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This paper proposes unconventional control techniques for a portable power supply consisting of electric double-layer capacitors (EDLCs), a dc–dc converter, and a low-impedance load such a plasma load. Between the EDLCs and the plasma load consuming high power, a dc–dc converter is required to control the output voltage from the rapidly decreasing voltage of EDLCs. In addition, the dc–dc converter should maintain a set point by responding to arcs occurred in plasma process. This paper proposed hybrid analog and digital controls for a nonideal boost converter which was setup by theoretical analysis. The proposed system is verified with experiment and simulation. As a result, the proposed control method can maintain the constant output voltage longer than a traditional analog pulsewidth modulation control. [ABSTRACT FROM AUTHOR]

This paper has introduced two important indexes, turn-off surge voltage (TSV) on power switch and peak positive pole potential (PPPP) of storage batteries, which can be used to evaluate switching transient process of high-voltage energy storage system. Research on them is of great significance to power switch choice and high-voltage isolation design in engineering applications. Power switch response process at the turning off moment and transient process in freewheel stage have been analyzed by the established small-signal model of single power switch; then, a power switch test platform for hybrid energy storage system was built to verify it. Taking pulsed-power supply charging device with a novel inductor of low resistance and high inductance as a research object, this paper has analyzed dynamic process of the TSV and the PPPP at the turning off moment through establishing state space model of the whole system. Comparison shows that the numerical curves match the simulated curves well. Finally, the exactness of the employed model has been further verified in two pulse capacitor charging experiments. [ABSTRACT FROM AUTHOR]

Due to the volume and weight of the coaxial Blumlein pulse forming line (B-PFL) with liquid energy storage medium are very large and energy storage density is relatively small, a new solid-state coaxial B-PFL is designed for the pulsed power technology in this paper. There are three conductor cylinders in the pulse forming line (PFL): inner cylinder, middle cylinder, and outer cylinder. Ferroelectric ceramics is selected as the energy storage medium which is between the middle cylinder and inner cylinder, and middle cylinder and outer cylinder. The impedance, electric length, parameters such as pulsewidth and its required physical length calculation formula of the PFL is deduced, based on the coaxial cable of the related parameter calculation formula. The formula for determination of relative suitable radius size is obtained. The simulation of electric field of PFL is implemented in the simulation software Ansoft Maxwell, and the results show that the design of the coaxial B-PFL is feasibility. The pulse forming principle has carried on the detailed validation in the simulation software PSPICE, and the results show that the design scheme of PFL is feasible. The application of the PFL can largely reduce the volume and weight of the pulsed power device, and it has a good application prospect. [ABSTRACT FROM AUTHOR]

A portable dc power supply based on electric double-layer capacitor (EDLC) bank was established for high-power applications. EDLC bank needs a dc–dc converter to maintain a constant output voltage and current. Especially, a low-impedance load makes the voltage of capacitors discharge faster, and their discharging time is determined by RC time constant. The proposed system is designed as a fundamental concept, and deals with some issues occurring in a large-scale system. Also, this paper provides detailed information and consideration for a real establishment. Last, we performed a full-scale experiment using basic techniques. [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]

The U.S. Naval Research Laboratory is developing a rep-rate charger for a 60-kJ capacitor module. The charger is lithium-ion battery powered and must charge up the capacitive load 50 times over a 5-min period with roughly 1 s between each charge cycle. This paper examines some aspects of the design: lithium-ion battery energy storage, hard switched dc–dc converter, high-voltage rectifier, and capacitive load with pulsed power switching. The lithium-ion batteries are arranged in 12, 16-cell, 50 V modules that are connected in series to form a roughly 600 V prime power supply. A hard switched dc–dc converter with full-bridge rectifier is used to charge the capacitor and a pulse forming network is used to discharge the capacitor into the load. This paper will discuss the system design and available test data. [ABSTRACT FROM PUBLISHER]

This paper proposed the use of a ringer, a self-switched inductive storage system, for applications involving reluctance accelerators, a kind of electromagnetic launcher, and compatible with applications where portability is a requirement. There will be shown three different useful approximations for the analysis of the ringer, employed as a power source for a reluctance accelerator. First, it described the equations governing the que behavior of an ideal unloaded ringer, and then the equations for the ringer with an uncoupled inductive load, and ultimately a Lagrangian model for the ringer as an inductive power source for a reluctance accelerator, capable to make predictions about the currents through the circuits and the exit speed of the projectile for a given firing. The accuracy of the predictions made with the third approximation, the Lagrangian model, was tested experimentally. [ABSTRACT FROM AUTHOR]

The rail life is an important factor that influences the rail-type electromagnetic launch (EML) engineering. This paper gives an introduction about the structure of the rail-type EML system, makes an analysis of some indirect or direct factors that affect the rail life, and points out the sectional characteristics of the rail life. By optimizing the armature-rail structural design and material matching and taking measures to control the discharge waveform of pulse current, it is possible to prevent the rail surface from being damaged. However, the mechanical fatigue caused by multiple launches and the plastic deformation under thermal stress will result in a decrease in performance of the rail. [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]

