Showing papers on "Marx generator published in 2013"

Marx dc–dc converter for high-power application

Abstract: This study presents a dc-dc converter based on the Marx generator principle of charging capacitors in parallel followed by reconnection in series for discharging and for creating higher voltage. The topology uses solid-state switches like IGBTs as well as diodes. The concept and the operation of converter are described as well as design steps. The validity of the design is confirmed using PSCAD/EMTDC software package. The topology is compared with the conventional boost where the Marx dc-dc converter is shown to be competitive and even advantageous for higher dc gain. A cascade configuration is also presented and a 5 kW prototype with two stages made of two capacitors per stage is presented for experimental validation of the concept.

Initial Performance of the Primary Test Stand

Abstract: The primary test stand (PTS) is a multiterawatt facility with a current of 8-10 MA and rise time of 90 ns, which is being built for Z-pinch studies at the Institute of Fluid Physics, China Academy of Engineering Physics The PTS consists of 24 modules that are connected in parallel Each module is based on the Marx generator and water pulse forming line as well as laser-triggered spark gap switch working at 5-MV level The nominal total stored energy of the PTS is 72 MJ All the Marx generators and laser-triggered spark gap switches had been tested at full voltage level before the PTS was assembled The design and installation of the PTS are described In this paper, the most recent results of the PTS commissioning will be introduced

Solid-State Dual Marx Generator With a Short Pulsewidth

Abstract: A solid-state Marx generator with a short pulsewidth not restrained by the maximum operating frequency of the employed semiconductor switches is proposed for adapting to various pulsed power applications. This repetitive generator is capable of controlling the voltage level, polarity, pulsewidth, and frequency for each pulse. The proposed topology is based on a fully solid-state Marx concept using a series connection of full-bridge switch-capacitor cells (SCCs). Independent control and combination of each SCCs' operation mode result in a greater freedom of control of the pulse parameter. An eight-SCCs stage prototype was implemented using 1200 V insulated gate bipolar transistors and tested. In the experiments, the bipolar pulses of from -4 to 4-kV amplitude are achieved, and the pulsewidth was adjusted down to 300 ns.

A compact bipolar pulse-forming network-Marx generator based on pulse transformers

Abstract: A compact bipolar pulse-forming network (PFN)-Marx generator based on pulse transformers is presented in this paper The high-voltage generator consisted of two sets of pulse transformers, 6 stages of PFNs with ceramic capacitors, a switch unit, and a matched load The design is characterized by the bipolar pulse charging scheme and the compact structure of the PFN-Marx The scheme of bipolar charging by pulse transformers increased the withstand voltage of the ceramic capacitors in the PFNs and decreased the number of the gas gap switches The compact structure of the PFN-Marx was aimed at reducing the parasitic inductance in the generator When the charging voltage on the PFNs was 35 kV, the matched resistive load of 48 Ω could deliver a high-voltage pulse with an amplitude of 100 kV The full width at half maximum of the load pulse was 173 ns, and its rise time was less than 15 ns

Development and Analysis of PFN Based Compact Marx Generator Using Finite Integration Technique for an Antenna Load

Abstract: This paper presents the design and development of a compact Marx generator based on pulse forming network (PFN) along with a peaking capacitor rated at 300 kV and 64 J. Proposed scheme consists of identical PFNs connected across the charging and grounding resistors according to the Marx generator scheme. Modular construction of the Marx generator is useful in altering the stage capacitance to obtain varying pulse rise time and wave shapes at the output. A peaking capacitor connected at the output of the Marx generator significantly improves the rise time from 25 to 5 ns suitable for driving an antenna load. The effect of peaking capacitor on the intensity of far-field radiation is simulated using finite integration technique for a distance of 15, 20, 30, 40, and 50 m and the results are presented and discussed.

