F. Kerl

Fabrication of the superconducting coils for Wendelstein 7-X

The Max Planck Institute of Plasmaphysics is building up the stellarator fusion experiment Wendelstein 7-X (W7-X) at the branch institute in Greifswald. W7-X continues the line of stellarator experiments at IPP. To allow for steady state operation W7-X has a superconducting coil system with 50 non-planar and 20 planar coils. The coil system is grouped in five equal modules, each consisting of two mirror symmetric half modules. The half modules are assembled from five different non-planar coils, two planar coils and a sector of the coil support structure. All cryogenic parts are enclosed in a cryostat to protect them from ambient temperature. The magnet system was ordered from the European industry. The production of superconductor, winding packs and encasings are under way. The main focus of this contribution aims on the fabrication state of the coil system.

Final design and construction of the Wendelstein7-X coils

The Stellarator of the Wendelstein 7-X (W7-X) experiment contains a system of 50 non-planar and 20 planar superconducting coils. The coils were designed by the IPP. The coil manufacturing and inspection is shared between several European enterprises and consortiums. The coils consist of the winding pack embedded in a stainless steel casing and of the related instrumentation. Design details, tolerances and guarantee values and differences between the coils types are described in the contribution. The features of the superconductor are described separately. Finally, the contribution indicates measures adopted by the W7-X project to ensure the quality of the coil design and manufacturing.

The superconducting busbar system of Wendelstein 7-X

The superconducting magnet system of the stellarator Wendelstein 7-X (W7-X) consists of 50 non-planar and 20 planar coils grouped in five periodic modules. Ten coils of a given type of non-planar and planar coils will always be connected electrically in series with nominal currents ranging up to 18 kA. Because of the 5-fold symmetry five busbar systems are to be routed. Electrical connection of the busbar system will require 184 disconnectable joints with a resistance below 5 nΩ. The paper describes the design features of the busbar systems and their installation in the stellarator. Requirements for the design and qualification of the disconnectable joints will be pointed out.

Status of the construction of the W7-X magnet system

The stellarator of the Wendelstein 7-X (W7-X) experiment contains a superconducting magnet system comprises 70 coils and a central support structure. The magnet system has been designed with respect to the physics aims of the experiment. Based on these main features, the components have been ordered from European industry. The subsequently detailed design of the single components and recent prototype test results required the modification of some features. The final design of the components is described in the contribution.

Structure of divertor for the optimised stellarator W7X

For the HELIAS stellarator W7X design studies of the divertor are presented. Under stationary conditions for energy and particle exhaust high local load to target plates with values up to 10 MW/m 2 is expected. The modular target area and the associated baffle plates use the inherent divertor properties of the magnetic configuration of W7X along the helical edge. Therefore, 10 independent divertor elements will be toroidally arranged. The formation of the target area and the proposed open divertor system seems an acceptable compromise in respect to the high flexibility for shaping the plasma boundary to study the transport and accumulate a data base for the extrapolation to reactor needs.

The layout of the WENDELSTEIN 7-X magnet

Abstract The superconducting magnet system for the new stellarator WENDELSTEIN 7-X, to be located at Greifswald, Germany, consists of 50 non-planar and 20 planar large magnetic coils. A central support ring carries the coils and keeps them in their geometrical position. Additional lateral stiffening elements between the coil housings together with the support ring, generate a complex 3D-framework system which has to balance the considerable Lorentz forces, typically in the range of 1–5 MN for the single coil and 10 MN residual value for centripetal directions. The paper presents the detailed design of the magnet system, its functional layout for the achievement of the necessary geometrical accuracy, and the elements for the force transmission. The actual status of industrial activities for the realisation of the magnet components is presented and the magnet assembly conditions are discussed.

Divertor Engineering for the Stellarator Wendelstein W 7-X

For the new HELIAS stellarator W7-X which will become operational on 2004 in Greifswald an “open divertor” concept was developed. The geometry of targets and baffles is optimised in respect of the magnetic structure of the plasma boundary. For the integration inside the vessel a compact and flexible design of the components and interfaces was found. Some critical components, especially the target plates are described.

MODULAR MECHANICAL DESIGN OF THE ADVANCED STELLARATOR WENDELSTEIN VII-AS

The design of WENDELSTEIN VII-AS, a stellarator experiment, is carried out at Garching to investigate hot high density plasmas /1/. A system of twisted coils, split into five periods, allows a modular design of structure and vessel. Following the special symmetry conditions for the magnetic forces within one coil period, the modules of the structure were adapted to this periodicity to transmit forces and bending moments into the existing structure of the WENDELSTEIN VII device. Also the vacuum vessel can be integrated into the above mentioned periodicity.