Development of tungsten coatings for application in fusion experiments

In the development of nuclear fusion into a future peaceful energy source, the scheme of magnetically confined fusion plasmas has experienced substantial progress in the last decades. Some of the main remaining materials issues are the high heat loads and the erosion of plasma-facing components by erosion from particle impact. Since component lifetime considerations and the negative influence of impurities on the plasma lead to opposite conclusions about the materials choice, an experimental investigation of the applicability of tungsten as plasma-facing material is currently performed at the tokamak fusion experiment ASDEX Upgrade in Garching, Germany. For this purpose an industrial scale method to coat graphite tiles with tungsten thin films was required. Therefore a comparative study of the heat load behaviour of coatings deposited with various PVD techniques was performed. Tungsten coatings on graphites and fiber reinforced carbons were investigated with respect to their properties relevant for fusion research including electron-beam loading with heat loads exceeding 20MW/m(2).