Effect of magnetic topology and injection location in DIII-D real-time wall conditioning experiments*

Modeling with EMC3-EIRENE reveals the role of the parallel impurity forces, including the scrape-off layer (SOL) main ion flows, on the edge transport of injected material and ionized impurities. New analysis compares impurity powder injections in DIII-D lower single null, upper single null, and double null configurations with plasma edge transport and dust migration and ablation modeling. Materials in powder and granular form have been injected into various divertor configurations for real-time wall conditioning, ELM control, and divertor power exhaust mitigation at DIII-D. Changes in the divertor configuration lead to a re-direction of SOL flows associated with changing drag forces acting on the injected material favoring conditioning of plasma-facing components on either the low field side or the high field side. Poloidal shifts of the injection location can also modify the penetration depths and trajectories of injected materials in the plasma boundary. Such changes ultimately affect the local deposition of materials on plasma-facing components, which is critical for active conditioning and replenishment of functional coatings in future long-pulse scenarios.