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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 compact all-solid-state pulsed power modulator was designed based on Marx generator and pulse transformer. It is consisted of a six-stage Marx generator using power MOSFETs as switches to generate primary voltage pulses and a pulse transformer through a closed magnetic core to boost and convert the polarity of the output high-voltage (HV) pulse. A MOSFET driver circuit based on optical–electrical isolation was designed for controlling the Marx generator. It shows that the output pulse shapes, especially the rising and falling phases, are determined by the design of the pulse transformer such as its leakage inductance, distributed capacitance, magnetization inductance, and step-up ratio. The designed modulator is able to generate HV pulses with amplitude ranging from −35 to 35 kV, repetition frequency up to 10 kHz, minimum pulsewidth 250 ns. Various types of plasma discharges, including air microdischarge for local treatments, plate-to-plate air dielectric-barrier discharge, underwater discharge, are able to be driven with good reproducibility by this compact pulse modulator. [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]

NBImag is a code suitable for the design and optimization of complex magnetic field configurations, such as that of a multiaperture, multistage negative ion source and accelerator. The NBImag code has been developed for the design of the ITER neutral beam injector, whose full-size prototype, MITICA, is presently under construction in Padua, Italy. The ITER injector shall produce a focused beam of neutral particles (H or D) having an energy of about 1 MeV and a total power of 16.5 MW for 3600-s continuous operation. The NBImag code is based on an integral formulation and allows an efficient calculation of any static magnetic field configuration on the basis of the geometry of the magnetic sources, with linear material and permanent magnets. NBImag also includes magnetic force and inductance calculations, based on the same formulation. Thanks to the capability of efficiently describing a large number of permanent magnets with limited computational effort, NBImag has also been integrated with different automatic optimization procedures for the solution of inverse magnetic problems. This paper describes the formulation of the code and optimization algorithms, the validation against analytical models and experimental measurements, and the application to the design of MITICA. [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]

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]

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]

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]

Nowadays lunching masses to faraway distances is an important issue. One of important electromagnetic launcher for this purpose is duble-projectil railgun because it can launch synchronously two separated projectiles. It has been obtained before that two-turn railgun have better inductance gradient and performance than simple railgun. Also, self-inductance gradient and mutual-inductance gradient in two-turn railgun depend on the initial position of armatures. In this paper, we want to calculate the inductance gradient of a new structure that we named it plus railgun. The plus railgun has one barrel between two-pair rails by two separated armatures and two pairs of rails are powered by one pulse power at the same time. A 3-D finite-element method is applied to the transient analysis of the magnetic field, current distribution, and the inductance gradient of railguns. Finally, we will compare the parameters of two-turn and plus railguns. [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]

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]

An experimental study on plasma focus fusion mechanisms is presented in this paper. Simple diagnostic techniques such as current derivative, voltage, and time-integrated neutron detectors are used. This paper allows us to obtain information and fusion mechanisms present in a medium energy plasma focus [Auto Confined Plasma (PACO), 2 kJ, 31 kV, and T=2.9~\mus]. The current sheet (CS) inductance is calculated through the anode voltage and current derivative signals, for some 80 shots performed within the pressure range 0.8–2.1 mbar of deuterium. It is concluded that the CS inductance is consistent with the behavior of a unique plasma sheet moving between two coaxial electrodes. From the information collected, it is concluded that the main fusion mechanism in this device is the beam-target one. [ABSTRACT FROM PUBLISHER]

This paper is concerned with the development and testing of a compact flat format multichannel electrically triggered rail spark gap. It is tested for multichannel discharge under atmosphere for high reliability. Multichannel discharge rail spark gaps can be developed using laser trigger or fast rising trigger voltage pulse (>5~kV/ns). The extra volume and weight added by laser or fast triggering circuits limit the use in pulse power applications. An electrically multitriggered low-inductance spark gap is developed. It is used as a multichannel low-inductance discharging element in a fast rising high-current generation system. The trigger of such rail gap is realized using the set of round copper pins similar to single trigger pin in a field distortion spark gap. In parenthesis, five different trigger pins are located in main trigger plate and these are isolated with high impedance. Therefore, five different trigger signals are generated with time difference of tens of nanoseconds. The major material erosion at five points of both stainless steel main electrodes confirms the multichanneling discharge. The main gap spacing in this switch is 4 mm and the trigger is located close to the ground electrode for reducing the delay time and jitter in delay time. This paper shows the trigger circuit design, main gap voltage, and trigger voltage effect on the closing of the spark gap and picture of electrodes after use. [ABSTRACT FROM AUTHOR]

