SPECIAL ASPECTS OF MAGNETOHYDRODYNAMIC EQUILIBRIUM CALCULATION FOR DIVERTED TOKAMAK CONFIGURATIONS

In this paper we present special aspects of calculation the fixed and free boundary MHD equilibria for an axisymmetric divertor tokamak configuration. A "classical" flux coordinate system, amended by a "cast function", has been used. Thus, the unknown moments the solution of the equilibrium equation are determined by the difference between the real flux surface contours and those described by the cast function only. With this procedure, the necessary number of moments to describe the flux surfaces in a quite complicated separatrix configuration is small enough to make computations time-efficient. Finally, an exact equilibrium solution to serve as benchmark for the numerical results is presented.