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Tearing mode formation is investigated for ohmic density limit discharges on the ASDEX Upgrade tokamak at medium and high safety factors (q(95) = 3.8, 4.9, 6.0). Low electron temperatures inside magnetic islands and the observation of localized C III impurity radiation suggest that a thermal instability, as proposed by Rebut and Hugon, destabilizes the (m,n) = (3,1) and (4,1) islands, which grow during the current profile contraction phase. In contrast, the (2,1) islands appear to be thermally stable. Minor disruptions lead to step-wise loss of confinement, first localized at the q = 2 surface, then after a time delay comparable to the resistive time-scale, at the q = 3 surface and after a second time delay, at the q = 4 surface. It is found that (3,1) islands, unlike (2,1) islands, are quenched by the high heat flux during minor disruptions.

Additional information

Authors: SUTTROP W ET AL, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Article: Nuclear Fusion, Vol. 37 (1997) No. 1, pp. 119-125
Record Number: 199710335 / Last updated on: 1997-04-14
Original language: en
Available languages: en
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