Compulsators have been considered appropriate pulsed power supplies for electromagnetic railguns. In order to ensure a high projectile mean to peak acceleration ratio, it is desirable to provide a flat-topped pulse for the railgun. This paper analyzes a two-axis-compensated compulsator, which is a refined selective passive compulsator having an orthogonal displacement between compensating winding and field winding. During the discharge process, the quadrature-axis compensation is provided by the compensating winding, when direct-axis compensation is provided by the field winding. Compared to the traditional selective passive configuration, this arrangement is able to provide another degree of freedom to compensate the armature reaction, thus an output of a current waveform with more flexibility. In this paper, the self-excitation and discharge process of a two-axis-compensated air-core compulsator is simulated based on a finite-element model. Analysis of the current waveform sensitivity to compulsator design parameters is also carried out, as well as the regulation strategy to generate a flat-topped pulse. The research process mentioned in this paper could help to optimize the design of compulsators in future applications. [ABSTRACT FROM PUBLISHER]

In pulsed power supply for electromagnetic launchers, air-core pulsed alternators have obvious advantages to enhance the power and energy densities with a compact and lightweight structure, and it is gradually to be the prime candidate for pulsed power supply. Compared with conventional machines, an air-core pulsed alternator will supply large amounts of energy over millisecond time with a huge current as high as 1 MA and a high voltage reached several kilovolts. Since the short history of the air-core pulsed alternator in China, the related theoretical research is not enough and the fabrication experience is absent. At present, research has shown that the performance of the air-core machine cannot be evaluated by the 2-D method due to the nonexistence of ferromagnetic materials, and it is very necessary to carry out the 3-D analysis by a finite-element method (FEM). This paper will present a 3-D model of the machine according to the accurate geometric size, and the model is used to develop electromagnetic analysis by the FEM and a transient simulation about the no-load EMF is carried out too. In order to understand the mechanism and process of electromechanical energy conversion, it is obviously important to figure out the magnetic field distribution in the machine. Meanwhile, in order to evaluate the strength of the windings, the calculation of electromagnetic forces and torques is developed when the machine drives the electromagnetic rail gun with a current of 1 MA. [ABSTRACT FROM PUBLISHER]

Monolithic C-type armature is one of the most important armatures in electromagnetic railgun. Some key parameters of monolithic C-type armature in rectangular caliber railgun system—width of armature X, height of armature Y, thickness of armature’s throat d0 , length of armature’s tail d1 , thickness of trailing edge of armature’s tail d2 , and angle of armature’s tail $\theta $ —are studied in this paper. By introducing current carrier margin coefficient named $\alpha $ , ratio of armature thickness to armature width named $\beta $ , ratio of armature height to armature width named $\gamma $ , and ratio of length of armature’s tail to armature height named $\kappa $ , equations of some key parameters of monolithic C-type armature in rectangular caliber railgun system are proposed. Based on analysis of mass of armature, electromagnetic contact force between armature and rail, mechanical strength of armature’s tail, and inductance gradient, relationship of some key parameters of monolithic C-type armature in rectangular caliber railgun system are proposed. Conclusion can be drawn that increase of $\theta $ can reduce mass of armature and improve mechanical strength of armature’s tail, but electromagnetic contact pressure between armature and rail will be decreased. Decrease of $\gamma $ could be a considerable way to remarkably increase inductance gradient, and then increase launch system efficiency. [ABSTRACT FROM PUBLISHER]

