Accurate Derivative Evaluation for any Grad-Shafranov Solver
It addresses the need for accurate derivative evaluation in magnetic confinement fusion simulations, where previous methods on coarse grids were insufficient.
The paper presents a numerical scheme for computing first and second partial derivatives of solutions to Poisson or Grad-Shafranov equations with the same convergence order as the solution, enabling accurate evaluation of magnetic field and current density in fusion simulations on coarse grids.
We present a numerical scheme that can be combined with any fixed boundary finite element based Poisson or Grad-Shafranov solver to compute the first and second partial derivatives of the solution to these equations with the same order of convergence as the solution itself. At the heart of our scheme is an efficient and accurate computation of the Dirichlet to Neumann map through the evaluation of a singular volume integral and the solution to a Fredholm integral equation of the second kind. Our numerical method is particularly useful for magnetic confinement fusion simulations, since it allows the evaluation of quantities such as the magnetic field, the parallel current density and the magnetic curvature with much higher accuracy than has been previously feasible on the affordable coarse grids that are usually implemented.