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(EX/D1-4) Operation of ASDEX Upgrade with Tungsten Coated Walls

V. Rohde1), R. Neu1, R. Dux1, A. Geier1, X. Gong1, A. Kallenbach1, K. Krieger1, S. Lindig1, H. Maier1, W. Mueller1, R. Pungno1, W. Schneider1
1) Max Planck Institut für Plasmaphysik, Garching, Germany

Abstract.  An alternative for low-Z materials in the main chamber of a future fusion device are high-Z materials, but the maximal tolerable concentration in the plasma core is restricted. A step by step approach to employ tungsten at the central column of ASDEX Upgrade was started in 1999. Meanwhile almost the whole central column is covered with tiles, which were coated by PVD with tungsten. Up to now 9000 s of plasma discharge covering all relevant scenarios were performed. Routine operation of ASDEX Upgrade was not affected by the tungsten. Typical concentrations below 10- 5 were found. The tungsten concentration is mostly connected to the transport into the core plasma, not to the tungsten erosion. It can be demonstrated, that additional central heating can eliminate the tungsten accumulation. These experiments demonstrate the compatibility of fusion plasmas with W plasma facing components under reactor relevant conditions. The erosion pattern found by post mortem analysis indicates that the main effect is ion sputtering. The main erosion of tungsten seems to occur during plasma ramp-up and ramp-down.

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IAEA 2003