Propylene carbonate (PC) has a good application prospect in compact pulsed power source as the energy storage medium of pulse forming line. However, its insulation strength is susceptible to impurities, temperature, pressure, and other factors. Hence, it is of great significance to study the effect of temperature on breakdown characteristics of propylene carbonate. In this paper, the effect of temperature on breakdown characteristics of PC was carried out under microsecond pulse. First, pulsed breakdown setup was built. The temperature of PC varied from −50 °C to 50 °C. Breakdown voltages were captured with a capacitive voltage divider and streamer patterns are obtained by ultrahigh-speed cameras. Second, the experimental results are obtained. The breakdown strength of PC increases with increasing temperature. It is 239 kV/cm at −50 °C and rises to 407 kV/cm at 50 °C. At low-temperature breakdown, electron current is more concentrated and breakdown voltage is more stable. Moreover, the energy release for streamer at low temperature is more concentrated, but it is more dispersed for streamer at high temperature. At last, considering the CO2 solubility in PC, PC generates more bubbles and the increase of temperature benefits the release of bubbles at low temperature, resulting in lower breakdown strength. Because of the moisture in PC, breakdown strength of PC falls slightly near 0 °C. Thus, the experimental results are explained by use of stream theory and bubble breakdown theory. PC can adapt to wide-range temperatures, effectively expanding practical applications of the PC in pulsed power source. [ABSTRACT FROM AUTHOR]

An oversized $G$ -band backward wave oscillator (BWO) driven by a weakly relativistic electron beam less than 100 kV is studied. Rectangular corrugations are used as the slow-wave structure (SWS), which have surface waves with upper cutoff frequencies of above 150 GHz [ $G$ -band (140–220 GHz)]. In this paper, we examine the starting conditions for intense $G$ -band BWO operation by varying the beam parameters and SWS lengths. It is shown that a starting energy exists for the $G$ -band BWO and that the starting energy is more critical than the starting current in the oversized BWO. Above the starting energy, very intense output powers on the order of 10 kW are obtained. The oscillation-starting condition for such intense operation may play an important role in high-intensity terahertz wave sources. [ABSTRACT FROM PUBLISHER]

A novel circuit with the better performance for the inductive pulsed power supplies in the electromagnetic launch system is proposed in this paper, namely, the meat grinder with capacitive pulse forming unit (CPFU). Its working process is qualitatively analyzed stage by stage. Its practical feasibility is verified through a 7.5-kJ experiment. From the perspectives of circuit structure and working principle, this circuit can be regarded as the combination of a meat grinder and a CPFU. Compared with its preceding circuits, this circuit possesses following advantages: 1) the self-recovery of the capacitor precharged voltage can easily be achieved, which is conducive to continuous operations of the whole circuit and 2) the waveforms of the inductor currents contain no capacitive components, which can promote the energy storage density of the inductors. [ABSTRACT FROM PUBLISHER]

The opening switch is one of the critical technologies in the development of inductive pulsed-power supply. The power requirement is very high when the opening switch is desired to commutate a large current. This paper presents a zero-current opening circuit for inductive pulsed-power supply based on a high-temperature superconducting pulsed-power transformer. First, there are two types of current flowing through the opening switch, one comes from the secondary side of the pulse transformer, and the other one comes from superconducting energy storage inductance. The orientation of the two current is opposite. Then, when the current flowing through the opening switch closes to zero, the switch is opened and this restrains the over-voltage pulse of the opening switch. The simulation results indicate that this zero-current opening circuit is feasible and has potential applications for high-energy systems in the future electromagnetic launcher. [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 proposes a flyback-circuit-based design of a trigger circuit for a high-power gas switch. By incorporating a flyback circuit in a high-power gas switch, it is possible to generate a high step-up ratio and high-voltage pulse by using a transformer. Furthermore, simple trigger circuit having the minimum possible number of components (transformer and switch) can be realized. When an inductor is used as an energy storage element, energy is stored as a current source, and thus, the element can operate reliably when low impedance exists between the trigger node of the switch after triggering. According to the fundamental operating principle of a flyback circuit, the proposed trigger circuit is designed considering the maximum trigger voltage and energy required for a high-power gas switch. To verify the proposed design procedure and feasibility of the trigger circuit, a compact trigger circuit (7.5 kV, 1.3 mJ/pulse) is simulated using the PSpice program and implemented. Based on this compact circuit, a trigger circuit (20 kV, 100 mJ/pulse) for a triggered vacuum switch (TVS) is developed, and the tests with an actual TVS (3.3 kJ) are carried out. [ABSTRACT FROM AUTHOR]

