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Wendelstein 7-X (W7-X) is a superconducting stellarator under construction at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany. The magnet system consists of 70 superconducting coils providing magnetic confinement-fields. Before assembly every coil had to pass an acceptance test at the French partner-institute CEA, Saclay, to examine its performance on leak tightness, high voltage strength, ampacity, and hydraulic flow at cryogenic conditions. The testing procedure was mandatory, as access for maintenance or repair after installation will not be viable. Testing followed a well specified routine including tests in warm conditions, during cool down, in cold conditions, during warm up and at last in warm conditions. Measurement was obtained firstly by the facility's instrumentation and secondly by the coil-casing's instrumentation. The received data was transmitted to different ASCII-files for each gauge. To record testing in detail, a meta-document was edited, which follows in its structure the routine mentioned above. Accordingly, the main distinctive functions of the coil during testing are recorded in so called test reports, while deviations from given thresholds and parameters are described in non conformity reports. During testing, organizational and technical challenges had to be mastered and the test program was regularly updated to meet technical improvements, manufacturing requirements and revised assembly schedules. This paper will present the acceptance test program, its development and the gained experiences. [ABSTRACT FROM AUTHOR]

The W7-X machine is a low-shear stellarator of the Wendelstein line being assembled in Greifswald, Germany. The manufacture of its superconducting magnets is in a well advanced phase. After the acceptance tests in the factory, the magnets are tested in cold conditions in a dedicated facility at CEA Saclay. This paper gives an overview of the status of the manufacture of the W7-X coils, including the production of the superconductor, the windings and casings for the magnets, the final assembly and in-factory test procedures. Several design changes and re-work have been implemented in the course of the manufacture due to more detailed engineering analyses or weaknesses and quality problems found in some components. The status of the cold tests of the coils will also be presented. [ABSTRACT FROM AUTHOR]

The magnet system of the Wendelstein 7-X stellarator (W7-X) consists of 50 nonplanar and 20 planar coils. In particular, the winding packs of the nonplanar coils are densely packed and compressed in the area of inter-layer joints and coil terminations, which brings some risk of inter-turn and inter-layer short circuits. The paper describes methods deducted from impulse and ac tests performed on the coils, which enable demonstrating the absence of short circuits and weak points of low inter-layer insulation resistance. In the impulse test, frequency and damping are compared for coils with and without short circuits and coils with an external low resistance bypass. With ac voltage, a drastically reduced impedance clearly indicates a short circuit. Therefore both tests represent excellent QA (quality assurance) tools for checking the uniformity of the electromagnetic performance of a serial production of magnet coils. [ABSTRACT FROM AUTHOR]