Understanding of Liquid Lithium Wettability in Porous Tungsten Fusion Plasma Facing Components

Exposure of solid plasma-facing components (PFCs) to high irradiation conditions in fusion reactors leads to significant erosion and re-deposition under high-duty cycle conditions. High heat and particle flux can also undermine structural properties of PFCs such as fracture strength and creep rate. Liquid metal (LM) PFCs may be a practical alternative due to their ability to continually replenish material. Their finite residence time helps them tolerate both steady-state and transient heat fluxes within fusion reactors. However, the generation of thin liquid films of low-Z materials has been difficult due to poor adhesion and high surface tension. The work presented here explores the use of nano- and meso-porous substrates as an alternative to improve wetting using capillarity-driven effects such as: imbibition, percolation and wicking. Liquid lithium will be applied to tungsten substrates fabricated by atmospheric plasma spray and field-assisted/spark plasma sintering with an in-vacuo lithium dropper in the IGNIS-2 facility at Penn State's Radiation Surface Science and Engineering Lab. Wettability of liquid Li and porous tungsten samples will be imaged and video recorded in-situ at surface temperatures up to 400 C. Wetting angles will be measured to determine which tungsten substrates and surface microstructures are the most wettable by Liquid Li coatings.