The major strengths of inductors in energy density and power density make an inductive pulsed power supply (IPPS) a promising option for pulsed power supplies in an electromagnetic launch system. Among the circuits for an IPPS, the capacitor-aided meat grinder circuits constitute an important branch. An analytical method for the working processes of these circuits is proposed in this paper. The core of this method is the decoupling of a high-order circuit into the superposition of a resistor–inductor first-order equivalent subcircuit and a resistor–inductor–capacitor second-order equivalent subcircuit. The validity and accuracy of this method have been verified through comparison with a numerical simulation. The results show that this method possesses both satisfactory accuracy and excellent computational speed. With the same circuit parameters and time step, the time cost of this method is three orders of magnitudes lower than the time cost of a numerical simulation. Moreover, this method contributes to more intuitive understanding and more essential insight into the working principles of the capacitor-aided meat grinder circuits. [ABSTRACT FROM PUBLISHER]

As the most efficient and compact sources in pulsed power supply for electromagnetic launchers, the air-core pulsed alternator can supply a current as high as 1 MA with a voltage reached several kilovolts. The machine performs various functions, such as kinetic energy storage, electromechanical energy conversion, and power conditioning, making the electromagnetic launch system compact and lightweight. But due to the short history of the machine and the absence of fabrication experience in China, the air-core pulsed alternator is still in an exploratory stage, and there are lots of key technologies and problems needed to be researched deeply. Taking technical risks and manufacturing costs into consideration, a seven-phase air-core pulsed alternator has been proposed and the machine is under development. In this paper, operation principles of the electromagnetic launch system are presented in detail. The mathematical models of the seven-phase alternator and the rail gun are introduced. Based on the mathematical models, a simulation model about the electromagnetic launchers is built, and it is useful to help us figure out the operation characteristic when the self-excitation machine drives the electromagnetic rail gun with a 200-g projectile. As a result, it is convincing by simulation to prove the drive current can be as high as 1 MA and the projectile is with a velocity of 2 km/s at the exit. Simultaneously, violent transient situations will be illustrated in this text, such as the electromagnetic torque and the rotor speed. Meanwhile, simulation results can verify the analytical method and present the current and voltage straightforwardly. They also have great significance on choosing the proper high power switching devices. [ABSTRACT FROM PUBLISHER]

For the electromagnetic rail launcher, the parameters variation has obvious effect on the dynamic performance and efficiency. This paper constructs the system simulation model of the electromagnetic rail launcher by using of Simulink software, and then analyzes the influences on the system dynamic performance for main devices. Based on the parameters and large current condition, the launching efficiency model is constructed, and the energy distribution characteristics are obtained. The loss of rail, armature, and feeder equipment is 38.7%, and the loss of arc extinguishing equipment is about 4.76%, so the heat loss is about 43.46% of total loss. When considering that the other loss is 33.37%, the system energy efficiency is 23.17%. Based on the design of the small prototype, the energy loss characteristics of the full prototype in launch rail and its temperature features are discussed in detail. The peak temperature is 276 °C after 11 continuous shots with converting coefficient being 5000 W/( \textm^2\cdot \text K ), and it can decrease 58 °C if the better convection boundary condition is achieved, which means the rail can meet the requirement of the thermal management. [ABSTRACT FROM PUBLISHER]

It is important to choose the appropriate railgun scaling method to extrapolate research findings from subscale to full scale. Aiming at the partial shortcomings of existing field scaling method, this paper proposed one kind of approximate field scaling relations for matching projectile velocity under the condition of linear geometric scaling and identical materials. Analytical derivation and numerical simulations were conducted to assess the similarities of projectile velocity and physical fields. The results show that projectile velocity can be matched approximately according to the scaling method, while the physical fields cannot be matched well. But the general values of the physical fields of full-scale launcher are lower than or approximately equal to the subscale launcher. Consequently, the launching condition of the full-scale railgun can be better than that of the subscale when designing and constructing with the approximate scaling method. [ABSTRACT FROM PUBLISHER]

Measuring the armature speed in bore and the rail current is very important in doing a further research for the launcher design. The B-dot probe method we often used has limited number of probes and its mathematical fitting curve has no actual physical meanings. Therefore, the current waveform’s shape information was used to improve the B-dot probe method’s result. The combined method could give an armature’s velocity at an arbitrary position, and the current waveform could also be calculated out at the same time. Although the combined method was suitable for the measurement, the transient situation limited the accuracy of the results. According to the transient current, the inductance gradient and the distance between rails and a probe are changing during the launching process. In this paper, this two varied parameters that influence the combined method are discussed. The experimental data shows that the improvement of the combined method is more reliable and suitable. [ABSTRACT FROM PUBLISHER]

