Manufacturing and assembly status of main components of the Wendelstein 7-X cryostat
Introduction
Wendelstein 7-X (W7-X) is the world's largest superconducting helical advanced stellarator (Fig. 1). It is presently under construction at the Max-Planck Institut für Plasmaphysik (IPP) in Greifswald, Germany. W7-X is provided with an internal vacuum vessel, the ‘plasma vessel’ (PV), whose complex toroidal shape follows the designed contour of the stellarator plasma. The PV is the first barrier for the ultra-high vacuum (≤10−8 mbar) of the plasma chamber. The superconducting magnet system, the coil support structure, the liquid helium cooling pipes and the thermal shield are enclosed between the PV and a second external toroidal vacuum vessel, the ‘outer vessel’ (OV). An intermediate vacuum (≤10−6 mbar) is established between the vessels.
Section snippets
Plasma vessel
The plasma vessel consists of 5 similar modules, each extending for 72°, which are joined together along radial–poloidal and radial–toroidal planes. The inner surface is protected against the plasma heat by the actively cooled panels of the in-vessel components. Its outer wall is covered with the thermal shield consisting of an actively cooled glass fibre and copper shell with multi-layer super insulation which minimises the thermal radiation from the PV to the coils [1].
The maximum outer
Ports
The 254 ports provide the access to the plasma vessel. All ports are equipped with bellows which vary between 100 mm circular to 1170 mm × 570 mm rectangular sizes. The bellows allow relative movements between the outer and the plasma vessel. During various load-cases the axial and lateral stiffness of all bellows will create a resulting spring-force which acts directly on the vessel supports. The ports can be divided in two main groups. The so-called diagnostic ports contain the different systems
Outer vessel
The outer vessel and the plasma vessel form the boundaries for the cryostat. The outer vessel is designed as a torus with an outer diameter of approximately 16 m. The internal diameter of the cross-section is 4.4 m. It is made of the same material as the plasma vessel. The nominal wall thickness of the shell is 25 mm. The outer vessel is also made of 5 modules. Unlike the PV each OV module is divided into an upper and a lower half-module shell. The outer vessel rests on 15 supports, which are
Support structure of the magnetic system
The cryostat encloses different support systems for the magnetic system. The so-called Central Support Structure (CSS) consists of several types of structural components. The main one is the Central Support Ring (CSR) to which the superconducting coils are connected through Central Support Elements (CSE).
The CSS is subjected to various loads during the life of the W7-X experiment. The main loads are generated during coil de-energisation and subsequent magnetic forces. Additional loads can occur
Conclusion
The assembly of the first two modules is well in progress. As described some of the named main parts in the cryostat were not only delivered but also assembled. They could show that the assembly requirements were achieved. In general it can be resumed that all parts which are named in this paper are on the recent internal time schedule. From this point of view there are no doubts to complete the assembly up to 2014 (Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8).
Because of the
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Manufacture of cryostat components for Wendelstein 7-X
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Cited by (2)
Structural analysis of W7-X: From design to assembly and operation
2011, Fusion Engineering and DesignCitation Excerpt :The planar support elements (PSE) connect the two types of PLC (A, B) to the NPC. One PSE per coil (PSE-A1, PSE-B1) is a fixed bolted connection, while other PSEs follow the NSE design [4]. The cryostat system consists of the plasma vessel (PV), outer vessel (OV), the ports and the machine base.
Lessons learned from designing and manufacturing of the coil support structure of W7-X
2011, Proceedings - Symposium on Fusion Engineering