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TEXTOR was designed in the late seventies as a tokamak with an unsaturated iron core. To achieve a significant prolongation of the pulse duration and an increase of the plasma current from 500 kA to 800 kA, the transformer flux swing of presently 4.4 Vs will be doubled. Since the central iron core has to be operated far beyond saturation (up to 5 T), an increase of the magnetisation current from the present value of 100 kA to 10 MA is necessary. This requires new magnetising coils and corresponding power supplies, a switching circuit for 36 kA and 25 kV, as well as a new overvoltage protection system. This overvoltage protection system is required to control both the stored high energies in the case of the saturated iron core and the high voltages in the case of unsaturated iron core during disruptions. Blocking diodes protect the rectifiers against overvoltage during plasma initiation, and varistors cut off overvoltage spikes during disruptions. Fast vacuum switches are used to take over the power within 40 ms. The paper describes the overvoltage protection system in detail, while the power supplies and the coil systems are considered briefly.

Additional information

Authors: GIESEN B, Forschungszentrum Jülich GmbH (KFA) (DE)
Bibliographic Reference: Article: 17th Symposium on Fusion Technology, Rome (IT) : Proceedings, Vol. 1 (1993) pp. 852-856
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