Global simulations of tokamak microturbulence: finite beta effects and collisions

In this paper, we present global nonlinear gyrokinetic simulations including finite beta effects and collisions in tokamak geometry. Global electromagnetic simulations using conventional delta-f particle in cell methods are very demanding, with respect to numerical resources, in order to correctly describe the evolution of the non-adiabatic part of the electron distribution function. This difficulty has been overcome using an appropriate adjustable control variate method in the conventional delta-f scheme. Linearized inter-species and like-species collision operators have also been introduced in the model. The inclusion of the collisional dynamics makes it possible to carry out simulations of microturbulence starting from a global neoclassical equilibrium and to study the effect of collisions on the transport induced by electrostatic microinstabilities.