ELMFIRE gyrokinetic study of turbulence and equilibrium asymmetries at the FT-2 tokamak edge

Figure 1: Toroidal configuration for simulations of FT-2. The blue torus materialises the outer wall. The red circles are the poloidal limiter diaphragms (punctual in the toroidal direction, in simulations). We approach the modelisation of the plasma boundary from first-principles using the gyrokinetic (GK) turbulence code ELMFIRE, in conjugation with experimental studies on the circular-section, limiter tokamak FT-2. We perform simulations with a fixed analytical magnetic background with circular concentric flux surfaces: B = B0 1+ε cosθ ( êφ + q êθ ) , where ε = r/R0 is the inverse aspect ratio, and q the safety factor. ELMFIRE uses the particle-in-cell (PIC) method to simulate turbulence in a plasma of GK ions (including impurities) and drift-kinetic (DK) electrons with high E×B flows [6–10]. The nonlinear polarisation of ions is included by accounting for shifts in the Lagrangian trajectories with an analytical form for the ion polarisation drift. The equations of motion—for (R,U) the gyrocenter position parallel velocity—and quasineutrality equation read: