In situ measurements of low energy D plasma-driven permeation through He pre-damaged W

Abstract

Experiments concerning the effect of helium (He) plasma exposure on deuterium (D) plasma-driven permeation (PDP) through tungsten (W) foils in a linear plasma facility has been performed. 0.05 mm thick W foils were exposed to ~2×1020 m-2s-1 He plasma with various fluences at 883 K. After He irradiating, D permeation tests were performed for the samples and retention was also measured by high-resolution thermal desorption spectroscopy (TDS). It was observed that He pre-irradiation resulted in a significant reduction of D permeation and retention in W. Microstructure observation indicated that the surfaces of samples after He irradiation turned rough and He nanobubbles were formed near the surface. The defective structure including He nanobubbles very likely enhances D reemission and accordingly reduces the permeation and retention in He pre-irradiated W.