Improvement of the moments method for MHD equilibrium calculation in a divertor tokamak configuration Original Research Article

In this paper we present a method to calculate the fixed boundary MHD equilibrium 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. As an example of our approach, the metric coefficients for a particular equilibrium configuration of the ASDEX-Upgrade tokamak have been computed.