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P: Plasmaphysik

P 12: Plasma Wall Interaction, Diagnostic and Low Temperature Discharges (Poster Session)

P 12.7: Poster

Freitag, 6. April 2001, 12:30–15:00, AT2

B₄ C limiter experiments at TEXTOR-94 — •B. Schweer¹, A. Pospieszczyk¹, A. Huber¹, G. Sergienko¹, J. Linke², G. Mank¹, V. Philipps¹, P. Wienhold¹, H. Bolt³, S. Kötterl³, and H. Renner⁴ — ¹Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, EURATOM Assoziation, Trilateral Euregio Cluster, 52425 Jülich — ²Institut für Werkstoffe und Verfahren der Energietechnik, Forschungszentrum Jülich GmbH — ³Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, 85748 Garching — ⁴IPP-Teilinstitut Greifswald, EURATOM Assoziation,17491 Greifswald

Outside the divertor region at W7-X the actively cooled stainless steel panels should be covered by low Z-materials. Plasma sprayed B₄C shows good thermo-mechanical properties and a continuous boronisation might offer low sputtering yields and oxygen gettering. Vacuum plasma spray B₄C coatings on copper limiters have been tested in discharges of TEXTOR-94. Since the limiters could not be actively cooled, large Cu blocks were selected to avoid significant temperature rises. Plasma conditions expected at W7-X are achieved in the plasma boundary of TEXTOR-94 about 1cm behind the last closed flux surface. The C-tiles of the top and bottom poloidal limiter were replaced by B₄C coated Cu-blocks. The limiter were exposed to the plasma for several hundred discharges. Additionally the material was introduced in 2 limiter locks, where the distance to the LCFS was varied. At that locations the surface and bulk temperature were recorded. These limiter were exchanged after about 40 discharges for visual and post-mortem analysis. The erosion of the limiter surface was monitored by spectroscopic methods.