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P: Plasmaphysik

P 4: Diagnostics II

P 4.1: Vortrag

Dienstag, 3. April 2001, 16:30–16:45, 2032

Measurement of the C⁶⁺-Density in the Edge-Plasma-Region of the W7-AS Stellarator — •Hartmut Ehmler, Kent McCormick, and W7-AS Team — Max-Planck-Institut für Plasmaphysik

Since summer of 2000, W7-AS is operating with an island-divertor. One of the major goals of the divertor is to control particle and power exhaust in such a way that sputtering of the graphit targets is minimized, since a high amount of carbon in the plasma leads to significant radiation losses.

At W7-AS the amount of C⁶⁺-impurities in the edge plasma is measured by means of the Lithium-beam-diagnostic using the light emitted by charge-exchange with fast injected Li-atoms. The concentration of C⁶⁺ is determined at 14 radial positions simultaneously by a new photomultiplier-based system. The results show that the C⁶⁺-density increases linearly during a variation of the central electron density from 2× 10¹⁹ up to 7× 10¹⁹ m⁻³. As a second parameter the influence of the magnetic configuration is studied.