Showing papers on "Marx generator published in 2023"

A Compact Repetitive Marx Generator for Generating Intense Electron Beams for HPM Sources

Abstract: A 500 kV, 80 Hz repetition rate compact Marx generator has been designed and developed for producing high intense relativistic electron beams for high-power microwave (HPM) sources. This Marx generator comprises eight bipolar stages (16 stages of unipolar) using energy storage capacitors for achieving improved performance in repetition mode operation. The maximum charging voltage per stage is 50 kV, producing an erected voltage of 800 kV. However, the load voltage will vary according to the impedance of the load connected across the generator. Custom-designed energy storage capacitors were developed to allow voltage reversal of up to 30%–50%, enabling the system to deliver a higher current. A small pulse transformer-based triggering unit with an output voltage of 30 kV was used for triggering the generator. The system’s performance was tested in pulse repetition frequency (PRF) mode with resistive and diode loads and achieved a repetition rate of 80 Hz. An energy density of ~460 J/m3 was achieved in the developed system. A vircator device was connected and tested to benchmark the Marx generator for its repetitive and burst mode operations. The test results show the measured RF output power of 100 MW.

Fast and Flexible, Arbitrary Waveform, 20-kV, Solid-State, Impedance-Matched Marx Generator

Abstract: We developed a new pulsed power supply to study the influence of the high-voltage (HV) pulse shape on the generation of plasma-activated water (PAW). This article shows the design and implementation of the generator and evaluates its performance on resistive loads. The design is an improved version of the solid-state impedance-matched Marx generator (SS-IMG) concept as previously developed at Eindhoven University of Technology. The IMG concept allows for sub-nanosecond rise time pulses, to be able to create a nonthermal plasma very efficiently. A conventional SS-Marx generator (SS-Marx) circuit is taken as the starting point, and a careful implementation is made with most electrical connections analyzed as transmission lines (TLs). All these TLs are impedance-matched to each other and the load. The implemented generator is able to generate 25 ns to $\mu \text{s}$ duration pulses of 20 kV up to 10-kHz repetition rate in a 50- $\Omega $ load with about 8 ns rise time and arbitrary pulse shape. Future improvements are suggested which will increase the repetition rate and decrease the pulse rise time to the sub-nanosecond regime.

Effect of Dielectric Coating on Breakdown Strength in High Pressure SF6

Abstract: With the development of high voltage devices, various methods have been taken to avoid the insulation failure. Ceramic coating, as one of the methods, can be used as electrical insulation in demanding conditions, like high-temperature ambience or other harsh environment. However, the breakdown characteristics of ceramic coating switch have been little discussed, especially under pulse voltages. In this paper, to study the effect of alumina coating on breakdown characteristics, the high voltage experiments have been carried out in 0.3 MPa SF6 under nanosecond pulses. The electrode substrates were treated by a method of plasma electrolytic oxidation (PEO) to produce a layer of alumina coating. Four pairs of electrodes with varied thickness of alumina coating (20$\mu$m, 60$\mu$m, 100$\mu$m and 120$\mu$m), as well as one pair of electrodes without coating, were employed in this experiment. The applied voltage was produced by a compact Marx generator, and the rise time of it was about 40 ns. The breakdown voltage and breakdown time delay have been measured. The results showed that the thickness of coating layer have little effect on breakdown strength. And as the pulse steepness increased, the effect of coating will get strong at first and then go into a gently-changed period. Comparing the secondary electron emission coefficients of steel and alumina and the U-t curves of the four pairs of electrodes, the different process of discharge initiation and time delay might be the main causes for this phenomenon. Since the discharge initiates differently from cathode and anode, the coating electrode was utilized respectively as cathode and anode to investigate the effect of coating layer on initial process.

