1. Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, D 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 , 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 )
- 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 , 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,
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
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
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)