Hybrid energy storage device for electromagnetic launch has the characteristics of high energy density and high power density. The device will release a lot of heat in both charging and discharging processes, which will have a direct impact on the stability of the whole system. Through the analysis of the structural feature and the principle of discharging, this paper compares the effect of air-cooling and water-cooling method for the high temperature rise problem in the process of repeated large rate discharging. In order to effectively reduce the temperature and evaluate the thermal management effect, an experimental platform for electromagnetic launch is built. This paper takes kilovolt level discharging and charging experiments on the platform with air-cooling devices, and the temperature rise is within the upper limit. The simulation analysis of the two kinds of cooling methods during discharging process is taken. And the experiment and simulation result can ensure the safe and continuous operation of electromagnetic launch, with practical engineering significance. [ABSTRACT FROM PUBLISHER]

Superconducting pulsed-power supply (SPPS) provides an efficient method for both high-density inductive energy storage and high current pulse generation. An SPPS consisting of eight high-temperature superconducting pulsed-power transformer (HTSPPT) modules with XRAM methodology was designed and simulated in preliminary studies. It recycled the leakage flux energy and reduced the voltage across the opening switch with a capacitor in primary. However, the SPPS with XRAM methodology has two problems. The first one is that it can provide high pulse amplitude, but cannot provide enough width. The other one is that the ratio of the maximum capacitive energy over the total inductive energy is relatively large, which cuts down the overall system energy density. This paper proposes a modified topology of SPPS with capacitor reuse methodology. Multiple HTSPPT modules are divided into several groups. Each group shares the same capacitor. The procedure of the modified SPPS is presented in detail. A 270-kJ SPPS with capacitor reuse methodology is designed and simulated to illustrate the modified topology. With the load parameters of a small railgun, the peak value of the load current is 207.15 kA and the pulse half-height width is 5.56 ms, the ratio of the maximum capacitive energy over the total inductive energy is 11%. The characteristics of the modified topology are also described in detail in this paper. [ABSTRACT FROM PUBLISHER]

With pancake-coil electromagnetic launcher as a research object, the experimental platform of the pancake-coil electromagnetic launch intercepting system with 50-kV pulse capacitors as energy storage was built and tested for discharge to study the electromagnetic launch intercepting system. The oscillation problem of the current flowing through freewheeling loop was solved by connecting the reverse-cut diode stack in series with trigger vacuum switch (TVS). However, due to limiting power component, the experimental system can work normally at 9.4-kV capacitor voltage. A proportional 3-D model of the pancake-coil electromagnetic launcher and an external excitation circuit model were established based on the structural and circuit parameters of the experimental system to perform simulation. The accuracy of the simulation model was proved by comparing the simulated and measured currents obtained under same capacitor parameters. Based on the established finite element model, maximum launching capacity and energy efficiency of the experimental system platform were estimated through simulation, and the space–time distribution characteristics of the magnetic field were analyzed during the launching process. In addition, the electromagnetic-structure coupling simulation was carried out to study the deformation problems of components of launcher by sequential coupling. All the work done in this paper provides guidance for a detail research, and we want to try to improve our electromagnetic launch experimental system. [ABSTRACT FROM AUTHOR]

The high-power pulsed power supply based on homoploar inductor alternator (HIA) was successfully used as a primary power supply of the pulse load. This type of power supply has the advantages of high-power density and high reliability. The efficiency of this power supply is an important parameter in the design of this power supply. This paper presents the analysis and test efficiency of it. The theoretical calculation is consistent with the test, and the results show that the efficiency is 75%–80%; the armature copper losses account for the largest proportion of total losses, and the iron losses take the second proportion. The large armature copper losses are due to the extremely serious skin and squeezing effects. The analysis and test results are benefit for estimating the required inertial energy storage. Finally, the design aspects about the losses of pulsed HIA are discussed, and it is helpful for the optimal design of a high-efficiency pulsed HIA for capacitor charge power supply. [ABSTRACT FROM AUTHOR]

In this paper, the capacitances of the two-stage bushing that is installed in the 1-MV test bed for neutral beam injectors in the future fusion reactors are calculated by modeling the bushing in a 3-D electrostatic code. One of the modeling results is the stored energy in the bushing, which corresponds to 1/2 CV2. After evaluating the bushing capacitance, a MATLAB/Simulink model is presented to model the possible breakdown in the bushing and between the electrodes in the 1-MV test bed. When a breakdown occurs between anode and cathode, an overcurrent is drawing that can cause damage in the electrode surfaces while an overvoltage takes place when the breakdown happens between the bushing stages. Such damage has been observed experimentally in the past. This paper also presents some of the possible protection against the breakdown in the 1-MV test bed to dissipate the stored energy in order to protect the electrode surfaces and the bushing. The suggested protections presented in this paper are damping resistors, surge arrester individually, and both of them. Also, a coil can be added to the DR either in series or in parallel. [ABSTRACT FROM AUTHOR]

