Deuterium permeation through carbon-coated tungsten during ion bombardment

Abstract

Deuterium permeation during ion bombardment through tungsten membranes coated by amorphous carbon films was investigated and compared with the permeation through bare tungsten. The membrane was bombarded by D3+ ions with energies of 200 and 1200 eV/D at a temperature of 873 K. The thickness of the amorphous carbon film was 120–170 nm. Detailed characterization of the carbon films were performed using AFM, NRA, RBS, FIB/SEM and XPS. The influence of the carbon films on permeation were strong for both ion energies, but different for each energy. In the case of 200 eV/D ions, the film was completely removed by the end of permeation due to intensive chemical sputtering, the lag time of permeation was much longer than for the bare membrane, and the permeation rate rose to a maximum value close to the bare membrane and then decreased to lower values. In the case of 1200 eV/D, the films were sputtered only very slowly, the lag time was much longer than in the case of the bare membrane but shorter than at 200 eV/D, and the permeation rate increased steadily up to several percents of the incident flux.