Structure of metallic coatings for impurity control in MACROTOR

The properties of atomic metal condensates are to a large extent determined by parameters such as: microstructure, temperature during deposition, interfacial phenomena, and deposit thickness. At elevated first wall temperatures (200-6000C), a homogeneous metallic film deposition can be achieved. For example, hydrogen embrittlement and flaking through hydride formation, currently a problem in fusion devices, can be avoided. The thickness of Ti-layers for acceptable impurity control must be at least a few hundred Angstroms because effective impurity control requires the physical covering of the impurity adsorbents on the surface. It is shown that thick coatings (micron range), which get formed by repetitive Ti-'gettering' in Macrotor, are likely to form a stable first wall, if properly deposited at elevated temperatures. (orig.)