High-voltage Nanosecond Pulse Generator Research Articles

Nanosecond pulse electric field treatment initiates mitochondrial apoptosis pathway by inducing mitochondrial morphological changes in myocardial cells.

As an emerging myocardial ablation technique, the mechanism of nanosecond pulse electric field (nsPEF) ablation is currently less studied. Mitochondria are one of the important membrane structure organelles in cells, participating in numerous life activities within the cell. This study aimed to explore the morphological changes of mitochondria in living cells following nsPEF treatment. Myocardial cells were treated with a self-made solid-state LTD high-voltage nanosecond pulse generator with a pulse width of 100ns for 80 times. The changes in mitochondrial membrane potential and cell apoptosis in rat myocardial cells after nsPEFs were investigated using JC-1 assay kit, apoptosis double staining assay kit, and mitochondrial fluorescence probe. The results showed that after nsPEF treatment, the mitochondrial membrane potential decreased, apoptosis increased, and the average mitochondrial area decreased from 0.48 µm2 in live myocardial cells to 0.16 µm2. The average circumference ranges from 3.17µm dropped to 1.60µm. The shape factor decreased from 1.92 to 1.41. The aspect ratio has decreased from 2.16 to 1.59. nsPEF treatment induces changes in the morphology of myocardial cell mitochondria. Based on the results of mitochondrial membrane potential and apoptosis, it can be inferred that under this equipment and parameter conditions, nsPEF treatment first causes changes in mitochondrial morphology, and then initiates the mitochondrial apoptosis pathway, which may provide experimental basis for investigating the potential mechanism of nsPEF ablation of myocardial cells.

New concept of two-cascade energy compression systems based on drift step recovery diodes

A new concept of effective high-voltage nanosecond pulse generators based on two compression cascades of drift step recovery diodes (DSRDs) is presented. The main advantage of the proposed approach arises from the decoupling of the operation cycles of DSRD cascades while using a single primary switch. This greatly improves the overall efficiency of the system. The first DSRD cascade operates with low pulse current densities. Its operation cycles can be extended resulting in an increase of the compression factor and pulse energy, whereas the loss level is kept at a minimum. The second DSRD cascade operates with high current densities, but the duration of its cycles can be chosen much shorter which ensures good efficiency too. Furthermore, an extension of the working cycle of the first DSRD cascade makes the requirement for the primary switch milder so that even relatively slow low-voltage switches can be employed.

High voltage nanosecond pulse generator based on pseudospark switch and diode opening switch.

With the development of technology, low-temperature plasma plays an increasingly important role in industrial applications. The industrial application of low-temperature plasma has the following requirements for plasma, high electron energy, low macroscopic temperature, and uniformity. Low-temperature plasma driven by nanosecond pulses reflects more significant advantages in these aspects compared to direct current plasma and alternating current plasma. In this paper, a simple topology is proposed, which is based on the pseudospark switch and the diode opening switch. A pulse generator is developed, which can eventually output pulses with an amplitude of 106kV, a rise time of 15.5ns, a pulse width of 46ns, and a maximum repetition rate of 1kHz on a 260Ω resistive load. The pulse generator can successfully drive needle-plate discharge plasma in ambient air. It has excellent parameters, stability, compactness, and a long lifetime. The proposed topology may be helpful for nanosecond pulse generators with amplitude ranging from tens to hundreds of kilovolts, which could be widely used in industry.

Transmission and multiple reflection mechanisms of guided streamers propagating through grounded annular electrode and interacting with grounded surface electrode