Recently, inductive energy storage systems have attracted interests due to high energy densities. The high-temperature superconducting pulsed-power supply (HTSPPS) is one inductive PS topology for electromagnetic launching system. The topology can achieve a high amplitude load current and cut down the electrical losses due to the zero resistance characteristic of superconducting inductors. However, in this topology, the integrated gated commuted thyristor is used as a switch and cannot withstand high current, which limits the expansion of the system. Besides, it has significant current amplification ability as a single unit, but one module cannot provide sufficient amplitude and appropriate pulsewidth for the load current of the electromagnetic launching. In this paper, by applying the principle of inverse current commutation with semiconductor devices (ICCOS) in the HTSPPS, a novel circuit topology called HTSPPS with ICCOS is presented. This topology is analyzed and the multiple modules system is established. Simulation results show that the HTSPPS with ICCOS exceeds the current limitations of the original one and ensures the reliable cutting off of the main switch. It has potential applications in the future of high-energy systems while reducing the cost greatly. By asynchronous cooperative triggered discharge of the multiple HTSPPS with ICCOS modules in parallel, the appropriate amplitude and flat shape current of the load can be achieved through the careful design of the trigger time. [ABSTRACT FROM AUTHOR]

An air-core pulsed alternator is extremely attractive for driving the electromagnetic launchers. The reason is that the machine can offer high voltage and current performance in a single-element energy storage device, a smooth pulse profile, and naturally cycled current zeros, which can allow for extremely low muzzle currents and simplifies switching requirements. But because of the short history of the air-core pulsed alternator in China, the relevant theoretical research is not enough and the experience in fabrication is absent. It is really necessary to summarize a preliminary design method in order to rapidly determine the size and approximately evaluate the electrical performance of the machine. The optimization will be based on this first-stage design scheme. In this paper, based on the requirements of the railgun, some important design considerations of a seven-phase and six-pole air-core pulsed alternator are presented in detail. In addition, it is significant to obtain the analytical formulas for the first-stage design requiring less costs; these formulas intuitively allow us to expedite the design process and optimize the design scheme. Finally, some basic output parameters of the machine are given for the preliminary design; the designed pulsed alternator will generate 1.4 kV and drive a train of 1-MA pulses into a 5-m railgun, accelerating 200-g masses at 2 km/s. [ABSTRACT FROM PUBLISHER]

This paper proposes a mathematical model for electrical discharge plasmas between moving electrodes under ac condition, which happens in ac switching apparatuses. The modeling work is started by converting the problem to a conventional RL network that treats the arcing phenomenon as a black box and proposing a transient differential equation to represent the breaking arc process. A resistance–time relation model developed from the classic Mayr model is then proposed. A conceptual unit-arc approach is used to deal with the issue of variable arc length as the contacts move. Experimental data from ac contactor tests are used to approximate the resistance–time function by a nonlinear curve fitting. The model is solved computationally and compared with the experimental data. It is that the model adequately describes the breaking arc phenomenon. [ABSTRACT FROM PUBLISHER]

Paralleled pulse-forming units (PFUs) with different triggering delays might be a paramagnetic way for generating flat-topped current wave for electromagnetic launch. Many researchers have reported that multiple capacitive storage PFUs were implemented such current waves in laboratories. However, due to its low energy density, the applications of the capacitive pulsed-power supplies are limited. Since the inductor has advantages in energy density, the inductor pulsed-power supply becomes one of the hottest topics recently. The slow transfer of energy through capacitive hybrid meat grinder with inverse current commutation with semiconductor devices proposed by Tsinghua University has demonstrated its advantage and applicability recently. Using this kind of topology, this paper proposes the design of an inductive storage PFU with a stored energy of 100-kJ. The maximum load current reaches to 50 kA and its pulsewidth is at least 5 ms. The optimized inductive storage PFU shows superiority in contrast to the capacitive storage PFU with the same energy. This paper offers the theoretical analysis and the testing foundation for investigating the inductor pulsed-power supply with higher energy. [ABSTRACT FROM PUBLISHER]

Electromagnetic launching mass driver system (projectile) has been examined and evaluated as an eligible alternative to the chemical propulsion systems, in space transportation. The projectile has been arranged to reach to its orbital speed at delivered altitude, with an energy transferred externally to a projectile all the flyway through the electromagnetic launcher. The multistage electromagnetic launcher structure contains the capacitors for storing energy and transfers this energy through a switching inductor to a mass driver. The mass driver is synchronously being energized by a voltage through an oscillating coil-capacitor circuit. This paper presents dependence and optimization of design and performance parameters of coilgun equations. Cost estimations of electromagnetic launching system are also calculated in energy per unit mass. [ABSTRACT FROM PUBLISHER]

