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

Abstract

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.

Progress in the production of the W7-X divertor target modules

“…About 8% of the TEs were HHF tested in the GLADIS [8] facility at IPP. The performed statistical assessment confirmed the stable production and the high thermal performance of the delivered TEs [9].…”

Summary of the production of the divertor target elements of Wendelstein 7-X

“…The applied procedure was based on a statistical assessment of the standard tiles with the further possibility of tests on demand to detect any quality deviation [13]. Only a reduced number of the lower loaded edge tiles, typically 2-4 edge tiles per element type, were tested.…”

Local copper coating of the connectors of the divertor target elements of Wendelstein 7-X

“…During the incoming inspection performed by IPP, 5% of the target elements of the second production phase (33 over 680) did not pass the He leak test in vacuum oven. About 10% of the series target elements were high heat flux tested in the GLADIS facility [4]. In addition only one element developed a He leak after testing in GLADIS.…”