New multistage converter promises a new sub-nanosecond high-voltage pulse generator

High voltage pulses with a sub-nanosecond rise time have wide applications in many areas such as high-power microwave generation, gas discharge and laser physics. In recent years, solid-state high voltage generators have been a popular developing trend as they demonstrate new possibilities for generating stable short pulses. As a new technology for converting the shapes of high-voltage pulses, nonlinear transmission lines provide a new perspective for developing all solid-state high voltage generators.

A nonlinear transmission line (NLTL) is a coaxial oil line with the interelectrode space filled with an assembly of ferrite rings. When the ferrite is saturated by an external magnetic field, NLTLs sharpen voltage pulses due to the nonlinear ferrate gyromagnetic property. In a recent paper, Ulmaskulov et al. developed a novel, multistage pulse-shape converter composed of a series of cascaded NLTLs, which can operate in two modes as a “short pulse former (SPF)” and a “microwave generator (MG)” and produce extreme parameters of the output pulses.

The researchers found that the key to generating high voltage pulses with a short rise time and a large modulation depth in their scheme is to employ NLTL output sections with small cross-sections. At the SPF output, the researchers obtained a unidirectional pulse with shortened voltage rise time of around 45 picoseconds and a record-breaking voltage rise rate of 15.5 megavolts per nanosecond. At the MG output, a sequence of sub-nanosecond pulses with a large modulation depth of 70% were produced.

This work also demonstrates the possibility of conducting engineering calculations of the generation frequency for a given amplitude of the initial pulse using the classic ferromagnetism theory, which could be useful for scientists to design NLTLs and all solid-state generators.

Source: “Multistage converter of high-voltage subnanosecond pulses based on nonlinear transmission lines,” by M.R. Ulmaskulov, S.A. Shunailov, K.A. Sharypov, and M.I. Yalandin. Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5110438 .