The effect of W fuzz growth on D retention in polycrystalline W

The retention of hydrogen isotopes in W is one of the main limiting factors affecting the design and development of next-step fusion reactors, such as the international thermonuclear experimental reactor (ITER). Here, we report on D retention behavior under the steady-state He/D ion irradiations of polycrystalline W. We find that the D retention behavior in the W bulk is completely suppressed by the growth of high surface-to-volume W fuzz layer (1.1–4.0 μm thick) over the surface. Our analyses show that due to their frequent collisions in the W fuzz layer, the dose of D ions greatly decreases when they collide into the W bulk beneath the fuzz layer. The W fuzz layer with a high surface-to-volume ratio becomes an effective shield against the ion driven diffusion processes.