Search

A new modular pulsed-power source with fast rise time and step-wise arbitrary output waveform generation is currently under development to drive the Gepulste Elektronenstrahlanlage device investigated at the Institute for Pulsed Power and Microwave Technology (IHM). Acknowledging the complex design procedures necessary to set up a modular pulsed-power source for voltages of up to 120 kV, this paper focuses on the circuit design for a single stage and its validation prior to the generator assembly. Using a semiconductor-based Marx generator topology, the stages are designed to have an output voltage of 1 kV with a pulse current of up to 600 A. When connected to an ohmic load, the measured current rise times are in the order of 46 ns resulting in the current rise rates of up to 10 kA/ $\mu \text{s}$ using the commercial devices. The step-wise arbitrary output waveform is created by generating the switching commands on the stage using a microprocessor and a fast optical synchronization unit. Effective stage shielding is verified by operating the stage in a 100-kV, 2.5-kA electromagnetic interference test bed. This paper presents the design considerations and the corresponding measurements. [ABSTRACT FROM AUTHOR]

The linear induction launcher consists of two parts: the barrel section and the projectile section. The barrel contains of a long coaxial sectionalized group of coils that are energized by a capacitor bank or generator sets. This paper deals with the design, implementation, and experimental test of a coreless axial-flux permanent magnet (AFPM) pulsed alternator with a flywheel system as an energy source for linear induction coil launchers. The proposed coreless AFPM generator has a low internal inductance and resistance of stator windings without compensation windings when compared with the conventional iron core machines. This paper describes the coreless AFPM generator configuration and shows the simulation findings. [ABSTRACT FROM AUTHOR]

A novel brushless self-excited air-core compensated pulsed alternator (BSACPA) is presented in this paper. It consists of two submachines in cascade, among which one serves as an exciter and the other works as a generator. The rotor windings of the two submachines are connected by a reverse phase sequence to realize reversal of the magnetic field. The stator windings are connected by a rectifier to realize the brushless self-excited structure. As an air-core compensated pulsed alternator (CPA) of new topology, it is necessary to derive its mathematical model and carry out a comparative design. Thus, this paper focuses on the detailed design and analysis of a BSACPA prototype, which includes dimensional design and equivalent circuit establishment. In addition, the critical speed is also acquired. Accordingly, the numbers of winding coil turns are designed to increase the discharge current and power based on the theoretical analysis. Finally, the analysis and design are verified by finite-element analysis (FEA). [ABSTRACT FROM AUTHOR]

This paper presents the results of the experiment with an overmassed wire-array $Z$ -pinch load that is powered by a current pulse (amplitude ~4.3 MA and rise time $\sim 0.9~\mu \text{s}$) from a multidisk magnetocumulative generator. Interesting feature of the experimentally recorded soft X-ray (SXR) pulse is short (~10 ns) duration at a microsecond current rise time with total energy of several hundreds of kilojoules. Obtained results are the evidence of high-quality implosion of the current-carrying plasma. The 2-D magnetohydrodynamic code FLUX-rz was used for the numerical simulation and analysis of the obtained results. The calculations indicated that only ~30% of the initial load mass took part in the SXR generation. The main peculiarities of the overmassed $Z$ -pinch implosion are discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of plasma influence on the germination rate of brown mustard seeds (Brassica juncea L.). It was found that five pulses of a nanosecond microspark have a suppressing action increasing the time of the seeds germination by 5 h; the plasma influence and UV-radiation of the nanosecond surface discharge with the frequency of 1 Hz for the course of 15 min being at a distance of 25 mm from the surface of the seed have a stimulating action on it reducing the germination time by 3 h; a combined treatment using the discharges of both types showed that germination rate may look as two-pulse mode. Repeated experiments confirmed this conclusion. Visual observation of the seeds after the UV-radiation and plasma treatment revealed cracks on the seed coats. The cracks significantly increase moisture penetration into the coat. [ABSTRACT FROM PUBLISHER]

A novel high-voltage direct current (HVdc) power supply which has no transformer or voltage multiplier circuit is presented and analyzed in this paper. This is made possible upon the diodes storage delay phenomenon. This proposed power supply is compact, lightweight, and low cost. Its basic structure includes a diode with a proper reverse recovery specification that plays the role of a step-up transformer in the conventional HVdc supplies and a high-voltage capacitor which stabilizes the output voltage. This structure has remarkable advantages over the conventional transformer-based HVdc supplies, such as compactness, a low ripple output, and a low-cost power supply. Performance of the proposed method and its accuracy are investigated in this paper. The results are verified by implementation of a 1.2-kV prototype supply. [ABSTRACT FROM AUTHOR]

