Search

Graphene has attracted great interest for its distinctive band structure and physical properties. Results from previous studies show that a graphene cathode can provide stable field emission and intense emission in a vacuum. In this paper, a graphene cathode was fabricated using chemical vapor deposition (CVD) on copper electrodes, and the breakdown of the cathode in a high-pressure gas was studied. A low-jitter, self-breakdown gas spark switch based on a graphene cathode is proposed in this paper. The impulse-breakdown characteristics of this switch in a quasi-uniform electric field were studied. When the gap length is 5 mm, and the gas pressure is 0.6 MPa, the average breakdown voltage ($U_{\mathrm {BD}}$) is nearly 85.9 kV, and the voltage jitter is only 3.2%; these values are much lower than those for pure copper cathodes and graphite cathodes. The graphene cathode is found to be a suitable choice for use as a high-power gas switch in applications requiring an intense emission source. [ABSTRACT FROM AUTHOR]

This paper has introduced two important indexes, turn-off surge voltage (TSV) on power switch and peak positive pole potential (PPPP) of storage batteries, which can be used to evaluate switching transient process of high-voltage energy storage system. Research on them is of great significance to power switch choice and high-voltage isolation design in engineering applications. Power switch response process at the turning off moment and transient process in freewheel stage have been analyzed by the established small-signal model of single power switch; then, a power switch test platform for hybrid energy storage system was built to verify it. Taking pulsed-power supply charging device with a novel inductor of low resistance and high inductance as a research object, this paper has analyzed dynamic process of the TSV and the PPPP at the turning off moment through establishing state space model of the whole system. Comparison shows that the numerical curves match the simulated curves well. Finally, the exactness of the employed model has been further verified in two pulse capacitor charging experiments. [ABSTRACT FROM AUTHOR]

The planned China fusion engineering test reactor (CFETR) needs one or more negative-ion-based neutral beam injectors (N-NBIs) with a beam energy of 500 or even 1000 keV. In order to prepare for CFETR, a prototype of CFETR N-NBI is being designed. The prototype needs an acceleration grid power supply (AGPS) rated at 200 kV/25 A with a maximum pulselength reaches to 3600 s. The AGPS adopted a single-stage inverter-type high-voltage power supply (HVPS). The output voltage ripple is an important specification of the AGPS, which can affect the efficiency and stability of N-NBI system by influencing the beam divergence. However, the conventional methods cannot be used to limit the output voltage ripple of the inverter-type HVPS used as AGPS of CFETR N-NBI prototype. This paper simplified the AGPS to an insulated three-phase three-level (TPTL) dc–dc converter connected with a dual dc link. The working process of the TPTL dc–dc converter with duty-cycle modulation has been analyzed, and two main continuous conduction modes are described. The influence of key parameters such as duty cycle of inverter, leakage inductance of transformer, and output current on output voltage ripple is analyzed. Based on the analysis results, a so-called combined control strategy was proposed to keep the output voltage ripple at a level. The proposed strategy is suitable for the cases where the object output voltage is below 175 kV. Some simulations were carried out by using MATLAB/Simulink. The results showed that the analysis in this paper is reliable and the proposed control strategy has a good performance. [ABSTRACT FROM AUTHOR]

This paper proposes unconventional control techniques for a portable power supply consisting of electric double-layer capacitors (EDLCs), a dc–dc converter, and a low-impedance load such a plasma load. Between the EDLCs and the plasma load consuming high power, a dc–dc converter is required to control the output voltage from the rapidly decreasing voltage of EDLCs. In addition, the dc–dc converter should maintain a set point by responding to arcs occurred in plasma process. This paper proposed hybrid analog and digital controls for a nonideal boost converter which was setup by theoretical analysis. The proposed system is verified with experiment and simulation. As a result, the proposed control method can maintain the constant output voltage longer than a traditional analog pulsewidth modulation control. [ABSTRACT FROM AUTHOR]

This paper discusses a novel methodology to increase the voltage droop compensation range in generalized solid-state bipolar high-voltage Marx modulators with one resonant stage. To maintain the modularity characteristic of bipolar Marx modulators, the imbedding of additional resonant stages is not straightforward. Nevertheless, this paper proposes to add a second resonant stage to the already existing resonant-type voltage droop compensation stage. This second stage increases the voltage droop compensation percentage of a generalized solid-state bipolar Marx generator. The compensation of the bipolar pulse voltage droop is now achieved by adding two auxiliary synchronous compensation resonant voltages, to the output capacitive decaying voltage. Simulation and experimental results are presented for six Marx plus two resonant stages, 16% voltage droop, with 3-kV pulse amplitude, 100- $\mu \text{s}$ pulsewidth, 40-ms relaxation time, and 10-Hz pulse repetition rate. [ABSTRACT FROM AUTHOR]

This paper presents the design and construction of a sample of Marx pulsed generator based on boost converter (BC) pulse-forming networks (BCPFNs). BCPFN is used instead of the conventional Marx floors for constructing this pulsed generator. BCPFN is carried out by connecting inductors and capacitors in series and parallel modes, respectively, by using solid-state switches, and during this procedure the pulsed generator converts to BC temporarily and increases the voltage of capacitors uniformly to a considerable value. This technique causes an increase in the discharging voltage level to the load that is many times more than its dc voltage source by charging the capacitors to a greater level. In order to take advantage of the benefits of Marx generator and PFN, this paper suggests a new circuit with the minimum number of switches. It means, to compose BCPFN and Marx, we have tried to design the circuit with fewer switches and instead of it we have achieved our desired performance with changing the operating mode in the states of BC, PFN, BCPFN, and BCPFN Marx. The results are simulated with MATLAB software. At the end, the experimental results of the construction of the above-mentioned system at low-power levels are presented, and the topology’s accuracy is proved by comparing them to the results of simulation. [ABSTRACT FROM AUTHOR]

