Composition of the plasma facing material Tokamakium

In experiments with magnetically confined hot plasmas in respect to controlled thermonuclear fusion, such as tokamaks or stellerators, the surface layers of the vessel walls are modified by the plasma by erosion, redeposition, hydrogen isotope implantation and heating due to the power load from the plasma. Thus, the composition and structure of the surface layers are finally different to those of the material initially installed. This new material at the surface layers of tokamak experiments is sometimes also named ‘Tokamakium’. Generally, all elements ever introduced into the vessel can be found in the surface layers of the plasma-facing wall tiles. At all areas of the plasma-facing components both erosion and deposition have been observed including the deposition of metal droplets. Some areas are erosion dominated, while at others deposition dominates with atomic depositions of up to several μm, which partly flake. The elements of dust particles introduced into the vessel by in-vessel works get mostly incorporated as impurities into the surface layers of the plasma facing material.