To enhance the heat dissipation of high-power light-emitting diodes (LEDs), corona wind based on corona discharge was promoted. In this paper, we aimed at reinforcing the intensity of corona wind by modifying the needle electrode with graphene solution. To explore the differences in the graphene-coated electrode and the original bare electrode on the electrical characteristics, the intensity of corona wind, and LED heat dissipation, a corona wind cooling system and a thermal test system were built for the experimental study. The results showed that the graphene-coated electrode system could produce corona wind at a lower voltage. In addition, the discharge current of the graphene-coated electrode system is higher than that of the bare electrode system under the same discharge voltage. The graphene-coated electrode system can induce a faster corona wind and the highest speed is about 3.4 m/s, showing that it is more efficient than the bare electrode system in corona wind production. Moreover, the temperature drop of LEDs for the graphene-coated system is greater, which means that the corona wind cooling system can reduce the junction temperature of the LED chips effectively. Ultimately, as the discharge power increases, the average convective heat transfer coefficient increases. Indeed, the result of this paper can be used for the wide variety of the graphene-coated corona wind generator application as a promising technology for the LED heat management. [ABSTRACT FROM AUTHOR]

A single-phase tubular permanent magnet linear generator (TPMLG) with a novel structure for Stirling engines is presented in this paper. TPMLG can directly convert mechanical energy into electrical energy and it is the main energy conversion device in Stirling power generation system. Its 3-D geometry and initial dimensions are given in detail. Due to the structural characteristic, the finite element (FE) method (FEM) is used to analyze the electromagnetic field. An FE model is established from the magnetic field perspective. Isolines of magnetic vector potential can be obtained, as TPMLG locates at −0.015, 0, and 0.015 m. The dynamic performances of TPMLG under different reciprocating frequencies are compared and analyzed. Compared with three different kinds of machines, it can be concluded that the proposed TPMLG can produce electricity with less weight and materials. [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]

The challenging demands of pulsed electron beam devices (such as the GESA device) with respect to their pulsed power supply have led to the development of a new semiconductor-based Marx generator. At a maximum output voltage of 120 kV and 600-A pulse current for a duration of up to 100 $\mu \text{S}$ , stepwise arbitrary output waveforms are desired. A fast rise time of the generator is achieved by using fast switching circuitry, low inductance capacitors, and a low inductance stage arrangement. For low jitter triggering of all stages and efficient signal transmission, the generator uses an optical bus system for communication. Due to the inherent dynamic load characteristics of the GESA device, the generator features a fast overcurrent protection scheme. This paper presents selected design aspects of the generator and their validation in a small-scale assembly able of delivering up to 8 kV at 600-A load current. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of effect of high-power UV-radiation plasma, generated by electric discharges, on germination rate of Altaic flax seeds (Linum altaicum). It was found that UV-radiation scarifies flax seeds by means of cracks formation in the seeds’ coat. The cracks shorten moisture penetration time to a seed bud thus twice increasing the germination rate. It is found that the germination rate function has the three-stage character; the velocity-growth function has the view of three pulses, which separates the seeds into three subgroups. Division of the group into subgroups is stipulated by the probabilistic nature of the cracks formation. The number of subgroups is equal to the number of layers +1. We calculated average times of natural moisture penetration through the flax seed coat layers: $T_{s} =11.8$ h through the spermoderm and $T_{e} =17.7$ h through the endosperm. It is possible that scarification of the flax seed coats can shorten the germination time for these times. We also noted that some seeds could die due to the effect of high-power UV radiation. So, it is necessary to find more sparing regimes of the seeds UV irradiation. [ABSTRACT FROM AUTHOR]

This paper demonstrates the improved simulation of a Z-pinch experiment with 2-D magnetohydrodynamic code FLUX-rz developed in RFNC-VNIIEF. A Z-pinch load was nested wire array powered by a helical magnetocumulative generator with the current pulse $I_{\max } \approx 4.2$ MA and effective rise time $\tau \approx 400$ ns. Validation of X-ray spectral measurements carried out with scintillation detector filters pointed out a necessity to take into consideration both the scintillator “dead” layer and oxide films on the aluminum filter surface. [ABSTRACT FROM AUTHOR]

