Electric Field and Hot Spots Formation on Divertor Plates
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Abstract
In this paper, we consider the intensive erosion of tungsten brush-type armour structures that face the plasma in divertor fusion reactors. Surface erosion caused by multiple transient events (ELMs, disruption, etc.) could lead to the formation of a corrugated wedge-type shape. Our analysis shows that the augmentation of surface roughness increases the electric field at the vicinity of the wedge-type tips, thus enabling the formation of electric arcs. Specifically, under reactor conditions, the breakdown of the sheath potential may trigger unipolar arcs that will strongly contaminate the plasma with the resulting tungsten ions. We show that the erosion caused by arcs is almost two orders of magnitude larger than that caused by DT ion sputtering and comparable with that caused by self-sputtering.
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