NOVA: A nonvariational code for solving the MHD stability of axisymmetric toroidal plasmas

A nonvariational approach for determining the ideal MHD stability of axisymmetric toroidal confinement systems is presented. The code (NOVA) employs cubic B -spline finite elements and Fourier expansion in a general flux coordinate (ψ, φ, ζ) system. At least as much accuracy and faster convergence were obtained in comparison with the existing variational PEST and ERATO codes which employ linear finite elements. This nonvariational approach benchmarked here on the ideal MHD problem is a prelude to a future extended version applicable to problems having non-Hermitian eigenmode equations where variational energy principles cannot be obtained.