This paper describes the design strategy for a new Marx generator, based on SiC metal–oxide–semiconductor field-effect transistors (MOSFETs), proposed for Kicker magnet applications. As a starting point, the possible replacement of a thyratron tube associated with an existing kicker system, at CERN, is considered. The specifications of the output pulse are: 40-kV, 3.2-kA, 3- $\mu \text{s}$ flat top duration, 30-ns rise- and fall-time, and 1-Hz repetition rate. A theoretical study for a Marx generator topology, using 50 stages, each 800-V stage comprising 24 SiC MOSFETs in parallel, each MOSFET conducting approximately 140-A pulses is considered. In addition, a four-stage prototype has been evaluated, with almost full current and 3 kV, based on the proposed design, in order to assess the technological advantages of such a system and limitations for the scale up. First tests using parallel SiC MOSFETs are described and results discussed in light of the proposed topology and the physical structure of the assembly. [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]

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]

The results of an experimental study of the generation of runaway electrons (REs) during the formation of a negative streamer in an 8.5-mm-long point-to-plane gap filled with air are presented. Negative nanosecond voltage pulses (18 kV, $\tau _{0.5}\approx 10$ ns, and $\tau _{0.2-0.9} \approx 4$ ns) were applied across the gap. In this paper, we attempted to determine when REs are generated relative to the appearance of the streamer. In our previous studies of a positive streamer, we have shown that the formation of the streamer is accompanied by a dynamic displacement current (DDC) caused by the redistribution of electric field strength in the gap. This current can be easily measured with a collector placed behind a grounded grid electrode. The collector is typically used to measure the current of REs at negative polarity. In this paper, we were able to measure together and separately the DDC caused by a negative streamer and the RE beam current. This allowed us to accurately determine the moment of generation of REs. [ABSTRACT FROM AUTHOR]

Ferrite spiral delay lines intended for synchronization of high-voltage generators. The results of output pulses’ time stability are presented. All testes were carried out in both single- and two-channel systems. Adjustable precise synchronization of two nanosecond high-voltage generators (−150-kV, 5-ns full-width at half-maximum) are analyzed in this paper. The trigger high-voltage pulse was split into two channels to switch on identical double forming lines of each generator through controlled high-pressure spark gaps (nitrogen 60 atm). Designed coaxial ferrite spiral lines with an external bias field were installed in both synchronized channels. Adjustment of the bias field not only sharpens the trigger pulse but also varies its front delay and, respectively, the start of the driven generators. The maximum delay of one channel relative to the other was 1.5 ns. The minimum standard time deviation (relative jitter) of two nanosecond high-voltage generators was determined at the level of 55 ps. [ABSTRACT FROM AUTHOR]

One of the perspective directions in high-energy-density physics is the creation of powerful electro physical facilities capable to form megampere current pulses with short front. This paper presents test results of the device based on five-element disk magnetocumulative generator DMCG480 and an explosive current opening switch. The current pulse of 15 MA with characteristic rise time of \sim 0.8~\mu \texts was obtained in the equivalent multiwire array load of 17 nH at circuit breaking with the current of 32 MA. [ABSTRACT FROM AUTHOR]

The ignition of LOVA gun propellants at low loading densities is of interest for future gun systems with insensitive modular charges. The ignition system in conventional propellant systems is traditionally optimized for high loading densities. There is a need to be able to control the ignition for the envelop of the system, to reduce unburnt propellant at low loading densities and, at the same time, avoid pressure waves at high loading densities. Plasma ignition is interesting for this application, with the possibility to vary ignition energy and with the plasma plume penetrating deep into the propellant bed to achieve uniform ignition. This paper presents results from plasma ignition experiments in a 45-mm gun system, using NL008, an RDX-based CAB-LOVA propellant. The plasma igniter is a capillary jet type, driven by a pulse-forming network. A zero-dimensional model for the plasma igniter has been developed and will be discussed in the context of the experiments. [ABSTRACT FROM PUBLISHER]

