Turbulent transport of impurities from the SOL into the core of DIII-D using Flan

A kinematic Monte Carlo trace impurity code Flan is used on a pre-computed plasma background from the gyrokinetic solver Gkeyll to simulate tungsten (W) and boron (B) transport into the core of DIII-D in an inner-wall limited negative triangularity discharge from hypothetical sources in the SOL. We show that electric field fluctuations at the separatrix are responsible for carrying the impurities into the core due to induced intermittent transport on the same time scale as the fluctuation period (~µs). A statistical treatment of the fluctuation characteristics along the separatrix are correlated with the inward particle flux to better demonstrate whether impurities primarily enter from the high or low field side. We find that the average impurity velocity at the separatrix can be significantly larger than expectations (~ +/- 1,000 m/s). Particles are transported by the Lorentz force, and a collision model serves to deflect the particle velocity at appropriately small time steps. With these results, we predict values for the radial diffusion coefficient for W and B in the far-SOL. While the current study is a thought experiment (W and B were not present in these discharges), they lay the groundwork for future simulations in more complicated discharge geometries where W and B were/will be present, like the 2016 DIII-D Metal Rings Campaign and the future tungsten-walled DIII-D.