The repeatable dynamics and the reversal propagation of guided streamers remains a major question of fundamental physics. In this article, trains of positive guided streamers are generated within an atmospheric pressure plasma jet supplied in helium and polarized by a high-voltage nanosecond pulse generator. The device is completed by two distant targets: a grounded annular electrode (GAEL) coaxially centered around the capillary through which guided streamers can propagate, and a grounded surface electrode (GSEL) on which they can interact. The resulting transmitted and multiple reflected guided streamers are measured combining optical characterization (fast intensified charge-coupled device (ICCD) imaging) and electrical characterization (high voltage probe and current monitors). While the electrical approach provides information on the capacitive/conductive nature of the current peaks as well as on their positive/negative value, fast ICCD imaging distinguishes whether the guided streamers are incident, reflected or transmitted. Combining these two techniques allow us to demonstrate experimentally that the reflected streamers are negative contrarily to the others. Besides, four types of reflections have been highlighted: a reflection (r) at the outlet of the capillary, a reflection on the GSEL (R) and two reflections (r′ and r″) observed when an incident guided streamer passes through the GAEL. The two techniques agree that the characteristic propagation times are always shorter for reflected negative streamers than for the positive ones propagating forward. Hence, for a GAEL placed 3 cm away from the high voltage electrode, propagation time is 80 ns for reflection versus 250 ns for transmission. These characteristic propagation times are even shorter when the annular electrode is brought closer to the surface electrode with velocities typically higher than 300 km s−1. In addition, the intensity ratios of reflected/incident guided currents drop sharply, typically losing one decade over a counter-propagation length of only 3–5 cm. Finally, all these experimental data are utilized to build an equivalent electrical model that allow to better understand the dynamics of the guided streamers and explain their transmission and reflection modes upon their interaction with the two distant grounded electrodes.

High voltage nanosecond pulse generator based on diode opening switch and magnetic switch.

Low-temperature plasma technology is widely used in various industrial fields, which require the plasma to be of large volume, diffuse, and stable. Furthermore, previous studies have shown that better plasma performance has been obtained by using generators with a high voltage, a high repetition rate, a fast rise time, and a short pulse duration. In this paper, a novel topology is proposed for such generators, which is based on magnetic switches and diode opening switches. A prototype is developed, and its output characteristics are investigated by varying essential parameters, such as the load resistance and the power supply voltage. The experimental results show that it can generate pulses with a voltage of 30.6 kV, a rise time of 7.1ns, a pulse duration of 8.2ns, and a maximum repetition rate of 12 kHz on a 300 Ω resistive load. The prototype has been successfully used to drive uniform plasma in ambient air. In the proposed topology, a diode is added to make the magnetic cores independent of each other, significantly simplifying the design calculation. It may help develop nanosecond solid-state generators.

High voltage nanosecond pulse generator based on avalanche transistor Marx bank circuit and linear transformer driver.

Avalanche transistor Marx bank circuits (MBCs) are widely used in high voltage repetitive nanosecond pulse generators, but problems exist with respect to increasing the output voltage due to the limited pulsed current. Accordingly, a novel topology based on an avalanche transistor MBC combined with a linear transformer driver is proposed, the latter of which exhibits advantageous stress distribution and modular structure. A four-module prototype with four units in each module is developed in the laboratory. The output characteristics are investigated by varying important parameters such as the main capacitance, the number of conducting units, the number of cascaded modules, and the trigger signal time delay. The test results verify the validity of the proposed topology. For a 50 Ω resistive load, the prototype can generate pulses with an amplitude of 10.9 kV, a rise time of 3.3ns, and a voltage superposition efficiency of 89%. The topology proposed in this paper may help to provide a method to further improve the output performance of avalanche transistor MBCs.

A Polarity-Adjustable Nanosecond Pulse Generator Suitable for High Impedance Load

This article presents a new method for forming nanosecond short pulse on high impedance load using the turnon and turn-off delays of dual Marx. The generator combines advantages of the traditional solid-state Marx generator's modular stacking design to easily stack high-voltage pulse, flexible pulsewidth, and compact size. It can output unipolar or bipolar pulses by controlling the driving signal of each Marx. And the delay time between bipolar pulses can be flexibly adjusted. The dual Marx of the pulse generator is designed by the same seven-stage module stack. The SiC-MOSFET with fast turn-off capability and high repetition rate is used as the main switch, which has superior performance under high-frequency conditions. Through theoretical analysis and prototype test, the generator can generate voltage amplitude ±5 kV under 2-kΩ noninductive resistance load, pulsewidth 10-30 ns continuously adjustable, and the delay time of positive and negative nanosecond pulses is 100-400 ns. This high-voltage nanosecond pulse generator has a repetition frequency of up to 1 MHz in the burst.

