Researchers have completed a comprehensive comparative assessment of 44 advanced plasma-facing materials (PFMs) at the DIII-D National Fusion Facility. The campaign, detailed in a new arXiv preprint, involved 12 institutions, including four public-private fusion partnerships, and aimed to generate qualification data to support material down-selection for the walls and divertors of future fusion pilot plants. Samples were exposed to a range of plasma conditions using the Divertor Materials Evaluation System (DiMES), providing a standardized basis for comparing novel materials against established benchmarks like ITER-grade tungsten. This effort represents a significant public-private collaboration to address one of the key engineering challenges for commercial fusion energy. Source: arXiv

The experimental protocol subjected the material samples to Ohmic, L-mode, and H-mode plasma discharges, including edge-localized modes (ELMs) characteristic of high-performance scenarios. Heat fluxes varied based on geometry, reaching 0.2-2.5 MW m⁻² on flush-mounted samples and a more demanding 10-15 MW m⁻² on samples angled at 10 degrees to the magnetic field lines. A subset of materials was also evaluated for fuel retention properties after being irradiated with neutrons to a dose of 0.3 displacements per atom (dpa) at 550°C. This dual focus on plasma-material interaction and neutron damage effects provides critical data for predicting material performance in a reactor-relevant environment. Source: arXiv

A subset of materials was also evaluated for fuel retention properties after being irradiated with neutrons to a dose of 0.3 displacements per atom (dpa) at 550°C.

Results for tungsten-based materials showed varied performance. Engineered architectures, such as long-fiber tungsten-fiber-reinforced tungsten (Wf/W), successfully retained their structural integrity and demonstrated clear crack-arresting behavior. Tungsten-rhenium (W-Re) and potassium-doped tungsten (K-doped W) alloys exhibited responses nearly identical to standard ITER-grade tungsten. In contrast, additively manufactured tungsten-tantalum (W-Ta) displayed a heat-flux-sensitive response, with mass losses of 0.64 mg for the flush sample and significantly higher losses of 2.19-2.87 mg for the angled samples, indicating potential performance limitations under high heat loads. Source: arXiv

The study also yielded important insights into fuel retention and alternative materials. Neutron-irradiated ITER-grade tungsten retained 2.8 times more deuterium than its pristine counterpart, highlighting the impact of neutron damage on tritium inventory. Among the materials tested under Ohmic conditions, titanium diboride (TiB₂) showed the lowest deuterium release. For refractory multi-principal-element alloys, VTaHfMo was identified as the most stable. Carbide ceramics like NbC and (Nb₀.₅Ta₀.₅)C also performed well, maintaining integrity with minimal mass loss of 0.02-0.03 mg, suggesting they are viable candidates for specific PFM applications. Source: arXiv

This large-scale comparative qualification provides a valuable dataset for both public programs like ITER and the growing private fusion industry. By testing materials from multiple developers under identical, well-diagnosed conditions in the DIII-D tokamak, the campaign accelerates the technology-readiness timeline for pilot plant construction. Future work will likely focus on higher-dose neutron irradiation and longer-duration plasma exposures to further assess the most promising candidates identified in this study, particularly their resilience to the synergistic effects of high heat flux and neutron bombardment over a component's lifetime. Source: arXiv