Changes in ion temperature with impurity content at the DIII-D tokamak*

New experiments at the DIII-D tokamak using the impurity powder dropper system [1], have permitted the comparison of plasmas with and without active carbon powder injection in both hydrogen and deuterium. Experimental data indicates that under similar input power, steeper ion temperature gradients for main ion and carbon species can be achieved in both the core and edge with greater carbon impurity content (6n_c/n_e = 0.1→0.2) in both hydrogenic isotopes. Using the turbulence modeling code TGLF [2], these experiments will be modeled in an attempt to disentangle the isotope and impurity physics at play in these plasmas. Potentially important considerations include turbulent transport physics such as Ion Temperature Gradient (ITG) instability modification by main ion dilution, and neoclassical transport physics changes such as modified (mass dependent) electron-ion collisional energy exchange. This research, in L-mode and H-mode electron heat dominant plasmas (Q_e > Q_i), will have potential implications for understanding how helium ash accumulation may impact reactor plasmas performance by ion temperature regulation.