Magnetic pulse compression (MPC) systems are suitable for generating dielectric barrier discharges (DBDs) owing to their capability of producing high-amplitude, short pulse voltage waves. This paper proposes a high-frequency, bipolar magnetic compression system to study DBD plasma characteristics. First, the principle of bipolar MPC is explained [a bipolar MPC system comprises a full bridge inverter circuit, pulse transformer (PT), and magnetic switch (MS)]. Additionally, the design of the PT and MS is described. Then, the waveform of the resistive load is tested and compared with PSpice simulation results. It was found that the nanosecond pulse generator produces a pulse on a resistor with an amplitude of 0–13 kV, a rise time of approximately 100 ns, and a repetition frequency of 0 to several kHz. Finally, this paper studies the plasma characteristics under the application of a high-frequency bipolar pulse, and the charge–voltage Lissajous figure of the discharge waveform is analyzed. Combining discharge photographs and theoretical calculation results yields the relationship between the discharge characteristics and the frequency, which enriches the theoretical study of high-frequency bipolar discharges. [ABSTRACT FROM AUTHOR]

High-voltage high-power pulse switches are built with semiconductor devices, preferably thyristor, due to the superior performance that they offer. Triggering methods classify the thyristor as electrically triggered thyristor (ETT) and light triggered thyristor (LTT). Due to the specialized gate constructions and many build-in protections, the cost of LTT is much higher than ETT. The operating modes in applications, such as crowbar, do not require all these build-in protections. In this paper, the operation of a crowbar is analyzed, and the build-in protections of LTT are reviewed. This paper proposes three experiments for the design selection of thyristor, between ETT and LTT, for crowbar applications. The experiments cover the electrical performance as well as electromagnetic emissions in a 10-kV, 1-kA crowbar built with both ETT as well as LTT, which can be used to benchmark the performance of the crowbar circuit. From the three experiments, the performance of ETT-based crowbar is found to be comparable with LTT-based crowbar. Based on the experiments carried out with the proposed benchmarking approaches, this paper shows that ETT-based crowbar is a cost-effective solution for crowbar applications. [ABSTRACT FROM PUBLISHER]

This paper presents the effect of stray capacitances in bipolar (negative and/or positive) pulses generated by the two different topologies of the solid-state Marx modulators. According to the analysis, the stray capacitances influence the energy transfer from the Marx modulator capacitors to the load affecting the bipolar (negative and/or positive) pulse rise time. This paper deals with the structure design to reduce the influence of the stray capacitance and to improve the pulse rise time of these bipolar solid-state Marx modulators. A four-stage laboratory prototype of the two topologies has been assembled using 1200-V insulated gate bipolar transistors and diodes, operating with 1000-V dc input voltage and 1-kHz frequency, producing 4-kV bipolar pulses, with 5- \mu \texts pulse duration and 120-ns rise time, into a resistive load. [ABSTRACT FROM PUBLISHER]

Studies have been taken into the breakdown voltage jitter of corona-stabilized switch at high repetition rate up to several kHz. It is thought that the gas recovery affect the jitter of breakdown voltage directly at high repetition rate, because the gas switch will breakdown at a low voltage if the gas cannot fully recover. The breakdown voltage jitter is called voltage jitter in the following paper. However, based on the experimental results, the voltage jitter still exists at low repetition rate, even at single-shot mode. This is not explained by the previous studies. In this paper, voltage jitter below 100 Hz of a corona-stabilized switch is investigated experimentally. A corona-stabilized switch is introduced, using a cylindrical electrode as the cathode and a plane electrode as the anode. The gas used between the electrodes is SF6. A negative pulse with a maximum width of 30~\mu \texts is used to charge this switch. The tested factors include gas pressure, gap space, repetition rate, and switch geometry. Experimental results show that voltage jitter is mainly affected by the gas pressure and switch geometry. It is seen that voltage jitter decreases as gas pressure increases and a suitable cathode geometry presents a low voltage jitter. Critical volume is a region close to the highly stressed electrode, where the presence of an electron will lead to an electron avalanche which attains a critical size and hence leads to a stabilizing corona. Critical volume is introduced to explain the experimental results. It is found that less voltage jitter can be achieved with a smaller and more concentrated critical volume, as well as efficient corona stabilization. The results indicate that voltage jitter may be reduced by optimize the critical volume at low repetition rate. [ABSTRACT FROM PUBLISHER]

High power pseudospark switches (PSSs) can control pulsed high voltage, high peak current discharges. In this paper, a PSS in series with a saturable inductor at the anode is investigated. The commutation process is analyzed with a time-resolved method. And the effects of the number of magnetic cores and anode voltages on discharge characteristics are studied experimentally. At the beginning of commutation process, when the anode voltage is 10.4 kV with four magnetic cores, the inductor is unsaturated, and there is a flat plateau of the forward voltage drop after the anode voltage drops rapidly to about 200 V, at the same time the current rise rate is 2.8 kA/ $\mu \text{s}$. When the inductor is saturated, there is a voltage spike that occurs at the end of the flat plateau, and the current simultaneously rises rapidly at the rate of 6.4 kA/ $\mu \text{s}$. The current sharp rise lags behind the voltage drop of the pseudospark gap, and the electrode erosion and energy dissipation reduce significantly. When the anode voltage is 15.6 kV, the commutation losses reduce by about 30% with seven cores in series at the anode. As a result, it is evident that the discharge process will speed up if the anode voltage is higher. And the trigger delay decreases by up to 8% when the anode voltage varies from 5.2 to 15.6 kV. Finally, in order to obtain a reproducible pseudospark discharge by the use of a saturable inductor, the number of magnetic cores has to be optimized for different anode voltages. [ABSTRACT FROM AUTHOR]

