Design and Preparation of Water-Cooled Plasma-Facing Mockups with Diamond/Copper Composite Interlayer

A monoblock mockup for a divertor uses too much tungsten of high gravity. Segmentation of tungsten armor in the monoblock or macrobrush mockups can reduce excess thermal stress caused by the about 3.5 times difference of thermal expansion coefficient between CuCrZr and tungsten, but it is not enough to avoid cracking of the welding interface between tungsten and CuCrZr because of initial semibrittlement and embrittlement of the tungsten armor in service. In this paper, an interlayer of diamond/Cu composite was inserted between tungsten and CuCrZr to reduce the interfacial stress of welded dissimilar materials. Armor of laminated or macrobrush tungsten was designed to decrease the stress concentration of the welding interface. A Cu foil was inserted between the tungsten armor and the diamond/Cu composite to increase welding strength. The plasma-facing mockups made of W-diamond/Cu-CuCrZr or W-diamond/Cu-12Cr RAFM were designed after optimizing by thermal analysis using finite element method and were prepared by a cubic press for producing diamond. The welding properties and microstructures of the dissimilar materials were investigated. Several mockups were connected to prepare a plasma-facing component by penetrating a CuCrZr tube into several CuCrZr heat sinks. The thermal expansion coefficient of the diamond/Cu interlayer is near that of tungsten, and its thermal conductivity is higher than that of CuCrZr. Plastic copper foils can relax thermal stress to avoid cracking in the welding interface. So, this water-cooled plasma-facing component should be better to dissipate the high heat flux of the divertor in fusion reactors.