Repetitive Nanosecond Pulse Generator Research Articles

Further Investigations on a Modified Avalanche Transistor-Based Marx Bank Circuit

Avalanche transistor-based Marx bank circuit (MBC) is widely used to generate nanosecond pulses with high amplitude, high repetition rate, fast rise time, and low jitter. Recently, the problem that avalanche transistors in the first several stages of $M \times N$ -stage MBC fail frequently has been alleviated by adopting auxiliary triggering topology (ATT). However, the reasons for improvement and the optimal design method have not been fully understood. In this article, a flexible $4\,\,\times10$ -stage MBC is developed to further investigate the output characteristics under different modified stages, capacitors, and loads through both experiments and simulations. The results show that on the one hand, adopting ATT will cause energy loss of the main capacitors to auxiliary triggering capacitors, which can decrease the output voltage; and on the other hand, transistors operating in the auxiliary triggering switching-ON mode have lower residual voltage than in the lower overvoltage switching-ON mode, which can increase the output voltage. This implies that there exists an optimal value of modified stages, which is 5 for the $4\,\,\times10$ -stage MBC. Besides, by adopting ATT, the waveform of output pulse changes, and the rising edge becomes faster. Finally, a repetitive nanosecond pulse generator is developed based on the optimized parameters, which can produce pulses with an amplitude of 9.04 kV, a rise time of 3.4 ns, a pulse width of 18.8 ns, and a maximum repetition rate of 1 kHz at the 75- $\Omega $ open-ended cable. Also, the feasibility of this modified MBC is validated by the preliminary experiments of driving atmospheric pressure plasma jet (APPJ).

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.

Effect of Airflows on Repetitive Nanosecond Volume Discharges**supported by National Natural Science Foundation of China (Nos. 51006027, 51437002, and 51477035)

Atmospheric pressure discharges excited by repetitive nanosecond pulses have attracted significant attention for various applications. In this paper, a plate-plate discharge with airflows is excited by a repetitive nanosecond pulse generator. Under different experiment conditions, the applied voltages, discharge currents, and discharge images are recorded. The plasma images presented here indicate that the volume discharge modes vary with airflow speeds, and a diffuse and homogeneous volume discharge occurs at the speed of more than 35 m/s. The role of airflows provides different effects on the 2-stage pulse discharges. The 1st pulse currents nearly maintain consistency for different airflow speeds. However, the 2nd pulse current has a change trend of first decreasing and then rapidly increasing, and the value difference for 2nd pulse currents is about 20 A under different airflows. In addition, the experimental results are discussed according to the electrical parameters and discharge images.

Optimization Design of a Repetitive Nanosecond Pulse Generator Based on Saturable Pulse Transformer and Magnetic Switch

Saturable pulse transformer (SPT) and magnetic switch (MS) are widely used together in pulse generators (PGs). It is easy to obtain a desirable output with a high voltage and low rise time when choosing the suitable PG topology. A compact, unipolar, and repetitive high-voltage nanosecond PG, which is based on SPT and MS, is designed and constructed. The operation principles of the resonant charging based on SPT and MS are described. The design and performance optimization of the magnetic components including SPT and MS are presented. The minimum volume of the SPT is derived and verified in the experiment. The core volume and turns of the MS are determined both considering the charging process and the output characteristic. The saturation times of the pulse transformer and MS can be optimally determined based on the $B$ – $H$ curve, which is obtained under the same working conditions. It reveals that the design and performance optimization methods of the SPT and MS are reasonable and can be used to guide the design of pulse transformers and MSs in pulsed power, power electronics, and industrial electronics.

Optical and electrical investigation of a cylindrical diffuse-discharge chamber

More and more attention has been attached to atmospheric-pressure air diffuse plasma due to its enormous potential applications. In this paper, we designed a large-scale, cylindrical diffuse-plasma chamber using wire electrodes and a repetitive nanosecond pulse generator. The plasma chamber can be completely exposed in the open air without any barrier dielectric, and the length of cylindrical plasma chamber was extensible. Using optical and electrical measurements, we investigated the effects of electrode distance, electrode length, pulse repetition frequency, and electrode angle on the uniformity of discharge space. Four discharge regions were distinguished based on different spectral characteristics. Additionally, it was found that the discharge uniformity was improved as the electrode distance decreases, but remained almost constant with the variations of electrode length and pulse repetition frequency. Both of the plasma uniformity and the power density increased significantly as the electrode angle reduced.