This paper describes a study on the high-voltage compact solid-state pulsed-power modulator for parallel reactor operation. The current capacity of the pulsed modulator has been improved to drive multiple reactors in parallel. The pulse discharge switch uses the IXYK120N120C3 (1200 V/120 A) insulated-gate bipolar transistor for a high current output. The gate driver has been improved according to the characteristics of the replaced switch. The output specifications of the modified pulsed-power modulator are a maximum output voltage of 40 kV, a maximum output current of 300 A, a pulsewidth ranging from 1.5 to $5~\mu \text{s}$ , a maximum repetition rate of 3 kHz, and an average power of 13 kW. The modulator has the dimensions of $450 \times 475 \times 600$ mm3, a maximum peak power of 12 MW, and a maximum power density of 93 kW/L. A resistive load experiment and a plasma reactor parallel drive test were performed. Four parallel reactors were driven using one modulator. In addition, a 50% reduction in the concentration of toluene was obtained through the experiment of the toluene gas treatment using only parallel plasma reactors. [ABSTRACT FROM AUTHOR]

Amorphous magnetic core has been widely used in pulsed power technology with applications including plasma science research, high-power microwave generation, and material surface treatment. For different applications, dynamic properties of the magnetic core will vary with stimulated magnetic field which determines by magnetization time and waveform of the driving voltage. In this paper, toroidal amorphous magnetic core ($\Phi ~540$ – $740\times25$ mm) was investigated theoretically, numerically, and experimentally. Specifically, the circuit is analyzed. A high-voltage test stand, which can generate different driving voltages with same components, was designed and developed in our laboratory. Dynamic properties, including magnetic induction change, coercive force and losses, were studied under three different typical waveforms with the same magnetic flux. Driving voltages of the pulses were 12, 12, and 6 kV and the magnetization rates were 0.6, 1.2, and 0.6 T/ $\mu \text{s}$ , respectively. Experimental results show reasonable agreement with the numerical analysis. [ABSTRACT FROM AUTHOR]

This paper addresses the design of a solid-state bipolar pulsed-power modulator based on a series of stacked power cells that realize a simple and robust structure. Each cell is charged in parallel by an LCC resonant converter independently of the discharging loop. A passive cell-balancing design is implemented. The power cell using insulated gate bipolar transistors (IGBTs) can operate in bypass mode without an additional component, and the circuit operation was analyzed. A simple gate driving method, which provides synchronized gate signals without an extra power source of each gate driver using two control loops and isolation transformers, is implemented for the proposed bipolar pulsed-power modulator based on stacked cells. Moreover, an unexpected gate turn-on problem was solved by an additional off signal. To validate the proposed structure and the gate driving scheme, a three-cell, 1.2-kV, 110-A, 1.5- to 4- $\mu \text{s}$ , 3-kHz laboratory experimental prototype test was conducted. The results proved the reliability of the proposed solid-state bipolar pulsed-power modulator. [ABSTRACT FROM AUTHOR]

This paper proposes a flyback-circuit-based design of a trigger circuit for a high-power gas switch. By incorporating a flyback circuit in a high-power gas switch, it is possible to generate a high step-up ratio and high-voltage pulse by using a transformer. Furthermore, simple trigger circuit having the minimum possible number of components (transformer and switch) can be realized. When an inductor is used as an energy storage element, energy is stored as a current source, and thus, the element can operate reliably when low impedance exists between the trigger node of the switch after triggering. According to the fundamental operating principle of a flyback circuit, the proposed trigger circuit is designed considering the maximum trigger voltage and energy required for a high-power gas switch. To verify the proposed design procedure and feasibility of the trigger circuit, a compact trigger circuit (7.5 kV, 1.3 mJ/pulse) is simulated using the PSpice program and implemented. Based on this compact circuit, a trigger circuit (20 kV, 100 mJ/pulse) for a triggered vacuum switch (TVS) is developed, and the tests with an actual TVS (3.3 kJ) are carried out. [ABSTRACT FROM AUTHOR]

Marx generator using all-solid-state devices has been studied for many years. Higher parameters are always the demand for new applications. Traditional all-solid-state Marx generator can output high voltage due to its series topology, but the current is always limited by the switch. In this paper, a stage-stage paralleled topology of Marx generator for high current has been proposed. Topology structure and driving mode comparison for current balance have been analyzed. The paralleled driving mode for the current balance and the shaping waveform has been proposed. For experiment, a four-stage-four-paralleled Marx generator with metal–oxide–semiconductor field-effect transistors (MOSFETs) has been constructed with output pulses 2.2 kV, 730 A (depending on the load), rise time of 31 ns, fall time of 56 ns, and adjustable pulsewidth from 400 to 800 ns. [ABSTRACT FROM AUTHOR]

This paper describes the development of a small field-distortion spark gap switch. Comprehensive experimental studies made with the switch revealed its self-breakdown characteristics, voltage operating range, time delay and jitter, repetition frequency, and finally the electrode erosion processes and duration of its service lifetime. A series of design improvements were required to be implemented in the switch design. For example, to reduce the structural inductance of the switch and to improve its working characteristics, the main electrode was designed as a circular track structure. Similarly, to increase the operation stability and reduce the self-breakdown probability, the trigger electrode was designed as a disk-like structure. Moreover, to balance the gas pressure in the discharge region and increase the stability during closure, a circular hole was added at the center of the trigger electrode. The compact switch has a small size of only 150 mm $\times42$ mm, a weight of 1.5 kg, and can be successfully operated at a voltage over 110 kV, at a repetition rate between 1 and 50 Hz and having a jitter of less than 4 ns. It was experimentally demonstrated that during normal operation conditions, the switch lifetime exceeds 100 000 shots. [ABSTRACT FROM AUTHOR]

Working performances of laser-triggered vacuum switch (LTVS) mainly rely on the interactions of laser with target materials. Influences from target configuration, which is one of key factors in the interactions, are neglected so far. The trigger performances of LTVS with different target configurations are studied in this paper. Relevant influence factors about target configurations are discussed briefly based on theoretical analysis about the trigger process. The test prototype is established based on detachable vacuum chamber. The trigger characteristics of LTVS with different target structures, target depths, and laser focal positions are compared. The relationships between target configurations and trigger performances of LTVS are analyzed and discussed. The preferred targets in LTVS are suggested while considering its lifetime. The test results prove that the conical target shows the best trigger performances compared to other targets. Due to the enlarged laser irradiated area and shortened plasma moving distance, the delay time of LTVS reduces with the decrease in conical target angle and the increase in target depth, while the delay time is controlled within 32 ns. Benefited from laser reflection and plasma collision, the trigger performances of conical targets can be enhanced by focusing laser on the target side surface. In particular, the 90° conical target with 1.5 mm depth is suggested to be employed in LTVS products. [ABSTRACT FROM AUTHOR]

