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.

As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 109 Ω m, and low freezing temperature (−49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that have been developed at the National University of Defense Technology (NUDT) in China. The history and roadmap of the compact IEBAs used to drive high-power microwave (HPM) devices at NUDT are reviewed. The properties of both de-ionized water and glycerin as energy storage media are presented. Research into the breakdown properties of liquid dielectrics and the desire to maximize energy storage have resulted in the invention of several coaxial PFLs with different electromagnetic structures, which are detailed in this paper. These high energy density liquid PFLs have been used to increase the performance of IEBA subsystems, based on which the SPARK (Single Pulse Accelerator with spark gaps) and HEART (High Energy-density Accelerator with Repetitive Transformer) series of IEBAs were constructed. This paper also discusses how these compact IEBAs have been used to drive typical HPM devices and concludes by summarizing the associated achievements and the conclusions that can be drawn from the results.

A compact PFN (pulse forming network)-Marx generator, which is based on mica capacitors, is constructed to generate intense electron beams for the purpose of high-power microwave generation. The key components of the generator, including a PFN-Marx, a trigger source, a multi-stage gas switch, and a load, are introduced in this paper. The PFN-Marx is composed of 19 PFN modules, which are formed by four mica capacitors in parallel. The temperature characteristics and pulse characteristics are tested in this study. The mica capacitor is insensitive to the temperature, and its lifetime is tens of thousands. Considering the influence of the ultraviolet light pre-ionization, gas gap switches are assembled in a nylon house. The trigger source, which is a mini-Marx generator based on the integration into the magnetic transformer and the magnetic switch, is used for increasing the stability of the switches. The generator has been tested on a water load and a relative magnetron. The experimental results show that this generator can deliver electrical pulses with the pulse width of 120 ns and the amplitude of 400 kV on a 40-Ω water load at a repetition rate of 50 Hz. In addition, utilizing the generator to drive a Ku band magnetron at a voltage level of 330 kV, a 500 MW microwave pulse with the pulse width of 50 ns at the frequency of 14.4 GHz is obtained.

The solid-state pulsed power generators (PPGs) are widely used in various modern industrial applications for their high repetition rate and long lifetime. The output characteristics of the generators are significantly affected by the dynamic characteristics of the semiconductor switches. Wide bandgap (WBG) semiconductor power devices, such as silicon carbide metal–oxide–semiconductor field-effect transistors (SiC MOSFETs), have the potential to structure solid-state PPGs due to many advantages, such as a high rated voltage, low on-resistance, high operational temperature, and fast switching speed. Typically, these devices are used in series/parallel connections to enhance the power level of the generators. However, this approach often leads to increased parasitic inductance of the switching modules, which results in flattened rising edges of the output pulse and reduced power transmission efficiency. The chip-on-board (COB) packaging method exhibits excellent high-frequency performance by allowing current paths to be more flexible, which is suitable for constructing the power module. This article proposes a solid-state PPG with Blumlein pulse forming network (BPFN) and COB packaging SiC-based switching module. The switching module is based on a four-layer printed circuit board (PCB). SiC MOSFET bare dies, gate drivers, and auxiliary elements are directly soldered on the top layer of the PCB. Separate conducting layers are connected to the terminals of the switching module by vias, which provides extra flexibility in designing and enables the stray inductance of the power loop to be minimized to 5.14 nH by optimizing the current communication loops. A 5-kV prototype of the solid-state PPG is fabricated based on the designed switching module. Under a resistive load of 2.8 $\Omega$ , a quasi-square pulse with a 62-ns pulsewidth and a 45-ns rise time can be obtained. Additionally, this generator has been tested at a 500-Hz repetition rate in the burst mode, and the di/dt of the switching module is about 80 A/ns, proving the effectiveness of the solid-state PPG.

To meet the application needs for producing long-pulse electron beams and high-power microwaves, a pulse-forming network Marx generator with a pulse duration of 260 ns is presented in this paper. This generator is composed of 20 stages of pulse-forming network modules. Each module is formed with nine capacitors connected in parallel. The generator functions at 44 kV, which is lower than the rated voltage of the mica paper capacitor, to improve the lifetime. The impedance of the generator is designed to reach 45 Ω. To avoid the strong coupling between the adjacent stages, the physical layout of the generator adopts a zigzag design. The generator is housed in a gas pressurized vessel of 600 mm in diameter and 580 mm in length. Across a 50 Ω load, it can deliver quasi-rectangular pulses with a pulse duration of 260 ns and an amplitude of 500 kV for a single shot. The output pulse features a plateau duration of 160 ns and a leading edge of 45 ns. In burst mode, it can steadily output ten pulses of 450 kV at a repetition rate of 10 Hz on either a resistive load or a diode.