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

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

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

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

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

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

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)

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

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

W7-X, magnet system BNN, G / Ansaldo, I / Tesla, GB 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)

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, 22.10.09

Wendelstein 7-X, coil fabrication I Coil winding (ABB, Augsburg) Tempering of cast casing /half shell (Österby, Sweden) HSB, 22.10.09

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

Wendelstein 7-X, superconducting coils

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, 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. HSB, 22.10.09

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

W7-X, support structure

W7-X, outer vessel and ports DWE, Germany Romabau, Switzerland ROMABAU volume 525 m3 surface 480 m2 mass 170 t vacuum < 10-5 mbar number of ports 254

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

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

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, 22.10.09

W7-X, assembly Module 5, February 2009

W7-X, torus hall October 13, 2009

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

W7-X, first upper shell of cryostat, 25.11.09

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

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

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

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