A quench protection switch (QPS) is indispensable to protect the magnet coils from the damage of quench in a superconducting Tokamak. In this paper, a QPS based on artificial current zero is involved. The vacuum circuit breaker (VCB), which is driven by a high-speed electromagnetic repulsion mechanism, is used as the main circuit breaker (MCB). Two kinds of commercial vacuum interrupters (VIs), which have contacts generating axial magnetic field (AMF) and transverse magnetic field (TMF), respectively, are applied. The breaking current with an amplitude of 10~25 kA is generated by an LC oscillating circuit. The countercurrent with frequency in the range of 500–3000 Hz is provided by a commutation branch. The interruption performance of the two kinds of VIs under different breaking current and countercurrent frequencies is investigated. The experimental results indicate that the differences in interruption performance under the two types of contacts are increasing with larger frequencies of countercurrents. [ABSTRACT FROM AUTHOR]

Because it possesses higher current turn-off capability, the inverse current commutation with semiconductor devices (ICCOS) is a better option for the opening switch of an inductive pulsed power supply than the integrated gate commutated thyristor. This paper investigates the counter-current capacitor, which is the key component that determines the turn-off result and the volume of the counter-current branch. The major contributions of this paper include the following: 1) deriving an analytical expression for the minimum precharged capacitor voltage that can reliably turn off the main switch; 2) verifying this expression through a series of experiments within a current range of 0 to 4000 A and an energy range of 0 to 50 kJ; 3) giving an approximate expression for the optimal capacitance that minimizes the precharged energy; and 4) investigating the variation trends of the optimal capacitance and the corresponding optimal precharged energy with varying inductor current. [ABSTRACT FROM PUBLISHER]

Compulsators are ac generators which are used for electromagnetic launch applications over the past few decades. This paper presents the work carried out by the authors to design a compulsator for a railgun which has been built and tested with a capacitor bank of 20 kJ as the pulsed-power source in the author’s laboratory. The generator topology selected for the compulsator is a single phase, two-pole machine with iron core and passive compensation. The design is based on the criterion of achieving maximum projectile exit velocity with the additional condition that natural current zero is synchronized with the instant of the projectile’s exit. The effect of varying the different parameters of the compulsator on the performance of the system has also been studied and discussed in this paper. By means of performance analysis, the necessary background for the design of the actual compulsator has also been achieved. [ABSTRACT FROM PUBLISHER]

Superconducting pulsed-power supply (SPPS) provides an efficient method for both high-density inductive energy storage and high current pulse generation. An SPPS consisting of eight high-temperature superconducting pulsed-power transformer (HTSPPT) modules with XRAM methodology was designed and simulated in preliminary studies. It recycled the leakage flux energy and reduced the voltage across the opening switch with a capacitor in primary. However, the SPPS with XRAM methodology has two problems. The first one is that it can provide high pulse amplitude, but cannot provide enough width. The other one is that the ratio of the maximum capacitive energy over the total inductive energy is relatively large, which cuts down the overall system energy density. This paper proposes a modified topology of SPPS with capacitor reuse methodology. Multiple HTSPPT modules are divided into several groups. Each group shares the same capacitor. The procedure of the modified SPPS is presented in detail. A 270-kJ SPPS with capacitor reuse methodology is designed and simulated to illustrate the modified topology. With the load parameters of a small railgun, the peak value of the load current is 207.15 kA and the pulse half-height width is 5.56 ms, the ratio of the maximum capacitive energy over the total inductive energy is 11%. The characteristics of the modified topology are also described in detail in this paper. [ABSTRACT FROM PUBLISHER]

Repetitive high pulsed electric field (PEF) is an effective method to kill microorganisms and bacteria in water treatment applications. The PEF can be generated by applying high-power electromagnetic pulse across the sample to be treated. There are two main types of high-voltage pulse generators, namely, unipolar and bipolar. In this paper, a full-bridge submodule-based modular high-voltage pulse generator, having the ability to generate unipolar and bipolar high-voltage pulses with different shapes from a relatively low-voltage input dc supply, is proposed. In the proposed configuration, relatively low-voltage insulated gate bipolar transistors (IGBTs) are required to generate the high-voltage bipolar pulses. A thyristor rated at the level of the pulsed output voltage is required in the proposed configuration to bypass the load during the charging process of capacitors. In the proposed approach, a thyristor is used instead of the self-commutated high-voltage switch (e.g., series-connected IGBTs), as thyristors are available with high-voltage ratings and possess inherent reverse voltage blocking capability. A detailed illustration of the proposed configuration and its operational concept are introduced in this paper. Simulation and experimental results are presented to validate the proposed approach. [ABSTRACT FROM AUTHOR]

This paper proposes an active resonance circuit based on multiple series gaps (MSG) with voltage-dividing network and self-charging trigger device. The working principle of active resonance circuit, MSG, and triggering device is described in detail. To determine the optimal parameter setting of MSG, the effects of the voltage frequency, equalizing resistance, and voltage-dividing capacitance on the voltage distribution of MSG are analyzed by simulation. To realize the interrupting process of short fault current and determine the operation requirements of the main devices of precharge direct current (dc) circuit breaker, a simulation model of interrupting short fault current is performed. Furthermore, an experiment of four-series gaps is presented to verify the turn-on characteristic of the MSG and an experiment of artificial current zero is set up to testify the feasibility of the active resonance circuit. The simulation and experimental results show that the active resonance circuit proposed in this paper can generate an artificial zero current and is suitable for precharge dc circuit breaker. [ABSTRACT FROM AUTHOR]