The dual representation of MARX (XRAM) pulse current generator with magnetic flux compression effect is a novel circuit for current multiplication, which has the advantages of both meat grinder and XRAM that are basic circuit topologies. It contributes to the multiplication of current in two aspects: first, increasing current by magnetic flux compression and second, the current can be increased by paralleled inductors. Compared with the standard XRAM topology, the proposed circuit topology can realize a larger factor of current multiplication more easily, and is better than the standard slow transfer of energy through capacitive hybrid meat grinder circuit topology in aspects of scalability and modularity. Meanwhile, its energy density is increased significantly, which is advantageous to the needs of actual electromagnetic launch. In this paper, theoretical analysis is done to illustrate the excellent performance of the proposed topology and preliminary experiment was conducted to demonstrate its feasibility. [ABSTRACT FROM PUBLISHER]

The air-core flat spirals of strip coil structure is a typical type of the tightly coupled energy storage inductors used in inductive pulsed power supplies. This paper improves the speed and the parameter scope of the inductance calculation method for these inductors. Specifically, the analytical expressions using the structural parameters to represent the performance parameters, e.g., the inductance, the resistance, and the current conducting capability of the primary inductor and the secondary inductor L1 , L2 , R1 , R2 , I\mathrm{ 1limit} , I\mathrm{ 2limit} , the total volume V\mathrm{ tot} , and the energy density \omega , are given. The validity of this method is confirmed by practical measurements of a set of constructed inductors with 2.67-mH total inductance. The absolute error is within 0.02 mH. On the basis of this method, parameter optimization on energy density is conducted for the 70-kJ energy level module. Results show that the energy density can reach 11.2 MJ/ \text{m}^{3} when the total inductance is 5.07 mH and the total volume is 6.3\times 10^{-3}~\text{m}^{3}$ . [ABSTRACT FROM AUTHOR]

The amount of stored energy is an important issue in the low-droop and high-precision pulse generation. Pulse forming network (PFN) simulating an open-ended transmission line seems to be useful due to its minimum stored energy. The drawbacks of the PFN include low-output pulse quality and constant pulsewidth, which limit their applications. Another limitation of generating rectangular pulses using PFN is that half of the charged voltage appears in the output when delivering the entire stored energy to the matched load. This paper proposes a structure of PFN-based pulse generator that overcomes the above-mentioned limitations. For continuous pulsewidth adjustment, a lossless scheme is presented. By increasing the ratio of the load magnitude to the characteristic impedance, the amplitude of the output pulse voltage would be approximately equal to that of the charged voltage. Therefore, the semiconductor switches can be utilized in the PFN pulse generator easily. In addition, the pulse quality is enhanced and faster rising time is obtained in comparison with the conventional PFNs. In this proposal, the stored energy quantity is limited to three times the energy needed for the output pulse in the case of RL=10Z0 . To verify the proposed structure, a prototype is simulated using PSPICE software, and the experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper discusses the modeling of a peaking switch to study the reduction in rise time for the subnanosecond duration pulses. The effect of the various shapes of input pulse, inductance, and interelectrode distance on the output voltage and wave shape is discussed in this paper. The modeling has been carried out using the electromagnetic and microwave modeling software of Computer Simulation Technology. [ABSTRACT FROM PUBLISHER]

Megavolt-class-triggered switches play a key role in large-induction voltage adder accelerators. This paper introduces a 2.8-MV, low-inductance, low-jitter, electrical-triggered, gas SF6 switch. The main section is a $V/n$ switch and the pretrigger section is a trigatron switch. Based on electric field simulation, experiment, and analysis, the structure and spacing of gaps, location of trigger disk, diaphragm, and switch inductance are all discussed. The primary test indicates that the switch can be operated in the range of 0.85–2.76 MV with the pressure of the SF6 changing from 0.1 to 0.9 MPa. The self-breakdown voltage is linearly related to the logarithm of the pressure, as the gap spacing and the voltage rise time are fixed. Three working modes were observed: self-breakdown, self-triggered, and ex-triggered. In the triggered modes, the switch jitter is <3 ns and the switch inductance is usually below 150 nH. [ABSTRACT FROM AUTHOR]

