Helium Blistering in Metals

In a fusion reactor, various parts will be exposed to an important flux of helium atoms. Under certain conditions this will cause blistering resulting in surface erosion and plasma contamination. Measurements of the following blister parameters: blister skin structure and thickness, helium depth distribution, and swelling are discussed. These data refer mainly to 10 to 20 keV He blistering of Nb and Cu where the blister skin is apparently two times thicker than in the ''gas pressure'' model. The observation of a depletion at the center of the helium distribution, of bubbles in the skin, and of approximately 40 percent swelling allow us to conclude that this model is still valid.