Magnetic pulse compression (MPC) system has been widely used over a few decades as a technique for producing short duration, high peak power pulses reliably. Novel MPC system which do not contain external demagnetization circuits, have broadened the appliance of MPC systems, in which circuit in each level of storage energy capacitors is composed of two capacitors in series, and the two-capacitance combination is connected to the output of previous stage, so that not only the pulse is compressed but also the voltage is doubled as well. In this paper, a 20-kHz high repetition-rate pulse generator with adjustable output amplitude based on Novel MPC system is presented. The pulse generator makes use of commercially available insulated gate bipolar transistor (IGBT), switching a capacitor bank into a ferrite transformer together with a voltage doubling circuit. The capacitor bank is charged to 530 V by a three-phase rectifier, also switched by a commercial diode. The amplitude of the output voltage of the pulse generator is controlled by the amplitude of the gate voltage of the IGBTs. Pulses with a width of 70 ns can be generated with repetition rates up to 20 kHz in burst. The amplitude can be controlled from 5 to 40 kV into a $500~\Omega $ resistive load. [ABSTRACT FROM AUTHOR]

In the real world application of railguns, the launch efficiency is one of the most important parameters. This efficiency directly relates to the capacity of the electrical energy storage that is needed for the launch. In this paper, the rail/armature contact behavior for two different armature technologies was compared. To this end, experiments using aluminum c-shaped armature and copper brush armature type projectiles were performed under same initial conditions. The c-shaped armature type showed a superior behavior with respect to electrical contact to the rails and in acceleration. A 300-g projectile with a c-shaped armature reached a velocity of 3100 m/s and an overall launch efficiency including the power supply of 41%. This is to be compared with 2500 m/s and 23% for the launching of a projectile using a brush armature. [ABSTRACT FROM PUBLISHER]

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]

Electrohydraulic shock waves (SWs) have been used for shale gas exploitation in recent years. The traditional method to generate SWs is underwater pulsed discharge with a water gap load or an electrical wire (EW) load, but the SW energy is limited heavily by the stored energy. To obtain stronger SW, the EW explosion ignited energetic material (EM) load is proposed here. To obtain a good ignition performance, the influence of capacitor charging voltage, stored energy, wire diameter, and wire material (Cu and Mo) were studied. The results show that the higher the charging voltage is, the more effective the ignition is; liquidation and vaporization will affect the discharge but will not ignite the EM explosion effectively; the EMs given in this paper are more sensitive to the arc plasma. Besides, the nonrefractory copper is more suitable for the EM ignition than the refractory molybdenum. [ABSTRACT FROM AUTHOR]

A 4.8-MJ capacitive pulsed-power system (PPS) was designed and fabricated for electromagnetic launcher (EML) experiment. The PPS consists of eight 600-kJ segments, which can be operated independently. In each segment, six 100-kJ capacitor bank modules, a charging power supply, a dump and charge panel, and control circuit were integrated. The capacitor bank modules in the segment are charged at the same voltage up to 10 kV, but the trigger time of each module can be set up differently. The overall PPS system is controlled by a control program, which sets charging voltage and trigger time of each module and monitors the states of system component. All the control signals are transmitted through fiber optic communication. The 48 unit modules are connected in parallel to EML with high-voltage coaxial cables. A current amplitude of more than 1 MA and a pulsewidth of several milliseconds were achieved by the PPS. The PPS has been applied to several tens of firing experiments of EML successfully. The design, fabrication, and the test results of the 4.8-MJ PPS were described in this paper. [ABSTRACT FROM PUBLISHER]

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

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

Railguns use electrical energy to accelerate projectiles to large velocities. The electrical energy for the launching process is provided by a pulsed power unit. A pulsed power unit usually consists of a capacitor, a switching device, a crowbar diode, and a pulse-forming inductance. The pulse-forming inductance is necessary to generate an appropriate current pulselength and amplitude. The idea of the energy storage augmented electromagnetic launcher is to use the magnetic field produced by the pulse-forming inductance to augment the magnetic field between the rails of the launcher. To maximize the augmentation of the magnetic field, it is necessary to place the pulse-forming inductance as close as possible to the rails of the railgun. The additional magnetic field causes not only an increased acceleration of the projectile but also a larger mechanical load of the railgun structure. This requires a reinforced housing compared with conventional railgun housings. In this paper, the design and the experimental setup of a railgun using an energy storage augmentation scheme as well as the results of experiments are presented. The results are compared with the previous results of a nonaugmented railgun configuration. The comparison shows an improvement of the energy efficiency. [ABSTRACT FROM PUBLISHER]

In the magnetic–structural simulations which are done by weak coupling, electromagnetic force data obtained by the simulation of the magnetic fields are to be transferred to the structural fields between meshes. However, in the different fields due to the different requirements of discretization scheme, such as the shape and distribution density of meshes, different finite-element models are used to analyze. Therefore, the data cannot directly be transferred between these nonmatching meshes. In this paper, we proposed a nonmatching meshes mapping method to deal with this problem. This method was used to a 3-D coupled magnetic and structural finite-element analysis of C-shaped armature in the railgun. Under the four different conditions of discretization scheme, the coupled simulations of the magnetic and structural fields were done by this method. The results were compared with reference values obtained by the same meshes mapping situation. The relative errors of the four cases are all less than 5%. Therefore, it proves the correctness and accuracy of this method. [ABSTRACT FROM PUBLISHER]

