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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]

ASELSAN Inc. has been conducting experimental research on electromagnetic launch technologies since 2014. The first prototype, EMFY-1, has 25 $\text {mm} \times 25$ mm square bore and 3-m-length rails. In addition, two capacitor-based pulsed-power supplies (PPSs) with 1- and 4-MJ stored energy are built to supply launcher. During the design process of EMFY-1, a 3-D finite element (FE) model has been developed to simulate the electromagnetic and mechanical aspects of the railgun. This paper presents the simulation and experimental results of EMFY-1 with C-type aluminum armature. FE model, developed using COMSOL Multiphysics, includes both launcher and the PPS system. In addition to the velocity and position of the armature with respect to time, it is possible to observe the magnetic field, current density distributions and breech voltage using the FE model. In the experiments, pulse currents of the PPS modules, breech, and muzzle voltages are measured. The velocity of the projectile is measured using the B-dot probes. In this paper, two experiments of EMFY-1 will be presented. In the first experiment, the launch package with 42-g total mass is accelerated to 2778 m/s, and in the second experiment, the launch package with 130-g total mass is accelerated to 1560 m/s. The simulation results of the proposed FE model are compared with the experiments. It is observed that there is a good agreement between experimental and simulation results. [ABSTRACT FROM AUTHOR]

Isentropic compression experiments (ICEs) are an important method to study the dynamic characteristics of materials at pressures, temperatures, and stress or strain rate not attainable in conventional shock experiments. Yet it makes high demands toward the precise current pulse tailoring capability of the source. The China Academy of Engineering Physics is now developing a 20-brick parallel discharge driver and a 256-brick parallel discharge driver (CQ-7) to improve the performance and flexibility of compact magnetic compression devices. The load current of ICEs is tailored by optimizing the switch trigger sequence and the brick charging voltage. This paper establishes the equivalent circuit model of the 20-brick parallel discharge driver, taking the distributed inductance, resistance, and capacitance of transmission plates into account based on the partial-element equivalent circuit method. Besides, the equivalent circuit model of discharge brick based on the switch arc resistance model is also established to study the influence of key structural parameters on the output current. Furthermore, by comparing the simulation and experimental results of simultaneous discharge of 20-brick driver, the accuracy of simulation model is confirmed. This paper is of great significance to the design and optimization of multibrick parallel discharge drivers. [ABSTRACT FROM AUTHOR]

Electromagnetic launchers (EMLs) including railguns, helical guns, and coilguns have been proposed for numerous applications. However, the scaling characteristics of EMLs are unknown. This paper examines the nonlinear operating characteristics of EMLs and derives the operating voltage and current scaling relationships as determined by the mass and velocity of the projectile and the length of the launcher. The scaling relationship is derived using the kinetic power relationship common to all types of EMLs. The scaling relationship is expressed as a simple function of the projectile velocity, projectile mass, and launcher length. This paper also defines the impedance of an EML. The accuracy of the scaling relationship and the EML impedance are verified in a comparison with the experimental results of practical EMLs. The effects of resistive losses and inductive energy storage on the scaling relationship are included in the analysis. [ABSTRACT FROM PUBLISHER]

The intelligent estimation method (IEM) is based on approximations which can be described by the configuration and behavioral characteristic of the problem. This paper used the IEM in time domain (IEM-TD) which can be utilized to predict the current distribution and maximum current density. A detailed IEM technique to compute the current distribution over the surface of a rail, current profile around the rail, and maximum current density ( J\max) formula will be presented in this paper. The current distribution is computed for rectangular and circular rails that are shown in color figures. Finally, this paper considers the effect of the rail dimensions and material on these parameters that are shown in several figures. The results of this paper are compared to other published studies and FEM simulation. [ABSTRACT FROM AUTHOR]

