First Mirrors Test in JET for ITER: An overview of optical performance and surface morphology

M. Rubel, J.P. Coad, G. De Temmerman, A. Hakola, D. Hole, J. Likonen, Inge Uytdenhouwen, A. Widdowson, JET-EFDA contributors, Rachid Chaouadi

    Research outputpeer-review


    Metallic mirrors will be essential components of all optical systems for plasma diagnosis in ITER. A comprehensive First Mirror Test (FMT) has been carried out in the JET tokamak. The exposure was followed by a characterisation of mirrors and their carriers. The main results obtained by optical and surface analysis methods are: (i) reflectivity of all tested mirrors is degraded either by erosion with charge exchange neutrals or by the formation of thick deposits; (ii) deuterium and carbon are the main elements detected on all mirror surfaces and the presence of beryllium is also found in several cases; (iii) thick deposits show columnar structure; (iv) bubble-like structures are detected in deposits; their formation is a probable reason for deposits’ disintegration and peeling-off; (v) the deposition in channels in the divertor cassettes is pronounced at the very entrance and then it sharply decreases with the distance from the plasma, l ~5–7µm.

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