Impact of long-term PFC degradation on impurity influx

Determine how degradation of plasma-facing components (PFCs) during long-term tokamak operation influences impurity influx into the plasma, including quantifying the relationship between extended discharge durations, PFC damage mechanisms, and the magnitude and temporal evolution of impurity influx to the core plasma in reactor-scale devices.

Background

The paper highlights that in reactor-scale tokamaks, extended discharge times may lead to gradual degradation of plasma-facing components (PFCs), potentially increasing impurity influx into the plasma. Such impurity events (e.g., UFOs, flakes, dust) are known to trigger disruptions and influence runaway-electron dynamics, making their characterization critical for safety analyses.

Despite extensive modeling of tungsten-rich disruptions, the authors note that the connection between PFC degradation and impurity influx over long operational periods has not been established. Resolving this would improve predictive capability for impurity-driven disruptions and inform mitigation strategies and operational planning.