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The spark gap switch is the key element in any pulsed power system, which directly determines the pulse repetitive frequency of the system. The dielectric recovery data of the spark gap play a basic role, but they have not yet been adequately studied for repetitive pulse charge conditions. This paper describes some of the factors that affect the recovery of spark gap switch for pulse-charged operation. A two-pulse technique has been used, in which the first pulse is applied to the spark gap to overvolt the gap and initiate the breakdown and the second pulse is used to determine the recovery voltage of the gap. The effects of electrode size, pulse rise time, and conduction current on the spark gap recovery performance are presented. Experiments were performed by using a double-pulse generator capable of generating 40-kV pulses with a delay of 1 ms–1 s. Spark gap electrodes of 34-, 40-, and 68-mm diameters and a point type were used in the study. The effect of voltage rise rate was studied by changing the charging capacitor to 100, 500, and 1000 nF in the circuit. An intermediate plateau was observed in the spark gap recovery curves. In addition, an increase in the output impedance resulted in a decrease in the time taken for the recovery of the spark gap. Also, the switch recovery appears to be largely dependent on the electrode shape and size compared with the pulse rise time. [ABSTRACT FROM AUTHOR]

With the rapid developments in pulse power technology, the gas spark switch has broadened its application in both industrial fields and research fields, such as the extraction of unconventional gas resources and underwater electrical wire explosion. Thus, the repetitive switch needs high current capability, small breakdown voltage variance, and long lifetime in an airtight cavity. The performances of the switch directly influence the output characteristics of the system, but electrode erosion is inevitable, which may decrease the self-breakdown voltage and the lifetime. The purpose of this paper was to investigate the electrode erosion characteristics under adverse conditions. The cathode showed a worse erosion surface. Compared with the central zone of the electrodes, the outer zone showed a worse surface roughness for both the cathode and the anode. [ABSTRACT FROM PUBLISHER]

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]

In this paper, an adjustable magnetic switch (AMS) based on splice winding is investigated numerically and experimentally. The proposed AMS has advantage of high power level, high repetitive rate capability, long lifetime achievability, and electrical parameters tunability, which meets the growing requirements of the military and industrial application of pulsed power technology. Adjustment of the electrical parameters of magnetic switch is achieved by altering the number of windings via the modification of the joint points between the AMS and the main circuit. Specifically, basic principle of the AMS is analyzed based on characteristics of the magnetic switch. Detailed design considerations are described for achieving modification of the winding’s number ranging from 1 to $M$ (positive integer larger than 1), which is limited by the insulation density, easily and reliably. In order to verify the design, two typical electrical parameters of an AMS are numerically calculated and simulated by the circuit simulation software. Accordingly, a test experiment platform was setup in our laboratory and the primary experimental study demonstrates that the AMS can successfully alter the electrical parameters with results similar to the calculation. A typical ( 1-\cos \omega t)$ pulse with rise times of 4 and 5 \mu \text{s} , a peak voltage of approximately 20 kV, and a peak current of over 1.0 kA was achieved on the capacitor load. The experimental results show reasonable agreement with the theoretical and numerical analyses. [ABSTRACT FROM PUBLISHER]

This paper describes a compact high storage density inductive–capacitive storage module. The module is based on high-power opening switches using inverse current commutation with semiconductor devices commutation principle and a high storage density Brooks inductor. These opening switches, being able to switch-OFF pulse currents up to 14.5 kA by the counter-current subcircuit, make use of the general property of a standard high-power thyristors impedance transition from closing state to blocking state. The experimental results show that with the primary capacitor and counter-current commutation subcircuit charged voltage 3 and 2.5 kV, respectively, the charged current of the Brooks-type inductor is about 14.5 kA, with a charged time of about 4.5 ms. The output peak current of the inductive storage module is about 21 kA. The total stored energy is about 54.9 kJ while the energy density of the inductor is approximately 6.69 MJ/ \textm^3 , which is not including the primary storage and commutation unit. [ABSTRACT FROM PUBLISHER]

Many approaches exist for energy storage and delivery to the load, including high-power relativistic applications. One of the best solutions for the driver of high-power relativistic applications is the Marx generator. This paper describes the design, fabrication, and experimental validation of a Marx generator consisting of capacitors, spark-gap switches, and resistors. It is designed as an eight-stage Marx circuit to reach an output voltage level as low as −500 kV, and it is directly connected to the Blumlein pulse-forming line (PFL) to achieve more than 100 ns of the full-width at half-maximum. Experiments are performed with a solution load in a manner similar to having a coaxial structure in a high vacuum with a pressure of below 0.5\, \times \, 10^-5 torr, to prevent breakdown and measure the amplitude of the negative high-voltage pulse waveform. The solution load is designed to capture the short-pulse output of the PFL with a rise time of less than 25 ns and a voltage level of approximately −500 kV. The experimental results show that the output pulse can be used as a source to generate an intense relativistic electron beam at the gun for high-power relativistic applications. [ABSTRACT FROM PUBLISHER]