As the energy level in the projectile increases, it becomes necessary to use multiple pulsed alternators discharging in parallel into the electromagnetic launcher. Another reason for having more than one machine is that one needs to compensate for the torque and gyroscopic effects of the pulsed alternator. This requires that machines be built in counter-rotating pairs. These machines are identical in all respects except for their direction of rotation. A study was conducted to determine how the machines can be motored so that they stay in lock step in speed and phase as they are motored to full speed. The methods of connecting these multiple machines are discussed. The aim of the connection scheme is to allow the machines to naturally stay locked in speed and phase throughout its operating range. Sensitivity of the performance of these machines to small variations in the machine parameters, which is to be expected in the machines, is discussed. Sensitivity of the discharge performance to small phase angle mismatches due to tolerances is also discussed. To verify the conclusions of the paper, an experiment was performed on two identical 50-kVA machines discharging into a low impedance load. The motoring system that is discussed in this paper was implemented in this experiment, which kept the machines in lock step. This motoring system is described. Thereafter, discharges were made at various speeds and field current levels. Phase angle mismatches were introduced between the two machines to see how it affected current sharing. The results and conclusions of these tests are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper reports on analysis of two different types successive underwater shock waves generated by a device incorporating a compact shock-wave generator with a magnetic pulsed compression circuit. To generate shock waves, underwater pulsed electric discharges in high-impedance saline water were used. The saline water made possible underwater shock waves propagation in tissue with low reflection between the solution and tissue boundary, owing to their similar acoustic impedances. A cylindrical electrode holder and a semiellipsoidal shock-wave focusing reflector/generator were used in this paper. The diameter of the compact shock-wave reflector was 20 mm. Two kinds of successive underwater shock waves, one generated by electric discharge plasma expansion and the other by bubble collapse, were observed. The shock waves were studied by time-resolve high-speed visualization and direct pressure measurement using a fiber optic probe hydrophone pressure transducer. The former method elucidated propagation of underwater shock waves and behavior and collapse of the bubble near the electrodes, while the later measured two kinds of underwater shock waves pressures at different voltage amplitudes using the cylindrical electrode holder and the shock focusing generator. This paper clearly shows the importance of the secondary shock waves, their control, and damping, for effective and safe medical application of shock waves. [ABSTRACT FROM PUBLISHER]

High-power microwaves are generated using high voltage (HV) pulses, which are generated using a Marx generator connected to a peaking stage. The output of the peaking stage is the input to the half transverse electromagnetic (HTEM) horn-type antenna. This paper discusses the effect of isolation distance between HV tapered arm and the grounded reflector on the variation of characteristic impedance and gain with respect to the length, flair angle, and tapering angle of the antenna. This paper also discusses the radiation loss on the side and back of antenna. An experiment has been described using an available Marx generator and HTEM antenna. Using the experimental and simulation results, the optimal design parameters of antenna are obtained. [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]

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]

In recent years, all solid-state Marx generators have been found more and more extensive applications in industrial, environmental, and biological fields. All solid-state Marx generators have many requirements for their drive circuits, such as good synchrony for driving signals at different stages, fine isolation between control signals and the main circuits, adjustable pulsewidths and frequencies, and good driving abilities. This paper proposes a high-performance drive circuit for a 24-stage Marx generator based on IGBTs. A half-bridge circuit using IR2110 outputs a high-current turning-on drive signal (positive) and a turning-off drive signal (negative) with adjustable dead time. The control drivers are input to the common primary side of 24 nanocrystalline magnetic transformers, which isolate the control circuit and the main circuit. Through gate circuits at the second sides of the magnetic cores, the turning-on drive signal charges 24 gate–emitter capacitors to required voltages and consequently all IGBTs move into on state until the turning-off signal arrives. Similarly, the negative turning-off drive signal charges all gate–emitter capacitors to a negative voltage which ensures all IGBTs stay in the off state. Therefore, the pulsewidth is determined by the phase difference between the turning-on and turning-off drive signals. Equipped with this drive circuit, the 24-stage Marx generator is able to produce stable high voltage pulse with a peak value of −9.6 kV, PRF $0.05\sim 5$ kHz, and different pulsewidths. In this paper, the design details and experimental confirmation of the proposed drive circuit are illustrated. [ABSTRACT FROM AUTHOR]

Recent studies have shown that rectangular high-voltage pulses have a high-performance in dielectric barrier discharges (DBDs). To generate the rectangular pulses used in the Marx generators, the most common way is driving two sets of switches synchronously with a different sequence. Because of the fast-changing current and voltage, the electromagnetic interference (EMI) will affect the circuit. Therefore, if two groups of switches were triggered mistakenly at the same time, it would cause the partial short-circuit phenomenon. In this paper, a new driving circuit with overcurrent protection for the Marx generators is proposed. It used only one synchronous signal to control two sets of switches. Experimental results showed that the short current could be limited within 100 A. The proposed driving circuit was applied to a seven-stage Marx generator, and 5-kV rectangular pulses can be obtained steadily at 1 kHz, which can greatly improve the stability of the system. [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]

