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Abstract: The superconducting magnet system of the Wendelstein 7-X (W7-X) experiment consists of 50 non-planar and 20 planar coils, 121 bus bars and 14 current leads. The connection between bus bars, coils and current leads will be provided by 198 joints. The joints have to be insulated manually during the assembly of the machine in constraint positions and a tight environment. In general the insulation is based on glass tapes impregnated with epoxy resin and special G10 insulating pieces embedded in the glass tape insulation. In critical areas Kapton®-foils are embedded in the insulation. All types of insulation were qualified at mock-ups in a 1:1 model of the expected environment in W7-X. The qualification programme comprises thermal cycling between room temperature and 77K and high voltage tests under air, under vacuum and under reduced pressure (Paschen test). The paper describes the main principles used for different types of handmade Paschen-tight insulations in W7-X and the visual and electrical tests during and after assembly. [Copyright &y& Elsevier]

Abstract: The superconducting fusion experiment WENDELSTEIN 7-X (W7-X) is presently under construction at the Greifswald branch of the Max-Planck-Institut für Plasmaphysik (IPP). The magnet system consists of 50 non-planar and 20 planar coils which are connected by 121 bus bars in series of 10 groups of seven coils each. The connection of the bus bars will be provided by 184 joints each with a maximum allowable resistance of 5nΩ. The principle of such a joint was tested by two joints in SULTAN Test facility CRPP, Switzerland in 2003. Both joints showed resistances less than 1nΩ at 25kA in a magnetic field of 2T. In the meantime efforts to modify the design of the casing and clamping parts for the serial production of joints have been carried out and tools for the installation at W7-X and mounting procedures were developed. The essential modifications and the latest test results at the SINTEZ of the Efremov Institute in St. Petersburg, Russia will be presented. [Copyright &y& Elsevier]

The magnetic diagnostics foreseen for the Wendelstein 7-X (W7-X) stellarator are diamagnetic loops to measure the plasma energy, Rogowski coils to measure the toroidal plasma current, saddle coils to measure the Pfirsch–Schlüter currents, segmented Rogowski coils (poloidal magnetic field probes) to add information on the distribution of the plasma current density, and Mirnov coils to observe magnetohydrodynamic modes. All these magnetic field sensors were designed as classical pick-up coils, after the time integration of induced signals for 1/2 hour had been successfully demonstrated. The long-pulse operation planned for W7-X causes nevertheless significant challenges to the design of these diagnostics, in particular for the components located inside the plasma vessel, which may be exposed to high levels of microwave (electron cyclotron resonance) stray radiation and thermal radiation. This article focuses on the tests and modelling performed during the development of the magnetic diagnostics and on the design solutions adopted to meet the conflicting requirements. All pick-up coils foreseen for the initial operation phase of W7-X and their signal cable sections inside the plasma vessel and the cryostat are now installed, and their electronics and data acquisition are under preparation. [ABSTRACT FROM AUTHOR]

Abstract: Forschungszentrum Jülich has taken over the design, manufacturing and assembly of the superconducting busbar system for the stellarator Wendelstein 7-X. This includes the busbars itself, the support structure consisting of supports and clamps, and the joints for electrical and hydraulic connection of the busbars and coil terminals. Apart from providing the required electrical connection scheme, the busbar system has to be designed for relevant electrical and mechanical loads. Numerous interfaces and geometric boundary conditions define the confined space to accommodate the busbars and their support elements. This article describes how the individual challenges to engineering have been met in the course of the project. This includes design concepts and the method for iterative design of supports with respect to the individual load distribution caused by the supports itself. [Copyright &y& Elsevier]

Abstract: The superconducting magnet system of the Wendelstein 7-X experiment consists of 50 non-planar and 20 planar coils. The coils are connected by 121 bus bars arranged in a series of seven groups each of 10 coils. The electrical and hydraulical interconnections of the bus bars will be provided by means of 184 joints each with the required resistance of less than 5nΩ. The joint structure should withstand the internal pressure arising from the quench event. In order to permit joint replacement and repair after installation the joints have to be designed as demountable structures. Based on a conceptual design for an internal pressure of 30bar and a current of 18kA, the disconnectable joints have been redesigned for a pressure of 200bar and a current of 20kA. The report describes design, tests and stress analysis. [Copyright &y& Elsevier]