Diffusive Behaviors of Deuterium in Nickel under Irradiation of Helium-3.

Abstract

Diffusion, permeation and trapping of deuterium in nickel exposed to a deuterium plasma were studied experimentally at temperatures of 455 to 568 K. One side of a nickel membrane was exposed to the plasma and the plasma-driven permeation was monitored. A beam of 3He irradiated the same side simultaneously to observe deuterium concentrations near the surface by means of the nuclear reaction analysis. The beam also produced traps and the observed concentration increased to be nearly saturated with the dose of 3He, while all deuteriums were dissolved at low doses. The trap concentrations were in the orders of 10−4 to 10−3 atom fraction. They tended to increase with decreasing temperatures. The traps were not bubbles but would be associated with radiation induced defects. The traps would cause a large amount of hydrogen isotopes retained in plasma-facing walls even at elevated temperatures.