Effect of Argon Ion Sputtering of Surface on Hydrogen Permeation through Vanadium, (II) Effect of Sputtering of Both Side Surfaces

As part of studies on plasma-wall interactions of fusion reactors, the effect of Ar ion sputtering of both the upstream side and the downstream side surfaces of a V coupon upon its H₂ permeability has been studied. The H₂ permeability measuring apparatus has been modified to install another ion gun for the use in sputtering the downstream side specimen surface. The H₂ permeation rates were measured at 673K by changing the H₂ pressure and sputtering mode. The downstream side sputtering has been observed to enhance the H₂ permeability, though its degree was smaller than that due to the upstream side sputtering. The both side sputtering resulted in the largest H₂ permeability value ever obtained for V. The rate of H₂ permeation through V seemed to be determined by the surface processes including the downstream side rather than the bulk diffusion even after the both side sputtering. Based on AES measurements, the enhancement of H₂ permeability caused by sputtering was attributed to the diminishing of the surface O impurity.