Dependencies in impurity turbulent transport in ITER Baseline plasmas on DIII-D

This work presents results of core impurity transport studies in ITER Baseline Scenario plasmas on DIII-D. The studies identified plasma conditions with either Ion Temperature Gradient (ITG) or Trapped Electron Modes (TEM) dominance based on linear gyrokinetic modeling with CGYRO and TGLF. Profiles of electron density and temperature, ion temperature, and density of added trace impurities ranging from low Z (Helium) to high Z (Tungsten) were calculated. The calculation was achieved by using TGYRO with TGLF and, separately, by leveraging recent advances in surrogate-accelerated nonlinear gyrokinetic profile prediction [Rodriguez-Fernandez et al., Nuclear Fusion, 2024]. A strong dependence of impurity turbulent transport on the dominant turbulent regime was determined. The trend of impurity peaking factor with respect to impurity charge was found to change, from proportional to ∼1/Z to proportional to ∼Z when switching from TEM to ITG-dominated plasmas, in agreement with previous works [Howard, N. T. et al., Physics of Plasmas, 2024; Fülöp, T. and Nordman, H., Physics of Plasmas, 2009]. Implications of these dependencies for ITER are studied using the calculated diffusion and convection coefficients (D and v) in STRAHL to predict impurity radiation and confinement time.

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