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Plasma Physics (Physics/ECE/NE 922) Seminar
“Controlling plasma-material interactions with real-time powdered material injection”
Date: Monday, April 8th
Time: 12:00 pm - 1:15 pm
Place: 1227 Engineering Dr
Speaker: Florian Effenberg, PPPL
Abstract: In the DIII-D tokamak, coatings up to 10 nm thick were grown on plasma-facing components (PFCs) at 1 nm/s using boron (B) and silicon (Si) injections in both powder and pellet forms during L-mode and H-mode discharges. Utilizing the impurity powder dropper (IPD) and the impurity granule injector (IGI), materials were injected at rates of 1-200 mg/s, with varying sizes and speeds, enhancing wall conditions akin to glow discharge boronization by reducing impurity influxes and significantly increasing the density-to-gas fueling ratio. Post-mortem analysis confirmed the formation of B-C layers with average surface composition B:C∼1. Si pellet injection at a rate of 1-15 mg/s yielded Si-rich layers on the divertor tiles of at least 1 nm in thickness. The in-situ growth of thin films in real-time demonstrates the capability of surface material replenishment during long-pulse plasma operation or steady-state devices without ramp-down of the magnetic fields.

Concurrently, B and BN powder injections into the SAS-VW divertor demonstrated significant effects on heat flux and W erosion control without adversely affecting H-mode performance. Specifically, B injections at rates up to 25 mg/s resulted in a notable decrease in W deposition. In contrast, BN injections led to substantial X-point radiation, prominently reducing heat fluxes and W erosion through detachment. These outcomes underline the efficacy of powder injection techniques in managing plasma-material interactions, particularly in high-Z environments, highlighting their potential in next-step long-pulse devices.
Host: Prof. Oliver Schmitz and Prof. Carl Sovinec
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