The Quench Detection-Wire-Feedthrough Plug-In of W7-X

The stellarator fusion experiment Wendelstein 7-X (W7-X) is presently under assembly at the Greifswald branch of the Max-Planck-Institut für Plasmaphysik (IPP), Germany. To allow the steady-state operation, W7-X has a superconducting magnet system. It consists of 50 non planar coils, 20 planar coils, a superconducting bus bar system and 14 current leads. For continuous on-line monitoring of the superconducting state 1624 Quench Detection-wires (QD-wires) are connected at the joints of the coils and the bus bars. The signals of these wires must be fed through the Outer Vessel (OV) shell to the Quench Detection Units. The electrical feedthroughs, wires and wire connections have been designed and qualified for a test voltage of 13 kV under low gas pressure (Paschen test). Other important requirements are a maximum allowed integral helium leak-rate of l/s per QD-dome and a maximum allowed total heat load to the thermal shield of the OV of 140 W per QD-dome. The paper describes the design and qualification of the QD-Wire-Feedthrough-Plug-in, the assembly procedure as well as the tests carried out during and after assembly.