Effects of carbon impurity on deuterium retention in VPS-tungsten coatings exposed to JT-60U divertor plasmas

Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

“…The injected carbon migrated into the tungsten coating layer much deeper than the depth expected by thermal diffusion [9]. Deuterium was trapped predominantly by carbon accumulated in the tungsten coating layer, resulting in higher deuterium retention compared with that in layers exposed to pure deuterium plasma [8].…”

“…Depth profiles of deuterium, carbon, and tungsten were measured using a secondary ion mass spectroscope (SIMS, ULVAC PHI, ADEPT 1010) at a pressure below 5 Â 10 À8 Pa [8,9]. A 5-keV cesium ion beam (Cs + ) with a current of 200 nA was focused onto the coating layer with a diameter of $20 lm and was rasterscanned over an area of 300 Â 300 lm.…”

“…The effects of simultaneous injection of carbon and deuterium ions on deuterium retention in tungsten coating layers on divertor tiles have been investigated by exposure to divertor plasmas in JT-60U [8,9]. The injected carbon migrated into the tungsten coating layer much deeper than the depth expected by thermal diffusion [9].…”

Chemical Binding States of Carbon Atoms Migrated in Tungsten Coating Layer Exposed to JT-60U Divertor Plasmas

“…In these tokamaks, tungsten-coated tiles were installed to investigate feasibility of tungsten as the PFCs, for example, tungsten accumulation and its suppression in the core plasmas [5,6], tungsten migration [7,8] and in-vessel deuterium retention [9]. After experimental campaigns, a part of the tungsten-coated tiles were taken out and deuterium and carbon accumulation in the tungsten coating layers were investigated [10][11][12]. Carbon was injected and accumulated in the tungsten coating layer [10,11].…”

“…Carbon was injected and accumulated in the tungsten coating layer [10,11]. It was found that the carbon migration depth was longer than that of thermal diffusion length in tungsten lattice [12]. The deuterium atoms were predominantly trapped by the migrated carbon atoms in the tungsten coating layer [12].…”