Global simulations of tokamak microturbulence: finite-β effects and collisions

In this paper, we present global nonlinear gyrokinetic simulations including finite βe effects and collisions in tokamak geometry. Global electromagnetic simulations using conventional δf 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 δf 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. (Some figures in this article are in colour only in the electronic version)