Railguns are current-driven guns that allow reaching large muzzle velocities and energies. In the military context, the long-range artillery scenario makes use of these two capabilities to enable the launch of hypervelocity projectiles to target distances above 100 km. As of today, the most advanced railgun project is conducted by the Office of Naval Research, Arlington, VA, USA, and features railguns with a muzzle energy of 32 MJ. Such large artillery railgun systems with efficiencies above 30% are fed by a pulsed power system with a nominal energy content of about 100 MJ. In contrast to this, experiments with French-German Research Institute’s (ISL) most powerful railgun, PEGASUS, have reached muzzle energies of 2 MJ, only. The nearer future ISL has to answer two questions: 1) is the railgun technology adequate for a long-range artillery scenario? 2) can the railgun launch a hypervelocity projectile which is being developed by other groups in ISL? To do so and to support the development of the hypervelocity projectile, a larger railgun installation with a significant increase of the energy and free flight capability is required. In this paper, three different railgun systems were investigated using an electric circuit simulation code. The systems are referred to by the energy being stored in the capacitors as 25, 50, and 100 MJ. The aim of this paper is to investigate what masses can be accelerated to the relevant velocity range for the long-range artillery scenario by these different primary energies. The results of this paper can be used to aid the decision about the required size, with respect to the military scenario, of a potential future railgun system. [ABSTRACT FROM AUTHOR]

Reluctance coilgun (RCG) is a special coilgun which uses solid ferromagnetic material instead of induction coil as projectile. RCG has shown great advantages and potential in the application of antiterrorism weaponry due to its simplicity, reliability, and excellent controllability. As a compact lightweight pulsed-power supply (PPS), the compensated pulsed alternator (Compulsator) will play a key role in promoting this kind of electromagnetic weapon into practical applications. Focused on a specific RCG which has conductive rails and brushes, this paper deduced the electromagnetic force analytical formula by using the virtual displacement principle and researched the feasibility of the electromagnetic launch design scheme which uses compulsator as the PPS of the RCG system by co-simulation method. Finally, this paper finished tests of the system by taking advantages of a small demonstrative RCG and a scale-model prototype of the compulsator. The results indicate that the design scheme is completely feasible. [ABSTRACT FROM PUBLISHER]

An air-core strip-type high-voltage pulse transformer (HVPT) features a relatively simple structure in terms of design and fabrication. However, this HVPT requires considerable attention to prevent dielectric breakdown between the conductor windings. Because each spiral winding must be very thin, the field enhancement at the edges of the windings is very high. Therefore, it is important to develop proper methods to reduce the field enhancement factor and to prevent the dielectric breakdown at the winding edges. In this paper, in order to minimize the field enhancement, the proposed HVPT winding edges were folded, and each winding width was designed to decrease gradually to form a reverse trapezoid. These windings were insulated by multilayer insulators arranged in a specific manner. The requirement specifications are a maximum input voltage of 50 kV and an output voltage of 400 kV. This paper describes a design process and an electric field analysis to reduce the field enhancement. The simulation and experimental results confirmed the validity of the fabricated HVPT. The dielectric breakdown strength was tested up to 467 kV. [ABSTRACT FROM PUBLISHER]

Self-integrating Rogowski coil has been widely used for measurements of pulsed currents from nanosecond timescale to microsecond timescale in pulsed power systems. Appropriate designs of coil’s structure are vital to high-frequency response. This paper proposed a new structure of Rogowski coil so as to provide a better response to fast pulsed current. Four Rogowski coils with different structures were tested in three different platforms. Experimental results showed that the hybrid Printed Circuit Board Rogowski coil had the best performance in this paper, which could respond to square waves with fronts of $\sim 2$ ns and had a sensitivity of 0.585 V/kA. The designed maximal peak current was 100 kA. [ABSTRACT FROM PUBLISHER]

Compulsators are popular choices for various high-power electromagnetic launch applications, especially for the electromagnetic railgun. A two-axis-compensated compulsator with lower internal impedance and higher power density was proposed in the authors’ previous paper. The field windings and compensating windings are allocated electrical orthogonally, providing the opportunity to design the direct-axis and quadrature-axis compensations independently. Due to the excitation function of the field windings, as well as field windings and compensating windings at the same rotor periphery, the ratio between $d$ -axis and $q$ -axis compensation is determined not only by the waveform of the air-gap flux density but also by the occupied space of windings, electromagnetic force during discharge and temperature rise and cooling condition. All these aspects mentioned above were analyzed in this paper. Furthermore, the output performance for single pulse discharge of a 2-m railgun with 100-g armature and multiple pulses discharge of a 5-m railgun with 300-g armature was simulated and compared. The results indicated that the two-axis compensation could obtain benefits by introducing more sinusoidal discharge currents for single pulse mission comparing to traditional compensation structure, whereas no obvious advantages for a flat-topped current waveform for multiple pulses mission. [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]

