NICE (Newton direct and Inverse Computation for Equilibrium)
The NICE code computes tokamak plasma equilibria. Its equilibrium reconstruction functionalities are routinely used at CEA on the WEST tokamak, and at UKAEA by the STEP team since 2023. NICE is a code that fits with the required standards of the IMAS platform. This code allows for industrial applications. IMAS is a platform adopted from the fusion community in order to collect and operate different codes (plasma equilibrium, transport, and many others) together and which is/will be used for all physics modeling and analysis in tokamaks, particularly ITER. It uses a modular approach that builds around a standardized data representation that can describe both experimental and simulation data for any tokamak.
- Real-time plasma free-boundary only reconstruction and magnetic measurements interpolation.
The method used for this computation mode is based on the use of toroidal harmonics and on a modeling of the poloidal field coils and divertor coils to perform the 2D interpolation and extrapolation of discrete magnetic measurements in a tokamak and the identification of the plasma boundary. The method is generic and can be used to provide the Cauchy boundary conditions needed as input by a fixed domain equilibrium reconstruction computation. It can also be used to extrapolate the magnetic measurements to compute the plasma boundary itself.
- Feature point two
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). In this mode, the problem solved consists of the identification of the plasma current density, a non-linear source in the 2D Grad-Shafranov equation, which governs the axisymmetric equilibrium of plasma in a Tokamak.
- Feature point three
Direct and inverse, static and quasi-static evolution free-boundary equilibrium computations. In a Tokamak, at the slow resistive diffusion time scale, the magnetic configuration in the plasma can be described by the MHD equilibrium equations are inside the plasma, and Maxwell equations are outside. Moreover, the magnetic field is often supposed not to depend on the azimuthal angle. Under this assumption of axisymmetric configuration, the equilibrium in the whole space reduces to solving a 2D problem in which the magnetic field in the plasma is described by the well-known Grad Shafranov equation. The unknown of this problem is the poloïdal magnetic flux. In this computation mode, the direct problem consists of computing the magnetic configuration and the plasma boundary, given a plasma current density profile and the total current in each poloïdal field coil. The aim of the inverse problem is to find currents in the PF coils that best fit a given plasma shape. NICE gathers in a single finite-element framework different equilibrium computation modes and numerical methods from the former VACTH, EQUINOX and CEDRES++ codes developed within Castor project.
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NICE project leaders: B.Faugeras, C. Boulbe.
The JOREK non-linear MHD Code
Part of the Castor team participates actively to the non-linear extended MHD code JOREK resolves realistic toroidal tokamak X-point geometries with a G1 continuous flux-surface aligned grid including main plasma, scrape-off layer and divertor region.
Contact: H. Guillard, B. N’Konga.
