Global Gyrokinetic Particle Simulation of Turbulence and Transport in Realistic Tokamak Geometry

W X Wang, Z Lin, W M Tang, W W Lee, S Ethier, J L V Lewandowski, G Rewoldt, T S Hahm and J Manickam

A general geometry model has been developed for the gyrokinetic toroidal code GTC with a number of highly desirable features including a systematic treatment of plasma rotation and equilibrium E×B flow, realistic plasma profiles and corresponding magnetohydrodynamic (MHD) equilibria. A symmetry coordinate system is used to construct a relatively regular mesh in real space for strongly shaped toroidal plasmas, which also facilitates straightforward visualization. By rescaling the radial coordinate, grid size is correlated with the local gyroradius which may vary substantially from the core to the edge. Gyrokinetic transformation of potential and charge density between particle and guiding center positions in general geometry is carefully treated, taking into account the finite ratio of the poloidal to the total field (B_θ/B). The applied equilibrium E×B flow, which is believed to play an important role in determining the turbulence level, is calculated from our global neoclassical particle code GTC-Neo. In the large aspect ratio circular geometry limit, cross benchmarks with the original GTC code show good agreement in real frequency, growth rate, steady-state heat flux and zonal flow amplitude for the ion temperature gradient driven microinstabilities (ITG modes).