High-performance trigger generators with high amplitude, fast rise time, low jitter are essential for large-scaled pulsed-power systems. Most of the trigger generators are also tiny multistage pulsed-power systems with complicated structures. In this paper, a high-performance trigger generator was proposed by combining the advantages of low-jitter semiconductor switch and high-power gas switch. An avalanche transistor Marx circuit was developed. It was used to trigger a two-stage Marx generator based on trigatron switch. The output characteristics of the Marx circuit based on avalanche transistors and the two-stage Marx generator were studied. The experimental results show that a subnanosecond jitter, nanosecond rise time, high-voltage trigger generator can be achieved by triggering trigatron switch with an avalanche transistor circuit. [ABSTRACT FROM PUBLISHER]

A pseudospark switch with two hollow electrodes separated by a ceramic disc in between with a trigger plug inserted near the hole has been fabricated, and it was successfully operated. In this paper, a 29-kV anode voltage, 3.6 kA at 2.2 kHz with 11-ns rise time, has been achieved and operated, successfully. A simple trigger pulse has also been designed, built, and operated effectively reaching more than 1.6-kV trigger voltage that was sufficient to ignite the gas inside the cathode. The main plasma discharge produces 1-ns jitter time that occurred in a reliable manner for more than 6 h of operation continuously. [ABSTRACT FROM PUBLISHER]

In this paper, the basic structure and working mechanism of laser triggered vacuum switch (LTVS) are briefly introduced, the processes of primary plasma production and expansion are also analyzed. A series of experiments have been carried out under different conditions of LTVS, such as laser energy levels, voltages, and polarity configuration modes. The relationship of conduction and jitter time delays among the laser energy, voltage, and polarity are described, and the effect of main electrode and the expansion of primary plasma are analyzed. The theoretical basis for structure optimization design of LTVS is provided. Under positive polarity configuration that is beneficial to generate the cathode spots, the high working reliability and small time delay of LTVS are verified by the experiments. The results prove that the expansion of primary plasma is the growth of plasma sheath near cathode. [ABSTRACT FROM PUBLISHER]

Two-electrode graphite spark gap switch (TGSGS) is used as the main discharge switch and triggered by a reliable trigger generator in pulsed power conditioning system (PPCS). There would be 108 energy modules in PPCS working at the same time. The reliable operating and jitters of the trigger generators will have impact on the PPCSs performance. In this paper, the working modes of the TGSGS are discussed and the performance of trigger generators in PPCS is tested and presented. A protection strategy of the trigger generator in PPCS is introduced, and effect of the blocking capacitor on the trigger pulse transmission is analyzed and tested. The protection strategy of the trigger generator based on blocking capacitor and fuse can effectively prevent the energy anti-irrigation failure when the pulse transformer core saturated. The blocking capacitor has some effect on the trigger pulse transmission, and has the larger capacitance, getting the higher peak amplitude on the cathode of the TGSGS. It is tried to discuss the working characteristics of the thyristors, and proposes a selection reference of the thyristors in this and other similar applications. The combination of analysis and measurement would be useful for the selection of thyristors and other components. [ABSTRACT FROM PUBLISHER]

This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter—which has advantages of low ripple, high-efficiency, and high-power density compared with a single-phase converter—a high-voltage power supply with low ripple (<0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode—including soft switching, low conduction loss, and current source characteristics—the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5–20 kV), and low ripple (0.05%), with a high power density. [ABSTRACT FROM PUBLISHER]

A number of high-power applications require a transportable high-energy, high-current GW generator to drive a pulsed power system at the output. A first prototype, based on exploding wire technology and using an H-bridge circuit configuration, was developed at Loughborough University a few years ago and has been previously reported. The present stage of the work has necessitated the development of a more powerful and energetic source, and this is now based on inductive storage technology. A 400 kJ capacitor bank is connected by a high-Coulomb explosively driven closing switch with an air-cored 0.6 MV transformer, an exploding wire array, and a high-power diode based on a polarity-dependent spark-gap completing the arrangement. The GW generator, including the command and control module, is accommodated in two ISO containers. The various components of the generator are described in this paper, together with results obtained from full-scale tests. [ABSTRACT FROM PUBLISHER]

A repetitive 0.6 MV, 10 GW Tesla-driven Blumlein pulsed power generator, with an overall energy efficiency in excess of 90%, has been designed, manufactured and demonstrated by the Pulsed Power Group at Loughborough University. This paper describes the application of various numerical techniques used to design a successful generator, such as filamentary modeling and electrostatic and transient circuit analysis. All the major parameters of both the Tesla transformer and the Blumlein pulse-forming line were determined, enabling accurate modeling of the overall unit to be performed. The wide-bandwidth embedded sensors used to monitor the dynamic characteristics of the overall system are also presented. Experimental results obtained during this major experimental program are compared with theoretical predictions and the way ahead toward generating faster output voltage impulses is considered. [ABSTRACT FROM PUBLISHER]

Field distortion gas switches are extensively used in pulsed power systems. Switch performance typically degrades because of electrode erosion, which directly influences the output parameters, stability, and reliability of pulsed power systems. With the same value of $pd$ , different pressure and gap lengths in gas switches can affect electrode erosion property and thus, the subsequent performance degradation, but few results have been published. In this paper, repetitive discharges have been undertaken in a three-electrode field distortion gas switch with fixed pd$ to study the influence of pressure and gap length on electrode erosion and switch performance. The morphology of electrode surface and time histories of both trigger jitter and the probability of prefire have been investigated during the whole life cycle of the gas switch. The results show that when pd$ is fixed, high pressure and a short gap make for low trigger jitter at the start of the switch life cycle but lead to more severe electrode erosion, expediting the degradation of performance in field-distortion gas switches. Meanwhile, the probability of prefire increases rapidly with the increase of pressure. [ABSTRACT FROM PUBLISHER]