On the low-temperature plasma discharge in methane/air diffusion flames

Interest in methane has grown recently because of its encouraging characteristics. However, methane comes with serious concerns regarding stability and flammability limitations. Some methods have been proposed to improve the ignition characteristics of methane in diffusion flame burners such as electrical fields, dielectric barrier discharge, and low-temperature plasma. In this study, an innovative single-element coaxial shear injector coupled with a high-voltage nanosecond pulse generator has been used to study the effects of low-temperature plasma (LTP) discharge on methane/air inverse diffusion flame at different plasma and flow conditions. The stability analysis focuses on the detachment conditions of the flame and how RNP discharge can delay this phenomenon, explaining the presence of an optimal operating point with the least applied energy. Comparing the lean blow-off limits for the cases with and without plasma discharge, it is shown that low-temperature plasma discharge enhances the flammability of the diffusion flame. The effect of LTP discharge on laminar flames is also discussed using chemiluminescence photography. It shows that the shape of the diffusion flame becomes more similar to premixed flame with more air entrainment and stability. Resultantly, it is shown that RNP discharge can improve the flame stability and ignition characteristics.

Self-Triggering High-Frequency Nanosecond Pulse Generator

With the increasingly extensive and in-depth applications of all solid-state high-voltage nanosecond pulse generators in the defense and industrial fields, the development of traditional pulse generators faces many key issues, such as high-voltage drive isolation, compact design, and reduced weight. Hence, a novel circuit topology for a self-triggered high-frequency nanosecond pulse generator is proposed. Through high potential energy-gaining technology of the interstage capacitance, this generator does not need a complicated metal–oxide–semiconductor field-effect transistor isolation drive circuit, and there are also no switching dynamic and static voltage equalization problems. This kind of generator is very suitable for compact assembly with only a single external gate driver. High voltage output can be realized by quantizing multilevel module stacking according to actual needs. At the same time, the generator has a high repetition rate and long life. The characteristic parameters of the 20-stage superposition experimental prototype are as follows: an output voltage amplitude of 15.3 kV with a rising time of approximately 45 ns, a repetition rate of 10 kHz in the pulse train, and a pulsewidth of 200–1000 ns.

A Compact Series-Connected SiC MOSFETs Module and Its Application in High Voltage Nanosecond Pulse Generator

Nanosecond pulse discharge plasma has many prospects in industrial applications, and high-voltage repetitive nanosecond pulse generators with compact design and light weight have become one of the key issues limiting its development in some applications. This paper presents a high voltage series-connected silicon carbide (SiC) metal-oxide -semiconductor field effect transistor ( MOSFET s) module which can be served as the main switch in a repetitive high-voltage nanosecond pulse generator. This kind of series-connected MOSFET s module with only single external gate driver requiring very few components is very suitable for compact assembly. By analyzing the working principle, three topologies of series-connected MOSFET s module are proposed. The switching behaviors of the three different topologies with four SiC MOSFET s series-connected are compared experimentally. The variation of switching characteristics of series-connection SiC MOSFET s module with different numbers of devices are investigated. The layout is also optimized to shorten pulse front time and improve output pulse quality. Furthermore, a 10 kV SiC MOSFET s module with a turn- on transition time ∼10 ns is developed. The double pulse test result demonstrates excellent switching performances. Finally, a compact and high-voltage pulse generator composed of three 10 kV SiC MOSFET s module is tailored, with a typical rise time ∼40 ns and peak voltage of ∼30 kV.

