Commissioning Results of the Superconducting Magnet System of Wendelstein 7-X

Abstract

The superconducting fusion device Wendelstein 7-X went into operation in December 2015. One of the most important steps was the commissioning of the superconducting magnet system. It consists of 70 superconducting coils, 14 high temperature superconductor (HTS) current leads, and more than 100 superconducting bus bars. The system is divided into seven electrical circuits with ten coils, associated bus bars, and two current leads each. The commissioning of the magnet system was performed in two major steps: In the first step, the seven coil circuits were separately energized and operated at several current levels in a range between 2 and 12.8 kA. In the second step, all seven circuits were operated together. The adjustment of the quench detectors, the evaluation of the thermal and mechanical behavior, and the test of the magnet safety system were further work packages. Fast discharges were initiated to check the proper behavior of the magnet safety system. Steady-state operation of up to 8 h was performed to adjust the helium mass flows. The commissioning was successfully completed, the main goal of the magnet system is fully reached, which is also confirmed by magnetic flux measurements and the results of the first plasma operation.