Mixed-material hydrogen inventory and removal techniques in pisces

The deuterium inventory in mixed-material surface layers formed during plasma bombardment of beryllium and tungsten samples has been investigated. The temperature of the sample during the formation of the layer plays a dominant role in determining the deuterium content of the layers. For carbon containing mixed-material films, the retention properties of the films are similar to that of pure graphite and can easily dominate the retention expected in the underlying substrate material. Cathodic transfer arc cleaning has been investigated as a mechanism to remove mixed-material films after they have formed on plasma-facing materials. The arc cleaning technique has been demonstrated to reduce the amount of deuterium in the coated samples to levels below our detection limit. (author)