Numerical challenges for the simulation of magnetic fusion plasmas

abstract: The principle behind magnetic fusion research is to confine a plasma, which is a gas of charged particles at a very large temperature, around 100 000 degrees, so that the fusion reaction can generate energy with a positive balance. At such a high temperature, the plasma needs to be completely isolated from the wall of the reactor. This isolation can be achieved in toroidal devices thanks to a very large magnetic field. Due to the multiple and complex physical processes involved, theoretical research in this field relies heavily on numerical simulations and some problems require huge computational resources. After introducing the context of magnetic confinement fusion, we shall address different specific challenges for numerical simulations in this topic, which are in particular related to the multiple space and time scales that need to be spanned and to the geometry of the experimental devices. These can only be solved thanks to a close collaboration between physicists, mathematicians and HPC specialists. A few current research problems in this field going from the computation of a 3D equilibrium to fluid and kinetic simulations will be presented as an illustration.