Nonlinear electromagnetic stabilization of microturbulence by fast ions

e. Abstract In plasma physics, the specific aspect of the interaction between highly energetic ions and microturbulence is still an open problem and has a big impact on the plasma overall confinement quality. In the present work we investigate an experimental discharge where fast ions are thought to interact with the plasma and stabilize microturbulence activity, leading to an overall improvement of the plasma confinement on the ASDEX Upgrade tokamak. To quantify the impact of fast ions on the stabilization of Ion Temperature Gradient (ITG) microturbulence, and making use of state of the art codes GENE and FIDO, we simulate an experimental discharge in which high values of central ion temperature were measured. Due to the highly electromagnetic particularity of the discharges, a second class of instability is present, the Kinetic Ballooning Mode (KBM). Depending on the safety factor q, KBM instability can have a great impact on the final ion heat flux levels. Nonetheless, we find that fast ions have a pertinent impact on the reduction of ion heat flux for the discharges in consideration, and provide a microturbulence stabilizing mechanism.