Bipolar junction transistors (BJTs) have been widely studied and used in nanosecond high-voltage pulse generators due to the advantages of fast switching speed and high repetitive frequency. Usually the Marx-type circuit is used to raise the peak value of output pulses. In this paper, a traditional BJT-Marx circuit using charging resistors is analyzed theoretically and experimentally. Based on the results, the structure of a circuit is changed to decrease the isolation voltage across the resistors, and diodes are used to replace charging resistors to block capacitors discharging to resistors. Experimental results showed that the three Marx generators proposed in this paper output pulses with higher voltage amplitude, and the last improved circuit outputs pulses with faster fall times at a higher efficiency. [ABSTRACT FROM AUTHOR]

We present a new technique for the design and test of coaxial switched oscillators (SWOs). In this paper (Part I of a two-part paper), we concentrate on the electrostatic design of coaxial SWOs. We introduce a new design for the electrodes, which have been conceived as conformal surfaces in a geometrically convenient curvilinear space where Laplace equation is solvable. Analytical solution of the electrostatic fields is presented, discussed, and validated using numerical simulation. A prototype of an SWO based on this design is built and validated using experimental data. [ABSTRACT FROM AUTHOR]

This paper shows how to use modular Marx multilevel converter diode ( \textM^3 CD) modules to apply unipolar or bipolar high-voltage pulses for pulsed power applications. The \textM^3 CD cells allow the assembly of a multilevel converter without needing complex algorithms and parameter measurement to balance the capacitor voltages. This paper also explains how to supply all the modular cells in order to ensure galvanic isolation between control circuits and power circuits. The experimental results for a generator with seven levels, and unipolar and bipolar pulses into resistive, inductive, and capacitive loads are presented. [ABSTRACT FROM AUTHOR]

In this paper, we discuss and demonstrate the potential of normally-on GaN high-electron-mobility transistors (HEMTs) as opening switches in miniaturized pulsed-power circuits. The high-breakdown electric field of GaN (~3 MV/cm) makes it possible to fabricate high-voltage devices in small dimensions, resulting in smaller parasitics and faster switching times. GaN HEMTs as opening switches are compatible with inductive topologies, which offer more than one order of magnitude higher energy density than capacitive topologies, allowing further miniaturization of pulsed-power systems. In this work, we demonstrate the application of fabricated 1.5-kV normally-on GaN HEMTs on an inductive switching topology, resulting in 300-fold voltage step-up, which makes it possible to generate high-voltage pulses with a low-voltage dc source in miniaturized circuits. [ABSTRACT FROM AUTHOR]

High-frequency power amplifiers can be equipped with complementary pulse-compressor systems to fulfill the advanced cavity power requirements. Microwave pulse compression is a power extraction method based on pulsewidth reduction and electronic triggering. The cavity is fed by pulsed-RF source, the resonance is evolved at $t\geq t_{0}$ , $t_{0}=\textrm {cavity}$ filling time. Established standing waves or resonance condition is brokendown by triggered plasma switch programmed with adjustable delay and pulsewidth. This causes the stored energy to be transmitted as shorter output RF-pulse. The implementation of a microwave pulse compression system requires careful measurements and structural modifications to be able to tune design parameters for optimal setup. In the scope of this paper, the experimental results are obtained for different waveguide lengths and various load configurations (to exploit new opportunities). All connections, iris configuration, and precise adjustment of plasma triggering have been set up cautiously. The cavity gain is increased up to 23 dB with trigatron driving improvements. High power requirements and demands are investigated for many applications, particularly for biomedical science projects. [ABSTRACT FROM AUTHOR]

The multigap gas switch has been widely used in liner transformer drivers (LTDs), but there is still room for improvement on its self-breakdown and triggering characteristics. In this paper, based on the circuit model of the six-gap gas switch, the gap voltage distribution during the charging and triggering process is analyzed, and the optimization on self-breakdown and triggering characteristics by mounting resistors and capacitors in parallel with switch gaps are theoretically and experimentally investigated. The results indicate that compared with the original switch, when the self-breakdown voltage is about ±90 kV, the standard deviation is reduced from 7.5 to less than 3 kV; for a charging voltage of ±80 kV and by operating at 60% working coefficient, when the negative trigger voltage is 75 kV, the jitter of the switch is reduced from 6.1 to 1.4 ns. [ABSTRACT FROM AUTHOR]

In this paper, a modular topology is presented for generating high-voltage pulsed power. The proposed structure consists of Marx-type modules, which are based on the switched-capacitor (SC) concept. This module receives an input voltage and, depending on the requirement of the user, produces an output voltage either equal to the input or twice as much as the input voltage, which shows the flexibility of our model. The capability of the module to produce a doubled output makes it appropriate for applications with low input voltage sources. Also, the topology has the capability of generating combined wide and narrow pulses. The topology was simulated in MATLAB Simulink and a laboratory setup was built to test its operation. The results validate the theoretical basis of the structure. [ABSTRACT FROM AUTHOR]

This paper proposed the use of a ringer, a self-switched inductive storage system, for applications involving reluctance accelerators, a kind of electromagnetic launcher, and compatible with applications where portability is a requirement. There will be shown three different useful approximations for the analysis of the ringer, employed as a power source for a reluctance accelerator. First, it described the equations governing the que behavior of an ideal unloaded ringer, and then the equations for the ringer with an uncoupled inductive load, and ultimately a Lagrangian model for the ringer as an inductive power source for a reluctance accelerator, capable to make predictions about the currents through the circuits and the exit speed of the projectile for a given firing. The accuracy of the predictions made with the third approximation, the Lagrangian model, was tested experimentally. [ABSTRACT FROM AUTHOR]

