Results and consequences of high heat flux testing as quality assessment of the Wendelstein 7-X divertor

• One third of the series production of the actively cooled divertor target elements for W7-X is completed.
• A statistical analysis of the CFC bonding quality was developed on the basis of high heat flux tests of 100 cycles at 10 MW/m2.
• The application of this method on the 14,000 CFC tiles allows a reliable quality assessment with reasonable test effort.
• The results confirm the high thermal performance of the delivered divertor elements.

The series manufacturing of the first 282 Wendelstein 7-X divertor elements was concluded in 2011. The divertor is designed to remove a steady-state heat load of 10 MW/m2. 940 target elements of five different types made of CuCrZr heat sinks and covered with 16,000 CFC NB31 flat-tiles have to be produced. Additional to quality assessment during the manufacturing process, a final assessment of the delivered elements with operational heat load is indispensable to ensure a constant high thermal performance of the installed divertor.Based on the results of the pre-series testing a statistical quality assessment method has been developed for the series production. The application of this method to the series elements ensures their thermal performance with reasonable high heat flux test effort.