Avalanche Transistor-Based Nanosecond Pulse Generator in Plasma-Jet-Driven Magneto-Inertial Fusion Systems

Abstract: In plasma-jet-driven magneto-inertial fusion (PJMIF) systems, a high-voltage nanosecond pulsed power supply is required to drive the plasma gun. Marx bank circuit (MBC) is a good candidate to generate nanosecond pulse with high amplitude, fast rise time, narrow pulse width, and low jitter. However, the fundamental topology and operation principle of a positive nanosecond pulse generator are rarely discussed. In this paper, a comprehensive study on the conduction state of fundamental topology and traditional MBC is presented. Furthermore, an improved positive MBC with auxiliary triggering topology (ATT) is proposed. By changing the switching mode from “overvoltage switching-on” to “triggering switching-on”, the system reliability is improved. The output characteristics under different modified stages, triggering capacitors, and main capacitors are investigated. A $4 \times 4$ MBC prototype is implemented with optimized parameters to validate the feasibility of the proposed concept. With spark gap switch load, it can generate a high-voltage pulse with an amplitude of 5.04kV, a rise time of 12.4ns, and an FWHM of 12.6ns.

A Modular Unipolar/Bipolar High-Voltage Pulse Generator Suitable for High Resistive Load

Abstract: This article presents two novel high-voltage pulse generator (HVPG) structures. These modular topologies are based on the buck-boost converter (BBC) operated in discontinuous conduction mode (DCM). The proposed generators produce unipolar and bipolar bell-shaped pulses, which can be applied for applications with high resistive loads. In these structures, the capacitors can be charged up to several times the dc input voltage, simultaneously. Accordingly, they have a high voltage (HV) gain even with a low-voltage dc (LVDC) source. This allows for a compact structure with a low number of modules (switches, diodes, capacitors, etc.). By reducing the number of modules, the total cost and power losses are reduced and the reliability is increased and its maintenance and fault detection would become easier. The other significant advantage of the proposed topologies is the voltage rating reduction of switches and diodes. Also, the series connection of switches and diodes is not required in this structure, which decreases the complexity and costs. Furthermore, due to the simultaneous charging of the capacitors, high-frequency pulses can be generated. Moreover, pulsewidth and pulse rise time are designed arbitrary parameters in nanosecond to microsecond ranges and they are completely independent of the gate driver and switch speed. In the design section, the parameters of the structure are determined based on the pulse specifications. The structures are simulated in MATLAB/SIMULINK environment. The experimental results for 1 kV output voltage confirm the performance of the proposed structures.

10.1063/5.0132851.1

Abstract: The results of experimental research on the acoustic and electrical characteristics of underwater spark discharges facilitated by a preliminary discharge are presented. The latter was produced through the application of a short duration high-voltage pulse formed by a Marx generator. The application of this pulse lead to the formation of a low-density region in the form of a streamer which transformed to an oscillating vapor cavity. It was shown that this method provided a breakdown of a significantly increased interelectrode gap for the same charging voltage of the main capacitor and allowed the generation of stronger shocks. The temporal development of transient discharges in a long gap and the relationships between the hydrodynamic and electrical parameters of such discharges are reported and analyzed.

ghiDevelopment of a Bipolar Marx Pulse Generator Using Buck-Boost Converter

Abstract: A new structure of the Marx pulse generator for generating bipolar high-voltage pulses is introduced. This structure is composed of a buck-boost converter and connected to a low DC voltage source and several parallel diode-capacitor units. In the first stage, the inductor energy is supplied through the voltage source and in the next stage, the inductor energy is transferred to capacitors. For generating the pulses, voltage polarities of the capacitors are changed by a small inductor which is in resonant with the capacitors. Then, using a fast switch, the capacitors are connected in series to generate desirable high-level pulses. To have bipolar pulses, polarity of capacitors is inverted, alternatively. Modularity of the proposed structure enables us to increase number of the units for generating higher voltage level, straightforwardly.

Improved Marx Pulse Generator With Auxiliary Trigger Topology (2022)

Abstract: Marx multistage circuits based on avalanche transistors are widely used in high-power nanosecond pulse applications. In response to the low reliability of the conventional Marx circuit, this article analyzed the corresponding failure mechanism and discovered that the conduction modes were the main cause of failure. Based on this, a new topology is designed, by changing the conduction mode from “overvoltage switching-on” to “triggering switching-on”. The simulation and measurement results show that the new structure has the advantages of high efficiency, stable operation, low output delay, and short output pulse front. Meanwhile, to further improve the output efficiency, a multiplexed stacking solution is designed based on the new structure, and the simulation results show that the output efficiency is up to 95%. The research in this article can provide solutions for the accurate and reliable synchronous triggering of key units such as gas switches in pulsed power systems, and also provide references for the design of high-efficiency nanosecond pulse generators.

