The ANIMEC code is a nonlinear free-boundary 3D MHD equilibrium solver that uses limited CPU time and memory. It is an inverse solver that applies Fourier decomposition in the periodic poloidal and toroidal angular variables and special finite difference discretisation scheme in the radial coordinate. The equilibrium state is achieved through a steepest descent accelerated energy minimisation scheme. When the forces reach a suitably small level, a matrix preconditioning algorithm (GMRES) is applied to bring the force levels down to machine precision.

Helical core equilibrium computed by ANIMEC