Updates on protection system for Wendelstein 7-X superconducting magnets

摘要

The Wendelstein 7-X stellarator (W7-X), one of the largest stellarator fusion experiments, started the third plasma operation campaign in July 2018 at the Max Planck Institute for Plasma Physics in Greifswald, Germany. The W7-X experiment has a superconducting magnet system with 50 non-planar and 20 planar coils electrically connected in seven circuits. A quench detection system checks permanently the superconducting system regarding the onset of a quench. In case of a quench or a severe failure, the magnet protection system is activated and leads the current into discharge resistors. Based on new requirements and operation experiences, the discharge resistors of the non-planar coils were rearranged and improvements of several components were implemented in the last 12 month. The reconfigured discharge resistors slow down the discharge process, which increases the hot spot temperature in the conductor for about 18 K while the resulting peak voltage is reduced for about 30%. The simulated data for voltages and currents during the discharge process are in good correlation with the measured data from July 2018.