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

This paper suggests a design of pulsewidth modulation series-resonant converter (PWM SRC) for magnetron power supplies. The goal of this design is to make the PWM SRC have a wide output voltage maintaining mode 3 operation that shows good switching characteristics. To keep the mode 3 operation, a systematic design is required because the design is related to various parameters, such as resonant tank, transformer turns-ratio, magnetizing inductance, and duty-ratio. To establish the design procedure, converter analysis is performed related to the steady-state operation, input–output relationship, and critical design conditions, and several design equations are derived based on the analysis. Based on the design procedure, a PWM SRC with parallel-input-series-output-connected transformer has been designed for magnetron power supplies and verified. [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 pulse transformer is used in many applications to provide high-voltage pulses. In order to obtain high and narrow output pulses, it is necessary to reduce the leakage inductance of the pulse transformer. The circuit of a high-voltage power supply is analyzed and simulated to study the effect of the leakage inductance on the pulse waveform. Afterwards, the winding structure is analyzed. Three transformer models were built based on the asymmetric parallel winding, the traditional parallel winding, and the taper winding. Their leakage inductances and parasitic capacitances are calculated and compared. The 3-D finite element simulation is adopted to compute the leakage inductance precisely. The simulation results demonstrate that the asymmetric parallel winding in this paper reduces the leakage inductance effectively with small parasitic capacitances. In addition, using the asymmetric parallel winding, a pulse transformer prototype is manufactured and tested. The experimental results verify the accuracy of the simulation method and the feasibility of the asymmetric parallel winding. [ABSTRACT FROM PUBLISHER]

The pulsed high-power supplies in this paper employs a homopolar inductor alternator (HIA) as the motor/generator integrated energy storage pulsed alternator. Lumped parameter design equations are developed, which is used to establish the mathematical model of the HIA, and the analytic calculation method of inductance matrix is derived. Prototype flywheel energy storage was built, and the basic structure of HIA is analyzed by using finite-element method (FEM). This paper proposes a simplified equivalent 2-D salient-pole synchronous generator model to simplify the 3-D FEM of HIA and investigates the motor control method of HIA based on the simplified 2-D equivalent model. The experiments were conducted for speed up to 8000 rpm and the six-step inverter drive strategy presented in this paper achieves the motor/generator integrated control on inductor energy storage pulsed alternator (IESPA). Most experimental results were in line with designed value. [ABSTRACT FROM PUBLISHER]

Based on the urgent needs for modularization and miniaturization of the inductive pulsed power supply system, this paper proposes the conceptual design and comparison of 100-kJ inductive storage power modules including four circuit topologies, three of which are proposed in our previous researches. The four circuit topologies are the STRETCH meat grinder, the XRAM with STRETCH meat grinder unit, the XRAM with strongly coupled inductors, and the XRAM with magnetic flux compression effect. The maximum load current of each constructed module is set to be 50 kA and its pulsewidth is at least 5 ms, which are the same as the main electrical properties of an existing 100-kJ capacitive module. A comparative study on energy density among the constructed inductive modules and the existing capacitive module is carried out in depth. Results show that the inductive modules, considering the volume of semiconductor switches and their control circuits, have higher energy density than that of the capacitive module. Among four constructed inductive modules, the XRAM with strongly coupled inductors module has the highest inductive energy density, and the XRAM with magnetic flux compression effect module has relatively better comprehensive performance. This paper offers the theoretical analysis foundation for investigating the inductive pulse power supply with higher energy. [ABSTRACT FROM PUBLISHER]

This paper presents a novel brushless doubly-fed pulsed alternator (BDPA) in the direct-drive power supply system for high-energy pulsed lasers. There are two sets of stator winding which are embedded in the stator slots of BDPA. One is called power winding and another is called control winding. The rotor winding is short circuit. Because there is no brush, compared with the compensated pulsed alternator, BDPA has higher reliability and can run at higher speeds to get higher energy-storing density. Besides, when the system works on the state of continuous multiple pulses, with a decrease of speed, the BDPA can maintain the frequency and voltage of the power winding constant basically. In this paper, the design procedure of BDPA is proposed according to the requirement of the high-energy pulsed lasers. Utilizing the finite-element model of the alternator, we can analyze the electromagnetic properties and calculate inductance parameters of the BDPA to verify the design scheme. Meanwhile, the simulation model of the direct-drive power supply system is established in MATLAB/Simulink to analyze the output performance of the flashlamp load. The simulation results confirmed the feasibility of design scheme of BDPA for the system. [ABSTRACT FROM PUBLISHER]