The slow transfer of energy through capacitive hybrid (STRETCH) meat grinder circuit is a widely used topology in inductive pulse power supply. Therefore, it is important to understand the relationship between the STRETCH meat grinder performances and the inductor parameters when improving the system performance and designing the inductor. From the perspective of inductor designing, this paper uses four indicators to present the STRETCH meat grinder performances, i.e., the charging current, the current amplification, the inductor energy density, and the discharge efficiency, and uses two indicators to present the inductor parameters, i.e., the total inductance and the ratio of the inductance L1 to L2 . First, the meanings of the indicators are explained or defined. Second, simulations and experiments are carried out, respectively, to analyze the trends of the four performance indicators along with the changes of two parameters indicators. Finally, both simulation and experiment results show that the increase of the total inductance leads to the decrease of the charging current and the discharge efficiency; moreover, the increase of the ratio of the inductor L1 to L2 leads to the increase of the current amplification and the discharge efficiency, but causes the decrease of the inductor energy density. [ABSTRACT FROM AUTHOR]

The field-reversed configuration heating experiment (FRCHX) was designed to form closed-field-line magnetized target plasmas for magnetoinertial fusion and other high energy density plasma research. These plasmas are in a field-reversed configuration and are formed via a reversed-field theta pinch on an already magnetized background plasma. To extend the duration and temporal uniformity of the pinch, the capacitor bank driving the reversed-field discharge is crowbarred near the current peak. Four parallel rail-gap switches are used on the FRCHX for this application to ensure a low-inductance crowbar discharge path and to accommodate the large magnitude of the discharge current (often greater than 1 MA). Historically, parallel operation of spark gap switches in a crowbarring arrangement has often proved to be difficult due to the very low voltage present on the bank and across the switches at the time of peak current. In a low-inductance design, triggering can be further complicated by the rapid collapse of what little voltage there is across the switches as soon as the first spark gap begins conduction. This paper reports on the efforts that were made to develop a low-inductance crowbar switch for the FRCHX and to ultimately enable successful triggering and operation of the four parallel rail-gap switches used in the crowbar. The design of the low-inductance parallel switch assembly is presented first, followed by a description of the triggering scheme employed to ensure conduction of all four switches. [ABSTRACT FROM AUTHOR]

This paper demonstrates the practical application of the explosive magnetic generator (EMG) as a source of high-power pulses for mobile testing complex EMG (MTC EMG). Hereinafter, the name of explosion generator is used on a par with the name of helical explosion-magnetic generator. Laboratory sample was brought to a level of modern complex, which is able to solve the applied problems in the grid power systems. MTC EMG is able to reproduce the output currents, similar to lightning currents, so it can be used to simulate a pulse impact on the energy system. The report contains: a description of the basic physical and electrical solutions underlying the construction of the generator of lightning currents, output characteristics, and results of MTC EMG field testing. Optimization of schemes including the different impedances of EMG and inductive resistive load with the use of transformer coupling allowed the effective energy transfer from the EMG to the load. Pulse currents and voltages on the load and also the response of soil between ground loops under the action of lightning currents, generated by MTC EMG, were registered in the testing. Autonomous measuring instruments included in the complex were protected from electromagnetic interference. [ABSTRACT FROM AUTHOR]

This paper details the experimental evaluation and simulation of a 4-kV n-type gate turn-OFF thyristor (GTO) designed for pulsed power applications. The primary criteria of evaluation are rate of current rise ( dI/dt ), turn-ON delay time ( T_{D}) , and resistance of the device during turn-ON transients [ R_{\mathrm{\scriptscriptstyle ON}}(t)$ ]. The device under test (DuT) is an n-type asymmetric-blocking GTO manufactured by Silicon Power (Part No. 14N40A10) with a rated dc blocking voltage of 4 kV. A test circuit was specifically designed to minimize stray inductance in order to capitalize on the dI/dt$ capabilities of the DuT. Experimental data collected from resistance measurements are used to develop a single-switch approximate model for use in simulation. The results of dI/dt$ experiments provide a profile of DuT dI/dt$ operation beyond rated values; specifically dI/dt were readily achieved. The turn-ON delay time of the DuT is also characterized and determined to be $\sim 225$ ns on average. [ABSTRACT FROM AUTHOR]

