A compact and modular pulse forming network (PFN)-Marx generator with output parameters of 5 GW, 500 kV, and 30 Hz repetition is designed and constructed to produce intense electron beams for the purpose of high-power microwave (HPM) generation in the paper. The PFN-Marx is composed by 22 stages of PFN modules, and each module is formed by three mica capacitors (6 nF/50 kV) connected in parallel. Benefiting from the utilization of mica capacitors with high energy density and a mini-trigger source integrated into the magnetic transformer and the magnetic switch, the compactness of the PFN-Marx system is improved significantly. The structure of the PFN module, the gas switch unit, and the connection between PFN modules and switches are well designed for modular realization. Experimental results show that this generator can deliver electrical pulses with the pulse width of 100 ns and amplitude of 500 kV on a 59-ohm water load at a repetition rate of 30 Hz in burst mode. The PFN-Marx generator is fitted into a cuboid stainless steel case with the length of 80 cm. The ratio of storage energy to volume and the ratio of power to weight of the PFN-Marx generator are calculated to be 6.5 J/L and 90 MW/kg, respectively. Furthermore, utilizing the generator to drive the transit time oscillator (TTO) at a voltage level of 450 kV, a 100 MW microwave pulse with the pulse width of 20 ns is generated.

https://www.mdpi.com/2079-9292/10/5/545/pdf

A Compact Modular 5 GW Pulse PFN-Marx Generator for Driving HPM Source

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.

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.

/pdf/study-of-an-ultra-compact-repetitive-marx-generator-for-high-1urntk59p2.pdf

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

The essential demand for high-power microwave (HPM) devices for both military and civil applications, such as convoy protection and car stopping, requires compact repetitive pulsed-power generators. We report on the latest developments in the technology of our balanced, coaxial Marxtype generators, which distinguish themselves by using a fundamental modular concept for reasons of scalability. The Marx generators especially make use of inductive charging technology to ensure high-repetitive operation. The Marx stages were completely redesigned. Marx generators with a variable number of stages were assembled and successfully tested up to charging voltages of 50 kV for up to 10 stages and up to 40 kV for the 20 stages. Burst mode operation for a duration of 10 s at a pulse repetition frequency of 100 Hz is reported. In order to gain an in-depth insight into the behavior of an inductive Marx generator during the charging and the discharging phases and to derive precise information for the design of future generators, we developed an advanced PSpice simulation model. The breakdown dynamics of the spark gaps was implemented by making use of the Vlastos formula; parasitic eects, such as stray capacitances, were taken into account.

J. P. Duperoux

Papers

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

Modular, Ultra-compact Marx Generators for Repetitive High-power Microwave Systems