20-MW-long-pulse solidstate-klystron modulator

Summary form only given, as follows. For the TESLA Test Facility (TTF) at DESY Hamburg a long, pulse klystron modulator has been designed to drive the 5-MW-klystron-TH2104C and the new 10 MW-multibeam-klystron TH1801. Pulse length max. 1.7 ms, primary voltage max. 12 kV, primary current max. 1.7 kA, repetition rate max. 10 Hz. The main goal of the development at PPT is to reach a reliable and cost-effective design to allow for production and easy maintenance of about 700 modulators as planned for the TESLA linear collider. To meet these requirements we have tried to reduce the construction complexity and to focus on components widely used in industrial application e.g. traction industry. Following the original design of FERMI Lab the pulse forming system is a solidstate switched capacitor discharge, droop-compensated by an appropriate bouncer-circuit. The main features of the new design are: 1.) A rugged compact IGCT-switch stack. The seven-stage semiconductor stack with integrated gate driving circuits and a current turn-off-capability 4 kA replaces the former complex GTO- and IGBT-multi-element arrangements. 2.) A volume optimized storage capacitor bank using high energy capacitors with self-healing, segmented metallized polypropylene technology. The technology allows for the storage of 100 kJ within a volume of less than 0.75 m3 (three cans) without any external protection circuit. Similar optimized capacitors (two cans) are used for the bouncer circuit. 3.) A 300-kW-switched mode power supply (four 75-kW subunits) with a new regulating system to avoid the generation of powerful subharmonic distortions back into the mains. A novel gas-filled, high coloumb switch HX3010 is under test to replace the standard NL8900 ignitron for crowbaring the 100-kJ storage capacitor bank in case of a short circuit fault. First results of the modulator tests as well as cost- and lifetime estimations are presented.