Turbulent particle transport driven by ion and electron modes

Paper in proceeding, 2012

The topic of the present work is the turbulent transport of main ions and impurities driven by ion modes (ITG) and electron modes (TE and electron scale ETG). Particle transport in regions relevant to the pedestal region of H-mode plasmas, i.e. with steep density gradients, are of particular interest. Using the code GENE, quasi- and nonlinear gyrokinetic simulations are performed, and the results are compared with a computationally efficient fluid model. The transport properties are quantified by locally finding density gradients (R/Ln ) yielding zero particle flux, which are directly related to the balance of convective and diffusive transport. This measure of the impurity peaking is calculated for ITG and TE mode turbulence in source-free regions of the plasma, and scalings are obtained for the driving gradients and the impurity charge number (Z). Further, the quality of the helium ash removal is studied for ITG and TE mode drive turbulence. For ETG modes, the focus is on the main ion transport, and the density gradient leading to zero main ion particle flux, related to the formation and sustainment of the edge pedestal, is estimated.