High-performing advanced tungsten materials under high particle flux and intense transients in DIII-D

High-performing advanced tungsten (W) materials were tested in the lower divertor of DIII-D as part of investigations of plasma facing material candidates for ITER and beyond. First, samples of micro-structured W, tungsten fiber reinforced tungsten (W_f/W) composites and ITER-grade W (IGW) were exposed to low-power L-mode plasmas using DiMES manipulator to study surface modifications, gross erosion and hydrogenic retention. The maximum target heat flux ~0.9 MW/m² for retention studies was determined using SMITER and Aria thermal modeling with input from IR camera measurements. Micro-structured W showed no surface modification. Comparison of the post-mortem D retention measurements for micro-structured W and IGW with simulations performed using ITMC-DYN package is discussed. Next, in H-mode experiments with ~40 Hz ELMs, ~2 MW/m² inter-ELM and up to 6 MW/m² intra-ELM heat fluxes, little to no surface damage was observed on small Ø 6 mm samples of W_f/W and IGW. Erosion measurements and surface characterization for these samples are presented. A Ø 34 mm W_f/W disk angled at 15 degrees towards the incident heat flux was exposed under the same H-mode conditions, causing partial edge melting. Post-exposure electron microscopy shows that fibers inhibit cross sample crack propagation.