An overview of the numerical methods for tokamak plasma equilibrium computation implemented in the NICE code

Abstract The code NICE (Newton direct and Inverse Computation for Equilibrium) enables to solve numerically several problems of plasma free-boundary equilibrium computations in a tokamak: plasma free-boundary only reconstruction and magnetic measurements interpolation, full free-boundary equilibrium reconstruction from magnetic measurements and possibly internal measurements (interferometry, classical linear approximation polarimetry or Stokes model polarimetry, Motional Stark Effect and pressure), direct and inverse, static and quasi-static free-boundary equilibrium computations. NICE unifies and upgrades 3 former codes VacTH [1] , EQUINOX [2] and CEDRES++ [3] . The strength of NICE is to gather in a single finite element framework different equilibrium computation modes. It makes intensive use of Newton method and Sequential Quadratic Programming method to solve non linear problems. NICE is used routinely for WEST tokamak operation. It is also adapted to the IMAS (ITER Modelling and Analysis Suite) format which makes it usable on many different fusion tokamak reactors. In this document we give a general overview of the numerical methods implemented in NICE as well as a number of computation examples.