Repetitive nanosecond pulse generator based on Tesla transformer

The combination of pulse transformer and sharpening switch is a relatively mature way to generate nanosecond pulse. In this way, a compact high voltage repetitive nanosecond pulse generator (HRNPG) based on Tesla transformer and spark switch is developed in this paper. The pulse generator mainly consists of a repetitive charging module, a Tesla transformer and a sharpening switch. Repetitive charging module is mainly implemented by temporal coordination of two thyristors, Tesla transformer is the core of the pulse generator and main booster module, sharpening switch is a three electrode self-breakdown type gas switch, which is used to sharpen the transformer secondary voltage into nanosecond pulse waveform. Each part of the HRNPG is presented and tested in detail. Applied to a 6 k resistor, the HRNPG prototype is capable of generating a pulse with 100 kV peak voltage and 30 ns rise time at the maximum repetition rate of 500 Hz.

Tesla变压器型重复频率纳秒脉冲源的研制

Tesla变压器型重复频率纳秒脉冲源的研制

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Resonant Charging Performance of Spiral Tesla Transformer Applied in Compact High-Voltage Repetitive Nanosecond Pulse Generator

The compact, small-sized device based on a pulsed transformer combined with a semiconductor switch is a feasible solution that generates the high-frequency and high-voltage pulse. Compared with other types of transformers, spiral Tesla transformer is much easier to achieve a high output-voltage ratio. By an in-depth analysis of the resonance circuit of Tesla transformer, the expressions of secondary voltage, transformation ratio, peak, and steepness of the primary current are deduced and analyzed in this paper. The development test of a small-size Tesla transformer prototype has been performed. The key electrical characteristics are further measured, estimated, and discussed. The specification parameter selection of the primary semiconductor switch must rely on the characteristics of primary current. Applied to a 6.0 kΩ resistor, the high-voltage repetitive pulse generator based on the Tesla transformer prototype can generate a series of pulses with a peak voltage of 100 kV and a rise time of 40 ns at the repetition rate of 200 Hz. Atmospheric air nonequilibrium plasma can be formed using the developed pulse generator and some typical images are presented.

A Tesla-type repetitive nanosecond pulse generator for solid dielectric breakdown research

A Tesla-type repetitive nanosecond pulse generator including a pair of electrode and a matched absorption resistor is established for the application of solid dielectric breakdown research. As major components, a built-in Tesla transformer and a gas-gap switch are designed to boost and shape the output pulse, respectively; the electrode is to form the anticipated electric field; the resistor is parallel to the electrode to absorb the reflected energy from the test sample. The parameters of the generator are a pulse width of 10 ns, a rise and fall time of 3 ns, and a maximum amplitude of 300 kV. By modifying the primary circuit of the Tesla transformer, the generator can produce both positive and negative pulses at a repetition rate of 1-50 Hz. In addition, a real-time measurement and control system is established based on the solid dielectric breakdown requirements for this generator. With this system, experiments on test samples made of common insulation materials in pulsed power systems are conducted. The preliminary experimental results show that the constructed generator is capable to research the solid dielectric breakdown phenomenon on a nanosecond time scale.

Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air

Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ~30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented.

Experimental study of Q-V Lissajous figures in nanosecond-pulse surface discharges

A charge-voltage Lissajous figure is a standard method for the electrical diagnostics of DBD discharges. Based on a repetitive nanosecond-pulse generator, some experiments on surface discharges are carried out in open air. The effects of applied voltage amplitude, pulse repetition frequency, electrode gap spacing, and electrode width on the characteristics of the Lissajous figures are presented in this paper. Results show that two different kinds of typical discharge characteristics are observed, and the discharge characteristics vary between these two kinds of discharges when the discharge parameters change. The applied voltage has little effect on the shape of the Lissajous figure, and the total and barrier capacitances of actuator. Both transported charge and energy per pulse are proportional to the applied voltage amplitude. The applied voltage plays an important role in the discharge uniformity, intensity and length of surface plasmas. The pulse repetition frequency plays an important role in the energy and discharge intensity accumulation and has no effect the electrical parameters of surface discharges. The shape of the Lissajous figure gradually changes with the electrode gap and the transported charges proportionally decrease as the electrode gap increases. There is a transition gap spacing to obtain the maximum plasma energy and to achieve a relatively uniform plasma. The capacitances of the actuator, the transported charges and energy per pulse increase with the electrode width. The intensity of surface discharges is little affected by the electrode width, but the plasma uniformity tends to worsen with the increasing width. There is a corresponding relationship between the shape of the Lissajous figures and the uniformity of plasma distribution. The almond-like Lissajous figure is attained with a compromise between the electrode gap and width.

