A Novel Divertor Design Based on a Tungsten Wire Brush Tile

195 A Novel Divertor Design Based on a Tungsten Wire Brush Tile--Materials and Electrochemical Research (MER) Corp., 7960 South Kolb, Tucson, AZ 85706-9237; (520) 574-1980 Dr. Sumit Guha, Principal Investigator Dr. Raouf O. Loutfy, Business Official DOE Grant No. DE-FG03-97ER82423 Amount: $75,000 High heat flux and plasma facing materials are critical to the development of practical applications of magnetic fusion energy. Tungsten-, beryllium-, and carbon-based materials are candidates for plasma facing components (divertor tiles) to be bonded to a copper heat sink for thermal management during plasma disruptions. Among the metallic candidates, beryllium is less attractive due to its brittleness and the environmental hazards associated with fine particulates of beryllium itself and beryllium oxide. By comparison, tungsten is attractive due to its lower expansion coefficient, moderately high thermal conductivity, low sputtering rate, high melting point, and low cost; unfortunately, tungsten is also brittle at low temperatures. Residual stresses generated at the interface during bonding a tungsten tile to a copper substrate can result in cracks in tungsten tile or separation from the underlying copper heat sink, especially under severe thermal shock conditions. Such an event would have catastrophic consequences within a fusion reactor. By contrast, a tungsten wire brush bonded to a copper heat sink would alleviate the above shortcomings due to its increased compliance. This Phase I project will develop a tungsten wire brush with >95 vol. percent tungsten wire loading, and bond the tile to an underlying dispersion-strengthened copper heat sink using a graded interface. Commercial Applications and Other Benefits as described by the awardee: The processing approach will build on a unique composite processing technology developed at this company. The joint will be characterized for both its strength and thermal fatigue resistance by high heat flux testing at Sandia National Laboratories.