An overvoltage driver with inductive adder pulse for fast switching of series-connected MOSFETs module

A novel overvoltage driver is proposed to speed up the turn-on transition of series-connected MOSFETs module which serves as the main switch in high voltage pulse generator. In order to realize the overvoltage driver, a nanosecond pulse with the amplitude of hundreds of volts is superposed on a square driving signal by linear transformer driver scheme. The results show that, comparing to the commercial high current driver, the turn-on time of a 10kV MOSFETs module including ten devices with the proposed driving scheme can be shortened from ∼25ns to ∼7ns. The proposed overvoltage driver can be used to conveniently modulate the rise time and pulse width of high voltage nanosecond pulse generator constructed by MOSFETs. In addition, it is demonstrated that there is almost no influence of the overvoltage driver on the gate-source characteristics of device by analyzing the variation of C-f curves of input capacitances.

An MMC-based modular unipolar/bipolar high-voltage nanosecond pulse generator with adjustable rise/fall time

The rise/fall time of a high-voltage nanosecond pulse affects the application effect of the pulse; therefore, it is of great significance to study the adjustment of the rise/fall time. In this paper, a new type of generator topology based on a half-bridge modular multilevel converter (HB-MMC) is proposed that uses MOSFETs as solid-state switches to produce a unipolar/bipolar high-voltage nanosecond pulse with an adjustable rise/fall time. The proposed topology consists of 2 arms, each of which contains several HB-MMC submodules. The capacitors of each arm are charged with a positive voltage and negative voltage in parallel. By controlling the discharging sequence of the two arms, a unipolar or bipolar pulse can be generated. For each arm, by setting the switching sequence of the MOSFETs, the number of capacitors inserted into the discharging circuit can be controlled to allow a multilevel pulse to be generated. The rise/fall time of the output pulse can be adjusted by changing the number of levels and the duration of each level. Detailed illustrations of the proposed configuration and its operational concept are presented. Experimental results for a scaled-down prototype are presented to validate the concept.

Nanosecond Pulse Electroporator With Silicon Carbide mosfets: Development and Evaluation.

Nanosecond electroporation of cell organelles is being studied since more than a decade, but it is still not entirely understood. Unique prototype hardware equipment and challenging measuring methods may also be a contributing reason for this situation. In the scope of this paper, we improve the performance of the high-voltage nanosecond pulse generator by introducing silicon carbide (SiC) mosfets. We developed a new high-voltage diode opening switch (DOS)-nanosecond pulse generator for laboratory use for in vitro experiments in electroporation cuvettes. Analysis and comparison of the most commonly used switching technologies in pulse generators were made. The device is designed by two parallel two-stage Marx-bank circuits with SiC mosfets that generates up to 200 A in the resonant network. A driving circuit for stable simultaneous switching of SiC mosfets was developed. The developed generator can deliver from 500V to more than 6kV, approximately 8ns pulses to a 50Ω load. Even though the amplitude of the output pulse is not as high as expected, the multiplication factor [Formula: see text] is still approximately 9, which is an improvement compared to the previously published linear DOS generator. Measurement and evaluation process is described in detail. Additionally, we emphasize on the size of an error that occurs during measurements.

Low-pressure gas-discharge current interrupters in a generator of high-voltage nanosecond pulses with an inductive energy storage

Designs of grid units with slotted and multiple-aperture configurations of holes that allow an increase in the stability of the current-cutoff process and a reduction in the time to turn the device off in a high-voltage pulse generator with an inductive energy storage were created. Compared to a TGI2-500/20 thyratron, these designs made it possible to reduce the time instability of the instant of the current interruption by factors of 2 and 5 for switches with the multiple-aperture and slotted configurations of the grids, respectively. These constructions allowed the minimum time for disabling a device to be reduced by 25%.

Output voltage adjustment of a pulsed high-voltage nanosecond generator with inductive energy storage and a solid-state switching system

The possibility of adjusting the output voltage of a high-voltage nanosecond pulse generator with inductive energy storage and a solid-state switching system was investigated. All components of the adjustment system are installed in the low-voltage input circuit of the generator, whose voltage was less than 1000 V. The smooth adjustment of the output voltage in the range of 70–115 kV was achieved. The experimental setup and the obtained results are described.

