A repetitive ten-stage wave erection Marx generator is developed to investigate the electrical characteristics of such compact devices and potentially provide an economical approach to realize the miniaturization of intense electron beam accelerators. Compact design has been made for the generator in order to achieve a proper stray capacitance of the spark gap electrode with respect to the ground in each stage because these proper grounded stray capacitances are critical for obtaining a good wave erection process. This generator is initially resistively isolated for single-shot tests and then changed to inductively isolated for repetitive operation. In single-shot experiments, the generator is tested to be able to deliver a high-voltage pulse of 210 kV and a rise time of about 5 ns on a 90-Ω dummy load at a charging voltage of 40 kV. This result agrees basically with that of the PSpice circuit simulation, which adopts a self-breakdown spark gap model. The preliminary experimental results of repetitive operation show that at a charging voltage of 30 kV, the generator can operate at 8.5 Hz without gas blow-off from the internal spark gaps, producing an output pulse of 150 kV and a rise time of less than 20 ns. Differences in the output pulse waveforms between resistively and inductively isolated configurations are analyzed.

Development of a Repetitive Wave Erection Marx Generator

Compact pulsed power system based on compact Marx generator is widely used in terms of drive resistance and capacitive loads. This system usually adopts high performance components such as high energy density capacitors, compact switches, and integrated structure. Traditional compact Marx generator can only output double-exponential pulse profile. In this paper a compact, low-impedance Marx module which can output rectangular pulse profile is design and tested. This module has multiple circuits of different discharge frequencies in parallel to generate quasi-rectangular pulse. Discharge characteristic of an ideal module with infinite branches is calculated theoretically. A module with two branches has been designed and tested. Test results show that the impedance of the module is 1.2 Ω. When charging voltage is 100.6 kV and load resistance is 1 Ω, the peak output pulse is 45.2 kV voltage, the peak power is about 2 GW, the pulse width is about 130 ns, and the rise time is about 35 ns. The energy density and power density of the module are 15 kJ/m3 and 140 GW/m3, respectively.

Design of compact Marx module with square pulse output

Compact Marx generators (CMGs) are commonly used to provide high-power and high-voltage pulses. Generally, CMGs are composed of spark gaps, charging capacitors, resistors, connections, and a metal body. The stray capacitances between spark gaps and the body could play a significant role in the performance of these generators. This article presents modifications in the conventional structure of a ten-stage CMG to generate various voltage profiles through variations in stray capacitances. These capacitances have been calculated numerically for six reconfigured structures with COMSOL. Eventually, the modified CMGs have been simulated in MATLAB to statistically investigate the impacts of various modified structures on the features of the output voltage such as the voltage peak, the pulsewidth, and the rise time in comparison with the conventional structure. In light of the presented results, the proper and applicable structure would be utilized based on the type of the load.

Assessment of Different Compact Marx Generator Structures on the Voltage Profile

A solid-state quasi-square pulse Marx generator has been designed, constructed, and tested in this paper. The spark gap switches of a typical Marx generator have been replaced by a fractional-turn ratio saturable pulse transformer (FRSPT), and a three-section anti-resonance network has taken the role of pulse forming module in this quasi-square Marx generator. For the switches, thyristors are used as the primary switches and the FRSPT is used as the pulse modulating switch. The experimental results show that if the charge voltage is about 1000 V, the output quasi-square pulse has an amplitude of 18.5 kV and a pulse width of 3.15 μs, and the experimental results verify the feasibility of the concept of an all-solid-state quasi-square square pulse Marx generator based on an FRSPT and anti-resonance network.

Developing a solid-state quasi-square pulse Marx generator.

Marx generator is a voltage boosting device for power pulse compression, in which its capacitors are charged in parallel and discharged in series. To get a higher voltage boost ratio, high-voltage silicon stacks have been applied to substitute the isolated inductances in this study. Experiments with two isolation modes in the Marx generator have been carried out. Experimental results reveal that the high-voltage silicon stacks with the parameters of 50 kV/1 kA used in the Marx generator can increase the voltage step-up ratio to 168.6:1, up from 141:1 and 162.9:1 when isolating inductances and silicon-stacks with parameters of 50 kV/3 kA are applied, respectively. Moreover, the silicon stack-isolating-type Marx generator can almost eliminate the pre-pulse existing on the load if the isolated inductances employed. Therefore, it is crucial to choose appropriate high-voltage silicon stacks as the isolating devices in the Marx generator designed in this study.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/hve.2019.0138

Study on a Marx generator with high-voltage silicon-stacks instead of isolating inductances

The need for repetitive high-power microwave systems, for instance within the scope of convoy protection, requires the availability of compact, repetitive pulsed-power generators. The development and the first experimental results of an upgraded balanced ISL Marx generator for future repetitive operations at pulse repetition frequencies in the order of 100 Hz are introduced. A key objective is to keep the fundamental modular coaxial concept by reason of its scalability and compactness. Simulation models were developed under the PSpice software package in order to investigate the charging and discharging phases of the Marx generator and also to determine the design criteria for repetitive operations. The charging resistors were replaced by ultracompact inductors for rapid charging, being able to withstand pulsed voltages up to 60 kV and pulsed currents up to 1.4 kA during the discharge phase. An improved type of strontium–titanate high-voltage ceramic capacitor was successfully tested experimentally up to 70 kV. Each new elementary stage of the Marx generator consists of eight 1.1 nF sectors of a cylinder capacitors mounted in parallel, two charging inductors of about 17.8 μH and two halves of spherical spark gaps. The pressurized self-triggered gas switches are arranged along the axis for fast consecutive breakdown thanks to the UV radiation emitted during the breakdown in each gap. The stages are installed in individual fibreglass housings. First experimental results of a 4-stage Marx generator in repetitive operation, driven by a 4 kW capacitor charging power supply up to a maximum voltage of 40 kV, are presented.

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B. Martin

Papers

Study of an Ultra-Compact, Repetitive Marx Generator for High-Power Microwave Applications