The energy density of the inductive energy storage systems is one order of magnitude higher than that of the capacitive ones. The slow transfer of energy through capacitive hybrid (STRETCH) meat grinder with inverse current commutation with semiconductor (ICCOS) devices put forward by Tsinghua University is a typical inductive pulsed-power supply for electromagnetic launch system, which has remarkable current amplification ability as a single module. However, one module cannot provide enough amplitude and width for the load current of the railgun launching. Therefore, the collaborative work of multiple inductive source modules is necessary for practical usage. In this paper, the designed inductive power supply system of about 1 MJ is composed of 40 STRETCH meat grinders with ICCOS modules. All the main switches are opened simultaneously to reduce the magnetic field coupling among the modules and make the current rising edge steep. The modules are divided into several groups. The triggering delays of the thyristors between every two adjacent groups are carefully designed. After the first triggers for all the modules, the energy stored in the capacitors can be further utilized with the second triggers. The numerical simulation results show that the appropriate collaborative triggering delay can increase the adjustability of the output current width and the second triggers can further increase the current width and the system efficiency. Therefore, the load current with flat shape, appropriate amplitude, and longer duration can be provided with modular design and collaborate triggering discharge of the multiple modules. This can provide a theoretical foundation for the future study and implementation. [ABSTRACT FROM PUBLISHER]

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for use in a host of directed energy applications. Recent improvements in the energy and power density of electrochemical lithium-ion batteries have made them a very viable option for these types of applications where fast and rep-rate operation is of interest. Despite the proven ability of lithium-ion batteries to source high currents, it is still unclear how they age when they are used to repeatedly source high-rate currents in a pulsed manner, as they must when used in a repetitive rate prime power supply. Similarly, it is unclear how elevated rate recharge affects the life of the battery. Research has been performed at University of Texas at Arlington in which high-power, 2.6 Ah lithium-ion batteries have been repeatedly discharged and recharged at high pulsed rates. This paper will discuss the potential of lithium-ion batteries for use in these applications and will present experimental results performed when two 2.6 Ah cells were both discharged at 28 A (10.8C) and recharged at 9 A (3.5C) to 2.5 and 2.0 V, respectively. [ABSTRACT FROM PUBLISHER]

In electromagnetic launch (EML) applications, a compensated pulsed alternator is an effective form of pulsed power supply because of its high energy density and power density. The basic advantages of compensated pulsed alternators for EML applications are their higher energy density than capacitors and their export ac output that is suitable for transmission and transformation. In general, external excitation is adopted as a form of self-excitation or pulse excitation in compensated pulsed alternators with an iron core or air core. Using this form not only results in heavy and bulky components but also complicates and reduces the reliability of the system. This paper proposes a novel compensated pulsed alternator that is excited by permanent magnets (PMs) and equipped with an iron core or air-core stator. This system does not require any excitation converter or brush–slip ring, thereby making it more reliable, less massive, and less voluminous than the system with self-excitation or pulse excitation. In addition, analytical models are introduced to simulate the air-gap magnetic distribution, back-electromotive force, pulsed current wave, discharge torque, and energy exchange of this machine. A scale-model prototype of the PM-compensated pulsed alternator is designed, fabricated, and tested. The actual output voltage waveform and pulsed current waveform are sampled and compared with the predicted ones. The results show that the design of the PM compulsator is feasible and reliable. [ABSTRACT FROM PUBLISHER]

The objectives of this tutorial are as follows: 1) to help students and researchers develop a basic understanding of how pulsed-power systems are used to create high-energy-density (HED) matter; 2) to develop a basic understanding of a new, compact, and efficient pulsed-power technology called linear transformer drivers (LTDs); 3) to understand why LTDs are an attractive technology for driving HED physics (HEDP) experiments; 4) to contrast LTDs with the more traditional Marx-generator/pulse-forming-line approach to driving HEDP experiments; and 5) to briefly review the history of LTD technology as well as some of the LTD-driven HEDP research presently underway at universities and research laboratories across the globe. This invited tutorial is part of the Mini-Course on Charged Particle Beams and High-Powered Pulsed Sources, held in conjunction with the 44th International Conference on Plasma Science in May of 2017. [ABSTRACT FROM AUTHOR]

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

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]