Development of palm-sized gas treatment device utilizing streamer discharges generated by compact resonant high-voltage pulse generator

Abstract: A compact and lightweight gas treatment system integrated with a high-voltage pulse generator driven by SiC-MOSFET and wires-to-wires electrode. The maximum amplitude and pulse width of the output voltage of the pulse generator without load are 10 kV and 31 ns, respectively, and the maximum energy transfer efficiency reaches 88% with a load resistance of 0.44 kΩ. This pulse generator was applied to multilayered wires-to-wires electrodes, and the streamer discharges propagated between the electrodes were observed. Streamers initially propagate horizontally according to the Laplacian electric field near the high-voltage electrode. When they approach the ground electrodes, they curve and propagate toward the ground electrode due to the high electric field between the streamer head and the ground electrode. The velocity of the streamer propagation is with a velocity of 0.4 to 0.71 × 106 m s−1. Ozone production and ethylene removal characteristics are investigated in a sealed vessel. The result shows a high ethylene removal efficiency and high safety by suppressing the ozone concentration in the exhaust gas with a catalyst.

A Novel Boost Marx Pulse Generator Based on Single-Driver Series-Connected SiC MOSFETs

Abstract: This paper presents a new type of all solid state boost Marx pulse generator (BMPG). On the basis of the classic pulse forming Marx circuit, without changing the voltage level of each voltage module, a new switch is added for the isolated inductor energy storage and recovery, so as to realize the output of high-voltage nanosecond pulses. At the same time, in order to improve the voltage level of the semiconductor switch and break the limitation of the voltage of the single-stage pulse forming circuit, a series-connected SiC MOSFETs with a single external driver is designed. The series switch has a simple structure with few components and is extremely easy to use in a modular high voltage pulse generator. Its theoretical feasibility is verified by mathematical model and circuit simulation, and the 10-stage prototype is built in this paper. Under the condition of input DC voltage of 500 V, it can output 18 kV high voltage pulses of 200 ns-1200 ns, and the gain multiple has reached 36 times.

A Compact Gigawatt Pulsed Power Generator for High-Power Microwave Application

Abstract: Nanosecond square voltage pulse is of wide interest because of its potential military and industrial applications, such as high-power microwave (HPM). In this article, a gigawatt pulsed power generator (PPG) for HPM based on the multistage pulse forming networks (PFNs) with a voltage superposition using the Marx scheme, i.e., PFN-Marx generator, is proposed through the theory analysis, numerical simulation, processing manufacturing, and performance experiment. The PPG consists of the main subsystems of the primary power and pulse modulation subsystems. The primary power subsystem is a modular bipolar dc high-voltage generator based on the ac–dc–ac, high-frequency transformer, and voltage multipliers by using the power electronics switches. It can generate bipolar dc high voltage of $\pm$ 42 kV to charge the PFN-Marx generator. As for the pulse modulation subsystem, the PFN-Marx technique is preferred, which consists of 24-stage and six $\textit{L}$ - $\textit{C}$ sections. To verify the PPG, an experimental prototype is fabricated and tested. It has a characteristic impedance of about 40 $\boldsymbol\Omega$ and can deliver square voltage wave with an output voltage pulse of about 500 kV, full-width at half-maximum (FWHM) of 94 ns, and 10%–90% rise time of fewer than 35 ns, indicating its ability to deliver peak power beyond 6.25 GW. In addition, a transit-time oscillator was connected and can radiate microwave power of 0.8 GW at 12.89 GHz for the cathode voltage of 372 kV and the beam current of 9.3 kA.

High‐speed high‐voltage solid‐state Marx generator based on SiC MOSFETs

Abstract: This paper presents a high-speed, high-voltage, solid-state Marx generator based on silicon carbide MOSFETs. The objective was to develop a high-rate repetitive, short-pulse, high-voltage and efficient generator for medical particle accelerator applications. To achieve this goal, a 720 kV Marx generator forming from 1445 kV stages was designed. Each stage includes several SiC devices in series to reach desired voltage and speed. Compared to the existing Marx generators, the proposed Marx generator is capable of producing shorter pulses with higher voltage. We present the experimental results of a three-stage prototype Marx generator capable of producing 15 kV at 40 A output with a 200 nS pulse with a repetition rate of 500 Hz.

