(TH/P9-15) Plasma Rotation Effects on the Trigger of Reversed Shear Plasma Disruptions

Y. Ishii1), A.I. Smolyakov2), M. Takechi1)
1) Japan Atomic Energy Agency, Naka, Japan
2) University of Saskatchewan, Saskatoon, Canada

Abstract.  Nonlinear responce of a rotating plasma to an external perturbation is investigated in order to prpose a new scenario of a low β disruption of a reversed shear plasma. It is found that, in rotating plasma, magnetic islands formed around inner and outer magnetic resonant surfaces, which are stable for the tearing mode, by an external perturbation, (driven magnetic island) evolve with different growth rates during an initial growth phase. After an initial growth phase, an outer magnetic island grows explosively earlier and triggers an explosive growth of an inner one. At a final phase, enlarged magnetic islands flatten a q-profile in wide radial region including the plasma center. Though this final phase resembles closely a nonlinear destabilization of a spontaneous double tearing mode (DTM), this process can explain time delay of a plasma edge oscillation to trigger an internal MHD events and disruption, that is one of longstanding questions in a low β reversed shear plasma disruption. This process also shows a way that reversed shear plasma passes intermediate rational surfaces, though it collapses when the minimum of q value passes a low rational surface.

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