The complex geometry of the superconducting busbar System for Wendelstein 7-X, which interconnects the stellarator’s magnet coils. The picture shows how the busbars (in colour) “wrap” around vacuum vessel and magnet coils (grey). (Picture: Forschungszentrum Jülich)

Forschungszentrum Jülich (FZJ) with its great expertise in fusion technology took over the crucial engineering tasks for the construction of the Wendelstein 7-X stellarator at Greifswald. The project had a financial input of 30 million euros and came to an end successfully on 30th June 2010.

Jülich mastered the design, the manufacturing and also the qualification tests of the “busbars” – an important subsystem used to electrically interconnect the superconducting magnet coils of the stellarator. These connectors also need to be superconducting. The system consists of individual supports, clamps and joints for the electrical and hydraulic connection of the busbars and coil terminals. Major challenges arose not only from the complex geometry of the stellarator coils, but also from the mutual displacement of the components to be connected, the considerable electromagnetic loads and the limited space available for the accommodation of the busbar system. Moreover, the busbar insulation must withstand electrical fields corresponding to a test voltage of 13,000 Volts even after multiple mechanical and thermal load cycles down to a temperature of 77 K. In order to fulfil all these requirements, FZJ constructed a dedicated production and qualification hall full of computer-controlled machinery and tools.

In a ceremony at Jülich on June 30th 2010, project leader Dr.-Ing. Olaf Neubauer handed over the final busbar elements to Prof. Thomas Klinger, the representative of Max-Planck-Institut für Plasmaphysik in Greifswald. In total, Forschungszentrum Jülich had designed and manufactured about 400 supports, 700 clamps and 240 superconducting electrical joints for Wendelstein 7-X. The pre-assembly of these components had also been performed at Jülich before they were delivered to Greifswald.

Ralph P. Schorn, Forschungszentrum Jülich