Carbon diffusion from a-C:H coatings into the bulk of the TEXTOR liner
Long-term samples literally cut out of the TEXTOR liner after 31 months of tokamak operation and with 81 a-C:H coatings and corresponding wall-cleaning cycles have been analysed for carbon and carbide contents. The analysis consisted of AES depth-profiling, AES line-scanning, and electro-chemical etching of sample cross-sections. A 10 to 35 micron thick under-stoichiometric carbide layer with 10 at.% of carbon at the surface was found. There is an unpredicted correlation between the thickness of the individual coatings and the carbide layer, although 50% fluctuations in the toroidal distribution are observed. Apparently more than 20% of the carbon supply to the surface during coating is built into the liner surface, despite the glow discharge cleaning of the remaining a-C:H before each new deposition. The presence of the carbide layer may in general cause changes in the mechanical and thermal properties of the first wall in plasma devices which are routinely carbonised.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 162-164 (1989), pp. 881-886
Record Number: 199010365 / Last updated on: 1994-12-01
Original language: en
Available languages: en