Material erosion and erosion products under plasma heat loads typical for ITER hard disruptions

Plasma/material interaction has been studied in disruption simulation experiments. Candidate divertor materials were exposed to heat loads expected for tokamak-reactor disruptions. It is shown that sudden evaporation of a thin material layer produces a cloud of vapor plasma, which acts as a thermal shield protecting the surface from further excessive evaporation. In terms of evaporation reduction a shielding factor is above 100, Formation and physical properties of the shielding layer are analyzed. Target plasma converts the incoming energy Bur into photon radiation. Radiation from target plasma is so intensive that it may cause erosion of nearby components. Surface damages result not solely from atomic vaporization but also from melt layer splashing for metals and brittle destruction for carbon-based materials. Erosion products are emitted as droplets (metal) and grains (carbon-based material). Melt layer splashing results in greater surface damages than vaporization, A contribution of brittle destruction to net erosion is under investigation now. (C) 2001 Elsevier Science B.V. All rights reserved.