Plasma-surface interactions on extreme grain-refined tungsten tested under multi-scale fusion reactor conditions

Tungsten is being considered as one of the top material candidates for divertor and first-wall components of future plasma-burning magnetic fusion reactors. Future operation demands reliable performance under extreme environmental conditions including: multi-scale variables including: particle flux (e.g. 10$^{17}$-10$^{24}$ /m$^2$/sec), fluence (e.g. 10$^{19}$-10$^{28}$ m$^{-2}$), temperature (200-1500 C), incident particle energies (5-1000 eV/amu) and heat fluxes (10-50 MWm$^{-2}$). Recent studies have observed complex surface morphology evolved when exposed to He and D/He plasmas. Extreme grain-refined tungsten is investigated as a plasma-facing component material with possible radiation-resistant properties. A systematic study ranging from early-stage He irradiation conditions to fusion reactor-level plasmas has been conducted. Early-stage studies include \textit{in-situ} TEM analysis of He-irradiated nanostructured tungsten. Simulated conditions in future fusion plasma-burning devices are replicated using Pilot-PSI plasmas at DIFFER. Results shed light on critical gaps in our understanding of the surface response and nano-to-microstructural deformation behavior motivating pathways for improved theoretical and computational modeling strategies.