Multisegmented dual-stator pulsed linear induction motor (LIM) is suitable for electromagnetic (EM) catapult based on the former research. This paper mainly analyzes the numerical model of same and reverse mode of the dual stator, magnetic thrust and EM parameters, and the magnetic field distribution has been built by finite-element model and the static performance are gotten by the prototype machine. Based on the analysis results and static experiments, the closed-loop control models for the dual stator have been established, and the dynamic launch test has been performed by using of multisegment prototype LIMs. The test results show that the dual-stator LIMs can accelerate the 300-kg load to the speed of 15 m/s within 11-m launch stroke. The fluctuation of the slip frequency is quite small and the block transition is smooth during the launching process. The test results show good agreement with the commanded values, which verify the dual-stator LIM model and control strategy. [ABSTRACT FROM AUTHOR]

Great interest has been devoted to the study of nonlinear transmission lines (NLTLs) for radio-frequency generation. The two better known configurations of NLTLs are a dispersive line consisting of sections with nonlinear components and a continuous nondispersive line called gyromagnetic line. The goal of this paper is to study the gyromagnetic line through the effects of changing the NLTL parameters. This is done based on an analytical model supported by SPICE circuit simulations and validation of results with numerical analysis, focusing on the pulse rise time compression. Different models are studied by comparing simulations with corresponding results found in the literature. Such a technique could be used for the design of NLTL for space applications and mobile defense platforms of compact size. [ABSTRACT FROM AUTHOR]

This paper mainly introduces the design of the dummy load prototype, whose functions are to verify the capability of the International Thermonuclear Experimental Reactor magnetic power supply systems to operate at their rated power levels without energizing the superconducting coils. The rated inductance is 6.73 mH and the extreme pulse operation mode is 68 kA/15 s ON and 900 s OFF. Therefore, in order to meet the special requirements of the large inductance and the large pulse test current, a structure of dry-type air-core water-cooling prototype with epoxy resin casting technique is presented. The finite-element simulation analysis is introduced in detail, focusing on the thermal performance and dynamic stability, especially under the extreme pulse operation condition. In addition, the electromagnetic environment around the dummy load is also analyzed to provide the input for the instrumentations selection and the delimitation of personal safe area. Finally, seismic analysis is introduced to verify the antiseismic property of the dummy load. [ABSTRACT FROM AUTHOR]

This paper describes the prototype design of an external bypass that provides protection for the ITER poloidal field converter and magnets in fault conditions. The maximum peak pulse current of the bypass will reach to about 350 kA in the worst case. Three kinds of arm structures are compared according to the design requirement and the specific circumstances of branches. The structure, whose current flows in and out on the same side, is selected and combined with the installation and location. The external bypass structure model is analyzed and compared through analytical and numerical methods. Then a 3-D numerical model of an electromagnetic field is established based on Maxwell. Now a full prototype has been manufactured by China, and the dynamic stability test of the prototype has also been accomplished successfully. It shows that the prototype design can fully satisfy the design requirement and the reliability has been improved. [ABSTRACT FROM AUTHOR]

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]

An equivalent circuit for a core snubber is established in this paper. The circuit can approximately express a parallel resistance and inductance. The resistance can be directly calculated according to the resistivity of the magnetic core and structure dimensions of the core snubber referring to Fink–Baker–Owren (FBO) method, and the eddy current factor is adjusted to one. In this paper, the shunt inductance neglected by FBO is first considered, and it can be obtained from critical characteristics of the magnetic core and structure dimensions of the core snubber. The two electrical parameters are varied with saturated zone of the inner turn of tape. Then, the simulated model of a core snubber is set up. Finally, a miniature core snubber is analyzed, and its parallel resistance and inductance are obtained from the experiment condition. The test data validate the analytic model. The method presented in this paper is proved to be useful in the design of core snubber for the Experimental Advanced Superconducting Tokamak and the International Tokamak Experimental Reactor. [ABSTRACT FROM PUBLISHER]

