Impact of H-mode plasma operation on predamaged tungsten divertor tiles in ASDEX Upgrade

Karl Krieger (Corresponding Author), M. Balden, B. Böswirth, J.W. Coenen, R. Dux, H. Greuner, B. Göths, Antti Hakola, Aki Lahtinen, Jari Likonen, Th. Löwenhoff, P. De Marné, G. Pintsuk, V. Rohde, G. De Temmerman, M. Wirtz

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Abstract

The effect of continued plasma exposure on two divertor target tiles intentionally damaged before installation was studied for ASDEX Upgrade H-mode discharge conditions. On one tile, made of molybdenum alloy (TZM), superficial melt damage was created in the GLADIS high heat flux test facility. To measure the influence of the resulting surface corrugations on erosion, the tile surface was subsequently covered with a 20 nm tungsten marker layer. A second tile, made of tungsten, was pre-damaged by exposure to 2 × 105 consecutive ELM-like heat pulses in the electron beam test facility JUDITH, which resulted in formation of an extended crack network. Both tiles were placed at the outer divertor target of ASDEX Upgrade using the DIM-II divertor manipulator and exposed to a series of 15 identical H-mode discharges. The surface state of both tiles was documented pre- and post-exposure using electron scanning microscopy. SEM analysis of the crack network's microscopic structure did not reveal any additional damage created by plasma exposure but showed deposition of migrated wall materials inside shadowed areas. The erosion pattern of the W-marker layer revealed regions of net erosion as well as of net deposition in the corrugated melt zone. Net erosion up to complete removal of the W marker layer was found at elevated parts of the surface oriented towards the incident plasma flux whereas net deposition was found in corresponding shadowed areas. In contrast, the undamaged surface parts showed a uniform erosion pattern determined by incident plasma ion flux and temperature.
Original languageEnglish
Article number014037
Number of pages7
JournalPhysica Scripta
Volume2020
Issue numberT171
DOIs
Publication statusPublished - 4 Mar 2020
MoE publication typeA1 Journal article-refereed
Event17th International Conference on Plasma-Facing Materials and Components for Fusion Applications, PFMC 2019 - Eindhoven, Netherlands
Duration: 20 May 201924 May 2019

Keywords

  • plasma-facing components
  • components
  • tungsten
  • edge-localized modes
  • divertor

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    Krieger, K., Balden, M., Böswirth, B., Coenen, J. W., Dux, R., Greuner, H., Göths, B., Hakola, A., Lahtinen, A., Likonen, J., Löwenhoff, T., De Marné, P., Pintsuk, G., Rohde, V., De Temmerman, G., & Wirtz, M. (2020). Impact of H-mode plasma operation on predamaged tungsten divertor tiles in ASDEX Upgrade. Physica Scripta, 2020(T171), [014037]. https://doi.org/10.1088/1402-4896/ab4bb3