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Doerner, Russ

Publications and source records attributed to Doerner, Russ.

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

FY2018 Fusion Theory and Simulation Milestone on Plasma Materials Interaction (PMI) (Final Report)

The interaction of the boundary plasma with the material surfaces in magnetically confined plasmas is among the most critical problems in fusion energy science. In FY2018, perform high performance computing simulations with coupled boundary plasma physics and materials surface models to predict the fuel recycling and tritium retention of the ITER divertor for D-T burning plasma conditions, accounting for erosion, re-deposition and impurity transport in the plasma boundary, and an initial evaluation of the influence of material deposition on the recycling and retention.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Low-energy helium plasma effects on textured micro-porous tungsten

The effects of low-energy helium plasma on surface evolution and restructuring of micro-porous tungsten and tungsten-rhenium micro-engineered materials was experimentally investigated. Tungsten foam samples of 45 and 80 Pores Per Inch (PPI) of three types of textured surface architecture (nodular W, dense Re-pillars, and W-coated Re-pillars) were exposed to low-energy helium plasma at 80 and 200 eV to fluence levels of 1, 2, and 7 x 10 25 m -2 at 1123 K. The sidewalls of Re pillars exhibited surface holes due to trapped helium while their tips were found to form complex nano-scale web structures, 100's of microns across, rather than nano-tendrils (fuzz) that are often observed in flat W samples. A nano-necklace bead/string structure was observed for the first time on Re pillars, likely driven by a high density of nano-meter size helium bubbles crowded near pillar tips. W-coated Re pillars exhibited typical fuzz nanostructures seen on flat and untextured W-foam, albeit much shorter. While the height of W-fuzz was found to depend on the square root of ion fluence, the nano-web height was found to be linearly dependent on ion fluence. The fuzz was found to grow much slower on nodular foams as compared to planar tungsten, by as much as 25% slower in the W-coated Re pillar samples. Weight loss due to ion sputtering was found to be significantly reduced in nodular foam as compared to planar tungsten, but was found to be more pronounced with Re pillars. Surface coverage by nano-webs may provide insulation against plasma disruptions and act as a passive Thermal Protection System (TPS) that may be ablated during severe plasma disruptions, thus protecting the underlying surface. W-pillars or W-coated Re-pillars are found to allow trapped helium to diffuse out of the surface instead of building up sub-surface stress.

36 MATERIALS SCIENCE↗