whether
this is an edge collisionality threshold or a critical fraction of the Greenwald
density limit.