Evolution of Density and Temperature Full Profiles after Pure Ne and D₂Shattered Pellet Injections on DIII-D

We report detailed measurements of the electron density (n_e) and temperature (T_e) full profile evolution during pure neon (Ne) and deuterium (D₂) shattered pellet injection (SPI) shutdowns on DIII-D. In order to mitigate thermal and electromagnetic loads and suppress runaway electron generation in ITER it is planned to perform massive injection of high-Z and low-Z species respectively. To study temporal and spatial dynamics of such injections, pure Ne and D₂ were injected in the form of shattered pellets into DIII-D plasmas. The evolution of n_e and T_e profiles during the thermal (TQ) and current quench was measured using the Thomson scattering system recently upgraded with new capabilities to obtain low-T_e measurements as well as to trigger based on a pre-defined level of ablation light. It was found that after Ne SPI the n_e peak is located outside the q=2 flux surface and significant impurity mixing with the core plasma is predominantly observed only during and after the TQ when MHD activity is predicted to increase the radial transport. Similar accumulation of the impurity at the plasma edge is observed after D₂ SPI, however, low mixing with the core plasma is seen even immediately after the TQ in the most of cases: the n_e peak remains overwhelmingly in the outer half of the plasma radius. Initial modeling shows that this reduced mixing is due to the drift of a plasmoid formed around the ablation fragments.