Properties of tungsten coatings deposited onto fine grain graphite by different methods

Tungsten coatings on fine grain graphite with film thicknesses in the micrometer range were prepared by three different methods: electron beam evaporation, magnetron sputtering, and arc deposition. They were compared with respect to properties relevant for the application of such systems in the nuclear fusion experiment ASDEX Upgrade. The content of light impurities was determined by sputter XPS. A deposition parameter study for magnetron sputtered coatings is presented; the formation of compressive stress is identified to be the major drawback of this method. Furthermore, experiments with thermal loading by an electron beam facility are presented.