Non-linear Mhd Studies in Toroidal Geometry - Disruptive Phenomena in Tokamak Plasmas*

NON-LINEAR MHD STUDIES IN TOROIDAL GEOMETRY DISRUPTIVE PHENOMENA IN TOKAMAK PLASMAS. Sawtooth oscillations and related fluid excitations are studied analytically and computationally, and some modifications relevant to high temperature regimes are presented. The role of the ideal kink in the sawtooth crash and a new theory of density limit disruptions are discussed. 1. NONLINEAR MHD STUDIES IN TOROIDAL GEOMETRY A. Y. AYDEMIR, R. D. HAZELTINE, M. KOTSCHE],;REl'THER, J. D. MEISS, P. J. MORRISON, D. W. Ross, F. L. WAELBROECK, and J. C. WILEY Sawtooth oscillations and related fluid excitations are studied analytically and computationally, and some modifications relevant to high temperature regimes are discussed. 1.1 Toroidal Studies of Sawtooth Oscillations Tokamak sawtooth oscillations are studied computationally with a nonreduced, fully toroidal, resistive MHD (magnetohydrodynamic) model that includes ohmic heating and parallel and perpendicular thermal conduction. We examine the effects of transport on the type of sawtooth oscillations using simple models for the perpendicular heat transport coefficient, Kl.. With a constant li:l., simple, periodic sawtooth oscillations are seen (Fig. la). When the time evolution of li:l. is coupled to the dynamics by l~ttingx;l. ": p-l/2, * Supported by the US Department of Energy. 1 Present address: Institute for Fusion Studies, The University of Texas at Austin, TX 78712, USA~