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Abstract of JOREK-HR2 Project

The non-linear MHD code JOREK has been developed to study the physics of Edge Localised Modes (ELMs) in tokamaks. The numerical simulation of ELMs ranks among the most difficult MHD problems in tokamaks due to the medium to high toroidal mode numbers and the localisation of the instability on the open and closed field lines around the separatrix.

The JOREK code uses a finite element grid in the poloidal plane and Fourier harmonics in the toroidal direction. The code uses a fully implicit time evolution which leads to large matrices to be solved at every time step.

The start of the previous project, JOREK_HR, was complicated since a lot of time has been spent on porting JOREK to HPC-FF using the default environment settings. Especially, the default version of MPI has been updated by ParTec to work with the hybrid MPI-OpenMp direct solver PaStiX needed by Jorek code. The huge number of days of maintenance at the beginning of 2010 did not help. Although the previous project was too ambitious, presently, JOREK is available on HPC-FF for production. The largest cases have up to 10 million degrees of freedom. They were performed on HPC-FF using 2048 cores.

An increase in resolution is required for the resolution of the fine scale filaments that form during the ITER type ELM instability. The aim of this new step is the improvement of the parallelization of the code in order to run ITER relevant simulations (with finer meshes in the poloidal plane and more toroidal harmonics).