In order to analyze the performance of a fast linear transformer driver (FLTD) in different states, we develop a circuit model of nonlinear magnetic core. The circuit model contains controllable initial magnetic flux density and time-dependent loss resistance of the magnetic core. Afterward, the core model is added to the integral circuit to simulate the performance of the single stage FLTD; both the simulation and experimental results are given in this paper and the simulation results fit the experimental results very well under different situations. Moreover, this circuit model can be used to analyze the conditions when some faults occurred in the magnetic core. [ABSTRACT FROM AUTHOR]

Synchronous induction coilgun (SICG) has attracted more and more attention due to its advantages of simple manufacturing and no physical contact between armature and barrel. The armature, as an important component of SICG, will directly affect the launch speed and energy conversion efficiency. According to the distribution characteristics of eddy current and electromagnetic force, a new structural armature is proposed in this paper. The proposed inner conical armature is characterized by the maximum thickness at the tail end and the minimum thickness at the front end, with a gradual decrease in the thickness along the axial direction. The simulation results reveal that the proposed armature not only increases the mutual inductance between the armature and the drive coil but also enhances the electromagnetic force and weakens the armature capture effect. The experimental results verify that, compared with a traditional armature weighing 56.5 g, the new structure armature weighing 58.0 g enables higher muzzle velocities using the same set of pulsed power supply and drive coil, providing higher efficiency. [ABSTRACT FROM AUTHOR]

The driving coil, as a key element of synchronous induction coilgun, endures not only the radial expansionary force because of the magnetic flux compression but also the axial force due to the compressive force and counterforce of the armature. Dielectric breakdown and mechanical structure damage occurs frequently. Meanwhile, the driving coil should have high energy conversion efficiency as a pusher to accelerate the armature. Therefore, it is important to choose the appropriate structure and parameters in order to achieve a high launching performance. In this paper, the factors that influence the system efficiency are analyzed first. Different structure designs of the driving coil with the same inductance are evaluated. The effect of different calibers on the system efficiency is analyzed. The simulation result shows that the structure of the driving coil should be chosen according to the practical launching requirement while the magnetic coupling should be increased. Second, the electromagnetic force applied on the coil is calculated and the stress is analyzed. The thickness and displacement of the containment are calculated on the condition of unyielding. In order to validate the accuracy of the theoretical analysis, an electromagnetic-mechanical coupling finite element model is built. Comparing two calculation results, the error is small. Therefore, the method can be used to guide the design of the driving coil. Finally, a driving coil is fabricated according to the calculation results and experimented through static and dynamic tests. The experimental results show that the driving coil performs well and have high conversion efficiency. It provides a theoretical and experimental basis for the future design of multistage induction coilgun. [ABSTRACT FROM AUTHOR]

To deal with the uneven force on the inner and outer layers of the series coils as well as a large force on and temperature rise in its single layer under the influence of high pulse current during the electromagnetic launch (EML), this paper proposes a method of winding the wires of different diameters and turns by layers to make the multilayer coil parallel and the force on its layer uniform. But the prerequisite for the method is to ensure that the total current in the series coil and new-type coils keeps basically unchanged. The idea of designing the uniform distribution of coil current will provide a new approach to designing coils in the future. [ABSTRACT FROM AUTHOR]

In 2016, Hanwha Defense Systems Corporation commenced an electromagnetic launcher program to develop the next-generation “cold-launching” missile launcher system. This system is based on multistage induction coilguns with advantages such as controllability of energy transfer, reusability, and noncontact between the armature and the stators. The system requirement is to launch missiles to a height of 20 m with weight ranging from hundreds of kilograms to several tons. This paper presents the design, fabrication, and experiment results of a laboratory-scale electromagnetic launcher to demonstrate the feasibility of an electromagnetic launcher for heavy missiles. The effectiveness and performance of an electromagnetic launcher developed to launch heavy missiles have been demonstrated by accelerating a 21.68-kg projectile to 20 m/s. [ABSTRACT FROM AUTHOR]