This paper consists of two parts. In the first part, the emission was generated in air, and the waveform recording the spectral line at 337 nm (= prominent N2 laser line) was noted. The pulse forming network (PFN) Marx generator having a large ($50~\Omega$) internal impedance was used. The pulses of the nitrogen emission at 337.1 nm of long ($< 3~\mu \text{s}$) duration and of short (≈10 ns) duration were obtained. The photodiode registered both the spontaneous emission and the stimulated (laser) emission in the 337 ± 5 nm spectral range. The data show that the laser emission predominates in the pulses of long duration. In the second part of this paper, it is suggested that the ultraviolet (UV) radiations emitted by the sun, together with the electric fields present at high altitudes, are capable of exciting the N2 molecules to the upper excited $\text{C}^{3}\Pi _{u} $ level to yield the laser emission of long duration. On the basis of the laser energy content dissipated into the plasma, the size of the transient luminous events (TLEs) known as the elves and the sprites was evaluated. The dynamics of initially small size, highly compressed, and very hot plasma formed inside the sprite was presented. It is proposed that the TLEs named “crepuscular twilight in the sky of New York” observed on December 28, 2018; “mysterious bright flash” occurred in Russia on January 9, 2018; and maybe the Tunguska event happened in Siberia on the morning of June 30, 1908 should be included in the list of the TLEs. [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]

Low-temperature plasma ion mobility spectrometry (LTP-IMS) is the method to identify some materials by measuring concentration of gas phase ions. IMS used in a wide range of laboratory-based biomedical research studies. A nanosecond pulse generator is necessary for LTP-IMS apparatus to enable direct analysis of various chemical compounds without having to evaporate the analyte or seek a solvent or any reagent. In this paper, a dual Marx pulsed generator for LTP-IMS Ionization power supply is proposed based on a new combination of some solid-state switches including insulated gate bipolar transistor (IGBT) and avalanche bipolar junction transistors (BJTs). The compact dual Marx generator is composed of a series of avalanche BJTs and an IGBT as the trigger switch, where its rise time is reduced from 100 to 5 ns by using an avalanche BJT in its command circuit. In this way, a controllable high-voltage pulse generator has designed, built, and tested. The proposed circuit can be used to generate the repetitive high-voltage pulses necessary for low temperature ionization in advanced IMS apparatus. The output voltage has an amplitude of up to 6 kV with pulse widths in the range of 40–1000 ns and pulse repetition rates up to 2 kHz, having rise time and fall time less than 10 ns independent of the load specifications. [ABSTRACT FROM AUTHOR]

The vessel’s pulse load can intermittently produce pretty high power in a very short time. Considering their periodical charge-and-discharge process, the system variables of integrated power system (IPS) are characterized by a periodic alternating process rather than a single-equilibrium point. It is not suitable to evaluate the operational performance according to the equilibrium point. In this paper, a periodic orbit model of the IPS and its algorithm is proposed according to sensitivity analysis of end value of system variables to their initial value. The algorithm can be used for distributed compute of system variables, which adjust system variables according to the sensitivity to make the end value equal to the initial value. And, the calculation speed of the algorithm can be increased greatly. The model and the algorithm lay the foundation for assessing the operational performance of the IPS with pulse load. The proposed method has been verified by the simulation test. [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]

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]

Due to its low-loss and high dielectric strength, polypropylene is widely used as electrical insulation material in pulse capacitors. In order to study its breakdown characteristics for nanosecond voltage pulses, an experimental setup was designed to generate voltage pulses with a 10%–90% rise time of 38 ns and a full width at half maximum of about 90 ns. Tests of the three polypropylene films with thicknesses of 12, 15, and $18~\mu \text{m}$ were performed. In addition, hundreds of nanoseconds pulse and dc voltage were also applied for comparison. The experimental results reveal that most of the breakdown occurs during the front edge of the pulse for tens of nanoseconds pulse, and the breakdown strengths of the three kinds of polypropylene films are almost identical for different applied voltages, which show a weak correlation between the thickness of the dielectric and the breakdown field. The expected breakdown strength of tens of nanoseconds pulse defined in this paper is not significantly higher than the mean value of the hundreds of nanoseconds pulse and the dc condition, suggesting that the breakdown of a thin polypropylene film is mainly determined by the electrical field but not the voltage-time cumulative effect. All these observations strengthen the conclusion that the breakdown of a thin polypropylene film is an intrinsic phenomenon. [ABSTRACT FROM AUTHOR]