This paper describes a modular solid-state switching cell derived from the Marx generator concept to be used in topologies for generating multilevel unipolar and bipolar high-voltage (HV) pulses into resistive loads. The switching modular cell comprises two ON/OFF semiconductors, a diode, and a capacitor. This cell can be stacked, being the capacitors charged in series and their voltages balanced in parallel. To balance each capacitor voltage without needing any parameter measurement, a vector decision diode algorithm is used in each cell to drive the two switches. Simulation and experimental results, for generating multilevel unipolar and bipolar HV pulses into resistive loads are presented. [ABSTRACT FROM PUBLISHER]

This paper provides analysis of experiments aimed at defining the capabilities of plasma opening switch (POS) for energy transfer to a load of inductance comparable with the inductance of the energy store vacuum section. The analysis is performed using the substantiated technique that allows quantitative estimation of the POS efficiency. Under the same conditions with a conduction current of ∼1 MA and POS voltage of ∼1 MV, the energy transferred to the load depends strongly on the transmission line design. When the electrode gap in the line is ∼1 cm, the energy delivered to the load is ∼40 kJ. Increasing the gap to ∼4-cm increases this energy to ∼100 kJ. [ABSTRACT FROM PUBLISHER]

Fe-based nanocrystalline (FE-N) cores are widely used in pulsed-power and power electronic systems. In this paper, FE-N cores with high and low residual flux were tested and compared under single impulses. The loss density and permeability of the two FE-N types are evaluated in the usable flux swing range of \(\sim 0.0\) –1.4 T, and a range of magnetization rates of \(\sim 1.0~\mu \) s–6.0 T/ \(\mu \) s. When the loss density and average relative permeability are evaluated for magnetization from initial point to positive saturation based on the initial magnetization curves, the FE-N with low residual flux has lower loss density and larger average relative permeability than the one with high residual flux under low magnetization rates. The loss density and average relative permeability of the two FE-N types are almost the same values under high magnetization rates. The application of the measured results in magnetic switch design and performance analysis is presented. The presented results of the two FE-N cores can be aided in the practical magnetic designs of magnetic switches, pulse transformers, and inductors, but not restricted to those. [ABSTRACT FROM PUBLISHER]

In this paper, the charging precision of a 40-kW 3-kV soft-switching boost converter for capacitor charging is investigated. At the beginning, an overview on the topology and the control of the converter is given. Then, two different feedback controllers are presented and compared analytically to determine their sensitivity on noisy input variables. An algorithm to investigate the charging precision is illustrated. This algorithm considers the signal-to-noise ratio (SNR) of all measured signals, the controller output limitations, quantization related errors, the finite resolution in the digital domain, and the switching signal jitter to calculate the charging precision. All effects mentioned before are analyzed separately. This analysis shows that the output voltage measurement SNR is the key parameter for the charging precision. Then, measurements are performed to verify the model used to calculate the precision. These measurements show that the measured precision is only 6% higher than the precision predicted by the model for the used setup. Finally, the charging precision of the presented converter is analyzed including all considered effects. The repetition accuracy of the converter is determined to be 8.3 ppm at an output voltage of 3 kV, neglecting the load connection and the input voltage variation during one switching cycle. [ABSTRACT FROM PUBLISHER]

Utilization of power electronics converters in pulsed power applications introduced a new series of reliable, long life, and cost-effective pulse generators. However, these converters suffer from the limited power ratings of semiconductor switches, which necessitate introduction of a new family of modular topologies. This paper proposes a modular power electronics converter based on voltage multiplier as a high voltage pulsed power generator. This modular circuit is able to generate flexible high output voltage from low input voltage sources. Circuit topology and operational principles of proposed topology are verified via experimental and simulation results as well as theoretical analysis. [ABSTRACT FROM PUBLISHER]

The main characteristics of reversely switched dynistor (RSD) are infinite series, long lifetime, turning on in microseconds to nanoseconds, high-current rise rate (100 kA/\mus), and ability of passing through large current (several kiloamperes). With these advantages, RSD has a great potential of application in repetition rate pulsed power technology and the future HVdc field. To resolve the problem of residual voltage of RSD caused by insufficient precharge, which leads to nonuniform turn-on of RSD, this paper, based on the conduction mechanism of RSD devices, describes precharge circuit design requirements and establishes a second order circuit model to study the resonant triggering circuit of RSD. It is found that reducing precharge inductor can effectively increase precharge current, resulting in reducing the turn-on voltage of RSD. Finally, design for three improved circuit topologies (full-bridge, intense pulsed, and two-step triggering circuit) are presented and experiments show that these improved circuit topologies can enhance the precharge efficiency and reduce the turn-on voltage of RSD. [ABSTRACT FROM PUBLISHER]

