Berlin 2014 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 14: Poster Session - Theory and Modelling
P 14.4: Poster
Dienstag, 18. März 2014, 16:30–18:30, SPA Foyer
Growth of axisymmetric instabilities in ASDEX Upgrade — •Till Sehmer1, Karl Lackner1, Erika Strumberger1, Emiliano Fable1, Patrick McCarthy2, and Otto Kardaun1 — 1Max-Planck-Institut für Plasma-Physik, EURATOM Association Boltzmannstraße 2, 85748 Garching, Germany — 2University College Cork, Ireland
Modern poloidal divertor tokamaks, such as ASDEX Upgrade (AUG), produce elongated plasmas, which are unstable against vertical displacement. The growth rate of this 2D instability in the presence of stabilizing passive conductors (PSL) with finite resistivity was calculated for 5416 AUG typical equilibria. For this, a general ideal MHD code package (NEMEC, CAS3DN, STARWALL) was used, which is able to take into account also the 3D structure of the PSL. The comparison of the resulting growth rates with the previously used rigid displacement model (movement only in z-direction, no skin effect for PSL considered, no induced surface currents) shows that the latter simplified model gives a consistently lower limit for typical AUG parameters (elongation, triangularity, current profile and axis position in radial direction). A statistical analysis of the results of the rigid displacement model shows the expected dependencies except for the triangularity, which has a stabilizing effect in this model. Based on results of our present, more general model, we conclude that a rigid displacement model gives an over-optimistic result regarding the effect of triangularity, in line with the experimental observation on AUG of an increasing discrepancy between previously predicted and observed growth rates for strongly triangular plasmas.