Overview of the Second Stage in the Comprehensive Mirrors Test in JET

First Mirror Test for ITER in JET with carbon walls has been completed. 30 polycrystalline Mo mirrors including 4 coated with a 1µm Rh film were exposed to plasma in the divertor region and in the main chamber. The mirrors were installed in 8 cassettes of the pan-pipe shape. Reflectivity of all mirrors exposed in the divertor has been degraded by 80-90% because of formation of thick (>20µm) flaking co-deposits on surfaces. Only small reflectivity losses (5-10%) occurred on mirrors located at the channel mouth of the cassettes from the main chamber wall. This is due to the in-situ removal of deposited species by charge exchange neutrals. Deuterium, 12C and 9Be are the main isotopes detected on surfaces, but other isotopes (13C) are also found in some locations thus indicating differences in the material migration. Rh-coatings with initial reflectivity 30% better than that of pure Mo survived the test without detachment but their resultant reflectivity was the same as of the exposed Mo surfaces.
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