This paper presents the results of predictive calculations of the parameters of pulses of soft X-ray radiation (SXR) on a four-module electrophysical facility GAMMA-4 (the current pulse amplitude is ~3 MA with rise time of ~60 ns) that has been constructed in Russia. Scaling numerical simulation of implosion of a cylindrical single and nested multiwire array in 0-D, 2-D, and 3-D radiation magnetohydrodynamic– approximations is performed, taking into account, the updated double-loop equivalent electrical circuit of the GAMMA-4. The main purpose of the conducted studies was the numerical optimization of the multiwire array parameters to obtain the best characteristics of the SXR pulse generated as a result of Z-pinch implosion on the axis of the system. [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]

At Wuhan National High Magnetic Field Center, a 100-MVA/100-MJ pulsed generator and two 67.5-MW converter modules have been installed as power supply for pulsed magnets. Long-pulsed magnetic field with 50-T/100-ms flat-top has been produced and 100-T pulse magnetic field is under commissioning by utilizing this pulsed generator converter. In this high-power occasion, the three-phase voltages undergo serious harmonics, large notches, amplitude variation, rapid frequency fluctuation, and phase jump simultaneously. Synchronization method with fast dynamics, excellent harmonics rejection, and smooth time-domain response is expected, which is difficult for the conventional synchronous reference frame phase-locked loop (SRF-PLL). Therefore, this paper presents a new synchronization method based on compensation of phase deviation. In this method, the phase of three-phase voltages, which is achieved by summing filtered phase deviation and phase of a given $d$ - $q$ rotating reference frame, is open-loop computed directly. The main attributes of the method are the fact that its dynamics is independent of the input vector amplitude, better harmonics rejection/dynamics tradeoff, and smooth time-domain response. Comparative experiments are performed between the proposed synchronization method and SRF-PLL. [ABSTRACT FROM AUTHOR]

Recent work reported on the current density in pulsed-power-driven liners where a vacuum gap was introduced in the power feed connecting the liner to the generator. The resultant gap flashover generates azimuthally localized current-carrying plasma channels, which can create an azimuthal nonuniformity in the current density. The current density evolves during the current pulse, but nonuniformity is observed through the experiment timescale. Magnetohydrodynamic simulation work in 3-D demonstrates the difficulty in reproducing the experimental data within a limited computational domain, and those boundary conditions may dominate this paper. The development of current-driven instabilities in the plasma channels can explain the liner current density evolution, and specifically the ion acoustic instability can account for the main features observed in the experiments. [ABSTRACT FROM AUTHOR]

Three flywheel energy-stored impulse motor-generators (MGs) are used in the power supply system of HL-2A tokamak to produce short high-voltage or high-current pulse of desired parameters that are usually used for magnetic field coils and auxiliary heating equipment loads. The operation changing of these loads will cause disturbances in generator’s terminal voltage and the remarkable drop in MG’s rotating speed. This paper describes the implementation of an excitation controller using LabVIEW and CompactRIO for a 125-MVA impulse MG in power supply system of HL-2A/2M. Both a staged control strategy and digital PID algorithm built in LabVIEW are applied to the excitation controller that runs preciously in a 1-ms cycle to achieve voltage feedback control. The excitation controller, composed mainly of host computer and CompactRIO embedded reconfigurable system, is available to restore and stabilize terminal voltage in accordance with the desired voltage curves set by operators when pulsed loads and motor speed change quickly. It also implements real-time monitoring of the working condition and some electrical parameters of excitation system and communicates with central control system via Ethernet to either download discharge control files at time interval between two impulse discharges or upload waveform data generated in control process after a pulsed discharge. Engineering experiment results show that the use of excitation controller improves the voltage stiffness of the power supply system and provides the effective control of generator’s terminal voltage under the management of central control system. [ABSTRACT FROM AUTHOR]

In this paper, a new architecture of a high-voltage Marx pulse generator based on isolated gate bipolar transistors (IGBTs) is proposed. It allows continuous control of the output voltage by acting on the IGBTs activation time: “on-time.” The final after-charging capacitors' voltage can be higher than the double of the input voltage. A simplified mathematical description of the system was developed in order to find a relation between the output voltage and the “On-time” (an open-loop control law). A SPICE simulation was implemented to check the expected performances and to verify the developed model. A three-stage generator was built according to the proposed structure using commercial IGBTs with a maximum output voltage of 3.6 kV. All results were compared to check and confirm the validity of the proposed architecture. [ABSTRACT FROM PUBLISHER]

