Migration of artificially introduced micron-size carbon dust in the DIII-D divertor

Migration of pre-characterized carbon dust in a tokamak environment was studied by introduction of ∼30 mg of micron-size (∼6 μm median diameter) dust in the lower divertor of DIII-D using a DiMES sample holder. Direct exposure of the dust to high particle and heat fluxes in ELMing H-mode lower single-null discharges resulted in part of the dust being injected into the plasma. Following a brief exposure (∼0.1 s) at the outer strike point, 1.5–2% of the total dust carbon content (2 –3 × 1019 carbon atoms, equivalent to a few million dust particles) penetrated the core plasma, raising the core carbon density by a factor of 2–3. Individual dust particles were observed moving at velocities of 10–100 m/s, predominantly in the toroidal direction for deuteron flow to the outer divertor target, consistent with the ion drag force. The observed behavior of the dust is in qualitative agreement with modeling by the 3D DustT code.