A Multiparameter Adjustable, Portable High-Voltage Nanosecond Pulse Generator Based on Stacked Blumlein Multilayered PCB Strip Transmission Line

Several series and parallel Blumlein-type striplines designed on multilayered printed circuit board (PCB) are connected to match different impedance loads with different pulsewidths to develop a high-voltage nanosecond pulse generator for investigating the biological effects of a nanosecond pulsed electric field. First, the principle of a multistage series–parallel Blumlein stripline system is described. In particular, the multilayered strip transmission line is designed on the five-layered PCB to minimize the volume of the system whose maximum size is 300 mm (length) $\times \,\, 260$ mm (width) $\times \,\, 154$ mm (height), and the gate resistor capacitor and diode active equalizing circuit is used as the dynamic/static balancing tactic. Then, a single-stage Blumlein-type stripline and some multistage series–parallel Blumlein-type stripline are established to test their performance. As a result, the nanosecond pulse generator produces a rectangular pulse on a matched resistor load, with an amplitude of 0–1.7 kV, a pulsewidth of integer multiples of 100 ns, a rise time of $\sim 20$ ns or less, and a repetition frequency of 0 to several kHz. A variety of biomedical loads can be matched by parallel stacking mode, which will facilitate the analysis of the biological effects of the nanosecond pulsed electric field.

Nanosecond Pulse Generator Based on an Unbalanced Blumlein-Type Multilayered Microstrip Transmission Line and Solid-State Switches

This paper combines an unbalanced Blumlein-type multilayered microstrip transmission line with solid-state switches to develop a high-voltage nanosecond pulse generator. This study was performed to emphasize the importance of a compact nanosecond pulse generator for biomedical applications. The unbalanced Blumlein-type transmission line reduces current flow through the solid-state switches. A multilayered microstrip transmission line is stacked onto the four-layered printed circuit board to minimize the system volume. Voltage wave propagation analysis is used to explain the principle of the system, which produced a rectangular pulse. The strategy to produce different pulse widths and the controlled timing of the related solid-state switches is interpreted according to this analysis, highlighting the approach needed to achieve a 50–100 ns pulsewidth. Also, the relevant principle of the variable load impedance of the unbalanced Blumlein-type multilayered microstrip transmission line system is also analyzed. To demonstrate the performance of the generator, a miniaturized system is established. Eventually, the nanosecond pulse generator produces a rectangular pulse on a resistor load of 50 $\Omega $ , with amplitude of 0–2 kV, pulsewidth of 50–100 ns, rise time of approximately 20 ns, and repetition frequency of 0 to several kilohertz. Also, when a 500 $\Omega $ resistor is used instead of a 50 $\Omega $ resistor, the output of the nanosecond pulse voltage is approximately two times that of the applied charging voltage.

Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.

A nanosecond-pulse generator with an optimized diode switch

A diode-transistor generator of high-voltage nanosecond pulses, which is based on an inductive energy storage and an opening switch in the form of an assembly of drift step-recovery diodes (DSRDs) connected in series, is considered. It allows switching of a voltage pulse with an amplitude of 12 kV and a rise time of 4 ns into a load of 75 Ω at a frequency of 10 kHz. The results of investigations of the process of disabling DSRDs with different thicknesses of the base regions and different diffusion-layer profiles are presented. The design of optimized DSRDs with reduced energy losses during disabling is described. It is shown that the use of an assembly of optimized DSRDs in the developed generator provides a twofold increase in the limiting switched energy.

A compact 300 kV solid-state high-voltage nanosecond generator for dielectric wall accelerator.

Compact solid-state system is the main development trend in pulsed power technologies. A compact solid-state high-voltage nanosecond pulse generator with output voltage of 300 kV amplitude, 10 ns duration (FWHM), and 3 ns rise-time was designed for a dielectric wall accelerator. The generator is stacked by 15 planar-plate Blumlein pulse forming lines (PFL). Each Blumlein PFL consists of two solid-state planar transmission lines, a GaAs photoconductive semiconductor switch, and a laser diode trigger. The key components of the generator and the experimental results are reported in this paper.