Induction synchrotron (IS) has become the focus of improving the intensity of high energy ion beams in recent years. But because of the pulse voltage of the induction accelerating cell cannot adjust quickly, causing the mismatch of the magnetic deflection field and accelerate electric field, there is a serious beam loss problem in IS. The simulation of beams longitude dynamics proves that increasing the number of accelerating cells can effectively reduce the loss. In this paper, a novel compact induction accelerator module is introduced. Compared with the existing induction accelerator module of KEK, the new design can increase the number of accelerating cells to more than five times in the same installation space and improves the voltage top drop of the acceleration pulse significantly. [ABSTRACT FROM AUTHOR]

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

This paper presents a novel three-coil reconnection electromagnetic launcher (TCREL). Analytical calculations and simulation results indicated that not only does this model possess a higher structural strength, but also the launching efficiency is improved effectively compared with that of the traditional reconnection electromagnetic launcher (REL). In addition, take the TCREL model as an independent module; a toroidal REL (TREL) model can be obtained after several modules are uniformly placed and fixed around the circumference. The TREL model can reduce the magnetic flux leakage among driving coils, and further improves the launching efficiency. To verify the conceptual feasibility, two-stage TCREL and REL models were built and tested. The experiments demonstrate that the TCREL model possesses better launching performance than does the REL model; the former can obtain the desired launching efficiency of 15.818% but the latter only 8.248% in the contrast experiment. The experimental results are also in accordance with the simulation results. [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]

Large railguns require powerful power supply units. At the French-German Research Institute of Saint-Louis (ISL), most experimental railguns are driven by power supply units based on capacitors. Recent investigations at ISL explore the possibility to use coil-based systems to increase the energy density and reduce the footprint of the power supply. In this paper, an electrical circuit simulation is used to investigate the difference for railgun operation in between a capacitor and a coil-based power supply with respect to the current amplitude behavior, projectile velocity, and launch efficiency. For this, a scenario of a 25-MJ muzzle energy railgun is simulated with two different power supply options; one is based on capacitors, and the other is on coils. The circuit resistance determines a large part of the losses of the system and therefore defines the efficiency of the launch and the size of the power supply. Therefore, a range of different resistances were simulated as well. The interpretation of the results of the performed simulations leads to the conclusion that the capacitor-based system “naturally” produces a favorable current pulse trace with respect to launching a mechanical delicate payload. Further simulations show that the disadvantage of the inductor-based supply can be mitigated by increasing the power supply unit subdivision into smaller units. [ABSTRACT FROM AUTHOR]

For massive conductors with the characteristic sizes exceeding the penetration depth of variable or pulse magnetic field, it is possible to define the skin parameter, which affects transients in electrical circuits with massive conductors and does not depend on time and frequency. This paper describes the peculiarities of transients in circuits with massive conductors, defines and justifies the skin parameter, presents the methods of its calculation and measurement, as well as the results of calculation of transients in electrical circuits with massive conductors. [ABSTRACT FROM AUTHOR]

Electromagnetic induction coilgun systems have been receiving great attention, recently, due to the advantage of noncontact between the stator and armature coils. Several studies present the simulation and analysis of the coilgun system by using the finite-element method. However, there are still deficiencies in current modeling studies of the coilgun system. This paper presents a design of a multistage pulsed power induction coilgun system using the Taguchi method to maximize its efficiency and reduce the time and cost of the design process. A coilgun system is analyzed and designed using a state-space equation system. The Taguchi method is applied in order to evaluate and determine the geometric variables, the layer, turn layer numbers for both the stator and armature coils, and the trigger positions of each stage. Then, a 2-D finite-element model of the coilgun system using the MagNet program was developed to compare the design and analysis results. The energy efficiency of the three-stage coilgun system is 31.3%, and this is expected to increase with the increase in the number of stages. [ABSTRACT FROM AUTHOR]

