High heat flux performance of actively cooled divertor mock-ups

For the divertor of NET, actively cooled brazed CC/refractory metal mock-ups with an active length of 320 mm have been manufactured by Metallwerk Plansee, Austria, in order to evaluate the high heat flux performance of such structures. Seven tiles of CC material, 26 × 44.5 × 9 mm3, are brazed to an “interlayer” of TZM with a Zr braze. Subsequently this interlayer is brazed to a TZM body with a CuPd alloy. Inside the TZM body a tube of MoRe provides active cooling. In the ion beam test facility at KFA Jülich two test series were performed. In order to determine the maximum tolerable heat load, the applied power density was increased stepwise at constant pulse lengths of 30 s in screening tests. The thermal fatigue behaviour of the divertor components was investigated by thermal cycling.