High-voltage switching by means of a stack of thyristors

The use of a stack of 32 thyristors for production of a 20-kV pulse is reported. The pulse power is 50 MW and the pulse duration is 25 mu s. The thyristor stack serves as a line swith for a pulse-forming network which provides the input power for a 20-MW klystron. The klystron provides the rf power for the infrared free-electron laser FELIX. The choice of thyristors is motivated by the required relative voltage-stability during the pulse of 0.08%. Also the pulse-to-pulse reproducibility is required to stay within 0.08%. Detailed design considerations and operational results are presented.