Equilibrium Spline Interface ( ESI) for magnetic confinement codes

A compact and comprehensive interface, called ESI, between magneto-hydrodynamic (MHD) equilibrium codes and gyro-kinetic, particle orbit, MHD stability, and transport codes is presented. Its irreducible set of equilibrium data consists of four 2or 3-D functions of coordinates and four 1-D radial profiles together with their first derivatives. The C reconstruction routines (accessible also from Fortran), which are a part of the interface, allow the calculation of basis functions and their first derivatives at any position inside the plasma. After this all vector fields and geometric coefficients required for the above mentioned types of codes can be calculated using only algebraic operations with no further interpolation or differentiation. The interface is designed for 1. simple nested two and three dimensional configurations (a) with scalar pressure, (b) arbitrary pressure balance (within confinement limits); 2. magnetic configurations with magnetic perturbations (a) with scalar pressure, (b) arbitrary pressure balance (within confinement limits); Considering the simplest case of simple nested surfaces with scalar pressure as a default case, the interface specifies the the data structure, which should be generated for its input by equilibrium codes. In particular, ESI specifies what data should be provided in the ASCII (human readable form) and what is permitted to be binary. Leonid E. Zakharov, 12th US-EU Transport Task Force, San Diego CA, April 18, 2007 PRINCETON PLASMA PHYSICS LABORATORY PPPL 2