Plasma turbulence in the scrape-off-layer (SOL) driven by microinstabilities will play a cru- cial role in the plasma confinement and heat load to the tokamak wall. Also, understanding the parasitic absorption of radio frequency waves in the SOL region is still an open problem. It is believed that parametric decay instabilities will be a plausible cause for such absorp- tion [1, 2, 3, 4]. Microinstabilities, like ion-temperature-gradient (ITG) and trapped electron modes (TEM) are unstable due to the gradients of plasma temperature and density, and are known to drive robust turbulence activity. It is a critical challenge to capture both edge and core regions in an integrated global simulation due to the shape complexity arising in the SOL region by the divertor and X point. Presently, simulations within the SOL are primarily performed with fluid and gyro-fluid codes based on Braginskii equations. Fluid code, such as SOLPS [5], is widely used for ITER SOL and divertor modelling. The significant advan- tage of fluid code is that it needs less computational effort than kinetic approaches. Fluid simulations provide qualitative physics of SOL plasmas. However, it is believed that kinetic simulations are required for quantitative prediction of plasma properties. Another promising code Gkeyll [6], based on the discontinuous Galerkin algorithm, has been recently applied to study the curvature-driven turbulence in the open field line region and plasma wall interac- tions. Also, it is extended to the nonlinear electromagnetic simulations in a helical open field line system using National Spherical Torus Experiment (NSTX) parameters [7].
In the last three decades, our understanding of the microturbulence in the tokamak core region has vastly improved thanks to the development of several gyrokinetic simulation codes such as GTC [8, 9], GYRO [10], ORB5 [11], GENE [12], etc. These codes use flux coordinates, which at the magnetic separatrix surface encounter a mathematical singularity in the metric. To circumvent this problem, we have developed a new simulation code called G2C3 (global gyrokinetic code using cylindrical coordinates), similar in spirit to the XGC-1 [13], GTC- X[14] and TRIMEG [15]. Avoiding the flux coordinate system allows G2C3, XGC-1, and TRIMEG to perform the gyrokinetic simulations in arbitrarily shaped flux surfaces, including separatrix and X point in the tokamak. In G2C3, we have implemented fully kinetic (FK) and guiding center (GC) particle dynamics, but XGC-1 and TRIMEG only have guiding center particle dynamics. Also, TRIMEG uses a Fourier decomposition scheme, which is compu- tationally efficient for a single toroidal mode simulation. However, the toroidal spectrum is broad for nonlinear simulations, and the simulation can be more expensive than pure PIC code with field-aligned gather scatter operation. G2C3 uses field-aligned gather-scatter operation to achieve field-aligned mesh efficiency. Recently, GENE code is also updated to GENE-X to incorporate the SOL region based on flux coordinate independent approach [16]. The main focus for developing G2C3 is to couple the core and SOL regions for understanding the elec- tromagnetic turbulence using both the guiding center and fully kinetic particle dynamics.