In this paper, a mesoband pulse radiator fed by a spark gap switch is designed, and its radiation characteristics are analyzed. Initially, a modified equivalent circuit model of spark gap switch is proposed to enable detailed explanation and fast design. Then, dual resonant characteristic due to the higher order mode of a mesoband pulse radiator is newly analyzed by changing the dipole length and radius. According to the analyzed results, the variation of the dipole length affects not only the radiating power, but also the operating frequency and bandwidth. The measured 3-dB bandwidth of the designed pulse radiator is about 57% (\lambda=1.15~m), meeting the need for a mesoband condition. The radiated electric field at 4 m from the radiator has a peak of 7.19 kV/m. [ABSTRACT FROM PUBLISHER]

Switching time jitter is an important property to consider when selecting closing switches for pulsed-power systems. The corona-stabilized switch (CSS) is identified as an interest for low-jitter systems, in particular for systems where a high-repetition rate is required. In this paper, a commercial CSS is studied and its operating conditions are determined. [ABSTRACT FROM AUTHOR]

In this paper, the complicated arc phenomena in air dc circuit breakers that are widely used in rail transit and vessels are investigated with both experimental and numerical approaches. Initially, the basic arc motion characteristics in the switch are presented by the recorded waveforms and images in the carefully designed breaking experiments. Phenomena of arc stagnation and back commutation are revealed and the influence of arc chamber width on the arc stagnation is preliminarily discussed according to the experimental results. Then, to make the nature of arc motion clear and to determine the influence details of the arc chamber width on arc motion characteristics, a simplified model based on magnetohydrodynamics theory is built and four cases with the arc chambers of different widths are calculated. The simulated arc behavior is presented by the temperature distribution sequences. In addition, the formation process of back commutation is described in detail by the variation of arc column. The influence mechanism of arc chamber width on arc motion is analyzed according to the differences of pressure propagation and temperature distribution in the arc chamber. Furthermore, the calculated arc displacement curves show that the arc stagnation time could be shortened and the risk of back commutation could be reduced by decreasing the arc chamber width within the reasonable extent. [ABSTRACT FROM PUBLISHER]

Since bipolar high-voltage pulses is more effective in the treatment of air purification, water treatment, and other applications than unipolar pulses, a newly developed bipolar high-voltage rectangular pulse adder is proposed with a new control strategy. The structure of the all solid state pulse adder based on the half-bridge structure has been improved by changing the driving signal of the MOSFETS in the main circuit to obtain high-voltage rectangular narrow pulses. Magnetic ring transformers with a common primary winding and rectifiers were employed to charge capacitors under a high frequency. Improved phase shift control strategy is proposed, which makes it possible to generate unipolar or bipolar pulses with or without chopping off over resistive and capacitive loads. The bias voltage in the pulse removed and the size of magnetic cores is reduced. A nine-stage laboratory prototype is assembled. Experimental results show that unipolar and bipolar rectangular pulses with an amplitude of 4 kV, frequency of 12 kHz, pulsewidth of 600 ns– $4~\mu \text{s}$ , and rise time of 80 ns are obtained over different loads. [ABSTRACT FROM AUTHOR]

A compact magnetic pulse compression (MPC) topology with only two magnetic cores and a continuous repetition rate of 20 kHz is presented. The demand for higher average output powers of pulsed power systems can be achieved by an increase of the pulse rate frequency (PRF). The PRF is often limited by the switching speed or recovery of the main switch and also the complex behavior of the magnetic materials. With the advent of insulated gate bipolar transistors and the nanocrystalline soft magnetic material, PRFs of tens of kilohertz are feasible if a suitable MPC topology is applied. The presented MPC is based on an existing topology that has been significantly improved to enable high-frequency pulse generation. A design method using 3-D magnetostatic and transient magnetic simulations is introduced to enable optimization of the magnetic switching components. A 20 kHz, 60 kV, and 52 ns full width at half maximum (FWHM) MPC generator is designed, built, and tested for a $100~\Omega $ load. Simulations suggest that a PRF up to 50 kHz is achievable, but continuous operation will likely be limited by thermal management. [ABSTRACT FROM AUTHOR]

The trigger voltage is usually high in traditional three-electrode gas switch, which makes the trigger system large and complex in large-scale pulsed power system such as linear transformer driver. In this paper, a three-electrode gas switch triggered by microhollow cathode (MHC) discharge is put forward, which can be operated stably under low trigger voltage. MHC discharge is a kind of microplasma with the characteristics of low trigger voltage (several thousand volts), high electron density, and high gas pressure discharge. In this switch, three MHC triggers sharing the same cathode are designed as the third electrode of the switch in the middle. Positive and negative high voltages are applied to two main electrodes, respectively. The breakdown characteristics of MHC discharge triggered by pulse voltage are first studied. The trigger voltage can be as low as 8 kV at 0.3 MPa in pure N2 with the discharge peak current up to 80 A. A circuit simulation model describing breakdown process of MHC is also built. Then two operating modes of the switch, three-electrode mode (T-mode) and two-electrode mode (D-mode), are analyzed. The stable operation with the charging voltage from ±35 to ±50 kV is realized under different working coefficients from 64% to 92% and different trigger voltages from 8 to 15 kV. The turn-on parameters including delay time, jitter, and turn-on time are studied that the delay time and jitter of D-mode are longer than that of T-mode under the same condition. At last, the improvement of MHC trigger for the stable operation of D-mode with shorter delay time is described. [ABSTRACT FROM PUBLISHER]

