Study of brittle destruction and erosion mechanisms of carbon-based materials during plasma instabilities

Erosion damage due to plasma instabilities such as hard disruptions, edge-localized modes, and vertical displacement events remains a major obstacle to successful realization of the tokamak-reactor concept. As a result of these plasma instabilities, intense plasma energy that is deposited during short periods can cause severe erosion, structural damage, and surface modifications of the plasma-facing materials. Experimental work is being carried out at the high-power VIKA-93 plasma-gun facility in the Efremov Institute, Russia. Interesting results were obtained during preliminary heating of the samples (to 1200°C) and use of maximum plasma gun parameters, i.e., Ein=30 MJ/m2, τ=360 μs. In all samples, a large increase in weight loss (up to 80%) was observed during plasma bombardment when preheating was used. Scanning electron microscope investigations have demonstrated a considerable evolution of surface recrystallization processes, especially for preheated CFC materials. Significant differences among various carbon materials are found for specimens with and without preliminary heating.