A Novel Variant of Marx Generator Circuit Using Hybrid Energy Storage

Abstract: With the development of pulsed power technology and the expansion of its application areas, the requirements for pulsed high-voltage supplies are getting sophisticated. Many researchers are exploring new circuits or trying to improve the performance of the existing circuits. In this study, we introduce a variant circuit of the Marx generator based on hybrid energy storage (HES). This circuit topology, referred to as the LCL circuit in this article, allows two inductors and one capacitor to discharge simultaneously to obtain a higher output voltage. By observing the simulation results, we compared the performance of this proposed circuit with circuits based on other energy-storage methods, including capacitive energy storage (CES), inductive energy storage (IES), and the previously studied HES. After confirming the operation process of an LCL module, a two-stage experimental circuit has been built using power MOSFET switches for carrying out the verification experiments. With a charging voltage of 800 V, the output voltage of $\sim$ 8.4 kV with a rise time of $\sim$ 30 ns has been obtained on a 200- $\Omega$ load. The voltage addition of two modules has indicated the potential of a Marx circuit for a much higher output voltage.

A Marx generator based on thyristors triggered in a shock ionization wave mode

Abstract: Abstract Recently, a new trigger mode of thyristor which is called shock ionization wave mode is researched. Compared with the conventional trigger mode, this trigger mode can turn on the thyristor rather fast. In this mode, a trigger voltage with a high amplitude and fast rising speed is applied at both ends of the thyristor. Many single-tube conduction experiments are reported while the conduction threshold of shock ionization wave mode has not been investigated. Besides, the application of this trigger mode in some pulse power topology remains blank which is useful for this mode. In this paper, to explore the impact ionization wave mode conduction threshold of commercial thyristor, fast front high voltage nanosecond pulses are generated by avalanche tube Marx circuit. Pulse signals of different amplitudes are realized through the voltage division resistor. The impact ionization wave mode trigger threshold for commercial thyristors is about 2500 V in amplitude and 250 V/ns in voltage rising speed and the higher the rated parameter of the thyristor, the higher the threshold. To broaden the application of this mode, a novel Marx generator based on thyristors is proposed. A four-stage Marx generator is constructed and the amplitude of the output voltage can reach 1869 V.

The Development of Solid-state Pulse Generator based on Marx Circuit with Chopping Switch

Abstract: A solid-state pulse source is mainly formed by replacing the spark switch in a traditional pulse source with semiconductor switch device. Compared with conventional gas switch devices such as spark switches, semiconductor switch devices have the advantages of high work repetition frequency, long service life, small size, high efficiency, high reliability, easy control, and active shutdown. However, there are still problems, such as the solid-state switch being easily broken down by high voltage, the rising and falling edges of the pulse being slow, and the loss is enormous. In this paper, a solid-state pulse generator based on Marx with a chopping switch circuit is developed, which effectively solves the above problems. The pulse generator comprises DC power, a switching power circuit, a Marx circuit with a chopping switch, a serial port touch screen, and an optical fiber transmission circuit.

10.1063/5.0132851.2

Abstract: The results of experimental research on the acoustic and electrical characteristics of underwater spark discharges facilitated by a preliminary discharge are presented. The latter was produced through the application of a short duration high-voltage pulse formed by a Marx generator. The application of this pulse lead to the formation of a low-density region in the form of a streamer which transformed to an oscillating vapor cavity. It was shown that this method provided a breakdown of a significantly increased interelectrode gap for the same charging voltage of the main capacitor and allowed the generation of stronger shocks. The temporal development of transient discharges in a long gap and the relationships between the hydrodynamic and electrical parameters of such discharges are reported and analyzed.

