Effect of tungsten impurities on ITER’s disruption mitigation system

Ascertain how the presence of tungsten impurities affects ITER’s planned disruption mitigation system based on shattered pellet injection, specifically determining how tungsten modifies the operational window of neon and deuterium injection quantities required to balance runaway-electron suppression against preservation of sufficient ohmic current to avoid overly fast current quench.

Background

ITER’s baseline disruption mitigation relies on shattered pellet injection to suppress runaway electrons while maintaining enough ohmic current to avoid an excessively fast current quench. The paper’s simulations show tungsten can strongly alter plasma cooling and runaway generation dynamics, suggesting that impurity presence may shift or narrow the mitigation operational space.

The authors explicitly flag the need to evaluate tungsten’s impact on mitigation settings, indicating that current models and datasets do not yet provide definitive guidance. This question is central to operational safety for ITER, where tungsten is expected as a plasma-facing material.