When the poloidal field (PF) magnet power supplies (MPSs) of 11 units are operated, maximum power of 200 MVA is required to achieve long pulse operation of Korea superconducting tokamak advanced research (KSTAR). Motor generator (MG) system was installed to resolve the power shortage because the available grid power is only 100 MVA at the National Fusion Research Institute site. MG system is composed of mechanical devices (stator, rotor, bearings, etc.), power control devices (variable voltage variable frequency and exciter), power facilities (transformers, switchboard, uninterruptible power system, filter, dynamic brake, etc.), utilities (cooling water pump, heat exchangers, cooling fans, oil circulation pump, mechanical brake, etc.), and control systems. MG system supplies power to the PF MPS of 11 units. And we configure the reactive power compensator (RPC) and harmonic filter (HF) system to stabilize the MG power system. After installing the MG system, individual tests and dummy coil tests were conducted to determine the safety and performance of MG system. And we completed the commissioning of the MG system by carrying out the superconducting magnet coil load tests for the 2014 KSTAR experiment. MG system was operated up to 150 MVA of PF MPS with the RPC and HF system. And the maximum operating duration was about 100 s. In this paper, we discuss about the power characteristic results of the MG system according to the superconducting magnet coil load tests. [ABSTRACT FROM PUBLISHER]

This paper describes a high-frequency pulsed-power generator for various industrial applications such as water treatment, food and medical apparatus for sterilization, or polluted gas treatment. The system is made of silicon-controlled rectifier as a main trigger switch, capacitors, two-stage magnetic pulse compression stages, and a linear transformer to generate a maximum of 120-kV, 5-kA pulse. The parameters obtained through the development are: output voltage: 120 kV (maximum), pulse repetition ration: 300 pulse per second, pulsewidth: 0.25~\mu \texts , and mean power: 30 kW. The designed pulsed-power generator is confirmed to be used effectively for many high-voltage pulsed-power applications related to environmental industry by simulation and experiments. [ABSTRACT FROM AUTHOR]

Matching devices in the form of electro-exploded current opening switches (EEOSs) or explosive current opening switches (EOSs) are used for transforming current pulses of magnetocumulative generators (MCGs) into voltage pulses of hundreds of kilovolts at high-impedance loads. Current pulse sharpening is accompanied by significant losses of the stored energy. Using EOSs are more preferable to EEOSs from the point of view of the energy losses since it does not lead to efficiency decrease in the MCG operation. This paper considers magnetocumulative multimodule systems consisting of several synchronously operating and serially connected small helical MCGs. Each generator is equipped with an explosive current opening switch. The voltages generated at each opening switch are summarized into the load. Fast operation of MCGs allows using very thin foils in the opening switches and obtaining the short voltage pulse front. Results of the works on creating high-voltage devices based on helical MCGs of a 60-mm diameter and disk EOSs of a 200-mm diameter are presented in this paper. In the experiment, the device consisting of two modules provides a voltage pulse of 370 kV with a rise time of $\sim 170$ ns into a load of 29 $\Omega $ and an inductance of 0.5 $\mu $ H. Maximum power in the load is $\sim 4.3$ GW, and the emitted energy is $\sim 1.1$ kJ. The four-module device forms the pulse with the characteristic current rise time of $\sim 100$ ns in the similar load at twice smaller current. [ABSTRACT FROM PUBLISHER]

This paper develops a novel symmetric dielectric barrier discharge (DBD) plasma as an ion source for environmental mass spectrometry (MS) applications. The conventional linear-type DBD plasma generator suffers the drawback of floating voltage at the plasma outlet. This paper develops an innovative symmetric T-shaped DBD plasma generator to produce atmospheric plasma with zero-floating potential for high-sensitivity MS analysis. By changing the geometric configuration and the drive phase of the symmetric T-shaped DBD plasma generator, the resulting symmetric structural design can fully cancel the floating potential and noise signal. Therefore, the main objective of this paper is to compare the differences between traditional linear-type DBD and the symmetric T-shaped DBD designs using MS, spectroscopy, and some basic electrical measurements. The most suitable parameters are determined by changing the electrode design, voltage, temperature, gas flow rate, diameter, and other parameters of the plasma tube. The symmetric T-shaped design generator produces the zero-potential plasma that generates fewer ambient gas molecules to form ozone, NOx, water clusters, and other strong oxidizing molecules such that less damage to the MS samples occurs. This in turn results in a less fragmented ion signal and higher sensing performance for rapid MS applications. In addition, the proposed system can directly ionize gas, liquid, and solid samples at more than 10^7 -cm ^-3 ion concentration. Results show that more information-rich spectra can be obtained with the developed symmetric T-shaped DBD plasma generator compared with the typical linear-type DBD generator. [ABSTRACT FROM PUBLISHER]