A Novel All Solid-State Sub-Microsecond Pulse Generator for Dielectric Barrier Discharges

Abstract: This paper presents the design for a novel all solid-state sub-microsecond pulse generator for dielectric barrier discharges (DBDs). This generator consists of a MARX generator, Blumlein transmission lines (BTLs) and one magnetic switch (MS). As a power supply, the all solid-state MARX generator is capable of outputting nanosecond-pulses with a voltage peak of up to 20 KV. The key elements are BTLs which are charged by the MARX generator. Due to the unmatched impedance of DBD load, energy stored in BTLs begins to oscillate through DBD load after the MS turns on. The violent oscillation lasts until all the energy is consumed. During the violent oscillation, over ten discharges are excited in 5 μs under a single-shot condition. Thus, extremely intense plasma can be produced due to the accumulation effect. The alternating-current decaying voltage over the MS has a demagnetization effect, and DC reset circuit can therefore be spared. Experiments with matched resistor load were also carried out, and rectangular pulses with voltage up to 20 kV and duration of 220 ns were obtained. The ratio of the energy consumed by the resistor from the energy stored in the BTLs is 84.9%. The DBD images under a single shot and 100 Hz are presented.

Short-Pulse Marx Generator for High-Power Microwave Applications

Abstract: The generation of high-power microwaves can be used in the field of military (protection of convoys and improvised explosive device neutralization) and civil applications (study of biological phenomena such as electroporation, treatment of waste water, and so on). The implementation of such systems requires the use of a high-voltage pulsed source capable of operating in repetitive mode at 100 Hz for a few seconds or at 1 Hz during several hours. A pulse forming line (PFL) is used to convert the monopolar output signal of the generator into a bipolar pulse, which is more suitable to feed an antenna. It induces significant constraints for the pulse generator, which has to supply a mismatched load. Further constraints such as weight, volume, and energy efficiency have to be considered to facilitate the integration of the system on mobile platforms. It also has to be easily remote-controlled to facilitate its use in an operational context. A parametric study was conducted to design a short-pulse Marx generator dedicated to this kind of application. The best compromise was chosen to generate short-rise time high-voltage pulses with a low quantity of energy. For higher energy levels, other stages with a higher capacity can easily be used, using our modular coaxial structure. The tested 11-stage short-pulse Marx generator, connected to a PFL, reached an output voltage of 420 kV, with a rise time , at a 40-kV charging voltage. Inductive charging circuits allow operation in repetitive mode up to 100 Hz during a few seconds. The generator was operated at 1 Hz during several hours using a remote-controlled charging unit. For mobile applications, the generator can be charged by a battery-powered power supply unit.

A new kind of low-inductance transformer type magnetic switch (TTMS) with coaxial cylindrical conductors.

Abstract: As important devices for voltage boosting and switching, respectively, pulse transformer and magnetic switch are widely used in pulsed power technology. In this paper, a new kind of transformer type magnetic switch (TTMS) with coaxial cylindrical conductors is put forward to combine the functions of voltage boosting and switching in one power device. As a compact combination device of discrete pulse transformer and magnetic switch, the compact TTMS decreases the required volume of magnetic cores in a large scale. The primary windings of the TTMS have a parallel combination structure so that the TTMS which only has 3 turns of secondary windings has a step-up ratio at 1:9. Before the magnetic core saturates, the TTMS has low unsaturated inductances of windings and good pulse response characteristics, so it can be used to substitute the Marx generator to charge the pulse forming line (PFL) at the ranges of several hundred kV and several hundred ns. After the core saturates, the cylindrical conductors can decrease the saturated inductance of the secondary windings of TTMS to a level less than 400 nH. As a result, the proposed TTMS can be used as the boosting transformer and main switch of helical Blumlein PFL to form the quasi-square voltage pulse on the 160 Ω load with a short pulse rise time only at 60 ns.

High power solid-state step-up resonant Marx modulator with continuous output current for offshore wind energy systems

Abstract: This paper presents a new solid-state step-up resonant Marx modulator (S3RM2) with a continuous output current for offshore wind energy applications. The developed topology is based on the Marx generator concept, where magnetic switches are replaced by solid-state switching devices. The proposed converter is characterized by resonant switching transitions to achieve minimal switching losses and maximum system efficiency. Therefore, a higher switching frequency is conceivable to attain a higher power density. A double module consists of the 4-active switches operating at the output voltage up to seven times as high as the input voltage. An appropriate output capacitor size is considered to eliminate output voltage ripples and work as charge storage. The series-modular and cascade configurations of the S3RM2 have the advantage of being readily applicable to multilevel power switching converters with an arbitrary number of levels. The developed topology has been implemented on a 5-kW prototype converter to verify its feasibility.

