This title appears in the Scientific Report : 2014 

Roughening and reflection performance of molybdenum coatings exposed to a high-flux deuterium plasma
Eren, B. (Corresponding Author)
Marot, L. / Ryzhkov, I. V. / Lindig, S. / Houben, A. / Wisse, M. / Skoryk, O. O. / Oberkofler, M. / Voitsenya, V. S. / Linsmeier, Ch. / Meyer, E.
Plasmaphysik; IEK-4
Nuclear fusion, 53 (2013) 11, S. 113013 -
Vienna IAEA 2013
10.1088/0029-5515/53/11/113013
Journal Article
Plasma-wall interactions
Please use the identifier: http://dx.doi.org/10.1088/0029-5515/53/11/113013 in citations.
Optical diagnostic systems of ITER are foreseen to include metallic, plasma-facing, electromagnetic radiation reflecting components called first mirrors (FMs). Molybdenum coatings are important candidates for these components. Depending on the local plasma parameters of the reactor, the mirrors may be under net erosion or deposition conditions. In this work, we exposed molybdenum coatings to a high-flux deuterium plasma in order to test their roughening limits under erosion conditions. The high energy of deuterium ions (500 eV on average) results in more vigorous roughening of the surface compared with lower energy ions (200 eV). Longer exposure (3 × 1020 ions cm−2) of the 200 eV ions results in only a slightly increased roughness compared with shorter exposure (6.8 × 1019 ions cm−2). Both phenomena match to the theory regarding roughening dynamics of physical sputtering. A comparison of results in this work with previous studies gives support to the hypothesis that roughening is flux and temperature dependent. Partial delamination of the coatings is observed upon exposure at room temperature, but not at an elevated temperature (200 °C). In summary, Mo coatings will remain functional in the ITER environment under the expected conditions. However, changes in the expected conditions such as 500 eV mean energy of impinging charge exchange neutrals or <100 °C surface temperature of the mirrors can lead to gradual or sudden failure of the coatings.