The results of research of 100 kA pulse current switches built on light triggered thyristors (LTTs) are presented. Transients in a semiconductor switch are analyzed at a capacitor discharge on an inductor and in a pulse forming network (PFN), which incorporates an inductor and crowbar diodes. Maximal currents for a semiconductor structure, at which thermo-generation peaks appear on oscillograms of forward voltage drop, have been determined. The LTT switch-ON process has been investigated and the need for application of speedup $R$ – $C$ circuits for a fast and stable transition of the LTT semiconductor structure to the conducting state has been shown. Transients at reverse recovery of LTTs in a discharge circuit with an inductor have been analyzed, and the snubbers providing suppression of pulse overvoltages and survivability of semiconductors have been chosen. For PFN, the current switching into the crowbar diodes and pulse overvoltage generation at a reverse recovery of LTTs has been analyzed, and the snubbers for suppression of these overvoltages have been chosen. The results of testing performed at a pulse current up to 100 kA confirm the validity of the accepted technical solutions. [ABSTRACT FROM AUTHOR]

An X-band switched energy storage (SES) microwave pulse compression system is presented, and its theoretical analysis, numerical simulation, and experimental research are carried out. Detailed dimensions of the resonant cavity are theoretically calculated and numerically optimized by simulation. The operation mode of the resonant cavity is TE1,0,52 at the frequency of 9.3 GHz. The output power gain is theoretically calculated as 11.7. When the width of the rectangular coupling iris is 11 mm, the coupling coefficient is 1.05, which is beneficial for high energy storage efficiency. In the preliminary experiments, the output microwave with power of 350 kW and pulsewidth of 10 ns is produced by the SES pulse compression system under the input power of 54 kW, implying a pulse power gain of 6.5. [ABSTRACT FROM AUTHOR]

The rapid-fire railgun (RAFIRA) is a railgun, which can be operated in multishot mode. However, so far, the number of shots in a multishot experiment was limited to two shots per experiment. That is why RAFIRA was adapted electrically and mechanically and multishot experiments with shots 2, 3, and 5 per experiment were performed. In these experiments, fire rates between 40 and 80 Hz and muzzle velocities up to 1700 m/s were achieved. [ABSTRACT FROM AUTHOR]

Ultracapacitors (UCs) are of increasing interest in different application areas, such as microgrids and transportation, which demand high transient power and are growing in capability every day. New power system architectures have been proposed that may be well suited to reliably and efficiently supply power to these previously unseen applications. Among the architectures that hold a great deal of promise are hybrid energy storage modules that integrate energy dense batteries with power dense UCs into a single power supply that augments traditional generation technologies. Within such architecture, the UC is the element that may be utilized to sink and source power quickly, at the leading or falling edge of a transient event. Considerable advances have been made to increase both the power and energy density, respectively, of UCs. Significant reduction of the internal impedance has resulted in an increased power capability that makes UCs well suited for use in these applications. Hybrid UC technologies, such as lithium-ion capacitors, have been developed, which have much higher energy density with nearly the same power density. In an effort to better understand and validate the capabilities of new UC technologies, a series of experiments has been performed on cells from four different manufacturers. Novel experimental testbeds and methods have been used to measure each technology’s internal impedance and power density. The experimental testbed utilized, along with the results collected to date, will be presented. [ABSTRACT FROM AUTHOR]

A simple and effective classification method to distinguish type-I and type-III edge-localized modes (ELMs) in an experimental advanced superconducting tokamak is introduced and some key parameters affecting the type-I and type-III ELMy H-modes are analyzed. The results indicate that the heating power and the edge safety factor q95 have strong correlations with the appearance of type-I and type-III ELMs. By using the high-speed visible-light charge-coupled device camera system, the dynamic characteristics of ELM filaments are studied and the features of type-I and type-III ELM filaments have been compared. The radial outward velocity for type-I ELMy filaments can be up to 1.5–3.5 km/s while for type-III ELMs one is about 0.5–2 km/s. In the process of type-I and type-III ELMy filaments outward propagation, the width of filament decreases gradually, while the velocity of filament increases. In addition, during an ELM event, it can be observed that the earlier the burst of an ELM filament, the higher the radial velocity it will have. [ABSTRACT FROM AUTHOR]

Presented are results from the optical imaging of atmospheric ablations of thin aluminum foils. These experiments were performed to evaluate the growth of temperature perturbations attributed to the electrothermal instability (ETI). ETI has been shown to seed magnetohydrodynamic instabilities on pulsed power-driven ablations of initially solid metallic targets, a topic of interest to various programs in pulsed power-driven plasma physics that depend on stable liner implosions. Experimental observations presented herein demonstrate exponentially growing temperature perturbations perpendicular to the direction of current with growth rates consistent with the linear ETI theory. High-temperature regions were observed to enter the vapor phase before sufficient energy had been deposited in the bulk foil to overcome the latent heat of vaporization, indicating a significant spatial heterogeneity in energy deposition rates. The growth rates of these perturbations scale as the square of current density, the predicted behavior for long-wavelength ETI structures. The development of these structures was unchanged by physical deformation of the foil surface, but dramatically influenced by incorporating areas of local high resistance in the foil loads. Extending the observation window in time showed a transition from perpendicular to parallel filaments, which is significant because ETI is predicted to switch orientations when the bulk foil material transitions into the plasma state. Collectively, these results provide an experimental validation of many theoretical predictions regarding ETI. [ABSTRACT FROM AUTHOR]