High-voltage pulsed generators for electro-discharge technologies

Abstract: A high-voltage pulse technology is one of effective techniques for the disintegration and milling of rocks, separation of ores and synthesized materials, recycling of building and elastoplastic materials. We present here the design and test results of two portable HV pulsed generators, designed for materials fragmentation, though some other technological applications are possible as well. Generator #1 consists of low voltage block, high voltage transformer, high voltage capacitive storage block, two electrode gas switch, fragmentation chamber and control system block. Technical characteristics of the #1 generator: stored energy in HV capacitors can be varied from 50 to 1000 J, output voltage up to 300 kV, voltage rise time ~ 50 ns, typical operation regime 1000 pulses bursts with a repetitive rate up to 10 Hz.Generator #2 is made on an eight stages Marx scheme with two capacitors (100 kV–400 nF) per stage, connected in parallel. Two electrode spark gap switches, operated in atmospheric air, are used in the Marx generator. Parameters of the generator: stored energy in capacitors 2÷8 kJ, amplitude of the output voltage 200÷400 kV, voltage rise time on a load 50÷100 ns, repetitive rate up to 0.5 Hz. The fragmentation process can be controlled within a wide range of parameters for both generators.

A new kind of solid-state Marx generator based on transformer type magnetic switches

Abstract: In this paper, a new kind of solid-state Marx generator based on synchronous transformer type magnetic switches (TTMS) is put forward, and the TTMSs with new winding structures are used to substitute all the spark gaps in the traditional Marx generator for the purposes of solidification and long life time. As the new type of TTMS with high step-up ratio and low saturated inductances is employed, the proposed Marx generator becomes a compact combination of pulse transformer, magnetic switch, and Marx capacitors. The stages of the Marx capacitors can be synchronously charged in parallel before the magnetic core saturates, and these Marx capacitors also can synchronously discharge in series. The establishing time of the proposed Marx generator is at ns range. As the new type of self-reset TTMS is used, the input voltage of the Marx generator decreases to a low level less than 1 kV while the output voltage can easily reach a high level ranging from dozens of kV to hundreds of kV.

Features of 200 kV, 300 ns reflex triode vircator operation for different explosive emission cathodes

Abstract: To study the effect of explosive field emission cathodes on high power microwave generation, experiments were conducted on a reflex triode virtual cathode oscillator. Experimental results with cathodes made of graphite, stainless steel nails, and carbon fiber (needle type) are presented. The experiments have been performed at the 1 kJ Marx generator (200 kV, 300 ns, and 9 kA). The experimentally obtained electron beam diode perveance has been compared with the one-dimensional Child-Langmuir law. The cathode plasma expansion velocity has been calculated from the perveance data. It was found that the carbon fiber cathode has the lowest cathode plasma expansion velocity of 1.7 cm/μs. The radiated high power microwave has maximum field strength and pulse duration for the graphite cathode. It was found that the reflex triode virtual cathode oscillator radiates a single microwave frequency with the multiple needle cathodes for a shorter (

Einzel lens chopper and behavior of the chopped beam in the KEK digital accelerator

Abstract: The KEK digital accelerator (KEK-DA), which is a small-scale rapid-cycle induction synchrotron (IS), has commenced operation. A permanent magnet $x$-band electron cyclotron resonance ion source serves as the KEK-DA ion source and delivers various ions. A new Einzel lens beam chopper has been developed to provide the necessary pulse width of a few microseconds. The chopper is implemented by applying a rectangular pulse voltage generated by a solid-state Marx generator to the middle electrode of the Einzel lens. Momentum modulation at the bunch head and tail resulting from chopping in longitudinal direction has been observed. This intrinsic property of the chopped pulse has been clearly observed in a long drift (a free run in the circular ring) in KEK-DA.

