Deuterium retention of low activation ferritic steel and boronized wall in JFT-2M

Deuterium retention and erosion of F82H exposed to JFT-2M plasmas and the effect of boronization on the deuterium retention were examined based on material probe analysis. The amount of retained deuterium almost saturated after 300 tokamak discharges of deuterium. The retention of helium was clearly observed after helium glow discharge. The desorption temperature was approximately 600 K. While no significant change in the surface atomic composition was observed after the exposure of tokamak discharges, the mixture layer of carbon, iron and oxygen was observed after the helium glow discharge due to surface erosion and redeposition of eroded particles. After the boronization using trimethylboron, both carbon and boron deposited at the surface. The atomic ratio of B to C was 1/3. The amount of retained deuterium significantly increased, three times larger than that before the boronization, owing to that a large amount of deuterium is trapped in the carbon content.