Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, D-17491 Greifswald, Germany Main-Components of the Wendelstein 7-X Cryostat - Critical Manufacturing Aspects and Status of Assembly B. Missal, T. Koppe, B. Hein, A. Hansen, H. Jenzsch, R. Krause, H. Zeplien,. Chauvin, S. Mohr INTRODUCTION At the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald, the worlds largest superconducting helical advanced stellarator Wendelstein 7-X (W7-X) is under construction. Its ultimate goal is to verify that stellarator magnetic confinement concept is a viable option for a demonstration fusion power-plant. Its three dimensional shaped toroidal plasma (major diameter of 11 m) is directly enclosed by the Plasma Vessel (PV) of similar complex shape. Outside the PV are arranged magnetic coils and outside of them the Outer Vessel (OV). All Coils are vertical supported by a Central Support Structure (CSS), Cryolegs (CL) and radial by Inter Coil Supports (ICL) . The magnetic coils are enclosed by the cryostat witch is generated by the Plasma Vessel (PV) and the Outer Vessel (OV). The connection between PV and OV is realised by Ports for supply and diagnostics. To arrive a modular composition all components (with exception of OV) are subdivided into 10 HM (36°) which will be assembled for the present into Moduls (72°) and afterwards into the complete experiment (360°). Fig. 1 shows a schematic cut through the cryostat where are shown the main components Fig. 2 shows the realistic main components of one module . 1000 mm 2. Plasma Vessel Support 5. Cryoleg 6. Outer Vessel 7. Ports 1. Plasma Vessel 3. Coils 4. Central Support Structure Fig. 2: realistic main components of one module Fig. 1: Schematic cut of cryostat 1. Plasma Vessel (PV) Main function: Enclose the Plasma and assure the ultrahigh vacuum (10-8 mbar) inside. Main Composition: - 10 uniform Halfmodules (36°) - Free formed area following contour of Plasma Material: stainless steel 1.4429, s=17 mm Manufacturer: MDT GmbH Deggendorf/Germany Difficulties: free formed areas in closely tolerances Technology: cant plate stripes in different directions, afterwards welded to rings and sectors Manufacture Status: delivered since 2005 Assembly Status: (see Fig. 3 + 9) - 10 Moduls(72°) are welded and completed - Connection of two Moduls will start end of 2011 2. Plasma Vessel Support (PVS) Main function: - Withstand and transfer all vertical forces from the PV to the machine base - Allow horizontal movements Main construction: - 3 supports/Modul - pendulum support system - spherical bearings - vertical adjustable by hydraulic jacks - Bellows for gasketed to vacuum Material: stainless steel 1.4429, CuSn7Pb15 Manufacturer: MDT GmbH Deggendorf/ Germany Difficulties: high accuracy between the interfaces Manufacture status: delivered since 07/2008 (see Fig. 4) Assembly status: In four Moduls the PVS are connected from Outer Vessel to Plasma Vessel Fig. 3: PV HM 41 during preparation for assembly Fig. 4: PVS AEX welded in OV-Shell during Penetration-Test 3. Magnetic Coils Main function: Generate magnetic field for enclosure of plasma by cooling down to 4 K during experiment Main construction: - 50 non Planar Coils (NPC)+20 Planar Coils (PC) - housing by stainless steel cast - inside: helium cooled by supra wire system Manufacturer: Babcock Noell GmbH (Maliano, Spain) Difficulties: Complicated 3D construction with imbedded supra wire system and current connectors (see Fig. 5) Manufacture status: All coils (50+20) are delivered since 07/2008 and checked at CEA Saclay up to 08/2009 Assembly status: All coils are assembled 4. Central Support Structure (CSS) Main function: Support of all magnetic Coils Main construction: (see Fig. 6) Welded Pentagonal Ring 10 Halfmodules, Diameter: 10 m, h=2,5m Material: 1.4429, 1.3960 Manufacturer: ENSA (Maliano, Spain) ROVERA (Borgo San Dalmazzo, I) Difficulties: high accuracy and cleanness requirements Manufacture status: 10 Halfmodules are delivered Assembly status: All Halfmoduls are assembled with coils and conected to Moduls . Fig. 5: Non Planar Coils during preparation for assembly Fig. 6: Compete support modul during transport to the next Mounting Stand 5. Cryolegs Main function: - Support of Central Support Structure (CSS) (Highvacuum, 4K) vertically to machine base (atmosphere) - Allow horizontal temperature shrinkage of CSS. Main construction (see Fig. 7) : - 2 Cryolegs/Modul (10 for whole Cryostat), - sliding bearing at bottom for temperature shrinkage - middle part GFK-bush for temperature difference - stainless steel-flange for connection to Central Ring Material: 1.4429, glass fibre reinforced plastic (GRP), PTFE Manufacturer: ZANNON (Schio, Italy), IMA GmbH (Dresden, D), SKF Aerospace (Rodgau, D) Difficulties: High forces for GRP-bushes => many calculations and tests Manufacture status: All Cryolegs are are delivered Assembly status: All Cryolegs are assembled 6. Outer Vessel (OV) Main function: Form with Plasma Vessel the Cryostat Main construction: (see Fig. 8) - Torus, outer diameter 16 m - cross section 4,4 m, Wall thickness 25 mm - 524 domes for ports and accessibility - 15 supports directly to machine base Material: stainless steel 1.4429 Manufacturer: MDT GmbH Deggendorf Difficulties: - High accuracy of big welding construction - Elasticity of mainbody (without domes) Manufacture status: - All Moduls are delivered, - 1 Modul is in checking procedere Assembly status: - All Moduls are prepaired with thermal insulation - 8 Halfshells are assembled to 4 Moduls Fig. 8: OV-Modul during test-assembly of PVS Fig. 7: Cryoleg during test assembly 7. Ports Main function: Access to plasma vessel for diagnostics or supply Main construction (see Fig. 9): - Tubes of different shapes with bellows - Flanges outside tubes for heating and cooling Material: stainless steel 1.4429 Manufacturer: ROMABAU AG (Weinfelden, SUI) Manufacture status: Compete delivered 06/2007 Assembly status: - 2 Moduls are assembled CONCLUSIONS All main components are delivered. Many are assembled or are in preparation for assembly. A big effort of engineering was required to arrive this current status. It is important to define precisely in a very early period the specification and to have a very tight monitoring of the manufacturing process. The stellarator magnetic confinement concept is a viable option for a Demonstration fusion power-plant. This goal is a strong motivation for all colleagues of IPP. From this point of view there are no doubts to complete the assembly up to 2014. Fig. 9: 4 Moduls in Thorushall 09/2011 Fig. 9: Diagnostic Port AEK-V2 (Typ I)