空气中纳秒脉冲介质阻挡放电高速摄影

The dielectric barrier discharge (DBD) at one atmospheric pressure is excitated in a configuration of two water electrodes by a repetitive nanosecond-pulse generator with 40 ns rise time and 70 ns duration. The DBD characteristic is studied by the measurement of DBD voltage and current, DBD images of long and nanosecond exposures. Especially, the discharge images taken by ICCD with 2 ns exposure time are used to study the temporal behaviour of the discharge development. The results indicate that the nanosecond-pulse discharge is uniform and stable with the water electrodes in atmospheric air and there is a secondary discharge. The homogeneous discharge starts from the central part of the discharge area and spreads radially outward.

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

Nanosecond Repetitively Pulsed Discharge of Point–Plane Gaps in Air at Atmospheric Pressure

Atmospheric-pressure gas discharge excited by high-voltage pulses with fast rise time and short duration has attracted significant attention for various applications. In this paper, discharges are generated in a highly nonuniform electric field by point-plane gaps in air at atmospheric pressure by a solid-state repetitive nanosecond-pulse generator. Under different experimental conditions, the applied voltage, discharge current, and discharge image are recorded. The results show that there are four typical discharge fashions, i.e., corona, diffuse, filamentary, and diffuse-to-filamentary modes. With the variation of air gap spacing or applied pulse repetition rate, the difference among various discharge modes can be found in discharge current and luminous images. Moreover, the effects of repetition rate and air gap spacing on electrical characteristics and discharge modes are investigated. It is seen that the discharge tends to transit from the diffuse mode to the filamentary mode with the reduction of air gap spacing or the increase of repetition rate. In addition, the experimental results are discussed according to the electrical parameters and discharge images.

A compact repetitive high-voltage nanosecond pulse generator for the application of gas discharge

Uniform and stable discharge plasma requires very short duration pulses with fast rise times. A repetitive high-voltage nanosecond pulse generator for the application of gas discharge is presented in this paper. It is constructed with all solid-state components. Two-stage magnetic compression is used to generate a short duration pulse. Unlike in some reported studies, common commercial fast recovery diodes instead of a semiconductor opening switch (SOS) are used in our experiment that plays the role of SOS. The SOS-like effects of four different kinds of diodes are studied experimentally to optimize the output performance. It is found that the output pulse voltage is higher with a shorter reverse recovery time, and the rise time of pulse becomes faster when the falling time of reverse recovery current is shorter. The SOS-like effect of the diodes can be adjusted by changing the external circuit parameters. Through optimization the pulse generator can provide a pulsed voltage of 40 kV with a 40 ns duration, 10 ns rise time, and pulse repetition frequency of up to 5 kHz. Diffuse plasma can be formed in air at standard atmospheric pressure using the developed pulse generator. With a light weight and small packaging the pulse generator is suitable for gas discharge application.

Electrical characterization of dielectric barrier discharge driven by repetitive nanosecond pulses in atmospheric air

Dielectric barrier discharge (DBD) is an important method to produce non-thermal plasma, which has been widely used in many fields. In the paper, a repetitive nanosecond-pulse generator is used for the excitation of DBD. Output positive pulse of the generator has a rise time of about 15 ns and a full width at half maximum of 30–40 ns, and pulse repetition frequency varies from single shot to 2 kHz. The purpose of this paper is to experiment the electrical characteristics of DBD driven by repetitive nanosecond pulses. The variables affecting discharge conditions, including air gap spacing, dielectric thickness, barrier fashion, and applied pulse repetition frequency, are investigated. The relationship between electric field, discharge current, instantaneous discharge power across air gap, and estimated electron density with the length of air gap, dielectric thickness, barrier fashion, and pulse repetition frequency is obtained respectively, and the experimental results are also discussed. In addition, two typical images exhibiting homogeneous and filamentary discharges are given with different experimental conditions.

Breakdown Phenomena in Nitrogen Due to Repetitive Nanosecond-pulses

Nanosecond-pulse breakdown indicates special characteristics depending on the pulse rise-time and duration. Based on a repetitive nanosecond-pulse generator, breakdown phenomena of parallel-plane gaps in nitrogen were investigated with single pulse and repetitive bursts under different gap conditions. The relationships between applied voltage, pulse repetition frequency, breakdown time lag, repetitive pulse stress time and the number of applied pulses are presented. The curves regarding E-field strength, breakdown time lag and gas pressure are also obtained. The experimental results show that breakdown characteristics with repetitive nanosecond-pulses are different from that with single pulse. Repetitive nanosecond-pulse breakdown is concerned with the accumulation effect that is attributed to residual ions and metastable species survived from previous pulses. In addition, a modified empirical formula about E-field strength, breakdown time lag and gas density is given for the breakdown data.