Impact of impurity seeding on shattered pellet injection mitigations on the Joint European Torus

Plasma disruptions present a significant challenge to the viability of fusion energy production in tokamak reactors. Among disruption mitigation techniques, shattered pellet injection (SPI) has emerged as a promising approach. The results presented in this paper show novel findings of the impact of nitrogen and neon seeding on the disruption mitigation sequence following SPI on the Joint European Torus (JET). This study exposes an order of magnitude reduction in pre-thermal quench duration for highly seeded plasmas and pure deuterium SPI, a result with significant implications for staggered SPI schemes currently under development. Conversely, no reduction in disruption thermal load mitigation efficacy was observed for single neon and hydrogen mixed SPI across a range of seeding levels, indicating the robustness of this approach. A novel pathway for thermal load mitigation and enhanced runaway electron avoidance with pure deuterium SPI into strongly seeded plasmas is also presented.