Hydrogen trapping in carbon film: From laboratories studies to tokamak applications

Abstract

During the DITS (Deuterium Inventory in Tore Supra) project, inner vessel walls of Tore Supra tokamak have been loaded with deuterium during a specific plasma experiment based on long pulse operation. Then, and in order to determine where the deuterium used as a plasma fuel was lost in the plasma facing components, the Tore Supra limiter had been dismounted and post mortem analysis had been performed on samples coming from different places corresponding to erosion or deposited area. In this the thermo-desorption spectrometry (TDS) studies are presented. All the TDS spectra present independently to their origin the same behaviour e.g. 5 desorption bands at 560 K, 820 K, 1050 K, 1238 K and 1375 K. These bands correspond to different trapping processes in carbon material which are identified with the help of laboratories experiments. Finally, the spectra are fitted by a rate equation model in which one of the main parameter which is the exponential pre-factor is experimentally evaluated (2.7·1015 s−1). This gives the possibility to unambiguously determine the trapping energies for the 5 trapping processes: 1.8 eV, 2.8 eV 3.6 eV, 4.2 eV and 4.7 eV. The model uses a dispersion in energy around these values due to the complex structure of Carbon Fibre Composite.