He-cooled demo divertor: Design verification testing against mechanical impact loads

A modular He-cooled divertor concept for DEMO has been developed at Karlsruhe Institute of Technology. The design goal is to achieve a DEMO-relevant high heat flux of 10 MW/m2. The reference design HEMJ (He-cooled modular divertor with multiple-jet cooling) uses small finger modules, which consist of a tungsten tile and a thimble made of tungsten alloy. Both components are connected by soldering. They are cooled by helium gas (10 MPa, 634 °C) impinging directly onto the inner heated surface of the thimble. One of the most difficult to predict incident events is the disruption that may damage the divertor structure by an extraordinary impact loading. This danger is particularly acute by the brittle property of the tungsten material, which is generally characterized by the DBTT. In this paper an estimate of the mechanical impact loading induced by electro-magnetic forces during a disruption and an appropriate experimental setup are outlined, and the test results discussed.