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In recent years, many tokamak experiments have shown evidence for transport barriers in regions of negative magnetic shear (see, for instance, [1-3]).However, the control of the parameters of such discharges is a difficult task and the evolution of a configuration of this type may lead to instabilities due to the presence of multiple rational surfaces in the plasma. In particular, the double tearing instability may affect the confinement, since it may lead to relaxations of the electron temperature. Such relaxations have been observed in several experiments [4,5]. In particular, off-axis sawtooth relaxations have been found and interpreted [4] in terms of double tearing modes concerning two magnetic surfaces where q = 2. Similarly, periodic off-axis relaxations have been observed and interpreted [5] in terms of a double tearing mode, which develops about two magnetic surfaces where q=3.

Additional information

Authors: BERROUKECHE K, EURATOM-CEA,DRFC CEA Saint-Paul-lez-Durance (FR);MASCHKE EK, EURATOM-CEA,DRFC CEA Saint-Paul-lez-Durance (FR);SARAMITO B, Universite Blaize Pascal Aubiere (FR)
Bibliographic Reference: Article:Plasma Physics and Controlled Fusion Vol 40 (1998) p.1831-1844
Record Number: 199910399 / Last updated on: 1999-03-19
Original language: en
Available languages: en