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

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

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

A magnetic pulse compressor (MPC) transfers energy via $C$ – $L$ – $C$ resonance. The pulse width of the MPC is determined by the saturation inductance of the magnetic switch (MS). When using the MS, the pulse width is limited due to the stray elements. To increase the pulse compression rate, the number of stray elements must be reduced. In this paper, we propose an optimum design for an MS having the lowest impedance of stray elements, along with its analysis and experimental verification. The proposed model is designed to have a reduced magnetic path length while retaining the same saturation inductances as that of a common MS; this is accomplished by using the relationship between the magnetic field path length and the number of inductor turns. The experimental results show that the proposed MS decreases the full width at half maximum by 18% and increases the rise rate by 69%. This result demonstrates that the proposed MS increases the pulse compression rate of the MPC by reducing impedance of stray elements in the system. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of coilgun with stepped coil winding was designed. The performance of this structure was investigated and compared to the conventional coilgun with uniform diameter stator coil (UDSC) winding. It can be seen from the results that the trigger position of this new structure moves forward with respect to the conventional coilgun. In order to compare the results, the inductance of the two coils is set to the same. If the initial voltage of the capacitor is lower, as the armature at the optimum trigger position, the muzzle velocity of armature in the conventional UDSC coilgun is relatively larger. Conversely, if the initial voltage of the capacitor is higher, the muzzle velocity of armature in the new structure coilgun is relatively larger. According to the simulation results with the increase of voltage, the difference is more and more obvious. Through the single-stage preliminary experiment in our laboratory, the results were in good agreement with the simulation results. And the trigger position is more forward, so the interaction time between the armature and the coil will be longer. Besides, the coil with stepped structure will increase the efficiency of the coilgun when the voltage level is higher. [ABSTRACT FROM AUTHOR]

The test about simple central difference average (CDA) + MIK ( $\text{M}_{ik}$ mutual inductance between ith and kth component) quench detection method implemented a total of about 100 charging runs on EAST in the past two years, aiming at verifying this new method whether to apply it to ITER CS coils or not. This project is supported by the ITER Organization. To obtain this target, the whole instrumentation hardware have been developed and installed on EAST and used to generate experimental data. Considering the whole new CS coils connection configuration and the possible risk for EAST device, the typical achievement is to accomplish successfully plasma scenarios (the longest shot of plasma current around 250 kA and pulse 3 s) by using a simple CDA + MIK quench detection method on EAST for the first time. Moreover, the numerical quench detection model has been designed, and the numerical signals are in good agreement with experimental data. Recent experimental results showed that CDA + MIK technology is applicable to the ITER CS coils as a backup method but the sensitivity of this system should be improved greatly in order to meet experiment requirements for ITER operation in the future. This paper introduces the test program, typical achieved operation, and the results of preliminary analysis. [ABSTRACT FROM AUTHOR]

The Alfvén eigenmodes (AEs) excitation system has been designed and installed on the J-TEXT tokamak. The system consists of a series resonant power supply and an excitation antenna. Under the typical operating conditions of the J-TEXT, the excitation frequency is thought to be in the range of 200–700 kHz. In order to match the AEs frequency, the external excitation system needs to scan its frequency automatically in experiments. In the implementation process, the whole frequency band is divided into several segments. For each one of them, the resonant circuit matches different capacitors. Specifically, the resonant capacitor is arranged in the form of a fixed capacitor in parallel with a variable capacitor. In the last campaign, a 2.3-nF fixed capacitor and a 1-nF variable capacitor are picked up, so that the resonant capacitance could change from 2.3 to 3.3 nF. In addition, the matching units were applied to optimize the antenna currents. Finally, the formal plasma discharge experiments have been carried out on the J-TEXT. The results show that the excitation frequency can be changed from 445 to 510 kHz in 350 ms, and the output current is able to reach 50 A. This paper is focused on the design of the excitation system, particularly the strategy of frequency scanning. [ABSTRACT FROM AUTHOR]

Recent circuit driven electromagnetic particle in cell simulation of the United Nations University-International Centre for Theoretical Physics plasma focus device revealed regular oscillations in both the voltage and current profiles. The simulated voltage waveform agreed well with the experimental profile, where similar unaccounted oscillations were also observed. In this paper, the oscillations are attributed to the plasma inductance, whose value was calculated by circuit analysis and agreed reasonably well with the computed experimental value. A circuit simulation of the prebreakdown and postbreakdown phases, with the plasma inductance incorporated, reproduced with sufficiency accuracy the electromagnetic particle in cell generated waveforms and consequently confirmed our finding. [ABSTRACT FROM AUTHOR]

In a magnetic pulse compressor (MPC), the saturation inductance of the magnetic switch (MS) determines the energy transfer time. Thus, in general, the number of windings on the MS is modulated to vary the saturation inductance. Changing the number of windings also changes the energy transfer time and the saturation time. In this paper, we propose and analyze an MS with multiwindings to modulate the pulse width without affecting the saturation time of the MS. The parallel structure of the multiwindings on the MS decreases the energy transfer time without affecting the saturation time. Through experiments, we show that the energy transfer time is decreased by 13% via a double winding MS. Therefore, an MS with multiwindings can be used to modulate the pulse width at the last stage of the MPC without affecting the saturation time of the MS. [ABSTRACT FROM AUTHOR]

