VERTICAL STABILITY ANALYSIS OF TOKAMAKS USING A VARIATIONAL PROCEDURE

A variational procedure has been developed to determine the growth rat e and displacement of an arbitrarily shaped ideal magnetohydrodynamic (MHD) plasma in the presence of an arbitrary set of resistive conducto rs and feedback circuits. A simplified version of this formalism for c alculating axisymmetric (n = 0) stability of single and double null to kamaks has been incorporated as a module in the TEQ free boundary equi librium code. The speed of the calculation and the direct coupling to the equilibrium code allow for comprehensive examinations of design sp ace. This code has been used in the design of the Tokamak Physics Expe riment (TPX) and the International Thermonuclear Experimental Reactor (ITER). We discuss three of these applications: (1) an examination of vertical stability as a function of poloidal beta and normalized inter nal inductance, (2) a study of single null versus double null stabilit y, and (3) an exploration of feedback system design.