Chronic wounds are a major complication for diabetes mellitus (DM) patients, which cause discomfort and an increase in medical costs. The purpose of this study is to investigate the medical application and possible mechanisms of a cold atmospheric plasma jet in healing DM chronic wounds. In this paper, the genetic diabetic BKS.DB mice are used as the diabetic wound healing animal model, which have a stable glucose level and can avoid the effects or complications induced by surgical and chemical interventions. The helium atmospheric-pressure dielectric-barrier-discharge (AP-DBD) plasma jet is employed to treat the diabetic mice wounds with the fixed treatment time and distance of 15 s and 20.0 mm, respectively. The wound healing, histological, immunohistochemical, and cytokine analyses are conducted to evaluate the efficacy of the helium AP-DBD plasma jet on the chronic wound healing of the genetic diabetic mice. The experimental results show that the helium AP-DBD plasma jet treatment of wounds of genetic diabetic mice can regulate the secretion of transforming growth factor- $\beta $ (TGF- $\beta$) and fibroblast growth factors (FGFs), limit the inflammatory response and excessive cell proliferation, accelerate the process of re-epithelialization, and consequently, promote the chronic wound healing process. [ABSTRACT FROM AUTHOR]

Pulsed power applications are widespread, ranging from microscopic devices up to systems that are major installations and cost many millions of dollars. This paper describes some of the approaches used for the larger systems that have been built and discusses their engineering challenges. Basic energy storage approaches include electrostatic (capacitors), magnetic (inductors), inertial (flywheels), electrochemical (batteries), and fuel or explosives. Systems based on these approaches each have their own requirements and challenges but also have many common components. An example of one potential future large-scale opportunity—launch to space—is given and the need to develop more competitive economic approaches is discussed. [ABSTRACT FROM PUBLISHER]

This paper reports the estimation of the electric field from a large aperture cavity that generates a higher order mode by backpropagation of fields measured in free space. A higher order mode of a TE6,2 mode at 94 GHz is designed and fabricated using a quasi-optical manner for the analysis. The backpropagating field at the aperture is compared with the measured field. The field estimated at the aperture is used to analyze the mode information, such as the amount of mode mixture of two different rotating fields and the phase difference between two modes. This paper provides a quantitative way to analyze the rotating cylindrical modes generated from an oversized cavity. [ABSTRACT FROM PUBLISHER]

This paper reports an experimental study of luminescence excited in polymethyl methacrylate (PMMA) by a runaway electron beam and by a KrCl excilamp with a wavelength of 222 nm. It is shown that the major contributor to the luminescence of PMMA in both cases is a luminescence band with a maximum intensity at ~490 nm. Based on experiments with the excilamp, it is supposed that Cherenkov radiation with a wavelength shorter than 300 nm is bound to increase the intensity of this band. The luminescence intensity at ~490 nm varies proportionally with the number of beam electrons, allowing the use of this radiation to determine the number of high-energy electrons in electron beams. In PMMA with high absorption at 300–400 nm, one more luminescence band with a maximum intensity at ~400 nm is observed. It is confirmed that in gas diodes at a pressure of 760 torr, the intensity of Cherenkov radiation against the background of luminescence is low and undetectable. [ABSTRACT FROM PUBLISHER]

Atmospheric-pressure plasma jets (APPJs) are widely used in biomedical treatment, surface modification, and sterilization, among others because of their advantages of simple structure, strong chemical activities, nonthermal effects, and convenient handling. In this paper, a nanosecond-pulse power generator based on Marx circuit is proposed. The apparatus consists of a nanosecond-pulse generator with crowbar switch and a needle-ring structure electrode. The nanosecond-pulse generator is modularly designed with ten stages; MOSFETs are used as the main switch and crowbar switch on each stage. A field-programmable gate array is used to generate two-channel trigger pulse signals to control the turn-on or turn-off of switches. The generator can produce repetitive pulses with output voltages of up to 8 kV, pulsewidth of 100–1000 ns, rise time of less than 30 ns, and pulse repetition frequencies of 1 Hz to 1 kHz. The designed nanosecond-pulse generator and the needle-ring structure electrode are used to produce argon plasma jets into open air, and the experiments show that the nanosecond-pulse generator can sustain stable APPJs. This paper lays a foundation for the further exploration of the biomedical effects of APPJs. [ABSTRACT FROM PUBLISHER]

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]