Status of development of the EU He-cooled divertor for DEMO

A modular He-cooled divertor concept for DEMO is being investigated at Forschungszentrum Karlsruhe (FZK) within the framework of the EU power plant conceptual study. The design goal is to reach a heat flux of at least 10 MW/m. The reference design HEMJ (helium-cooled modular divertor with jet cooling) consists of a hexagonal tungsten tile which is brazed to a thimble made of W-1%La2O3. The cooling is realized by impingement jets of high pressure helium through an array of small jet holes located at the top of a cartridge made of ODS Eurofer. The current divertor work programme focuses on manufacture and high-heat-flux tests of prototypical tungsten mock-ups to demonstrate the manufacturability and the performance of the design. The tests were performed in a combined helium loop and Tsefey EB facility at Efremov. The first two high-heat-flux test series on 1-finger mock-ups in 2006-2007 already confirmed the divertor performance. Clear progress was achieved in the continuation third high-heat-flux test series in 2008 after the quality in mock-up manufacturing has been significantly improved. Technological study on fabrication of a 9-finger module of stain less steel was also successfully performed. First thermo-hydraulic tests showed uniform distribution of mass flow rates which agrees well with calculation results.