Pedestal turbulence characteristics during low Z and medium Z impurity injection on DIII-D

2D measurements of long wavelength density fluctuation characteristics have been obtained in the pedestal region on DIII-D with low to medium-Z (N₂, Ne, Ar) radiative impurity injection and are found to correlate with pedestal height and global confinement changes. Plasma confinement and pedestal pressure respond differently to these impurities, with some impurity accumulation and confinement improvement observed with Ne and Ar seeding. Pedestal density fluctuations are correspondingly slightly reduced and the appearance of a higher frequency band (measured by BES) is observed with Ne seeding. In an experiment with full detachment, fluctuations were observed to increase with N₂ seeding, suggesting an increase in pedestal transport; no improvement in global confinement was observed, in contrast to results observed on the AUG tokamak. Changes in characteristics of turbulence, such as amplitude, correlation lengths, turbulence decorrelation rate and turbulence flow velocity with different impurity seeding are investigated. This will provide insights into the mechanisms behind radiative impurity effects on transport in reactor-relevant conditions.