High energy super-H plasmas mitigated with single and dual Shattered Pellet Injection

Mitigation of high-energy super-H mode disruptions in DIII-D through Shattered Pellet Injection (SPI) may result in multiple radiation flashes, depending on pellet composition. The experiment used pellets of varying size and composition (changing Ne/D2 ratio) to examine effects that excess D2 may have on the mitigation. The majority of shutdowns with pellets composed of both Ne and D2 resulted in two radiation flashes -- one when the pellet hits the edge and another when the core thermal energy drops at the end of the thermal quench. Mitigation of super-H mode plasma disruptions using pellets composed only of pure Ne follow an outside-in mitigation with a single radiation flash, similar to typical DIII-D H-mode SPI mitigated discharges. Additional experiments using multiple shattered pellets at different toroidal locations show an increase in current quench duration for H and super-H mode discharges compared to single pellet injection with similar Ne and D2 quantities. A comparison of pre-thermal quench radiation profiles due to high-Z impurity injection by SPI and dual SPI into H and super H-mode plasmas will be presented.