High Repetition Frequency Subnanosecond Avalanche Marx Generator

Abstract: Ultrawideband electromagnetic pulses have sub-nanosecond rise time and repetition frequency above 100 kHz. Ultrawideband characteristics make it increasingly used in biomedical, intentional electromagnetic interference, and other fields. Avalanche Marx circuits are an important way to generate high-voltage sub-nanosecond pulses with high repetition rates. However, traditional avalanche Marx circuits (TAMCs) are difficult to achieve a repetition rate of 100 kHz and often fail when they reach kilohertz. The second-stage transistor is extremely vulnerable to damage, which is the principal cause of circuit failure. In this article, through the analysis of its discharge mechanism, it is found that the damage to the second-stage transistor is related to the slow on-speed of the first-stage transistor. In fact, the first-stage transistor is the last to be avalanche broken down, causing the already-opened second-stage transistor to be subjected to enormous electrical stress for an instant. This electrical stress is the passive lift voltage of the second-stage transistor, which is the direct cause of easy damage to the second-stage transistor. Therefore, an improved avalanche Marx circuit (IAMC) is proposed. By connecting a protection resistor in series with the second-stage transistor, the passive lift voltage is suppressed. In order to verify the high refrequency capability of this circuit, a 20-stage pulse generator using an IAMC is developed. It achieves a rise time of 230 ps in a 50- $\Omega $ load, an amplitude of 1.65 kV, and a repetition rate of 100 kHz. After adding the necessary cooling device, it finally achieves a stable output of 230-ps rise time, 730-V amplitude, and 700-kHz repetition rate on a 50- $\Omega $ load.

An Inductive Isolation-Based 10 kV Modular Solid Boost-Marx Pulse Generator

Abstract: The solid-state Marx pulse generator is widely used in various fields such as biomedical electroporation, food processing, and plasma material modification. In this paper, an inductor is chosen as an isolation device and by adding a switch to the circuit, a solid-state boost-Marx pulse generator (BMPG) is formed. On the one hand, the inductor forms a boost circuit to multiply the output voltage gain, and on the other hand, it solves the shortcomings of conventional Marx pulse generators where the charging speed and total efficiency during high-frequency pulse generation are drastically affected by the isolation resistor. The selection criteria for inductors is well derived. Based on the PSpice simulation verification, a 12-module prototype of BMPG is built. The test results show that the circuit can achieve 10 kV high-voltage pulse output with a pulse width of 200–1000 ns and an adjustable repetition frequency of 0–10 kHz. While the input DC voltage requirement is only 235 V, the pulse voltage boost multiple is up to 42.5 times. Additionally, with the different switching sequences, the proposed BMPG can realize the adjustable change of pulse rising time and falling time.

An All-Solid-State Rectangular Current Pulse Generator Based on Coupling Inductor

Abstract: To explore the application of pulsed current in biomedicine, an all-solid-state rectangular pulse current generator (RCPG) is proposed. The RCPG uses a field programmable gate array (FPGA) as the control system and a solid-state semiconductor switching metal–oxide–semiconductor field-effect transistor (MOSFET) as the control switch. The RCPG is modular in design, with each module consisting of a diode, a switch, and a coupled inductor. Each inductor of the RCPG is coupled to each other, increasing the energy storage density of the system. When the switch is on, the inductors are charged in series. And when the switch is off, the inductors are discharged in parallel to the load. The energy on the inductor can be superimposed on the load in the form of a current. Through simulation, the principle of RCPG topology and its feasibility is verified. Finally, a five-stage RCPG miniaturized prototype was developed. The experiments show that the RCPG can be adjusted by adjusting the inductor parameters to meet different load requirements, such as biomedical. In addition, the number of modules can be increased to achieve higher current output.

Study of underwater discharge initiated by a high-voltage preliminary pulse produced by a Marx generator

Abstract: The results of experimental research on the acoustic and electrical characteristics of underwater spark discharges facilitated by a preliminary discharge are presented. The latter was produced through the application of a short duration high-voltage pulse formed by a Marx generator. The application of this pulse lead to the formation of a low-density region in the form of a streamer which transformed to an oscillating vapor cavity. It was shown that this method provided a breakdown of a significantly increased interelectrode gap for the same charging voltage of the main capacitor and allowed the generation of stronger shocks. The temporal development of transient discharges in a long gap and the relationships between the hydrodynamic and electrical parameters of such discharges are reported and analyzed.