Max-Planck Institutfür Plasmaphysik

Construction of Wendelstein 7-X

Hans-Stephan Bosch

Max-Planck-Institut für PlasmaphysikGreifswald

Institute of Plasma Physics, CAS, Hefei, October 18, 2010

2

Stellarator Wendelstein 7-X

Modular stellarator,

Superconducting coils

Fully optimized numerically

Optimisation criteria small neo-classical transport good confinement of fast particles minimised bootstrap current good MHD stability good finite b-equilibria feasible modular coils

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

Target modules10 units: 7210 kg

Glow discharge electrode10 units

Port protection (optional)100 m2: 3127 kg

Cryo-vacuum-pumps10 units: 600 kg

Wall protection + piping62 m2: 5527 kg

Poloidal closure10 m2: 634 kg (panel type)

Protection of divertor aperture10 m2: 634 kg

Toroidal shielding5 m2: 608 kg (baffle type)

Plug-ins, water pipes4000m, 3583 kg

Baffle modules10 units: 6115 kg

Heat shield (high loaded)47 m2: 4280 kg

Plasma vessel

Control coils10 units: 1450 kg

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

heat shields • structure in manufacturing • The graphite tiles are also in manufacture

Target plates • prototypes finished• manufacturing started

wall panels• all 320 panels have been delivered by MAN DWE (Germany)

8

W7-X, plasma vessel

volume 110 m3

surface200 m2

mass 33 t vacuum < 10-8 mbar baking up to 150o C tolerances < 2 mm

9

W7-X, plasma and plasma vessel

20 welded rings per half-module

Multi-Layer Insulation 20 layers of crinkled Kapton

foil glass mats in betweenThermal shield glass fibre panels, Al coated Cu braids for connection to water cooling

10

W7-X, magnet system

magnetic field in plasma 2.5 T (< 3T)

magnetic field energie 600 MJ NbTi superconductor (>3.4 K) 50 non-planar coils (5 types) 20 planar coils (2 types)

BNN, G / Ansaldo, I / Tesla, GB

11HSB, 22.10.09

NbTi superconductor for W7-X

cabling

243 single fibres (3 x 3 x 3 x 3 x 3)

Cable-in-Conduit (Coextrusion)In up to17.6 kA

fibreNbTi with Cu

0,58 m

12HSB, 22.10.09

Wendelstein 7-X, coil fabrication I

Tempering of cast casing /half shell(Österby, Sweden)

Coil winding(ABB, Augsburg)

13

Wendelstein 7-X, coil fabrication II

Assembly of winding pack in casing

Overview ofproduction hall

(BNN, Zeitz)

14

Wendelstein 7-X, superconducting coils

15HSB, 22.10.09

Wendelstein 7-X, Cryogenic testing of coils

CEA Saclay, France:• Tests at 5K• Thermal properties• Cold leak tightness• Helium flow rates• Electrical insulation• Superconductivity

16HSB, 22.10.09

Wendelstein 7-X, Paschen testing of coils

• critical scenario: air influx into cryo vacuum causes pressure increase and quench of a coil High voltage @ 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.

17

W7-X, support structure

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

Ensa, Spain

18

W7-X, support structure

19

W7-X, outer vessel and ports

volume 525 m3

surface 480 m2

mass 170 t vacuum < 10-5

mbar number of ports 254

DWE, Germany

Romabau,Switzerland

ROMABAU

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

22HSB, 22.10.09

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

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 10s @ 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 30min @ 10MW