Design of a Compact Transmission Line Transformer for High Voltage Nanosecond Pulses

The area of pulsed-power technology covers a broad range of powers (up to 10¹⁴ W), voltages (up to 10⁶-10⁷ V), currents (as high as 10⁶ A or higher) and pulse durations (below 10^-8 s). State of the art systems have voltages up to a few hundred kilovolts at pulse lengths down to the nanosecond range. Special applications require extreme field strengths in the range of 1 GV/m. The design of a compact source, meeting the above requirement aims for 1 MV, 1 ns pulses. In this paper, we present a novel compact TLT (transmission line transformer). The TLT consists of 10 coaxial transmission lines which are connected in parallel at the input and in series at the output. To verify the theoretical analysis a model of the transmission line transformer has been simulated by a time domain electromagnetic field solver. An optimized transmission line transformer has been built and first measurements have been performed. The equivalent circuit model and the simulations agree with the experimental results. The effect of secondary mode suppression by means of ferrite has been investigated. Both simulations and experiments showed that ferromagnetic cores around each individual transmissions line in our design can be omitted.