Normal high velocity solid dust impacts on tiles of tokamak-relevant temperature

TL;DR

This study investigates high-velocity tungsten dust impacts on tokamak-relevant surfaces at various temperatures, finding that damage mechanisms are largely temperature-independent, supporting the use of existing empirical erosion laws.

Contribution

The paper provides experimental data on solid tungsten dust impacts at different temperatures, demonstrating the temperature independence of damage regimes relevant for fusion reactor materials.

Findings

Damage regimes are weakly dependent on temperature within the studied range.

Empirical damage laws from room-temperature experiments are applicable at cryogenic and elevated temperatures.

High-velocity impacts cause plastic deformation, bonding, and partial disintegration regardless of temperature.

Abstract

Runaway electron incidence on plasma facing components triggers explosive events that are accompanied by the expulsion of fast solid debris. Subsequent dust-wall high speed impacts constitute a mechanism of wall damage and dust destruction. Empirical damage laws that can be employed for erosion estimates are based on room-temperature impact experiments. We use light-gas gun shooting systems to accelerate solid tungsten dust to near-supersonic speeds towards bulk tungsten targets that are maintained at different temperatures. This concerns targets cooled down to $-100^{\circ}$C with liquid nitrogen and targets resistively heated up to $400^{\circ}$C. Post-mortem surface analysis reveals that the three erosion regimes (plastic deformation, bonding, partial disintegration) weakly depend on the target temperature within the investigated range. It is concluded that empirical damage laws based on room-temperature measurements can be safely employed for predictions.