500 ps/1 kV pulse generator based on avalanche transistor Marx circuit

Abstract: Ultra-short pulse generator based on Marx circuit, whose switch is avalanche transistor, could generate very short pulse with high peak voltage. The ultra-fast rising-edge of the pulse is mainly determined by transistor's avalanche effect. On the other hand, the avalanche effect have negative influence on the falling-edge, which lead to the waveform unacceptable for signal processing. In this paper, we analyze the oscillation of the falling edge and proposed a method to optimize the waveform of the pulse. Experimental investigation showed that, by optimizing the charging capacitors, pulse width can be effectively reduced and the waveform of the pulse is more close to zero order gaussian pulse.

New four-switches bipolar solid-state Marx generator

Abstract: Summary form only given. A novel solid-state Marx type topology capable of generating monopolar and bipolar high-voltage pulses is presented and discussed in terms of reliability for industrial applications and performance in comparison to other similar circuits. The novelty of this topology is that only four on-off switches are used per cell and the positive and negative pulses are generated using only one on-off switch per stage. The novelty of this topology is that only four on-off switches are used per cell and the positive and negative pulses are generated using only one on-off switch per stage. The application of positive followed by negative pulses, or vise-versa, in industrial processes such as liquid food sterilization, water and air pollution decontamination have shown evidence of higher effectiveness in relation to the use of monopolar pulse. However, from the point of view of the modulator, the generation of bipolar pulses imposes higher complexity, using additional switches in comparison to the needed in monopolar pulse generation. Nevertheless, topologies using additional semiconductors have higher operating flexible with respect to different load conditions, which can be industrially attractive. For this reason, it is very important to optimize this type of circuits. The presented circuit uses four on-off switches per stage, two for charging the energy storing capacitors, one for the positive pulse and another one for the negative pulse. This reduces the number of switches in relation to other Marx type topologies; however the pulse switches have to hold-off twice the dc input power supply voltage in each stage, which is a disadvantage in relation to other Marx type bipolar modulators. A comparative analysis regarding the number of switches per cell, semiconductor losses and hold off voltage of the semiconductor is made. The big advantage is the lower complexity in controlling the cell switches, which is industrially attractive. An industrial circuit topology is obtained as a compromise in terms of operating performance, complexity and switching losses that is tested into different types of loads.

Estimation of Surface Roughness due to Electrode Erosion in Field-Distortion Gas Switch

Abstract: Field distortion gas switch is one of the crucial elements in a Marx generator, fast linear transformer driver and other pulsed power installations. The performance of the gas switch, which is dramatically affected by the surface roughness due to electrode erosion during the discharge process, directly influences the output parameters, stability and reliability of the pulsed power system. In this paper, an electrode surface roughness (ESR) calculation model has been established based on a great deal of experimental data under operating current. The discharge current waveform, the peak height of the burr, the radius and the depth of etch pits in the electrode erosion region were used to predict the ESR. Also, experimental results indicate that this calculation model can effectively estimate the ESR of the test gas switch.

Marx generator with compact structure

Abstract: The invention relates to a Marx generator with a compact structure. In the generator, a charging power supply and a preceding-stage triggering source are installed in an integrated method and are positioned in a front-end metal barrel connected with an external barrel so that a size of the generator is reduced and operation complexity is reduced effectively. Insulating bodies are arranged between capacitors so that on a basis that effective insulating distances are ensured, inter-capacitor space is reduced and the size of the generator is reduced. Through cooperation of an internal barrel, a grounding-end insulating plate, an output-end insulating plate and an output positioning electrode, a switch rail and the capacitors are fixed at the center of the generator. In the Marx generator with the compact structure, structural design and electromagnetic shielding are focused on and parts of the minitype Marx generator are designed in an integrated method so that the minitype Marx generator, which integrates a generator body, the charging power supply and the preceding-stage triggering source, is developed successfully.

Comparative analysis on the fast rising edge pulse source with two kinds of avalanche transistor

Abstract: A fast rising edge pulse can be generated by Marx circuit based on avalanche transistors. The avalanche principle of a Marx circuit is analysed. and the triggering circuit and ten stages Marx circuit board are designed. A series of negative pulses with falling edge time about 2ns,voltage amplitude from about 700V to 1600V and pulse width below 6ns are obtained when the Marx circuit is ten stages based on the FMMT415 and FMMT417 by changing the charging voltage and the capacity. The pulse waveforms based two kinds of avalanche transistors are compared. The results are that a higher peak pulse can be get based on the FMMT417 than the FMMT415, the peak value will be lager when the charging voltage is higher, and pulse-width will be lager when the capacities are bigger within a certain limit.

