Simulations of tungsten and carbon dust transient influx in tokamak divertor plasma.

Dust is a type of impurities in fusion plasmas that can be formed on and ejected from tokamak walls due to various plasma-material interaction processes, such as surface layer cracking, peeling, and melting. The intensity of these processes is generally higher for larger particle and power flows to the wall components, particularly, in the divertor region. This leads to intermittent character of dust ejection into fusion plasmas, typically associated with transient high-intensity plasma events, such as edge localized modes. Experiments on various tokamaks have demonstrated that the ejected dust can have critical impact on performance of magnetic fusion devices affecting plasma parameters and stability. This work reports on computer simulation studies of transient influx of carbon and tungsten dust particles in divertor of a medium size tokamak. The simulations are performed with coupled plasma and dust transport codes, UEDGE-DUSTT, for low- and high-power plasma discharge conditions in DIII-D-like geometry. The evolution of edge plasma parameters, scrape-off-layer heat fluxes, and the core impurity accumulation are simulated and compared for different injected quantities of the low- and high-Z material dust. The results demonstrate complex synergistic phenomena involving evolving plasma conditions and the dust dynamics. The obtained results can clarify mechanisms of transient dust injection effects on the tokamak edge plasmas and help to direct future studies aiming to validate the simulation predictions and mitigate dust impact on fusion plasma discharges.