Construction of the vacuum vessels and the magnet supporting structures of Wendelstein 7-X

Wendelstein 7-X (W7-X) will demonstrate the possibility of a stellarator for a future fusion power plant. This stellarator fusion experiment is at present in the assembly phase at the MaxPlanck-Institut für Plasmaphysik (IPP). The main advance of the static plasma is caused by the three dimensional shape of the coils. But inside the Cryostat this extravagant geometry of the coils efforts also a three dimensional contour of the main mechanical components. One of the ambitious challenges is how to build up such complex machine. The manufacturing of these complex devices have been demanded the newest manufacturing methods. At 2014 Wendelstein 7-X will be the world's largest superconducting helical advanced stellarator. The toroidal plasma vessel geometry follows exactly the three dimensional shape of the plasma. It contains the plasma with a great diameter of 11m and an average plasma diameter of 1.1 m. To control the plasma geometry it is necessary that all the 20 planar and 50 non planar coils are not only extreme narrow positioned to the Plasma Vessel but also within a tolerance of 1.5 mm to each other. To meet this requirement and to withstand the high magnetic forces a complex coil support structure was created. The Central Support Ring have to bear the coils but the different inter coil supports canalize the forces by very stiff connections on one side and sliding areas on the other side. The coils and the support structure are enclosed within the Outer Vessel with its domes and openings. The Outer Vessel, the Plasma Vessel and the ports generate the boundaries for the Cryostat. The vacuum inside provides thermal insulation of the magnet system which is cooled down to 4 K. The 254 ports secure the access to the Plasma Vessel with all the supply lines and the diagnostics. Due to the different thermal movements the Plasma Vessel, Outer Vessel and the Central Support Ring have to be supported separately. The Central Support Ring is held by 10 cryo legs. The Plasma Vessel supporting system is divided into two separate systems, allowing horizontal and vertical adjustments to centre the Plasma Vessel during thermal expansion. Beside an overview about the main components in the cryostat like the plasma vessel, the outer vessel, the ports and the different support systems this paper describes the most demanding manufacturing methods. The author delineates some disparate and special problems during the manufacturing of the components at the companies in the different European countries.

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“…Because of this complicated form, the surfaces switch between convex and concave. The maximum outer diameter of the torus is approximately 12 m; the minimum inner diameter is 8 m. The wall is made of the austenitic steel 1.4429 (X2CrNiMoN17-13-3) and has a thickness of 17 mm [2]. The inner surface will be protected against the plasma heat by in-vessel components.…”

Section: A Plasma Vesselmentioning

confidence: 99%

“…The template will number citations consecutively within brackets [1]. The sentence punctuation follows the bracket [2]. Refer simply to the reference number, as in [3]-do not use "Ref.…”