This paper presents a new method to calculate stray capacitance of coil turns of magneto flux cumulative generator. The proposed method depends on the coil geometrical properties. The presented analysis in this paper is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and the central cylindrical liner of the generator for a single-layer coil with N series turns having an integrated round cross section. Moreover, the effects of the insulating coating of winding, winding pitch, distance of coil turns to the central cylindrical liner on the stray capacitance, and the sensitivity analysis of effective parameters in the creation of stray capacitance between coil turns and also between coil turns and the central cylindrical liner are considered in this paper. Simulation results show that the proposed method is very useful for the designing geometrical structure of the magneto cumulative generator coil. [ABSTRACT FROM AUTHOR]

The rail-type electromagnetic launcher (EML) has good development and applied prospects for military and civilian dual purpose. The inductance gradient is an important parameter to design the EML structure and evaluate the system performance. Based on the Biot–Savart law and current skin-effect behavior, we derive an analytic formula to predict the EML inductance gradient, which expands Batteh's formula by introducing rail thickness w and skin depth \delta. Our expression is more accurate because the geometrical parameters of both rails and armature are considered in this paper. We investigate the inductance gradient change as a function of the ratio of bore width to height s/ha, rail thickness w, and two-rail interval s. Finally, our results at different scales are compared with those of other formulas of the inductance gradient. This paper could be used directly to design and optimize the rail-type EML. [ABSTRACT FROM AUTHOR]

An electromagnetic launcher (EML) or railgun is a complex dynamically coupled system with interacting electric, magnetic, mechanical, and thermal subsystems. This paper formulates a bond graph systems model of an EML, including capacitor bank power supply; electric and magnetic response of rails; electric, magnetic, and mechanical response of armature; magnetic containment structure for flux; electric contact resistance between sliding armature and rails; generation of forward longitudinal motion; temperatures and heat transfer in the armature and rails; armature melt wear and plasma erosion; transverse contact mechanics of armature sliding on rails; and plasma contact for armature rail separation and transition. In this paper, the bond graph model is constructed, and from the bond graph, state equations are extracted. [ABSTRACT FROM AUTHOR]

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]

In order to improve the performance of a coil launcher, various cores and shells are considered in the structure design in this paper. Different geometry shapes and materials are loaded on the cores and the shells. A single-stage coaxial induction coil launcher is analyzed for simplicity based on Ansoft 2-D simulations. The conclusion can be summarized as follows. A magnetic core will improve the performance of a coil launcher greatly. Coil current and resistance loss of the system will be reduced while kinetic energy conversion rate and efficiency will be increased. A conductive core will reduce the performance because of eddy-current effect. A magnetic conductive core combines magnetization and eddy-current effect. Geometry of a core will also influence the performance of a coil launcher. In general, the greater the cross-sectional area and the length is, the better the performance. A shell takes little effect on the performance of a coil launcher, no matter what material and geometry is used. A magnetic nonconductive core with large cross-sectional area and enough length is suggested to be used in a coil launcher design. A detailed study will be presented in this paper. [ABSTRACT FROM AUTHOR]

A toroidal field coil is composed of several individual toroidal coils (ITCs) which are connected in a series and distributed in a toroidal and symmetrical form. Cross section of ITCs is rectangular or negligible. This paper presents analytical equations of mutual inductance of two ITCs applicable to tokamak reactors using the filament method. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The finite element method (FEM) is employed to verify the mutual inductance equations of ITCs. The results obtained using FEM, when dimensional parameters of ITCs are changed, confirm the analytical and empirical results showing an error of less than 0.2043% in the worst case. This indicates the reliability of the presented equations. This paper also employs FEM to obtain depth of penetration of electromagnetic waves in high-conductivity conductors (HCCs). The results show that the ratio of real depth of penetration, obtained by FEM, to ideal depth of penetration in HCCs is independent of frequency. This ratio shows that the magnitude of traveling plane waves in HCC decreases with e^-1.7916 rather than e^-1. [ABSTRACT FROM AUTHOR]