The plasma produced by a pulsed generator is an efficient tool for an airflow control. In this paper, a nanosecond pulsed generator constructed with a fast solid-state switch is designed for triggering synchronous discharges in plasma synthetic jet (PSJ) actuators connected in series. The generator delivers high-voltage pulses with a peak voltage varying from 0 to 20 kV, a rise time of 20 ns, a full-width at half-maximum of 200 ns, and a wide range of pulse-repetition rate varying from 0 to 5.5 kHz. It is proved that this generator is able to trigger synchronous discharges in three PSJ actuators in atmospheric air with a peak discharge current more than 90 A and a deposited energy per pulse of 39 mJ. A schlieren system is used to observe the airflow dynamics, which shows the high synchronization among the three PSJ actuators with a time triggering delay of about 20 ns. The synchronous operation of three PSJ actuators produces a plasma jet with a maximum velocity of 60 m/s and a precursor wave with a velocity of 350 m/s. [ABSTRACT FROM AUTHOR]

Using magnetic fields to control the vacuum arc is a major way to improve the breaking capacity of vacuum interrupters. Besides the single transverse magnetic field (TMF) and single axial magnetic field (AMF), new type of TMF-AMF contact and TMF-TMF contact structures have been put forward to control the vacuum arc in recent years. In this paper, three different structural contacts are used in the experiments. The arc evolution was captured by an high-speed digital video camera, and at the same time, the arc current and arc voltage wave were recorded. The experiment was conducted under current ranging from 5 to 20 kA (root mean square) and 10 mm of gap distance. There are 12 current shots performed on one contact design. There are four current levels in the experiment which are 5, 10, 15, and 20 kA, and three tests are taken for each current level. The results showed that for TMF-AMF contacts, under low current (I = 5 or 10 kA), the arcs of the two kinds of contacts both kept diffused and rotating. Under high current (I = 20 kA), the arc of the TMF-AMF contact with six slots was constricted and rotated on the plate, and the melting was uniform and slight. As for the eight-slot contacts, the arc was constricted but did not rotate which resulted in significant melting in the local region. As for TMF-TMF contacts, the result is similar under low current, while the arc was constricted and rotated quickly on the inner plate under high current. The simulation results show that when the arc core is located on the outer plate; the total Lorentz force is near zero. When the arc core is located on the inner plate, the direction of total force is counterclockwise. [ABSTRACT FROM AUTHOR]

This paper is aimed at finding the effect of varying inductive energy storage systems’ (IESSs) inductance on resistance of an electrically exploded conductor-based opening switch and profile of current transferred into load, which has not yet been fully understood. Based on experimental results obtained, it is observed that when the inductance of IESS is varied, the magnitude of load current changes so as to conform to the magnetic flux conservation law but its rise time remains unchanged. Resistance of the opening switch and energy deposited in it has been estimated using recorded voltage and current waveforms. It has been found that with increasing inductance of IESS, the resistance of switch increases, whereas energy deposited in it decreases. Using these estimated values of energy, a possible explanation of observed behavior in resistance is presented. Effect of a mismatch between the inductance of IESS and load is seen to only affect the energy transfer efficiency or magnitude of load current but not its rise time emphasizing the novel finding that for a given load, the rise time of load current is independent of the inductance of IESS. [ABSTRACT FROM AUTHOR]

In this paper, a high-voltage unipolar pulse power generator is introduced for electroporation applications. Operating principle of the proposed structure is based on the buck–boost (BB) converter. The generator is comprised of parallel modules connected to the converter through an SCR and is supplied by a low-voltage dc source. Each module consists of an insulated gate bipolar transistor (IGBT), two diodes, and a capacitor. In fact, the proposed topology is a combination of the Marx generator and BB (MG-BB) converter. In comparison with other modular MG-BB structures, the proposed topology achieves interesting advantages including simpler structure, reduction of IGBTs voltage rating, and reducing number of components (inductors and switches). In order to clarify the features of the proposed structure, it has been compared with other unipolar MGs considering different aspects including the number of circuit components, number of required input supplies, amplitude of the output pulse, and the maximum voltage across switches and diodes. To validate the effectiveness of the structure, simulation and experimental results are presented. The results confirm that the proposed topology is capable of generating unipolar pulses with desirable amplitude and repetition frequency using a low-voltage dc supply. [ABSTRACT FROM AUTHOR]

Recently, inductive energy storage systems have attracted interests due to high energy densities. The high-temperature superconducting pulsed-power supply (HTSPPS) is one inductive PS topology for electromagnetic launching system. The topology can achieve a high amplitude load current and cut down the electrical losses due to the zero resistance characteristic of superconducting inductors. However, in this topology, the integrated gated commuted thyristor is used as a switch and cannot withstand high current, which limits the expansion of the system. Besides, it has significant current amplification ability as a single unit, but one module cannot provide sufficient amplitude and appropriate pulsewidth for the load current of the electromagnetic launching. In this paper, by applying the principle of inverse current commutation with semiconductor devices (ICCOS) in the HTSPPS, a novel circuit topology called HTSPPS with ICCOS is presented. This topology is analyzed and the multiple modules system is established. Simulation results show that the HTSPPS with ICCOS exceeds the current limitations of the original one and ensures the reliable cutting off of the main switch. It has potential applications in the future of high-energy systems while reducing the cost greatly. By asynchronous cooperative triggered discharge of the multiple HTSPPS with ICCOS modules in parallel, the appropriate amplitude and flat shape current of the load can be achieved through the careful design of the trigger time. [ABSTRACT FROM AUTHOR]

One of the critical components of high energy density pulsed power systems used to generate short high-voltage and high-power impulses is gas-filled plasma closing switch (PCS). In recent years, significant research efforts have been aimed at finding environmentally friendly gases which can be used in the PCSs, and several gases including dry air, nitrogen, carbon dioxide, argon, and their mixtures have been considered as potentially suitable working fluids in such switches. However, the lack of knowledge of the breakdown characteristics of complex switching topologies filled with these gases limits their practical applications. Therefore, further investigation of the breakdown performance of PCSs is required, in order to establish their applicability for practical use in high-voltage pulsed power systems. This paper reports on the investigation of the breakdown characteristics of a triggered PCS topology with corona discharge electrodes. The self-breakdown voltage of the switch, variation in the self-breakdown voltage, time to breakdown, and jitter have been obtained for the switch filled with “zero grade” air, N2, CO2, and an Ar/O2 mixture up to a pressure of 10 bar (abs). It was shown that the switch can provide a stable breakdown performance with jitter as low as ~1 ns. [ABSTRACT FROM AUTHOR]

