Numerical challenges in particle simulation of kinetic diffusion equations in toroidal plasmas

Josef Höök
Division of Scientific Computing
Department of Information Technology
Uppsala University


Increasing the understanding of kinetic processes in toroidal plasmas is one of the main challenges towards a working power plant based on fusion technology. Currently the main power plant candidate is the tokamak, which is a toroidal, magnetically confined plasma device. The spatial and temporal scales in a tokamak plasma are extreme and the only tractable path for quantitative studies is to rely on computer simulations. Present day simulation codes can resolve only some of these scales. Nevertheless they still require the largest high performance computing resources available in the world.

In this talk, we discuss different variance reduction techniques applied to particle simulation of plasma kinetic diffusion and present a new adaptive delta-f method. We derive a second order accurate (temporal) scheme for the pitch-angle SDE based on operator splitting and the performances of these methods are tested on models that describe fast-ion thermalization and radio frequency heating of plasmas. The results show that some of these methods have the potential to open up for quantitative studies in new plasma regimes.