Induction coil launcher (ICL) is an electromagnetic accelerator that uses Lorentz force to accelerate a projectile with a conducting armature. In this paper, the effects of the height and starting position of the armature on the performance of the ICL were analyzed. Launching experiments were conducted to verify the analysis results. The speed of the projectile converged to a saturated value as the armature height increased. We found that there exists an optimal starting position of the armature for the highest speed. The concept of inductance gradient was adopted to explain the analysis results. It was possible to predict the acceleration characteristics and to estimate the optimal starting position using this concept. Results show that the armature height should be longer than the drive coil height ( \textH\mathrm {coil}) , and the bottom of the armature should be positioned between (1/4)H\mathrm {coil} and (1/2)H\mathrm {coil} at the start to obtain the highest speed. The experimental results showed good agreement with the simulation analysis results. [ABSTRACT FROM AUTHOR]

This paper proposed a railgun with sector of circular rails. The center of the sector of circular rails is located at the outside of the railgun bore. The distance between the sectors of two circles is s , opening angle facing outward \theta , the inner and outer radius are also assumed to be Ri and Ro , respectively. The influence of internal curvature of the rails, the rail thickness and the distance between rails on the current density, magnetic flux density, and inductance gradient ( L' ) have been studied and analyzed using finite-element method. First of all, the different values of \theta , s , , and R_{o} are calculated for various values of the area of the railgun bore ( S_{C}) and cross section of the rails ( SR) . The current density, magnetic flux density, and L' have been calculated for different values. The area of the railgun bore is assumed to be 9 and 10 cm ^2 and the area of rails are assumed to be 9, 6, 3, and 1 cm ^2 . In next section, L' is found as a function of s , Ri , and Ro for \theta =90 ^\circ , 120°, 150°, and 180°. Finally, $L'$ is compute for rail thickness equals to one-tenth of bore size and $\theta $ on the interval [180°, 360°]. According to the achieved results it can be observed the behavior of $L'$ in terms of railgun dimensions changes and it is compared with other geometries. [ABSTRACT FROM PUBLISHER]

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

This paper presents a novel brushless doubly fed alternator (BDFA) based on the differential mode and conducts research on its applications in a pulse capacitor charge power supply (CCPS). Since there are no brushes, the brushless doubly-fed alternator is expected to have high reliability and long service life. The excitation winding of the BDFA that is placed in the stator slots can be supplied with either dc or ac. In previous studies, regardless of the rotor configuration, the natural speed of BDFA is 60f/(p1+ p2) , i.e., based on the additive mode. To increase the alternator’s natural speed, expand the alternator’s operation as well as control range and to promote the alternator’s power density, this paper presents the differential mode, i.e., natural speed is equal to 60f/\vert p1-p2\vert . The author will introduce the detailed design method of the BDFA based on the differential mode. Utilizing the finite-element model of the alternator, we will analyze the magnetic field distribution and calculate inductance parameters of the BDFA. Subsequently, the inductance mathematic model of the BDFA will be established. We also establish the simulation model of the pulse CCPS. Finally, we will verify the feasibility of the design scheme for the BDFA through the simulation results in a pulse CCPS system. [ABSTRACT FROM PUBLISHER]

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]

Explosive and electroexploded opening switches (EEOSs) are used for current sharpening of magnetocumulative generators (MCGs). The EEOSs are well studied both in calculations and experimentally; the explosive opening switches (EOSs) have been studied mostly experimentally. Calculation and theoretical studies of the explosive current opening switches have been carried out by means of phenomenological model building or in 2-D gas-dynamic approximation. The mentioned approaches have some limits, and they do not allow completely revealing the complicated pattern of physical phenomena taking place during the opening switch operation. Whereas it is necessary to optimize the EOSs, it is almost impossible to solve this problem completely at expensive full-scale explosive experiments. The 2-D numerical magnetohydrodynamic simulation of the processes is very close to the reality. This paper compares calculation and experimental data on the circuit breaking of the MCG using the explosive current opening switch with the ribbed barrier. Investigation results of the electric circuit parameters, opening switch construction, and linear density of the breaking current dependence on the load current pulse characteristics are presented. Possible reasons of differences in calculation and experimental results are shown; ways of improvement of the calculation model and opening switch optimization are outlined. [ABSTRACT FROM PUBLISHER]