Repetitive high-voltage square pulses are of great importance for producing long-pulse electron beams and high-power microwaves. One of possible technologies for the generation of such pulses is a Marx generator using pulse forming network (PFN) stages, often combined with a pulse sharpening technique to reduce the rise time to a few nanoseconds (peaking stage). This paper presents an innovative design, named the “zigzag design,” for the optimization of the compactness and of the rise time of 400-kV–85-ns PFN-Marx. Thanks to this design, the 16 stages of this generator, which delivers an open circuit output voltage of 720 kV, fit in a 650-mm length. For a slightly overmatched load ($Z_{\mathrm {load}} = 100 ~\Omega$), the output voltage reaches 400 kV with a rise time as less as 5 ns. The inductance reduction associated with the innovative zigzag design, which allows this sharp rise time with no need for a peaking stage, is described. The 85-ns plateau duration of the pulse is given by the PFN construction of each stage, which is based on six ceramic capacitors (2.1 nF–45 kV) connected within a strip line. The 16 PFN stages are housed in a 360-mm diameter gas pressurized vessel. Burst mode operation for a duration of 10 s at a pulse repetition frequency of 100 Hz is reported, for a resistive load and for the electron beam diode of a X-band relativistic backward-wave oscillator (BWO). To reach further compactness, the BWO system is integrated on side of the generator vessel and a U-shaped gas pressurized line connects both systems through a compact conical vacuum insulator. [ABSTRACT FROM AUTHOR]

This paper presents a new capacitor bank topology for a pulsed power system to improve the efficiency of multistage synchronous induction coilgun. In the proposed method, a switch, such a gate turn-off thyristor, is inserted in parallel to a crowbar diode and load to generate an attractive force between the next stator and the armature. A mathematical model was developed, and finite-element method simulations were conducted to verify the proposed topology. The results show that the proposed method improves the energy efficiency and launch velocity. The improvement in energy efficiency is confirmed from the simulation results of a three-stage synchronous induction coilgun. [ABSTRACT FROM AUTHOR]

In this paper, the results of a 2.88-MW solid-state long-pulse modulator, which has been designed for the new linear collider at the european spallation source in Lund, are summarized. The presented modulator generates an output voltage pulse of 115 kV with a pulselength of 3.5 ms. The main components of the modular system, which include a series–parallel resonance converter, a high-voltage high-frequency transformer, and an output rectifier, are discussed. The modulator design is verified by measurements performed with a full-scale prototype, which is operated under nominal load conditions. A detailed output voltage ripple evaluation is given, and in addition, the system design has been proven by a 7- and 2/3-h heat run test. All specifications are well within the given limits, and the maximum occurring temperatures in the transformer stay below 110 °C even under worst case assumptions. The system achieves a pulse efficiency (determined by the pulse shape) of 96.78%, an overall electrical system efficiency of 91.9%, and a combined pulse system efficiency of 89%. [ABSTRACT FROM AUTHOR]

With the development of pulsed-power technology, more and more applications require high-voltage and heavy-current pulse switches. Laser-triggered vacuum switch combines laser technology, vacuum switch technology, and three-electrode trigger switch technology, and has the advantages of heavy current capability, good isolation from the main circuit, and short delay time. In this paper, the 1-D thermal conduction model was developed to analyze the influence of laser energy on the velocity of initial plasma. The relationship between the ablation area and the laser energy was derived. The theoretical analysis can be verified by the relationship between the trigger delay time and laser energy and the initial plasma microcurrent curve in the experiments. [ABSTRACT FROM AUTHOR]

The objective of this paper is to determine the influences of the transverse magnetic field (TMF) and the axial magnetic field (AMF) on prestrike inrush current arc behaviors in vacuum interrupters (VIs) during capacitive making processes. Two types of cup-type VI contacts were used: TMF contacts and AMF contacts. The contact diameter of the VIs was 48 mm. The insulating envelopes of the VIs were transparent, and there was no metal vapor shield inside the VIs, which were arranged for the observation of the prestrike arcs. The inrush current arc behaviors were recorded by a high-speed charge-coupled device video camera. The experimental results revealed that the VIs of cup-type AMF contact showed a higher dielectric strength than those of cup-type TMF contact during the making operations of inrush current. In addition, the arcs in VIs of cup-type TMF contact tended to be intense arcs that caused serious welding than those of VIs of cup-type AMF contact. Moreover, the cup-type AMF contact effectively reduced the prestrike arc erosion on the contact surfaces than those of TMF contact during the prestrike process of inrush current. [ABSTRACT FROM AUTHOR]

Power supplies have played crucial role to improve and extend plasma applications. Several dc, pulsed, and radio frequency (RF) stabilized power supplies have been developed over a wide range of frequencies and voltage waveforms. However, the influence of voltage waveform on the plasma densification, mainly due to the secondary electrons emission from the electrodes, has not been quite explored. This paper proposes an asymmetric pulsed bipolar power supply, adjustable in frequency, amplitude, pulsewidth, and number of pulses for generation of cold plasmas. Short period positive pulses, between longer negative pulses, increase greatly the secondary electron emission from the electrodes and, consequently, the plasma ionization rate. Short pulses (ns) are obtained by the phase shift between each carrier, and the high-intensity pulses are obtained by cascading the cell submodules in a half-bridge cascade topology, using a modular half-bridge converter configuration. The intensity of the positive and negative pulses can be varied independently. There is no unintended dc voltage level between the electrodes, which appear in RF plasmas. The plasma generated in this way is free of electric arc and can be kept stable within a broader range of operating parameters, mainly the voltage and the working gas pressure. [ABSTRACT FROM AUTHOR]

