Performance of Carbon Tiles and in situ Carbon Coatings in Jet and Textor

The Joint European Torus (JET) was initially built with metallic walls (Nicrofer 7612LC) and four graphite limiters. Gradually more and more graphite protection was added, and it now covers 50% of the wall. The inboard wall was covered with graphite tiles early in JET's operation to protect the wall from damage, and two toroidal belt limiters have been added to increase JET's power-handling capacity. Carbonization has been used as an additional tool to achieve certain benefits and has been developed at the Tokamak Experiment for Technically Oriented Research (TEXTOR) as a method to simulate, for a short time, an all-carbon machine and as a means to control density and impurity production. The benefits of the extensive use of graphite for protection and limiters and of the deliberate application of thin carbon layers are reviewed. Attention is given to the changes in the material under plasma exposure and the damage due to the plasma contact and the machine operation under those conditions. The role of the parameters of the scrape-off layer in the explanation and prediction of the plasma/wall interaction is emphasized.