Trapping of Hydrogen in Molybdenum Bombarded with Helium-3 Ions

Hydrogen trapping in molybdenum was studied by use of an in-situ observation technique of deuterium depth profiling. A sample sheet was exposed to a deuterium plasma and deuterium permeation through it was monitored. The plasma-facing side was bombarded with ³He ions and deuterium depth profiles were observed by a nuclear reaction analysis under the plasma exposure. The result showed that traps, probably vacancies associated with radiation damages, were produced by the ion bombardment. From consideration of an equilibrium between trapped and dissolved deuterium, the equilibrium constant was estimated from the experimental data and the trapping energy of 1.1 eV was obtained. The production rate of the traps was found to be 0.007 from evolution of the concentration of trapped deuterium with the number of atomic displacements.