Advanced Gyrokinetic Numerical Simulations of Turbulence in Fusion Plasmas

The problem of turbulent transport in magnetized plasmas is one of the major challenges in today's physics research. This level of transport is typically an order of magnitude higher than that caused by collisional processes. The ITER project now under construction will bring answers to these crucial questions. Direct numerical simulations of turbulence, based on first principles, have been developed recently. A complete description is provided by the so-called gyrokinetic theory. Various numerical techniques (Lagrangian, Eulerian and semi-Lagrangian) have been used to solve for the set of equations (a time-evolution PDE in 5D phase space and 3D integral-partial differential equations for the electromagnetic fields). The requirements for a full size simulation of the ITER plasma core are enormous: ~ 10¹⁰ grid points in 3D, ~ 10¹² markers or grid points in 5D, and ~10⁶ time steps. The main goal of this proposal is to develop state-of-the-art turbulence simulation codes that will be able to address the relevant physics in ITER-size plasmas thanks to the use of advanced algorithms that are expected to perform well on future HPC platforms. The project follows both routes of major code re-factoring and new code development. It is thus envisaged to formulate and implement the gyrokinetic equations in field-aligned coordinates into the Lagrangian code ORB5 developed at CRPP in collaboration with the Max-Planck Institute für Plasmaphysik (IPP). This will allow a reduction of the 3D grid for the field solver by orders of magnitude. The modular approach will enable us to implement the new field solver into the Eulerian code GENE developed at IPP in collaboration with CRPP. Various changes to the parallelization scheme are also envisaged.

• Dr. Stephan Brunner, EPF Lausanne
• Dr. Trach-Minh Tran, EPF Lausanne
• Prof. Laurent Villard, EPF Lausanne

• Dr. Alberto Bottino, Max-Planck IPP Garching
• Dr. Alessandro Casati, EPF Lausanne
• Dr. Sébastien Jolliet, JAEA Tokyo
• Sorhab Khosh Aghdam, EPF Lausanne
• Dr. Ben McMillan, EPF Lausanne
• Thibaut Vernay, EPF Lausanne