The engineering design of the dynamic ergodic divertor (DED) for TEXTOR-94

The installation of a Dynamic Ergodic Divertor (DED) is foreseen for the tokamak TEXTOR-94 in order to active influence transport parameters in the plasma edge and to study the resulting effects on effective heat exhaust, edge cooling, impurity screening, plasma confinement and stability. The paper concerns the engineering design of a multi polar helical coil system mounted on the inboard side of the TEXTOR vessel (temperature 250°C) and its power supply system. A special conductor has been developed for the 18 invessel coils. The coils are actively cooled. The layout of coils and support structure take into account requirements for conditioning of the outer tube and the vessel at 250°C, as well as thermal expansions (conductor, insulation, tube and vessel) and protections against disruptions (halo currents). The 4 phase rotating field can be generated by only two sets of power units (frequency converters) having a phase shift of 90 degrees and a frequency range from DC to 10 kHz. A converter with IGBTs produces the AC output voltage of 600 V and the output current of 1.5 kA. The paper describes the engineering design of the main components