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ABSTRACT: The conceptual design of a solid tungsten divertor for ASDEX Upgrade (AUG) is presented. The Div-III design is compatible with the existing divertor structure. It re-establishes the energy and heat receiving capability of a graphite divertor and overcomes the limitations of tungsten coatings. In addition, a solid tungsten divertor allows us to investigate erosion and bulk deuterium retention as well as test castellation and target tilting. The design criteria as well as calculations of forces due to halo and eddy currents are presented. The thermal properties of the proposed sandwich structure are calculated with finite element method models. After extensive testing of a target tile in the high heat flux test facility GLADIS, two solid tungsten tiles were installed in AUG for in-situ testing.
Physica Scripta 12/2011; 2011(T145):014068. · 1.20 Impact Factor
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J Boscary, B Böswirth,
H Greuner,
P Grigull,
M Missirlian,
A Plankensteiner,
B Schedler,
T Friedrich,
J Schlosser,
B Streibl,
H Traxler
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ABSTRACT: The assembly of the highly-loaded target plates of the WENDELSTEIN 7-X (W7-X) divertor requires the fabrication of 890 target elements (TEs). The plasma facing material is made of CFC NB31 flat tiles bonded to a CuCrZr copper alloy water-cooled heat sink. The elements are designed to remove a stationary heat flux and power up to 10 MW m−2 and 100 kW, respectively. Before launching the serial fabrication, pre-series activities aimed at qualifying the design, the manufacturing route and the non-destructive examinations (NDEs). High heat flux (HHF) tests performed on full-scale pre-series TEs resulted in an improvement of the design of the bond between tiles and heat sink to reduce the stresses during operation. The consequence is the fabrication of additional pre-series TEs to be tested in the HHF facility GLADIS. NDEs of this bond based on thermography methods are developed to define the acceptance criteria suitable for serial fabrication.
Physica Scripta 03/2007; 2007(T128):195. · 1.20 Impact Factor
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ABSTRACT: Vacuum plasma-spraying (VPS) can be used for the industrial deposition of thick W coatings on actively water-cooled components made of low activation steel or stainless steel. Mock-ups made of martensitic steels, EUROFER and F82H, as well as steel 316L, were coated with 2 mm thick W-VPS layers. The coated materials are candidates for first wall components (ITER and DEMO) receiving moderate heat load of up to 1 MW/m2. Mixed tungsten/steel interlayers were applied to reduce the residual and thermal stresses at the substrate–coating interface and to improve the adhesion of the coating. The advantage of this mixed interlayer is that no further (high activation) materials have to be introduced to improve coating adhesion.The characterisation of the W-VPS layers includes the evaluation of the coating microstructure, the measurement of physical and mechanical properties and the metallographical examination before and after heat load tests.Heat load tests with steady state operation up to 2.5 MW/m2 and cycling heat loads of 2 MW/m2, were successfully completed. They confirm the thermomechanical suitability of industrially manufactured W-VPS coatings for plasma facing first wall components made of steel.
Fusion Engineering and Design.
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H. Greuner,
M. Balden, B. Böswirth,
H. Bolt,
P. Grigull,
G. Hofmann,
T. Huber,
W. Kasparek,
A. Killinger,
M Mayer,
R. Neu,
H Renner
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ABSTRACT: The fabrication of the actively cooled high-heat flux divertor of the WENDELSTEIN 7-X stellarator (W7-X) requires the delivery of 890 target elements, which are designed to withstand a stationary heat flux of 10 MW/m2. The organization of the manufacturing and testing route for the serial fabrication is the result of the pre-series activities. Flat CFC Sepcarb® NB31 tiles are bonded to CuCrZr copper alloy cooling structure in consecutive steps. A copper layer is active metal cast to CFC tiles, and then an OF-copper layer is added by hot isostatic pressing to produce bi-layer tiles. These tiles are bonded by electron beam welding onto the cooling structure, which was manufactured independently. The introduction of the bi-layer technology proved to be a significant improvement of the bond reliability under thermal cycling loading. This result is also the consequence of the improved bond inspections throughout the manufacturing route performed in the ARGUS pulsed thermography facility of PLANSEE. The repairing process by electron beam welding of the bonding was also qualified. The extended pre-series activities related to the qualification of fabrication processes with the relevant non-destructive examinations aim to minimize the risks for the serial manufacturing and to guarantee the steady-state operation of the W7-X divertor.