This paper demonstrates a large-area, lightweight, conformal plasma device that interacts with propagating X-band microwave energy. The active elements are rugged plasma-shells— hollow ceramic shells encapsulating a controlled-pressure gas that can be ionized to controlled plasma parameters. Plasma-shells are electrically excited by frequency selective surfaces that are transparent to the frequency band of interest. The result is equivalent to large-area free-space plasma confined in a discrete plasma slab. A novel structure is designed with the aid of full-wave simulation and fabricated as a 76.2-mm square array, and transmission performance is tested across different drive voltages and angles of incidence. Switchable attenuation of 7 dB is measured across the passband when driven with 1400 Vpp at 1 MHz. Plasma parameters are estimated from theory and full-wave simulation, with electron density estimated to be 3.6\times 10^12~cm^-3. The proposed structure has potential for use on mobile platforms. [ABSTRACT FROM PUBLISHER]

This paper discusses charging modes of series-resonant converter (SRC) for an energy storage capacitor in terms of charging time, losses of switch, normalized peak resonant current, normalized peak resonant voltage, and switch utilization in three operational modes. Principles of operation on the full-bridge SRC with capacitor load are explained, and charging characteristics in discontinuous and continuous operational modes are analyzed. Based on the analysis and the simulation focused on the aforementioned five performance indexes, ms = 0.5 is evaluated to be the optimized operating frequency ratio for charging an energy storage capacitor. A 1.8-kJ/s SRC prototype is assembled with the TI 28335 DSP controller and a 40-kJ 7-kV capacitor. Design rules based on the comparative analysis are verified by experiment. [ABSTRACT FROM PUBLISHER]

Transmission line transformers (TLTs) are usually used for impedance match and pulse transformers, which have received gradual attention due to their excellent frequency response characteristics over conventional wire-wound transformers. This transformer basically consists of equal lengths of transmission line normally used by coaxial cables connected in parallel at the input side of the transformer and in series at the output side so that the output voltage can be boosted in proportion. For high-voltage and high-current pulsed system, a gas spark switch is usually used because of its large state current and high hold-off voltage. However, it is hard to get high repetition rate with gas spark switch, because of recombination of the ionized gas. Owing to the high working voltage, high pulse current, quick and steady fire lighting, low trigger voltage, reliable triggering, long life, light weight, small size, and ease of use, hydrogen thyratron, which selected hydrogen or deuterium as arc discharge dielectric, is widely used in the fields of scientific research, military, medical treatment, industry, etc. In this paper, we propose a high-power pulsed system based on TLT and hydrogen thyratron. The system is likely to work at higher voltage as well as higher repetition rate than what are for a conventional system made of wire-wound transfer and gas spark switch. [ABSTRACT FROM PUBLISHER]

Pseudospark switches are fast-closing low-pressure gas discharge switches with a hollow-cathode geometry. They can be triggered optically or by electron injection, where electrons emitted from a cold cathode emitter are accelerated in the electric field and initiate breakdown. The efficiency of charge carrier accumulation in the hollow-cathode structure determines the performance of the switch operation. The advantages of such switches include high hold-off voltage, high conduction current, fast current rise time, low delay and jitter time, and long lifetime. In this paper, the operating characteristics of a pseudospark switch, triggered by a carbon-nanotube (CNT)-coated electron emitter, are presented. The electron emitter is fabricated by coating randomly oriented CNTs on silicon substrate using chemical vapor deposition method. Field emission characteristics of CNTs are determined and then used as part of the trigger electrode which is integrated into an in-house constructed pseudospark switch. The operating characteristics of the switch are tested under different background pressures and different trigger voltages. Delay and jitter time under different working conditions are analyzed. Hold-off voltage and current rise time are also presented. [ABSTRACT FROM AUTHOR]

In this paper, a novel six-channels annular plasma-jet chamber is designed and embedded in the trigger electrode of the three-electrode gas switch to generate multichannel plasma jets without air flow, which is used to trigger the gas switch to form multichannel discharge. Results of this paper show that the plasma-jet triggering can be conductive to steady formation of multichannel discharge. [ABSTRACT FROM PUBLISHER]

Pulsed power technology is one of the technological foundations in high and new technology research, which has extremely broad development and application prospect. Gas switch is one of the key elements in pulsed power devices, and electrode erosion is a key restrictive factor in high-power gas switch development and application. According to the 1-D equation of heat conduction and thermal equilibrium equation near the electrode surface, this paper researches the electrode heat conduction mechanism, establishes the electrode erosion calculation model, calculates electrode erosion heat fluxes and their peak powers caused under different discharge conditions, and proceeds to calculate the depth of electrode etch pit. Calculation results indicate that arc joule heat is the main reason for electrode erosion when discharge current is not too high. In the light of different discharge parameters, that is, peak current, electric quantity, and current waveform, as well as single discharge electrode erosion experiments, the calculation formula of etch pit depth is fitted. The results indicate that model and fitted calculation results are relatively approximate to the experiment results. [ABSTRACT FROM PUBLISHER]

