Experimental measurement of deuterium concentration and depth profiling in tungsten by radio frequency glow discharge optical emission spectroscopy

Abstract

For a detailed understanding of fuel retention characterization, especially in-depth profile analysis of plasma-facing materials, radio frequency glow discharge optical emission spectroscopy (RF-GDOES) method was applied to determine the deuterium depth concentration. Tungsten or titanium targets were co-deposited in deuterium atmosphere by magnetron sputtering, and these deposited films with different deuterium contents and film thicknesses were used as the standard samples for RF-GDOES measurement. Rutherford backscattering spectroscopy (RBS) and thermal desorption mass spectrometry (TDS) were used to measure the metal and deuterium concentrations in the standard films, respectively. After the standardization of deuterium concentration and sample sputtering rate when tested by RF-GDOES, deuterium concentration and depth profiling of deuterium-exposed tungsten samples were obtained and subsequently verified by compared with results by TDS. Results showed the deuterium concentration in deuterium-exposed tungsten has a high concentration peak about 0.002–0.013 at.fr. within 125 nm near-surface, and then reduced by two orders of magnitude from surface to depth with a minimum concentration of few 10−5at.fr. With increasing the incident deuterium fluence, deuterium concentration increased obviously in the first 6 μm near the surface. Under low incident fluence, the total released deuterium amounts obtained from RF-GDOES and TDS methods agree within the experimental error. However, the total released deuterium amounts measured by RF-GDOES were smaller than those of the TDS method under high fluence due to reason of the increasing diffusion depth and inhomogeneity of deuterium in tungsten.