In order to generate bipolar high-voltage (HV) pulses across certain load from HV dc (HVdc) power supply, a voltage source inverter (VSI) stage should be inserted between the load and the supply. In order to meet the required HV level, series connection of semiconductor devices should be employed with dynamic voltage sharing between the involved devices. Modular multilevel converter (MMC) can be used instead of the conventional two-level VSI to alleviate the complexity introduced by the deployment of series-connected devices. The voltage level of the HVdc power supply and the voltage rating of the available semiconductor devices determine the suitable number of MMC voltage levels ( $N$ ). Capacitor voltage balancing is a vital issue for proper operation of the MMC. In general, conventional sensor-based balancing techniques require a significant amount of measurements, which increases the complexity of the system. In addition, the high dv/dt during switching times causes electromagnetic interference, which may adversely affect the accuracy of the measurements. In this paper, a sensorless voltage balancing technique is proposed for the MMC-based bipolar HV pulse generator that reduces the system sensitivity, cost, and complexity. A detailed illustration of the proposed approach is presented in this paper. The simulation and experimental results are used to validate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper discusses a study made for good asymmetric three-stage electromagnetic coilgun launching medium-weight projectile. Different lengths, number of turns, and switching times are chosen for each individual coil to get better results. Two detailed investigated models have been presented, including the effect of the switching time. Medium-caliber projectile of \text weight = 0.5 kg is employed in this paper. The results confirm that the second model asymmetric coilgun has 16.96% higher output speed, 63.92% lower length, and 57.5% lower launching time than the first model asymmetric coilgun. The obtained results have been recorded using the transient time electromagnetic simulations. [ABSTRACT FROM PUBLISHER]

This paper proposes a compact high-voltage pulse electron gun power supply (EGPS) consisted of interleaved capacitor-charging power supply (CCPS) with a series-resonant converter (SRC) to drive the electron tube. Requirement specifications are −40 kV, −7 A (280 kW), and continuous output lower than ±1% ripple stability lasted few seconds with <1 ms charging and discharging times. To meet the design specifications, eight stacks operate in parallel, and each stack has a 45° phase shift switching pulse width modulation (PWM) method. Each designed CCPS can supply −40-kV voltage and −0.9-A current. In addition, the proposed CCPS has the SRC to reduce the switching loss. The SRC is a famous topology, which presents main characteristics such as high-power density and efficiency. To prove the validity, this paper is confirmed by the simulation and experimental results of the fabricated −40-kV output CCPS with water load. Then, we implemented the fabricated EGPS to the electron tube. [ABSTRACT FROM PUBLISHER]

Paralleled pulse-forming units (PFUs) with different triggering delays might be a paramagnetic way for generating flat-topped current wave for electromagnetic launch. Many researchers have reported that multiple capacitive storage PFUs were implemented such current waves in laboratories. However, due to its low energy density, the applications of the capacitive pulsed-power supplies are limited. Since the inductor has advantages in energy density, the inductor pulsed-power supply becomes one of the hottest topics recently. The slow transfer of energy through capacitive hybrid meat grinder with inverse current commutation with semiconductor devices proposed by Tsinghua University has demonstrated its advantage and applicability recently. Using this kind of topology, this paper proposes the design of an inductive storage PFU with a stored energy of 100-kJ. The maximum load current reaches to 50 kA and its pulsewidth is at least 5 ms. The optimized inductive storage PFU shows superiority in contrast to the capacitive storage PFU with the same energy. This paper offers the theoretical analysis and the testing foundation for investigating the inductor pulsed-power supply with higher energy. [ABSTRACT FROM PUBLISHER]

Slow transfer of energy through capacitive hybrid (STRETCH) meat grinder circuit, which was proposed by the Institute for Advanced Technology, added a capacitor into the traditional meat grinder circuit. Even though its energy density is slightly less than the corresponding pure inductance system, it can reduce the voltage across the opening switch and maintain the high multiplication factor of the opening current. The performance of the STRETCH meat grinder circuit depends on multiple parameters. The inductance ratio ( n=L1 / L2) and the capacitance (C) are the two vital factors, which have a crucial influence on the system performance, such as the voltage over the opening switch ( V_{\rm Sopm}) , the current multiplication factor ( m$ ), and the ratio of the maximum capacitive energy over the total inductive energy ( $\eta )$ . Thorough studies have been carried out in this paper on the relationship between the above two factors and the three performance criteria. This paper also discusses and analyzes the chosen of the key parameters ( $n$ and $C$ ) for a single-stage STRETCH meat grinder with 2-mH total inductance, which is made up of two serial coils with 0.95 coupling factor. The opening current of the main switch is 1 kA, which constitutes a 1-kJ inductive pulsed-power supply. It fully takes the advantage of the STRETCH meat grinder topology, intensifies the study of the inductive pulsed-power supply with higher energies, and is easy to be utilized for practical application. [ABSTRACT FROM PUBLISHER]

The STRETCH meat grinder is one typical inductive pulsed-power supply topology for electromagnetic launch system. It has remarkable current amplification ability as a single unit, but one module cannot provide enough amplitude and width for the load current of the railgun launching. This paper discusses the effects of different triggering delays on the load current with two STRETCH meat grinder modules. To reduce the magnetic field coupling between the two modules, the two main switches are opened simultaneously. To make the load current waveform with no notch, the thyristor of the first module is triggered when its pulse-forming capacitor is fully reversely charged. For the thyristor of the second module, we consider several time points of triggering delay. Because of the practical constraint for the maximum rail current that ensures no rail erosion, the rectangular waveform is the most appropriate load current waveform. Therefore, the comparing criterion can be defined as the ratio of the load current waveform area and its maximum rectangle area at different current levels. Higher ratio means that the current is more like a rectangular wave and is better accordingly. Based on the above criterion and extensive simulation research, we found that the best delay time is the moment when the capacitor is reversely charging the inductor completely. This paper and the result are of great theoretical significance for the further study on the collaborative triggering of multiple STRETCH meat grinder modules. [ABSTRACT FROM PUBLISHER]