Kinetic simulation studies of laser-triggering in the Z gas switch

Abstract: Advanced z-pinch accelerators require precise timing of multiple mega-ampere drivers to deliver terawatt power. The triggering of these drivers is now largely initiated by laser ionization of gas switches. In this paper, we discuss detailed fully kinetic simulation of the Z laser-triggered gas switch involving detailed finite-difference time-domain particle-in-cell Monte Carlo modeling of the trigger section of the switch. Other components of the accelerator from the Marx bank through the pulse-forming line are described as circuit elements. The simulations presented here build on a recently developed model of electro-negative gas breakdown and streamer propagation that included photons produced from de-excited neutrals. New effects include multi-photon ionization of the gas in a prescribed laser field. The simulations show the sensitivity of triggering to laser parameters including focal plane within the anode-cathode gap of the trigger section of the switch, intensity at focus, and laser pulse length. Detailed electromagnetic simulations of the trigger section with circuit modeling of the upstream and downstream components are largely in agreement with Z data and demonstrate a new capability.

A 100 kV, 60 A solid state 4 kHz switching modulator for high power klystron driving.

Abstract: A solid state high power modulator capable of delivering 120 kV and 60 A developed in collaboration with the JEMA Corporation, ESS Bilbao, and the SNS (ORNL) for driving high power klystrons is presented. Pulses with less than 10 μs risetime and flatness under 0.1% are obtained with programmable frequency pulses between 2 and 50 Hz. Eight solid state switches combined with custom air-insulated high voltage transformers working at a switching frequency of 4 kHz produce high quality pulses by phase shifting the transformer drives. Each relative high frequency stage pumps a double stage high voltage Marx generator that supplies the output pulse shape and frequency. This merged topology between a Marx generator and direct modulator takes advantage of the strengths of both approaches. Low energy storage in the output stages assures safe operation in case of a load arc discharge. Real time voltage correction during the pulse is also provided to compensate for the droop inherent with the use of low energy storage in the output stages. Data at full power with a dummy resistive load are presented.

Nanosecond high-voltage pulse source, Marx generator and circuit simulation model of Marx generator

Abstract: The invention discloses a compact nanosecond high-voltage pulse source of a Marx generator, and a peaking circuit in an existing high-voltage pulse source is removed. The compact nanosecond high-voltage pulse source is composed of the Marx generator, a control unit and a high-voltage direct current charging power supply. The Marx generator comprises a shell, a pulse capacitor and a gas spark switch. The shell, the pulse capacitor and the gas spark switch are cylindrical and are coaxially arranged. The shell comprises a metal shell body, an input end insulating supporting cover and an output insulating supporting cover, wherein the input end insulating supporting cover and the output end insulating supporting cover are located at the two ends of the shell body and fixedly connected with the shell body. According to the full-circuit simulation model of the Marx generator, a self-breakdown switch can be simulated with a PSPICE model, when the circuit model is built, the PSPICE module block can be directly called, only few parameters need to be set, and the model is much convenient to use.

Affordable, short pulse Marx modulator

Abstract: Under a U.S. Department of Energy grant, Diversified Technologies, Inc. (DTI) is developing a short pulse, solid-state Marx modulator (Figure 1). The modulator is designed for high efficiency in the 100 kV to 500 kV range, for currents up to 500 A, pulse lengths of 0.2 to 5.0 μs, and risetimes <;300 ns. Key objectives of the development effort are modularity and scalablity, combined with low cost and ease of manufacture. For short-pulse modulators, this Marx topology provides a means to achieve fast risetimes and flattop control that are not available with hard switch or transformer-coupled topologies.