In this paper, limitations of compact and durable solid state modulators, using a 4.5-kV IGBT in combination with a pulse compression (PC) circuit are evaluated. Two investigated modulators uses two separate paths: one for ignition voltage and one for high currents. In the first modulator, ignition voltage is generated with a PC circuit based on saturable transformers, which is used to charge a series capacitor. After saturation, the capacitor is connected to the output. The second modulator combines together pulse transformer and magnetic switch. Parasitics have been estimated to find the optimal modulator configuration. Measurement results for validating the models as well as the simulation results are presented. Main limitation factors are described and possible solutions are discussed. [ABSTRACT FROM PUBLISHER]

Pulsed power systems often use a pulse transformer to generate high voltage pulses in some application such as radar systems, linear accelerators, and klystron modulators. Parasitic parameters include leakage inductance and capacitances are crucial for output waveform of pulse transformers. To ensure a rectangular pulse shape with a fast rise time, a required small overshoot and an acceptable voltage droop, theoretical calculation based on MATLAB is studied to optimize the design of the pulse transformer in this paper. Based on the theoretical calculation results, Finite Element Method simulations of magnetic and electric fields are carried out to obtain a more precise model for designing the transformer. Additionally, as the pulse transformer related in this paper works on the single forward state, a dc reset circuit, which can improve the utilization of the core material is implemented. Finally, accurate simulations of the pulse system equivalent circuit based on SABER are implemented. Meanwhile, output waveforms of pulse systems with different parasitic parameters and variable load are discussed. The simulation and experiment results showed that the optimum design of pulse transformer based on MATLAB programming and SABER simulation is effective to reduce the rise time of rectangular pulse shape to 1.5 \mus while the pulse duration is as large as 200 \mus. [ABSTRACT FROM PUBLISHER]

We have performed 2-D axisymmetric magnetohydrodynamic simulations for a single stage induction coilgun system and validated the results against in-house experiments. The simulations, besides computing the currents and electromagnetic forces, also capture the associated hydrodynamic phenomena. This paper highlights the importance of appropriate material strength for handling hydrodynamic phenomena and temperature-dependent electrical resistivity model for self-consistent electromagnetic calculations. These are very essential for accurate prediction of armature dynamics and velocity. Inappropriate resistivity model, even in case of no deformations, produced velocity deviation of up to 50% as compared with experiments. Inclusion of appropriate models shows <4\% average deviation when compared with experiments for known armature material (Al6061-T6). For higher energies, predicted armature deformations appear to be in a good agreement with experiments. If material deformation is ignored, velocities get over-estimated. Finally, subsequent to our validation at low energies, an optimized armature profile and dimensions are reported that have allowed our armatures to achieve velocity >200~m/s with single stage operation and 300 m/s with two-stage operations of the coilgun. This paper shows that accurate modeling of Joule heating and armature deformation, along with self-consistent evolution of currents, is essential for coilgun modeling. Although the system is not presently optimized for efficient energy conversion (\sim1.5\%), the performance of induction accelerator at moderate velocity of armature (50–300 m/s) is not only useful for validating our code, but can act as an effective catapult for impact testing of materials. [ABSTRACT FROM PUBLISHER]

Multipole field electromagnetic launcher (MFEL) is a new type of coilgun that can produce larger radial magnetic field compared to the axial magnetic field, the axial acceleration force of coilgun mainly come from radial magnetic field. Because of the similarity of the magnetic fields between inner and outer regions of MFEL, this paper proposed a double-armature MFEL. One armature coaxial with the drive coil placed inside of MFEL; the other armature coaxial with the drive coil placed outside of MFEL. A single-stage double-armature MFEL was studied by simulation and experimental methods. The simulation results indicated that the muzzle velocity of the double-armature launch is similar to that of the single-armature launch, and the efficiency of double-armature MFEL is obviously larger than that of single armature. To verify the conceptual feasibility, a small-size single-stage double-armature capacitor-driven MFEL was built and tested. The inner small armature weighs 63.13 g, the outer big armature weighs 88.38 g. The experimental results on single-armature launch show good consistency with the simulation results, but there is a little gap between the experimental results on double-armature launch and the simulation results. The causes of the existing differences are considered to be mainly from the consistency difference between the six driving coils and the mutual influence between the inner and outer armatures. [ABSTRACT FROM PUBLISHER]