Development of high-Z plasma facing components for ITER

During the ITER EDA (Engineering Design Activity), the US Home Team developed improved methods for fabricating tungsten armored plasma facing components. Thermo-mechanical modeling indicated the desirability of using "brush-like" structures (clusters of small filaments or rods) as a means of reducing thermal stresses. The commercial availability of tungsten welding electrode rods (1.6 mm and 3.2 mm diameter) significantly reduced the raw material costs. Three approaches were developed: (1) Cu is plasma sprayed to the W brushes followed by diffusion bonding or e-beam welding the copper backing to the CuCrZr heat sink, (2) Molten Cu is cast directly on the tips of the W brushes followed by the diffusion bonding step, and(3) W rods are sputter-coated with a bonding aid and are directly bonded to the CuCrZr heat sink using HIP or vacuum hot pressing. High heat flux testing was performed up to 18 MW/m(2) without damage to two small-scale divertor mockups.