Advancing Fusion Materials via Public and Private Sector Experiments in DIII-D

A suite of advanced plasma-facing material candidates, including tungsten (W) alloys, additively manufactured and doped W, high-entropy alloys (RHEAs), ultra-high temperature ceramics (UHTCs), SiC-based ceramics, and boron-based materials, was tested in reactor-relevant scenarios in the DIII-D tokamak to guide material selection for future fusion pilot plants. Incident target heat fluxes reached ~2.2–2.4 MW/m² inter-ELM and ~6 MW/m² during ELMs in H-mode on material samples developed by public and private partners. Angled targets saw fluxes up to 11 MW/m² with surface temperatures >800 °C. W-based materials, including cold-sprayed and laser-powder bed AM W-Ta, doped W (K, Re), W-Ti-Cr, Ta-Ti-V-W, and ITER-grade or neutron-irradiated references, showed varied thermal stability; some alloys exhibited improved crack resistance and reduced impurity release. RHEAs revealed constituent-selective erosion and modest impurity release. UHTCs (NbC, ZrC, (Nb,Ta)C) remained intact under transient heat loads. SiCf/SiC samples showed stable thermal behavior and distinct surface changes. B and Si-based ceramics, including pure boron aggregates, underwent measurable physical and chemical sputtering.

The data collected in DIII-D will support material choices for reactor-relevant environments.