Development activities of the high heat flux scraper element

Fusion Engineering and Design

Greuner

Ehrke

et al. 2016

Self Cite

h i g h l i g h t s• Aim of scraper element: reduction of heat loads on high heat flux divertor ends.• Design: actively water-cooled for 20 MW/m 2 local heat loads.• Technology: CFC NB31 monoblocks bonded by HIP to CuCrZr cooling tube.• Successful high heat flux testing up to 20 MW/m 2 . a b s t r a c tThe water-cooled high heat flux scraper element aims to reduce excessive heat loads on the target element ends of the actively cooled divertor of Wendelstein 7-X. Its purpose is to intercept some of the plasma fluxes both upstream and downstream before they reach the divertor surface. The scraper element has 24 identical plasma facing components (PFCs) divided into 6 modules. One module has 4 PFCs hydraulically connected in series by 2 water boxes. A PFC, 247 mm long and 28 mm wide, has 13 monoblocks made of CFC NB31 bonded by hot isostatic pressing onto a CuCrZr cooling tube equipped with a copper twisted tape. 4 full-scale prototypes of PFCs have been successfully tested in the GLADIS facility up to 20 MW/m 2 . The difference observed between measured and calculated surface temperatures is probably due to the inhomogeneity of CFC properties. The design of the water box prototypes has been detailed to allow the junction between the cooling pipe of the PFCs and the water boxes by internal orbital welding. The prototypes are presently under fabrication.

Section: Water Box Prototypementioning

confidence: 99%

Prototyping phase of the high heat flux scraper element of Wendelstein 7-X

Fusion Engineering and Design

Greuner

Ehrke

et al. 2016

Self Cite

“…Design activities have been carried out to prepare a possible fabrication of the water-cooled scraper for the second operation phase [6]. Full-scale prototypes have been manufactured and tested to validate the design and to develop required technologies.…”

Section: Introductionmentioning

confidence: 99%

Design and Test of Wendelstein 7-X Water-Cooled Divertor Scraper

IEEE Trans. Plasma Sci.

Greuner

Ehrke

et al. 2018

Self Cite

Abstract-Heat load calculations have indicated the possible overloading of the ends of the water-cooled divertor facing the pumping gap beyond their technological limit. The intention of the scraper is the interception of some of the plasma fluxes both upstream and downstream before they reach the divertor surface. The scraper is divided into six modules of four plasma facing components (PFCs); each module has four PFCs hydraulically connected in series by two water boxes (inlet and outlet). A full-scale prototype of one module has been manufactured. Development activities have been carried out to connect the water boxes to the cooling pipes of the PFCs by tungsten inert gas internal orbital welding. This prototype was successfully tested in the GLADIS facility with 17 MW/m2 for 500 cycles. The results of these activities have confirmed the possible technological basis for a fabrication of the water-cooled scraper.

“…A high heat-flux scraper element (HHF-SE), if placed in front of the divertor pumping gap, would intercept a portion of the convective flux and protect the divertor edges (see Fig. 1) [2]. This HHF-SE has been designed using carbon fiber reinforced carbon composite monoblocks which have been shown to withstand steady-state heat fluxes up to 20 MW/m 2 [3][4].…”

Section: Introductionmentioning

confidence: 99%

Design of the Wendelstein 7-X inertially cooled Test Divertor Unit Scraper Element

Lumsdaine

Fusion Engineering and Design

Fellinger

et al. 2015

The Wendelstein 7-X stellarator is scheduled to begin operation in 2015, and to achieve full power steady-state operation in 2019. Computational simulations have indicated that for certain plasma configurations in the steadystate operation, the ends of the divertor targets may receive heat fluxes beyond their qualified technological limit. To address this issue, a high heat-flux "scraper element" (HHF-SE) has been designed that can protect the sensitive divertor target region. The surface profile of the HHF-SE has been carefully designed to meet challenging engineering requirements and severe spatial limitations through an iterative process involving physics simulations, engineering analysis, and computer aided design rendering. The desire to examine how the scraper element interacts with the plasma, both in terms of how it protects the divertor, and how it affects the neutral pumping efficiency, has led to the consideration of installing an inertially cooled version during the short pulse operation phase. This Test Divertor Unit scraper element (TDU-SE) would replicate the surface profile of the HHF-SE. The design and instrumentation of this component must be completed carefully in order to satisfy the requirements of the machine operation, as well as to support the possible installation of the HHF-SE for steady-state operation.