Design, Tests, and Repair Procedures for the Electrical Insulation of the Superconducting W7-X Magnets

The Wendelstein 7-X (W7-X) stellarator fusion experiment is presently under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald Germany. The W7-X machine has a superconducting magnet system with 50 non-planar and 20 planar coils grouped in five equal modules. The operation of the W7-X machine requires a reliable insulation system of the superconducting magnets. Starting in the design phase the components have to consider the insulation system, weak points of the insulation must be identified and countermeasures must be taken, e.g. for the crossings of conductors inside the windings, the shape of handmade insulated areas and the quench detection cable design. The manufacturing has to be based on qualified procedures and materials, e.g. the vacuum pressure impregnation of the glass epoxy insulation as well as the hand-made glass epoxy wrappings must be thoroughly qualified and tested during the whole manufacturing process. A set of accompanying tests, especially high voltage tests, during the manufacturing and assembly process helps to assure the quality of the insulation.