Note: Complementary metal–oxide–semiconductor high voltage pulse generation circuits

Abstract: We present two types of on-chip pulse generation circuits. The first is based on CMOS pulse-forming-lines (PFLs). It includes a four-stage charge pump, a four-stacked-MOSFET switch and a 5 mm long PFL. The circuit is implemented in a 0.13 μm CMOS process. Pulses of ∼1.8 V amplitude with ∼135 ps duration on a 50 Ω load are obtained. The obtained voltage is higher than 1.6 V, the rated operating voltage of the process. The second is a high-voltage Marx generator which also uses stacked MOSFETs as high voltage switches. The output voltage is 11.68 V, which is higher than the highest breakdown voltage (∼10 V) of the CMOS process. These results significantly extend high-voltage pulse generation capabilities of CMOS technologies.

Frequency Dependence of the Anode-Cathode Gap Spacing in a Coaxial Vircator System

Abstract: The objective of this paper was to investigate how the frequency of an electromagnetic pulse generated by an inward-emitting coaxial vircator is dependent upon the anode to cathode gap distance (AK-gap) in the vircator. Experimental tests of three different AK-gaps 29.5, 32, and 34.5 mm, were conducted with the high power microwave (HPM) system Bofors HPM Blackout. The system is working within the L- to S-band and the vircator is powered by a 1.8-kJ Marx generator at a maximum voltage of 600 kV. In addition, the experimental models of the coaxial vircators were also simulated in ATK MAGIC2D particle-in-cell code and the experimental frequency was compared with the theoretical frequency. The experimental frequency increased with decreasing AK-gap.

A HV pulse generator for PEF applications

Abstract: In this work, a high voltage (HV) pulse generator for pulsed electric fields (PEF) application in treatment of liquid food is presented. A complete overview of the target application is followed by a detailed analysis and design of a 10 stages Marx generator. The pulse generator uses semiconductor switches to generate up to 30kV pulses of 2μs and 2400Hz frequency. Simulation of the electrical characteristics of the pulse generator and of the electric field, and temperature variations inside the chamber are presented as well as measured results of a 3-stage prototype.

Characterisation and Generation of High Impulse Voltages and Currents

Abstract: Transmission and distribution of electrical energy involves the application of high-voltage apparatuses like power transformers, switchgears, surge arrestors, insulators, power cables, transformers, etc. They are exposed to high transient voltages and currents due to internal and external overvoltages. Before commissioning, they are therefore tested for reliability with standard impulse voltages or currents. Depending on the apparatus and its proposed application, the specifications prescribe different types of test impulses, e.g., lightning, switching and chopped impulse voltages as well as exponential, rectangular and short-time alternating currents. For on-site voltage tests, oscillating lightning and switching impulse voltages are specified in addition. The standard impulses are defined by their test voltage value (or test current value) and at least two time parameters, with tolerances during generation and uncertainties during measurement. The background and specification of the new evaluation procedures in IEC 60060 concerning overshoots and oscillations superposed on lightning impulse voltages are treated in detail. This includes the presentation of the frequency-dependent test voltage function k(f) and the filtering method, obtained both as the result of world-wide round-robin tests. In the latter part of this chapter, fundamental circuits for generating high-voltage and high-current impulses are given, e.g., the multi-stage Marx generator for generating impulse voltages of up to several megavolts and the impulse current generator with crowbar gap arrangement for preventing undershoots of impulse currents.

Development of Transfer Function Model and Analysis of the Peaking Capacitor and Switch

Abstract: This paper discusses the development and analysis of a transfer function model of the peaking capacitor and peaking switch for an input from Marx generator and an output across load. The effect of variations of gap distance, pressure, peaking capacitor, and the input pulse rise time on the rise time of the output pulse is simulated using this model. For a given geometry, the modeling gives an optimum input pulse rise time and the effect of variation of peaking capacitor on various output parameters. The results obtained from modeling are validated with the experimental results.

Derivation of Load Peak Voltage, Power Consumption and Potential Energy Management in a Thyristor Controlled Marx Impulse Generator for Capacitor Discharge Application

Abstract: Calculation of the load peak voltage, potential energy and power consumption of a Marx impulse generator, as a function of time, are presented. The equations are generalized and can be used to the design of any type of n-stage Marx impulse generator. The results were validated for a thyristor controlled Marx impulse generator with a maximum number of stages of 10 and 3 kV input DC voltage, which used 1 MΩ resistors and 33 nF capacitors in its topology.