CONTAMINATION OF THE JET LIMITERS WITH METALS DURING THE DIFFERENT OPERATIONAL PHASES

The surface layers of tiles from the carbon limiters in octant 1, ocant 4 and the RF-antenna limiters were analyzed after the end of the first three experimental sessions of JET, 1983, 1984 and 1985. On all tiles contaminants were found from the vessel walls and the RF antennae. In general on all areas deposition and erosion was observed. At the part of the tiles in direct contact with the plasma the erosion dominates. whereas deposition dominates on the outer parts of the limiter radially further away from the plasma. In the small gaps between adjacent limiter tiles, deposited layers of carbon having a thickness of several mu m were found, which were partly flaked and contained metallic impurities. Electrical are tracks were observed on the limiter tiles and in the area between limiter tiles.