Section: Referencesmentioning

confidence: 99%

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X cryostat

Koppe¹,

Cardella²,

Missal³

et al. 2011

Fusion Engineering and Design

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Wendelstein 7-X (W7-X) will demonstrate the possibility of a stellarator for a future fusion power plant. This stellarator fusion experiment is at present in the assembly phase at the MaxPlanck-Institut für Plasmaphysik (IPP). The main advance of the static plasma is caused by the three dimensional shape of the coils. But inside the Cryostat this extravagant geometry of the coils efforts also a three dimensional contour of the main mechanical components. One of the ambitious challenges is how to build up such complex machine. The manufacturing of these complex devices have been demanded the newest manufacturing methods. At 2014 Wendelstein 7-X will be the world's largest superconducting helical advanced stellarator. The toroidal plasma vessel geometry follows exactly the three dimensional shape of the plasma. It contains the plasma with a great diameter of 11m and an average plasma diameter of 1.1 m. To control the plasma geometry it is necessary that all the 20 planar and 50 non planar coils are not only extreme narrow positioned to the Plasma Vessel but also within a tolerance of 1.5 mm to each other. To meet this requirement and to withstand the high magnetic forces a complex coil support structure was created. The Central Support Ring have to bear the coils but the different inter coil supports canalize the forces by very stiff connections on one side and sliding areas on the other side. The coils and the support structure are enclosed within the Outer Vessel with its domes and openings. The Outer Vessel, the Plasma Vessel and the ports generate the boundaries for the Cryostat. The vacuum inside provides thermal insulation of the magnet system which is cooled down to 4 K. The 254 ports secure the access to the Plasma Vessel with all the supply lines and the diagnostics. Due to the different thermal movements the Plasma Vessel, Outer Vessel and the Central Support Ring have to be supported separately. The Central Support Ring is held by 10 cryo legs. The Plasma Vessel supporting system is divided into two separate systems, allowing horizontal and vertical adjustments to centre the Plasma Vessel during thermal expansion. Beside an overview about the main components in the cryostat like the plasma vessel, the outer vessel, the ports and the different support systems this paper describes the most demanding manufacturing methods. The author delineates some disparate and special problems during the manufacturing of the components at the companies in the different European countries.

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“…The cryostat, providing the thermal insulation of the cold magnet system described before, consists of the plasma vessel, the outer vessel, the ports [18] and the thermal insulation of these components towards the cold mass.…”

Section: Cryostatmentioning

confidence: 99%

Wendelstein 7-X – a Technology Step towards Demo

Bosch

¹

,

team

²

2010

Plasma and Fusion Research

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Abstract:The optimized stellarator Wendelstein 7-X is under construction in Greifswald. Most of the components have been fabricated already and four out of ten half-modules of the magnet system have been assembled already. This paper presents an overview of the status of construction and a summary of the future developments.The Wendelstein 7-X stellarator, presently under construction in Greifswald, will be the first "fully-optimized" stellarator device which combines a quasi-symmetric magnetic field configuration, a steady state exhaust concept, superconducting coils and a size sufficient to reach high nTτ-values. W7-X has been optimized numerically by J. Nührenberg et al., based on the concept of quasi-isodynamicity. Its key element is an optimized magnetic field configuration, generated by 50 non-planar superconducting coils. It is the mission of this project to demonstrate the reactor potential of the optimized stellarator line.One key element of this mission is obviously to verify the numerical optimization. The other key element in demonstrating the reactor potential is steady state operation, required for an economic fusion reactor. Steady state operation is an intrinsic feature of stellarators/heliotrons, unlike of tokamaks where steady state operation is difficult to achieve and still requires extensive research and development efforts. However, the technical realisation of steady-state operation of fusion-relevant plasmas in a stellarator still has to be demonstrated. Therefore, Wendelstein 7-X has taken this as a key element of its mission.Steady state operation constitutes a complex task, composed of more technically oriented and more physics oriented issues. To be economically attractive, magnetic field coils in a steady-state fusion device have to be superconducting. Wendelstein 7-X has a system of 70 superconducting coils, one of the largest superconducting magnet systems worldwide.To provide steady-state power exhaust, Wendelstein 7-x will be equipped with an island-divertor which has already proven successful in the predecessor, Wendelstein 7-AS. Equipped with CFC-target elements and a correspondingly designed steady-state water-cooling system, this divertor has been designed to exhaust 10 MW in steady state. In addition to these technological aspects, however, also physics poses specific questions to steady state operation of a divertor and to the plasma-wall aspects of stellarator operation, like impurity confinement, neutral gas balances, helium transport and exhaust etc. This paper gives a broad overview of the construction status of Wendelstein 7-X with a special emphasis on those components, mentioned above, which constitute a genuine step in steady state technology towards Demo. Also the future works and the strategy for a two-staged approach to steady state-operation will be discussed.

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Construction of the vacuum vessels and the magnet supporting structures of Wendelstein 7-X

Cited by 9 publications

References 3 publications

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X Cryostat

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X Cryostat

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X cryostat

Wendelstein 7-X – a Technology Step towards Demo

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