The possibility of mode switching from one pulse to another in a 6-cavity gigawatt magnetron with axial extraction of radiation through a horn antenna (such a magnetron is known as the MDO, i.e., magnetron with diffraction output) using a weak (200–300 kW), short (15-ns), and single-frequency RF signal was demonstrated using particle-in-cell simulations in our earlier work. This mode switching exploits the symmetric nature of the MDO that facilitates the use of any eigenmode as the operating mode. All scenarios of mode switching were considered using common properties of dynamical systems with two stable states separated by an unstable saddle point. In this paper, we continue to study the problem of mode switching, but this time for a 12-cavity MDO, for which we found splitting of the radiation frequency for each eigenmode owing to its different longitudinal distributions. Since splitting manifests as a bifurcation of frequency for definite values of the applied axial magnetic field, scenarios of frequency switching for this 12-cavity magnetron are considered. [ABSTRACT FROM PUBLISHER]

The triggering discharge behavior of the rail gap influences the jitter of discharge delay and inductance of the spark switch due to the formation of multiple spark channels in the rail-gap switch, which is related with the development of avalanche in the discharge process under the nanosecond triggering pulses. In this paper, the PIC/MCC method is used to investigate the avalanche development under a triggering pulse. A model of intershielding is proposed in the PIC/MCC method considering the effect of the space charges. From the simulation and experimental results, it has been clarified that the avalanche process can be controlled by the statistical delay time of the effective primary electrons. The intershielding model can also explain the effect of the rise time of a triggering pulse on the avalanche development. [ABSTRACT FROM PUBLISHER]

In this paper, the circuit model capable of dealing with magnetizing characteristics of the magnetic cores and switch prefire is established for linear transformer driver (LTD) cavities in PSPICE. Through simulation, the effects of switch prefire on other components in LTD and its output current pulse have been analyzed associated with the variation of energy loss in magnetic cores. Simulation results indicate that a switch prefire in one cavity would produce oscillations added to the charge voltage of the other switches in this cavity and cavities adjacent immediately. The magnitudes of such oscillations have an intimate relation with the magnetic core loss equivalent resistance. The loss equivalent resistances in the range from 4 to 6 \Omega have produced moderate voltage oscillations. Experiments on the 300-kA LTD cavity developed by the Northwest Institute of Nuclear Technology proved that such oscillations added to the charge voltage of other switches are likely to increase the breakdown probability of them. [ABSTRACT FROM PUBLISHER]

A new pulsed-power generator based on a Marx generator (MG) is proposed in this paper with a reduced number of semiconductor components and with a more efficient load-supplying process. The main idea is to charge two groups of capacitors in parallel through an inductor and take advantage of the resonant phenomenon in charging each capacitor up to twice as the input-voltage level. In each resonant half-cycle, one of those capacitor groups is charged; eventually, the charged capacitors will be connected in series, and the summation of the capacitor voltages are appeared at the output of a pulsed-power converter. This topology can be considered as a modified MG, which works based on the resonant concept. The simulated models of this converter have been investigated in a MATLAB/Simulink platform, and a laboratory prototype has been implemented in a laboratory. The simulation and test results verify the operation of the proposed topology in different switching modes. [ABSTRACT FROM AUTHOR]

A compact wideband antenna integrated with a pulse-forming line for transient pulse radiation is proposed in this paper. It can be used in the fields such as ultrawideband (UWB) radar, ground-penetrating radar, UWB communications, etc. This antenna is integrated with a solid-state switch and a planar Blumlein pulse-forming line. The dimension of the antenna is 300 mm \times 300 mm \times 3 mm. In the experiment, the switch was triggered by a laser with a wavelength of 1064 nm. The peak power of a single antenna was 14.45 MW when the applied voltage was 17 kV. A Gaussian doublet pulse with a duration of 1.5 ns and a peak–peak amplitude of 305.7 V/m at a distance of 2 m from the antenna along the main beam direction was recorded in the experiment. The measured waveform was in good agreement with the predicted one. [ABSTRACT FROM AUTHOR]

It is difficult to design a standard gate driver for optimal switching control of a static induction thyristor (SI-Thy) because of its unique internal structure and the direct commutation switching characteristic between the gate and cathode terminals during the transient turn-on and turn-off switching phases. Therefore, it is important to develop a simple and effective gate driver for achieving optimal fast turn-on and stable switching operations in an SI-Thy under hard-switching conditions. To achieve faster turn-on switching time with shorter gate delay time, impedance matching between the SI-Thy and the turn-on driving circuit component in the gate driver can be realized with additional circuit modification through this paper. To ensure higher stabilities in the turn-off switching phase, forced commutation techniques and additional auxiliary circuits in the gate driver have been devised to suppress the latchup and to eliminate potential ringing possibility. We have demonstrated that our designed and tested gate driver for realizing optimal switching characteristics of an SI-Thy is effective, particularly in the gate driving circuits for various pulsed-power switching applications. [ABSTRACT FROM PUBLISHER]

In this paper, starting from the project requirements, a 1.2-MJ pulsed power supply (PPS) module for a high-power laser system has been developed. The main circuit of this module consists of a high energy density capacitor bank, a spark gap switch, a magnetic switch, a trigger generator, and a load subsystem. Due to the superiority in the stability and service life, the two-electrode construction for the spark gap switch, high peak currents, and rise time of the currents is selected. Since a two-electrode spark gap switch has no separate trigger electrode and must be directly overvolted by the trigger generator, a small Marx generator has been designed and constructed for the advantage of the proven compactness and electrical performance. The effect of the magnetic switch represents a couple of functions. One is to block the triggering pulse produced by the Marx generator. Another is to permit the discharging current coming from the main capacitor bank. Finally, the measured discharge current waveform of the 1.2-MJ capacitive PPS module is demonstrated to be over a 300-kA peak current and a 500- \mu\s pulsewidth. Moreover, the life test has proved that the switch–trigger system can support more than 1500 discharging processes. [ABSTRACT FROM AUTHOR]

