Design and test of the support elements of the W7-X magnet system

The Wendelstein 7-X stellarator is presently under construction and assembly in Greifswald, Germany. Its ultimate goal is to verify that such stellarator magnetic confinement concept is a viable option for a demonstration fusion power-plant. The superconducting magnet system, capable to generate a average magnetic field up to 3 Tesla at the magnetic axis, is basically composed of non-planar and planar coils, and of a central support structure to which they are connected. This system is a complex mechanical structure which has to fulfil demanding requirements in terms of accuracy of the magnetic field, capability to take the operational loads, suitability of the manufacturing tolerances and assembly scheme, interfaces. The magnet system is interconnected by support elements which have been conceived and designed in such a way to react to the loads in a "balanced way", while complying with the other requirements mentioned above. Given the unprecedented complexity of such mechanical scheme, an integrated programme of design, FE analyses, tests, assembly trials has been undertaken. This paper gives an overview of the way this structure is conceived, of its key support elements, and of the results of the analyses and tests carried out so far