1. Construction of Wendelstein 7-X Max-Planck-Institut für Plasmaphysik
Hans-Stephan Bosch
Max-Planck-Institut für Plasmaphysik
Greifswald
Institute of Plasma Physics, CAS, Hefei, October 18, 2010

2. Stellarator Wendelstein 7-X
Optimisation criteria
small neo-classical transport
good confinement of fast particles
minimised bootstrap current
good MHD stability
good finite b-equilibria
feasible modular coils
Modular stellarator,
Superconducting coils
Fully optimized numerically

3. Wendelstein 7-X, basic device
ports
fabrication completed
non-planar coils
fabrication + tests completed
planar coils
plasma vessel fabrication completed
cryostat
central ring fabrication completed
bus bar system
cryo-piping
fabrication completed
thermal insulation
fabrication ongoing
in-vessel components fabrication ongoing

4. W7-X, plasma
Pentagon-shaped  5 identical modules, each made of 2 flip-symmetric half-modules

5. W7-X, divertor 10 separate divertor units 2 in each of the 5 modules
designed for a maximum heat load
of 10 MW/m2

6. W7-X, in-vessel components
Two step approach requires intermediate components:
Inertial cooled divertor (TDU) for first operation phase
Actively cooled high-heat-flux (HHF) divertor for steady state phase

7. W7-X, in-vessel components, status
Target plates
prototypes finished
manufacturing started
heat shields
structure in manufacturing
The graphite tiles are also
in manufacture
wall panels
all 320 panels have
been delivered by MAN
DWE (Germany)

8. W7-X, plasma vessel volume 110 m3 surface 200 m2 mass 33 t
vacuum < 10-8 mbar
baking up to 150o C
tolerances <  2 mm

9. W7-X, plasma and plasma vessel
Multi-Layer Insulation
20 layers of crinkled Kapton foil
glass mats in between
Thermal shield
glass fibre panels, Al coated
Cu braids for connection to
water cooling
20 welded rings per half-module

10. W7-X, magnet system BNN, G / Ansaldo, I / Tesla, GB
magnetic field in plasma T (< 3T)
magnetic field energie MJ
NbTi superconductor (>3.4 K)
50 non-planar coils (5 types)
20 planar coils (2 types)

11. NbTi superconductor for W7-X
fibre
NbTi with Cu
0,58 m
cabling
243 single fibres
(3 x 3 x 3 x 3 x 3)
Cable-in-Conduit (Coextrusion)
In up to17.6 kA
HSB,

12. Wendelstein 7-X, coil fabrication I
Coil winding
(ABB, Augsburg)
Tempering of cast casing /half shell
(Österby, Sweden)
HSB,

13. Wendelstein 7-X, coil fabrication II
Assembly of winding pack in casing
Overview of
production hall
(BNN, Zeitz)

14. Wendelstein 7-X, superconducting coils

15. Wendelstein 7-X, Cryogenic testing of coils
CEA Saclay, France:
Tests at 5K
Thermal properties
Cold leak tightness
Helium flow rates
Electrical insulation
Superconductivity
HSB,

16. Wendelstein 7-X, Paschen testing of coils
critical scenario: air influx into cryo vacuum causes pressure increase and
quench of a coil
 High high pressure  Paschen discharge possible
Therefore all coils are tested under Paschen conditions (between
0.001 and 100 mbar) with 6 kV
This has proven to be a valuable measure to verify insulation quality.
HSB,

17. W7-X, support structure Ensa, Spain welded ring in 10 half-modules
mass: 71 t
Support of all coils, high precision
extensive inter-coil support
structure to prevent movement of
coils

18. W7-X, support structure

19. W7-X, outer vessel and ports
DWE, Germany
Romabau,
Switzerland
ROMABAU
volume m3
surface 480 m2
mass t
vacuum < 10-5 mbar
number of ports 254

20. W7-X, outer vessel and ports
All 5 modules delivered
Installation of Thermal Insulation ongoing

21. W7-X, pre-assembly Coils are threaded across the plasma vessel
Thermal insulation is completed
The coil support structure
is positioned in front of the
7-coil pack
Coils are bolted to the
central support ring

22. W7-X, pre-assembly II The flip-symmetric half-modules are aligned
The step-flange is bolted and the vessel half-modules are welded
Thermal insulation, Inter-coil structure are completed
HSB,

23. W7-X, assembly
Module 5, February 2009

24. W7-X, torus hall October 13, 2009

25. W7-X, 1. module inserted in cryostat lower shell, 29.10.09

26. W7-X, first upper shell of cryostat, 25.11.09

27. W7-X, 3. module on machine base, 18.08.10

28. W7-X, Assembly of ports in 1. module, 27.09.10

29. Assembly schedule Assembly of the five modules is running in parallel
All 5 modules are in the works at present
Major “new” work packages:
module connection
diagnostics
in-vessel assembly
The assembly schedule still contains half a year buffer times
Assembly will be finished in summer 2014
periphery installations

30. Operations planning stepwise approach
1st operation phase with 8MW, inertially cooled divertor
and only partial cooling of in-vessel components
shut-down (15 months) for completion and hardening
2nd operation phase to approach 10MW