Edge profiles and limiter tests in Extrap T2

New edge profile measurements, including calorimetric measurements of the p arallel heat flux, were made in Extrap T2. Test limiters of pure molybdenum and the TZM molybdenum alloy have been exposed in the edge plasma. The sur face damage was studied, mainly by microscopy. Tungsten coated graphite pro bes were also exposed, and the surfaces were studied by microscopy, ion bea m analysis and XPS. In this case cracking and mixing of carbon and tungsten at the interface was observed in the most heated areas: whereas carbide fo rmation at the surface was seen in less heated areas. In these tests pure M o generally fared better than TZM, and thin and cleaner coatings fared bett er than thicker and less dean. (C) 1999 Elsevier Science B.V. All rights re served.