Impurity transport studies in DIII-D H-mode plasmas: Experiment and Turbulence Modeling

The transport of impurities in tokamaks is anticipated to play a critical role in future fusion reactors. As a result, there is a strong desire to accurately measure and model impurity transport in current devices, to allow for extrapolation to burning plasma regimes. In this work we present a study of core impurity transport in DIII-D H-mode plasmas. The H-mode conditions have been studied in ITER baseline scenarios (IBS), and in ITER Similar Shape (ISS) plasmas. In IBS conditions, Al impurities were studied with gyrokinetic modeling, suggesting that slightly hollow profiles may occur to strengthen TEM activity outside of r/a = 0.8. The ISS plasmas were studied by comparing Aurora modeling and direct density measurements with gyrokinetic modeling. Low-Z impurities exhibit good agreement with experimental measurements over a wide radial range (inside ρ =0.8) while medium Z impurities (Ca) show some disagreement. Sources of possible error, including atomic physics, and the Z scaling of impurity diffusion will be discussed. Analysis of DIII-D low power (3-4 MW) H mode plasmas in ISS with transition from ITG to TEM dominated turbulent regime is currently underway. Profile and power balance analysis using TRANSP will be presented along with TGLF modeling of heat and particle transport.

This work was supported by the U.S. Department of Energy award DE-SC0014264 and DIII-D cooperative agreement DE-FC02-04ER54698.