It is our interest to design and develop a high-power pulser system employing an electrical discharge in a spark gap. The type of discharge generates short electric pulses capable of both the characteristics of a fast rise time and a high repetition rate. Such a switch pulser has wide applications in the industry. To generate the electrical discharge in the spark gap in an efficient manner is very important for the switching operation. The regime of the operation utilizes the residual plasma in the interpulse recovery of the spark gap to increase the repetition rate. Therefore, the mechanisms of the discharge in a controlled manner following the electrical breakdown of the spark gap, such as the plasma generation in the spark channel and the dielectric recovery process as well as the residual plasma in the post-spark-discharge period, are of great importance. The understanding of the type of the spark-gap discharge for the switching at a high repetition rate beyond 1 MHz has been the primary goal. The typical voltage and current ratings are below 1 kV and several amperes, respectively. In particular, this paper addresses the optimal set of several parameters, such as the spark-gap geometry, electrode gap distance, gas pressure, and gas type, in conjunction with a unique circuit scheme to drive the discharge in the controlled fashion. [ABSTRACT FROM PUBLISHER]

Electromagnetic (EM) interference and its suppression are one of the major issues in most current systems design. The electric device such as railgun generates the EM fields that unintentionally propagate away from the structure. Railgun that have significant amounts of radiated emissions may interfere with the normal operation of other devices in close proximity. Also during the accelerating run of rail launchers, and particularly during the ignition of the armature, the radiated EM fields can compromise the life of electronic devices, can influence the signal to noise ratio, and can generate electrical shock hazard. The short duration pulse signal, such as current pulse of railgun, switching and arcing between components of railgun is typically rich in frequency spectral contents. It should be noted that the propulsive force of current pulse in each time push the armature in motion direction and change the propagation parameters of railgun as a time varying antenna and can affect on the radiation pattern in the various frequency ranges. Furthermore, in each component of current pulse, armature is in special position in direction of motion along the barrel and the impedance of railgun that power source see in front is different with previous stage and radiation pattern is different too. In this paper, the relationship between pulse form of input current and electric field around railgun are analyzed and simulated with finite-element method, then by attention of the armature position in each time it will be investigated the radiation pattern of railgun. [ABSTRACT FROM PUBLISHER]

With inherent strengths in energy density and power density, the inductive pulsed power supplies (IPPS) have become an attractive option for the power supplies in electromagnetic launch systems. The meat grinder circuits, including the slow transfer of energy through capacitive hybrid (STRETCH) meat grinder circuit, the STRETCH meat grinder with inverse current commutation with semiconductor devices circuit, and the meat grinder with self-charged capacitor and thyristors circuit, constitute one major branch among the IPPS circuits. This paper summarizes the fundamental research work and contributions of the meat grinder circuits from the perspectives of circuit improvements, performance analysis, inductor design, module collaboration, and efficiency promotion. The future directions of single IPPS module are higher energy level, larger energy density, and higher efficiency. [ABSTRACT FROM PUBLISHER]

In this paper, measurement results of the arc erosion limitation in low voltage (LV) switches are presented. The reduction of the arc erosion in the analyzed electromechanical switches was achieved through an application of the hybrid switching in the tested alternative current circuit during interruption of the inductive current. The presented method is based on a commutation of the current during its interruption into a semiconductor branch that is connected in parallel to the operated switch. Thus, this approach is able to limit the electric arc energy efficiently, and as a consequence the arc erosion of the electrical contacts is also significantly reduced. For this reason, the application of the hybrid switching has a positive influence on a lifespan and a reliability of the operated switch. In order to evaluate the influence of the hybrid switching application on an effectiveness of the limitation of the arc erosion in the analyzed LV switches, 50 000 current interruptions were conducted in the tested circuit by each of four analyzed switches. Researches were performed for two standalone switches during a standard current interruption, as well as, for two switches with applied the hybrid switching system. In order to compare the arc erosion of the contact surfaces in both considered cases, scanning electron microscope method coupled with energy dispersion spectroscopy was applied. Moreover, photos of the electric contact surfaces are presented. Additionally, frames registered by high-speed camera during current interruption are presented for both considered approaches. [ABSTRACT FROM PUBLISHER]

This paper presents a power electronics converter to generate bipolar high-voltage pulses using low-voltage dc source. Converter is designed based on charging of different capacitors by a predetermined switching pattern and their discharging on the load for pulsed power applications. Low number of power electronics devices and bulky transformer elimination are main advantages of the proposed converter. According to new findings, bipolar high-voltage pulses may lead to higher efficiency in many applications, such as food sterilization industry. The proposed pulse generator generates bipolar controllable pulses with a modular circuit structure based on a capacitor-switched network. Experimental results are presented to verify the analysis. [ABSTRACT FROM AUTHOR]

