Special aspects of MHD equilibrium and stability calculations for a divertor tokamak configuration

A method is presented to calculate MHD equilibrium and stability in an axisymmetric divertor tokamak configuration. For equilibrium calculations, a 'classical' flux co-ordinate system, refined by a 'cast function', is used. Thus, the unknown moments - the solution of the equilibrium equation - are determined by the differences between the real flux surface contours and those described by the cast function only. As boundary conditions for the second order differential equation governing the tearing mode stability, 'natural' boundary conditions for the plasma boundary have been found by calculating the surface charge distribution (from potential theory), where the normal component of the perturbation is known. As an example for this approach, the metric coefficients for a particular equilibrium configuration and boundary conditions for the flux function perturbations, of different mode numbers, have been computed for the ASDEX Upgrade tokamak. (author). 12 refs, 1 fig