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Abstract

Ideal and resistive MHD instabilities degrade the confinement or even lead to disruptions in ASDEX Upgrade reversed shear discharges. Double tearing modes temporarily arise when the minimum q value passes the q = 2 surface. They usually become stabilized with increasing distance between the rational surfaces or by the large pressure gradient at the inner rational surface provided by central electron heating. Large pressure gradients in the region of weak shear between the two q = 2 surfaces drive infernal modes unstable. These modes can couple to external kink modes if the q value at the plasma edge is close to low order rational values. The resulting global mode usually causes disruptions. An optimized current profile has to avoid, therefore, close double rational q surfaces as well as large pressure gradients in the weak shear region.

Additional information

Authors: GNTER S, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);SCHADE S, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);MARASCHEK M, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);PINCHES S D, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);STRUMBERGER E, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);WOLF R, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);YU Q, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE);ASDEX Upgrade Team, Max-Planck-Institut f³r Plasmaphysik, Euratom Association, Garching bei M³nchen (DE)
Bibliographic Reference: Article: Nuclear Fusion, Vol. 40 (2000) No. 8, pp. 1541-1548
Availability: Nuclear Fusion (Journal)
Record Number: 200012381 / Last updated on: 2000-09-08
Category: PUBLICATION
Original language: en
Available languages: en