Erosion products of ITER divertor materials under plasma disruption simulation

Candidate ITER divertor armor materials: carbon–fiber-composite and four tungsten grades/alloys as well as mixed re-deposited W+Be and W+C layers were exposed in electrodynamic plasma accelerator MKT which provided a pulsed deuterium plasma flux simulating plasma disruptions with maximum ion energy of 1–2 keV, an energy density of 300 kJ/m2 per shot and a pulse duration of ∼60 μs. The number of pulses was from 2 to 10. The resultant erosion products were collected on a basalt filter and Si-collectors and studied in terms of morphology and size distribution using both scanning and transmission electron microscopy. Metal erosion products usually occurred in the form of spherical droplets, sometimes flakes. Their size distribution depended on the positioning of the collector. Simultaneously irradiated W, CFC and mixed W+Be targets appeared to have undergone a greater erosion than the same targets irradiated individually. Particles sized from 0.01 to 30 μm were found on collectors and on a molten W-surface. A model of droplet emission and behavior in shielding plasma is provided.