Behaviour of Si and Ti doped carbon composites under exposure to the deuterium plasma

Studies of the deuterium interaction with carbon-based substrates were perf ormed for graphite doped either with SiC or with TiC (5% or 10% of Si or Ti ) and carbon fibre composites doped with SiC (2.5; 8; 40% of carbide). Nond oped CFC and graphite were used as reference materials. The materials were exposed to the deuterium plasma in a tokamak or in simulators of plasma-sur face interactions. The main emphasis was on the determination of the deuter ium retention in the near surface region and in the bulk of the composites. Characterisation of the non-exposed and deuterium irradiated substrates wa s accomplished by means of RES, NRA, EDS, laser profilometry and ultra-high resolution microscopies. The most important observations are connected wit h the penetration of the deposited deuterium into the bulk of composites - even a few millimetres beneath the surface. The rate of the process was fou nd to be related to the structure of materials and, to a certain extent, to the content of dopants. (C) 1998 Elsevier Science B.V. All rights reserved .