Abstract
Investigations on dust in the full tungsten divertor tokamak, ASDEX Upgrade, are summarized. Newly designed collectors are used to distinguish plasma-produced dust from other kinds of debris. Whereas submicron particles are often tungsten spheres, larger ones are agglomerates from tungsten in a boron/carbon matrix. Extrapolation of the measurement yields 80 mg of carbon and 1200 mg of tungsten in the dust, including 510 mg of tungsten spheres. In the case of its mobilization, the amount of tungsten observed may constitute a significant impurity source. Droplets produced by arcs seem to be the production mechanism for tungsten spheres. The strong light emission of dust particles penetrating the scrape off layer (SOL) is rarely observed by a fast camera during normal discharges, but is very frequently observed after disruptions. As the particles follow straight lines, we infer only a weak interaction with the SOL plasma. This is also confirmed by the observation of fragile agglomerates.
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