Fusion Engineering and Design.
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ABSTRACT: The plasma facing components (PFCs) of the W7-X are designed in detail. The current design of the target plates, baffle plates and wall protection is presented which takes into account the requirements of the plasma heating, diagnostic systems and mounting. Prototypes of baffle elements were tested with heat loading to investigate the long term behaviour. The experimental results are compared with finite element calculations of the temperature and stress distributions in the elements. Based on these activities, the fabrication of the W7-X divertor PFCs and the graphite covered wall protection for W7-X can be initiated.
Fusion Engineering and Design, v.66-68, 447-452 (2003).
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ABSTRACT: A new facility for the testing of plasma facing components (PFC) under high heat fluxes is presently under construction at IPP Garching. The aim of this facility is to provide thermal testing capabilities for high heat loaded divertor components which have both active water cooling and large outer dimensions. The water-cooled test chamber is equipped with two ion sources for positive ion beam production. Initially, only one of the two individually controlled RF ion sources with 1.1 MW maximum beam power will be used for heat loading tests within an operating regime from 5 to 65 MW/m2 at the target position. This paper presents the details of the technical characteristics and the systems for vacuum generation, cooling, power supply, control, target diagnostics and data acquisition.
Fusion Engineering and Design.
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ABSTRACT: We performed investigations to determine the lifetime of tungsten coatings on carbon under high heat flux with respect to tungsten carbide formation. Tungsten coatings with a molybdenum interlayer were deposited by combined magnetron sputtering and ion implantation. These coatings were heat treated in a vacuum furnace. Subsequently the fraction of the coating thickness which had converted into carbide, was determined by focussed ion beam preparation and electron microscopy. This thickness was found to extend from 10 μm to 18 μm for heat treatments between 2 and 20 h at 1350 °C. Such coatings were then exposed to high heat flux pulses of 16.5 MW/m2 with pulse durations of 1.5 s. A clear threshold behaviour was found: While after 2 h of heat treatment no coating failure was found, the delaminated surface fraction was up to 5% after treatment for 5 h and up to 25% after treatment for 20 h at 1350 °C.
Journal of Nuclear Materials.
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H. Maier,
H. Greuner, B. Böswirth,
R. Neu,
Ch. Hopf,
M. Rasinski,
M. Balden,
S. Lindig,
A. Wiltner,
C. Ruset,
E. Grigore,
G Matthews,
G. Piazza,
T Hirai,
V. Philipps,
A. Schmidt
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Physica Scripta, v.T138 (2009).
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Physica Scripta, v.T138 (2009).
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ABSTRACT: The target elements of the WENDELSTEIN 7-X (W7-X) divertor are designed to sustain a stationary heat flux of 10 MW/m2 and to remove a maximum power of 100 kW. CFC Sepcarb® NB31 tiles are bonded to a water-cooled CuCrZr heat sink in two steps: active metal casting (AMC®) of an AMC®-copper interlayer to CFC tiles, electron beam welding (EBW) or hot isostatic pressing (HIP) of the AMC®-NB31 tiles to CuCrZr. The fabrication of the whole amount of CFC NB31 has been completed. The key target of the pre-series phase is the qualification of this bond based on a series of examinations. The introduction of silicon during the AMC® process significantly improved the strength of the joint between CFC and AMC®-copper. The strength of the bond is preserved after either EBW or HIP processes. High heat flux testing carried out in the ion beam facility GLADIS exhibited a too high percentage of defective tiles. Pre-series activities have been extended to reduce the stress concentration at the interface between tiles and heat sink by optimizing the design.
Fusion Engineering and Design. 82:1634-1638.
