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(EXP3/04) Some Features of the Disruption Instability in Reversed Shear TFTR Plasmas

   
I. Semenov ¹, S. V. Mirnov ¹, K. McGuire , M. G. Bell , E. Fredrickson , M. Okabayashi , P. Savrukhin ², G. Taylor , V. A. Vershkov ², L. Zakharov 
 
Princeton University, Plasma Physics Laboratory, Princeton, NJ 08543, USA
¹ TRINITI, Troitsk, 142092, Moscow Reg., Russia
² RRC ``Kurchatov Institute'' 123182, Moscow, Russia

Abstract
The behaviour of MHD perturbations before and during disruptions in the TFTR  Reversed Shear (RS) plasma with $\rm q_{min} \sim 2$ was analysed. In the $\rm q_{min}$ region tearing modes , wave-like modes, and mixed tearing plus wave-like modes are followed by disruption. Sometimes a helical snake  (helix) appears at the X-point of the $\rm q_{min}$ island. The local outward electron energy transport near the X-point can be explained by the development of ``positive'' magnetic islands. It is proposed that the disruption is initiated when the X-point of the magnetic islands coincides in one toroidal position near torus equator.

   

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