Gyrokinetic Simulation of Turbulence in ASDEX-Upgrade Scrape-off Layer Plasmas

It is important to study heat and particle transport in the scrape-off layer (SOL) of tokamaks to better understand power handling options in the divertor. Experiments on ASDEX-Upgrade (AUG) have reported a significant enhancement of perpendicular transport as the effective collisionality increases in this region due to a transition between the sheath-limited and the inertial filamentary regimes. We have performed 3D nonlinear full-f gyrokinetic simulations in this parameter regime of the SOL using the Gkeyll code to study this transition. To achieve a transition at collisionality similar to the experiments, we have scanned a series of initial density profiles. The magnetic geometry is set up with the numerical equilibrium taken from AUG for a direct comparison. Most importantly, in the high effective collisionality regime, an implicit BGK collision operator is utilized to overcome the restriction on the time step from explicit time integration schemes. In this poster, we study the correlation between the blob regime transition and the effective collisionality with results of turbulence statistics and blob dynamics.

Acknowledgements: Supported by a DOE Distinguished Scientist award, the CEDA SciDAC project and other PPPL projects via DOE Contract Number DE-AC02-09CH11466 for the Princeton Plasma Physics Laboratory. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a Department of Energy User Facility using NERSC project allocation 4907.