For the generation of short high-power pulses in many applications, power modulators based on capacitor discharge are used, where the peak power is drawn from the input capacitor bank. In order to continuously recharge the energy buffer during operation at a lower average power, usually, power supplies connected to the mains are used. Due to the worldwide variation in mains voltages and the desired ability to adapt the capacitor voltage of the modulator, the power supply has to support a wide input and output voltage range, whereby the supply should draw a sinusoidal current from the mains due to EMI regulations. Additionally, depending on the modulator concept, a galvanic isolation also has to be provided. In order to achieve the mentioned specifications for the considered power supply, a combination of an ac–dc and a dc–dc converter is proposed, whereas the mains voltage is rectified by a three-phase buck–boost converter to 400 Vdc, and thereafter, an isolated dc–dc converter charges the input capacitor bank of the power modulator up to 3.5 kV. This paper focuses on the basic operation and the design of the 3.5-kV/11-kW isolated dc–dc converter, which includes transformer design, efficiency-volume optimization, and component selection. In this paper, compared with the well-known flyback converter, the proposed full-bridge-based topology results in a much higher efficiency and power density. [ABSTRACT FROM PUBLISHER]

The extreme ultraviolet (EUV) spectrum has significant interest both for basic science and for industrial applications, especially lithography-related studies. Discharge-produced plasma (DPP) EUV source efficiently generates EUV radiation. Current pulse parameter is the most important and sensitive factor in DPP EUV source, which is determined by the discharge loop inductance. This paper reports on shortening the current pulsewidth by reducing discharge loop inductance on a xenon gas Z-pinch DPP EUV source. The inherent inductance of the discharge loop was reduced to about 17 nH from the previous 34 nH, and the short-circuit current pulsewidth was shortened to 85 ns. Pulsewidth of discharge plasma current was only about 110 ns. DPP EUV source was characterized in terms of EUV signals (7–16 nm) and images. The experimental results show that a shorter current pulse produces sharper EUV signals. Ultrashort current pulse discharge radiated a sharp EUV signal with a narrow pulsewidth [full-width at half-maximum (FWHM)] of only 10 ns. Axial and radial sizes (FWHM) of EUV-emitting plasma were 2 mm and 400~\mu \textm , respectively. EUV source resembles an ellipse differing from the jet shape driven by longer current pulses. Thus, a DPP EUV source driven by an ultrashort current pulse may suit high temporal and spatial resolutions required for EUV application. Corresponding plasma dynamics are observed and discussed. A comparison of time-resolved visible and EUV light images indicates that EUV emission radiates from two adjacent stagnated hot plasma columns and localizes along the central axis. This also differs from longer current driven plasma dynamics, in which EUV emission radiates from the neck part between two separate cooler plasma zones and moves with the current flow. This implies that ultrashort current pulse may inhibit axial development of EUV-emitting plasma, thus improving EUV source spatial stability and reducing EUV radiation size. [ABSTRACT FROM AUTHOR]

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]

The passively compensated pulsed alternator (PCPA) is one of the most competitive pulsed power technologies for future electromagnetic launcher systems. The PCPA is mostly designed for the high pulse repetition frequency military applications, such as the railgun, coilgun, and electrothermal chemical gun. The PCPA is a high-energy and high-power (sub-GW) electrical synchronous generator operating in a fast-transient, short-pulse regime. Due to its low internal impedance during the discharge, the pulsed alternator is capable of extremely high output current, almost two orders of magnitude higher than similar rotating synchronous generators of the same size. This paper has investigated the transient inductance of the armature winding of a PCPA, including the internal inductance and the end leakage inductance. A novel method is proposed to decrease the end leakage inductance in which the end windings are surrounded by totally enclosed conductive shields settled at the stator ends. The analytic formulas of the internal inductance and the end leakage inductance are deduced using the magnetic vector potential method. The concept of end winding shielding can be generalized to other types of compensated pulsed alternators, such as the selective PCPAs and actively compensated pulsed alternators. [ABSTRACT FROM PUBLISHER]