The power supplies for the glow discharge electrodes in Wendelstein 7-X

The conditioning of the Wendelstein 7-X (W7-X) plasma vessel will be done by glow discharges. Ten electrodes are placed inside of the vessel. Due to the three dimensional geometry the conditions for the ignition and the stabilization of a glow discharge can vary from one electrode to the other electrode. Therefore ten individual power supplies with maximum ratings of 3 kV and 3 A will be used. The ten power supplies are individually controlled by a PLC based control system. This control system is a major part of the overall glow discharge system, because it has to allow the combination of two or more power supplies to groups, which can be controlled in a similar way. The glow discharge is planned to run up to a week in steady state mode. This requires a sophisticated monitoring system of the parameters of the power supplies and the implementation of a proper matrix of reaction after failures. One aim of the Wendelstein 7-X control system is the remote control of all activities from the W7-X main control room. The glow discharge power supply control has to allow such operation and special procedures for exchange of control rights were implemented. The power supply system was developed, manufactured installed and tested in collaboration between IPP and PPT.