An Integrated Optimal Design Procedure for Pulse Transformer-Based Klystron Modulators for Long-Pulse High-Power Applications

Solid-state klystron modulators are typically based on oil-immersed high-voltage (HV) pulse transformers due to their high performance, robustness, and topological simplicity. However, in considering high-power multi-millisecond pulsed applications based on this topology, modulator power components and their design become increasingly complicated and, correspondingly, modulator size becomes problematic. In this article, practical models for the characterization and design of each main power component forming the pulse transformer-based modulator topology are developed. These models are then integrated in forming a complete optimization procedure suitable for long-pulse high-power applications. The developed design procedure is used in considering a complete pulse transformer-based modulator design for the case of the European Spallation Source klystron modulator requirements (a pulse amplitude of 115 kV/100 A, a pulselength of 3.5 ms, and a pulse repetition rate 14 Hz). The performance of the individual components as well as the complete modulator is studied and validated through the circuit simulation. Finally, fixing the pulse power parameters to that of typical high-power klystron load requirements, the optimization procedure is used in a parametric study sweeping the application pulselength and pulse repetition rate to explore the possibilities and limitations of the pulse transformer-based modulator topology.