The University of Alabama in Huntsville (UAH) in partnership with the National Aeronautics and Space Administration at Marshall Space Flight Center is working to develop a pulsed power facility. The facility, known as Charger-1, is a 1-TW pulsed power machine. The hardware was originally DECADE Module 1 from L-3 Pulsed Sciences Division in San Leandro, CA. The DECADE program enabled the construction of several pulsed-power modules. Together, they were used for high-energy X-ray generation and weapons effects testing. The module at UAH is being outfitted for z-pinch propulsion system and nuclear energy production experiments. Its primary envisioned goal is to support the development of a Pulsed Fission-Fusion propulsion system with experimental data. This document is intended to update the nuclear and pulsed power communities as to the progress of the facility development. An overview of the facility and its status is presented. [ABSTRACT FROM AUTHOR]

In many relevant cases requiring a net energy comparable with that of a household appliance, the power supplies (PSs) and the electrical systems must be oversized to sustain short peak demands. The same equivalent energy could be achieved by storing and distributing the power over the time. These considerations lead to a new PS concept based on the exploitation of the energy stored between the actual operations. The new compact ($60\,\,\text {cm} \times 120\,\,\text {cm} \times 190$ cm) PS is able to generate arbitrary currents up to 2 kA by an integrated energy storage system based on supercapacitors. The delivered output power (approximately 200 kW) is obtained from a very low and tunable input power (<1 kW). Furthermore, a portion of the injected power can be recovered in the storage system. Even though the system was designed for a specific project (the PROTO-SPHERA spherical tokamak), the presented approach can be applied to general-purpose PSs, and there are encouraging prospects to extend it to large facilities with higher currents and voltages. [ABSTRACT FROM AUTHOR]

The high energy density (HED) capacitor is the energy storage component in capacitive pulsed power systems. There is an obvious voltage decay phenomenon, when the capacitor is disconnected from the power supply, and the higher the energy density is, the faster the voltage decays. And the voltage maintaining performance (VMP) of capacitor is of special interests especially in the occasion, which has high requirement of the output energy efficiency. For the HED capacitor made of metallized films, there are three factors affecting the VMP: self-healing, dielectric leakage, and polarization. In order to investigate the effect of above factors on the VMP of HED capacitor, the experiments and analysis of self-healing characteristics, dielectric leakage in stable status, and slow polarization are carried out. For a 4 kV/0.8 MJ/m3 HED capacitor, the self-healing is responsible for 12.68% of the whole voltage decay, and the dielectric leakage contributes for 7.89% with the fact that the insulation resistance is in the range of $6.06 \times 10^{2}$ – $6.31 \times 10^{2}\,\,\text{M}\Omega$. Thus, the voltage decay is mainly caused by the slow polarization. Then a VMP simulation without considering self-healing process is established, and different working parameters such as charging time and holding time are studied by using the VMP simulation. When the charging time is 40, 13.3, and 1.3 s, the voltage decay in 60 s is 3.06%, 3.57%, and 3.85%, respectively, and when the holding time is 0, 10, 100, and 1000 s, the percentage of 60 s voltage decay is 3.06%, 2.71%, 1.23%, and 0.70%, respectively. The results based on the space charge reveal the facts that shorter charging time and holding time would result in faster voltage decay. With the consideration of the energy output efficiency and insulation voltage withstand capability, the charging time and holding time would be compromise values. [ABSTRACT FROM AUTHOR]

Underwater electrical wire explosion (UEWE) of the copper wire of 0.3 mm in diameter and 50 mm in length at high and low initial stored energies was compared. For this wire, the completely vaporization energy is 194 J. While the UEWE at high initial stored energy of 961 J show a good reproducibility, the shock waves generated by UEWE at low initial stored energy of 120 J have a poor reproducibility that is attributed to the partial vaporization of the exploding wire. As the initial stored energy was gradually increased from 110 to 1000 J, the deposition energy in the exploding wire was increased from 92 to 246 J. When the deposition energy is higher than the complete vaporization energy of the wire, the relative error in the shock wave is significantly reduced to 4%. The effect of the wire diameter on the UEWEs was investigated by keeping the initial stored energy at 120 J. It was observed that there exist two discharge modes, the mode of the cutting-off current with a partial vaporization for the wires of a diameter smaller than 0.5 mm and the mode of the continuous discharge with no vaporization for the wire of 0.5 mm in diameter. It was found that a partial vaporization of a vaporization rate as low as 6% is enough to generate the shock wave and the amplitude of the shock wave is determined by the vaporized mass of the wire. The more the vaporized mass, the higher is the shock wave. [ABSTRACT FROM AUTHOR]