To study the lighting shielding of ultrahigh voltage (UHV) transmission lines across mountains and the hillside effects on discharge process, experiments have been carried out with a reduced scale tower model. As the spatial electric field is changed by the slope, the space of shielding failure is enlarged. When the high-voltage electrode is 5 m to the transmission line, the vertical length of shielding failure is 8 m for the 30° slope, which is larger than 5.17 m for the flat ground. The maximum probabilities of striking the lines are 95% for the slope and 75% for the flat ground. When the vertical distance from the high-voltage electrode to the hillside is less than that to the transmission lines, the probabilities of discharge striking the flat ground are 85% for the 5-m gap and 94% for the slope for the same gap. When the vertical distance from the high-voltage electrode to the hillside is equal to that to the flat area, the hillside does not affect the average discharge voltage apparently but discharge time and discharge dispersity. The results of this paper are valuable for lighting protection of UHV transmission lines in mountainous areas. [ABSTRACT FROM PUBLISHER]

The superconducting inductive pulsed-power supply (SPPS) circuit consists of a high-temperature superconducting pulsed-power transformer (HTSPPT) and an auxiliary capacitor. The electrical losses and the power of the primary source can be cut down with the superconducting inductive energy storage. Although its energy density is slightly less than a purely superconducting inductive system, it can reduce the maximum voltage of the opening switch by the capacitor and achieve a high degree of current amplification factor. However, during the discharge process, the magnetic leakage flux energy stored in the primary of the HTSPPT requires the capacitor to have a certain capacity. The higher the ratio of the capacitive stored energy over the total inductive stored energy, the more the dominant position of inductive energy storage reduces. The current amplification factor ( \gamma ), the maximum voltage of the opening switch ( V_{S\max } ), and the ratio of capacitive stored energy ( \eta ) are the three main properties of the SPPS circuit, which depends on several intertwined critical parameters, such as the inductance ratio n = L2 /( L2+LL ) and the capacitance ( $C_{{\mathbf {1}}}$ ). This paper studies the influence of the critical parameters on the main circuit performance with a 1-kJ SPPS system. The detailed selection method of the critical parameters for the specific system is also discussed with a coupling coefficient of 0.95. Such a system is easy to be utilized for the basic experimental study of a small railgun. [ABSTRACT FROM PUBLISHER]

For electromagnetic emission applications that need a very high amplitude and an appropriate pulsewidth, a pulsed power supply based on multiple high-temperature superconducting pulsed power transformer (HTSPPT) modules is verified in this paper. First, the working processes of multiple HTSPPT modules are analyzed and two small experimental HTSPPTs are described in detail. Then, simulation is carried out to show the major pulse characteristics of two different discharge methods. To verify the feasibility of two discharge methods, high-current testing is carried out with the two HTSPPTs. The results show that a higher amplitude of current pulse can be achieved using synchronous parallel discharge and a larger pulsewidth of current pulse can be achieved using asynchronous parallel discharge. [ABSTRACT FROM AUTHOR]

A new design of powerful high-voltage high-current impulse source for nanosecond megavolt charging of short forming lines (SFLs) is proposed. The first stage of the device is based on inductive energy storage. It accumulates energy supplied by the current of magnetic flux compression generator (MCG), whereas the electro-explosive opening switch is used for the energy output into intermediate SFL. In the second stage, we use a Tesla transformer with oil insulation. The results of the earlier experimental study of submegavolt charging of intermediate forming line as well as the results of calculations of the two-stage facility given in this paper demonstrate the feasibility of the device based on MCGs for nanosecond charging of SFL up to about 3 MV. [ABSTRACT FROM PUBLISHER]

Vacuum surface flashover switch is a promising technique scheme of high repetitive frequency fast-closing switch applied to dielectric wall accelerator. In this paper, the switch is experimentally investigated, and a nanosecond pulse with 2.02-ns effective rise time is obtained. For a cylinder-fused quartz dielectric, the breakdown field of the switch is near 55 kV/cm, and the value for the frustoconical-shaped dielectric exceeds 120 kV/cm with a lifetime up to 69000 discharges. The repetitive frequency ability of the switch is better than 100 Hz, and the breakdown voltage increases slightly with higher frequency. [ABSTRACT FROM PUBLISHER]

In this paper, we investigated a water treatment method that sprays waste water droplets into a pulsed discharge space. To increase energy efficiency of this method, a pulsed power generator should output a pulsed power of a high peak and a short pulse width and be low circuit loss, high repetition rate, high power, and high stability. An inductive energy storage circuit using a semiconductor opening switch was studied to satisfy the above-mentioned requirement. Initially, effect of turn ratio of a pulse transformer (PT) in the circuit was investigated. Energy transfer efficiency and the pulsewidth of the output voltage increased with the PT turn ratio, resulting in an increase of the efficiency of the water treatment system. Then, the effect of the load impedance was investigated. The result showed that an optimum resistance to maximize the efficiency exists. From these results and a previous experimental report, we concluded that the optimization conditions are summarized below. The turn ratio and the inductance in the secondary circuit should be as high as possible under the condition, which does not output the very long pulse. The impedance of the discharge at an electrode for the water treatment should be a value that maximizes the energy transfer efficiency. Capacitance of capacitors in the circuit should be adjusted to obtain optimal peak voltage for the generation of active species. [ABSTRACT FROM PUBLISHER]