Abstract of MAG-2 Project

Understanding turbulence and heat transport in fusion plasma is a key challenge for future fusion devices like ITER. The field of core transport modelling in tokamak plasmas has now reached a certain maturity with non-linear 5D gyrokinetic codes in the world. However, their predictive capabilities are still constrained with respect to the energy content, in particular in optimized discharges. Challenging this gap requires pushing gyrokinetic modelling towards the edge region of the container vessel, and as far as possible addressing edge and core transport on an equal footing.

A toroidally‐symmetric limiter and a first wall have recently been implemented [1] in the GYSELA code [2,3] using penalized immersed boundaries for this purpose. However, the code is currently based on a simplified magnetic configuration with circular concentric magnetic field lines. One of the next objectives is to extend the code to more realistic magnetic configuration: D-shape configurations in the core at short term but also X-point configurations at longer term. This will imply to change both the semi-Lagrangian scheme for the 5D Vlasov equation and the quasi-neutrality (based on a modified 2D Poisson eq.) solver. The GEMPIC code [4], which is a fully kinetic PIC code that is being extended to realistic tokamak geometries also needs a Poisson solver for general magnetic geometries in the poloidal plane. Both solvers fit in the category of general elliptic solvers and will be solved in the same geometry, so that the development can benefit both codes.

This project proposes a continuation of last year project "Multigrid on adaptive meshes". The purpose of the extension is twofold: During last year's project two solvers, one on a mapped grid and one on a cartesian grid with embedded boundaries to describe the geometry have been developed based on the AMReX code [5]. With the new project, an extension to more complex domains with non-uniform meshes shall be achieved. Moreover, it is proposed to implement a C++ interface to couple the new solvers to the GYSELA code (mainly written in Fortran 90 with few routines in C) and compare their performance in the context of a gyrokinetic simulation.

[1] E. Caschera, PhD thesis (2019).
[2] V. Grandgirard et al., Comp. Phys. Com. (2016) 35, DOI: 10.1016/j.cpc.2016.05.007.
[3] Y. Sarazin et al., Nucl. Fusion 51 (2011) 103023.
[4] M. Kraus, et al., Journal of Plasma Physics 83.4 (2017).
[5] https://amrex-codes.github.io/