Large-scale gyrokinetic turbulence simulations with kinetic electrons from the summit framework

Kinetic electron physics is currently a primary challenge in the simulation of magnetic fusion turbulence and transport. A new kinetic electron model that uses a generalized split-weight scheme, where the adiabatic part is adjustable, along with a parallel canonical momentum formulation has been developed in three-dimensional toroidal geometry. This model includes electron-ion and ion-ion collisional effects and has been linearly benchmarked. It is found that for H-mode parameters, kinetic electrons increase linear ITG growth rate and there is a corresponding decrease in the critical ion temperature gradient due to trapped-electron drive. However, a nonlinear up-shift in the critical gradient or a super critical region still persists. The nonlinear energy flux increases more dramatically than the linear growth rate. However, the linear behavior of the zonal flow is little affected by kinetic electrons. The turbulent wave number spectrum is less dominated by purely radial zonal flow modes when kinetic electrons are included. All the gyrokinetic simulation work reported here is being carried out jointly through an open-source project called the 'Summit Framework'. (author)