Search

This paper explores the feasibility of improving the stability of the output waveform by giving the robust design of the whole linear transformer driver system (LTDs). The mechanism of the design is analyzed, and a 1-MV/1-MA LTD module is taken as an example to show the procedure of the robust design. The results demonstrate that it is necessary to design the network’s parameter considering the random deviations of electrical components’ value and time delay jitter of spark switches for the stability of the output of LTDs. In addition, the sensitivity analysis is conducted, and the tolerance design for electrical parameters of every brick is given, which would be the guideline for tolerance requirements for the components to guarantee the reliability confidence of the LTD. [ABSTRACT FROM PUBLISHER]

Medium and high beta cavities used in linear colliders or spallation sources are supplied by klystrons or inductive output tubes amplifiers. The cathode voltage for these amplifiers can be generated by long-pulse modulators generating highly accurate high voltage pulses in the length of milliseconds. With existing modulator topologies, all the demanding requirements like fast pulse rise time, high accuracy, and low voltage ripple hardly can be satisfied at the same time. Common designs like bouncer modulator topologies using pulse transformers become huge for long pulses. The series–parallel resonant converter (SPRC) avoids this drawback as the transformer is operated at high frequencies. In this paper, the comprehensive multidomain model of an SPRC including an electrical model of the inverter, a magnetic model, and an isolation design procedure of the transformer is verified with a prototype of a single module operated under full-load conditions. In addition, a comparison between the predicted parasitics like leakage inductance and stray capacitance of the transformer and the measured values are given. An evaluation of the isolation of the transformer, which is especially crucial for a series connection of the modules, is also performed. In addition, different possibilities to realize the desired series inductance are discussed. [ABSTRACT FROM PUBLISHER]

In this paper, an equivalent circuit model for a frequency-selective surface (FSS) embedded in a thick plasma layer is introduced. The plasma layer is a lossy and dispersive medium, and therefore, the equivalent model is not purely imaginary and consists of resistive elements as well as inductance and capacitance elements. First, a square patch FSS is simulated in a wide frequency range from 1 to 25 GHz by a full-wave electromagnetic software, and then all the circuit elements are calculated by genetic algorithm optimization to achieve reflection coefficient similar to the one obtained by simulation. It is shown that this model can mimic the simulated behavior with good approximation. Then values of different elements of the model through practical variations of cold plasma parameters are plotted, and the effects of electron density and collision frequency are investigated on circuit elements. [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]

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

Linear permanent magnet (PM) brushless dc motor (LPMBDCM) is used for electromagnetic catapult, which may offer significant advantages, in terms of efficiency, high speed and accelerations of heavy payloads, capability of high forces, and so on. In this paper, an LPMBDCM, which is constructed of transverse flux stator and PM mover, is investigated. First, the launch specifications and technical features under the condition of pulse power input are presented. Then, the magnetic circuit parameters including the calculation of the mutual and leakage inductance are derived, and the rated work performances are analyzed. The rated input voltage, current, thrust, and power efficiency are 4000 V, 18041 A, 1.389 MN, and 0.97, respectively, which can meet the requirements of electromagnetic catapult. The availability and reliability are validated as the temperature rise per launch is lower than 1 °C, and the demagnetization of the PM would not happen with high pulse current. Finally, to validate the characteristic of the basic design, the system simulation model including the power supply and power conditioning is built using of Simulink, and the launch trajectory is simulated by the model, which shows the launch can achieve a speed of 99.47 m/s along the distance of 99.47 m within 1.51 s. A small-scale prototype machine is fabricated and the validity of the proposed method has been verified by the experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a new approach for modeling electromagnetic railguns is proposed. The model’s simplicity makes it suitable for sensitive analysis and optimization procedures. For validation, the railgun is simulated by a 3-D finite-element method (FEM) using Maxwell software and the results are compared with existing experimental data. Circuit model simulation results verified the accuracy of the model as they are very close to the experimental ones. As multistage railgun is one of the greatest improvements in railgun expansions, a successful attempt is made for the new circuit model to include this, as evidenced by comparing the results of multistage railgun model with those of the FEM. [ABSTRACT FROM PUBLISHER]

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

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]

A model is developed to investigate the commutation process of a helical coil electromagnetic launcher (HCEML) structure. When the armature moves, the motion of the projectile coils’ magnetic energy would supply reactive power to move the leakage into and out of the coil windings of the launcher to accomplish the commutation. The energy conversion of the coil electromagnetic launcher can be considered as the process of energy transfer from the back commutation coils to the excited coils and then from the excited turns to the front commutation coils. In this paper, governing equations of the commutation were deduced theoretically, and finite-element model of HCEML was established in ANSOFT MAXWELL. Then a deeper circuit investigation into the overall performance of commutation was carried out by means of PSPICE software. The validity of the theoretical analysis and that of the circuit network model were finally verified by experiments. The results show that during the commutation process, the current of back commutation coils drops to zero with no energy remaining in the internal; the current of front commutation coils and drive–projectile coil system gradually changes to a stable value, which is related to the geometric parameters of the launcher; the drive–projectile coil system releases energy overall that is mainly used to increase the kinetic energy of the projectile; the power supply system has little effect on energy conversion and transformation at the commutating moment and just keeps the voltage and current from decaying due to the impedance and inductance of the launcher system. [ABSTRACT FROM PUBLISHER]

Railgun is a kind of electromagnetic launcher that can accelerate masses in the range from milligrams to tens of kilograms to velocities more than several kilometers per second. The cross-sectional area’s moment of inertia is one of the most important mechanical properties of the rails, affecting the critical velocity and launch performance. The current distribution in the railgun determines its efficiency and contact performance of rail/armature sliding. Factors that affect the electromechanical performance of the rails include geometry and material. To improve the electromechanical performance, two types of rails with convex and concave cross sections are designed by adding and removing arch forms to/from the conventional flat rails. Modified C-shaped armatures are constructed for each rail geometry. This paper presents the results on mechanical performance on the basis of structural analysis and current distribution from coupled EM-structural simulations. The results show that the moments of inertia of convex and concave rails are larger than those of flat rails for a given cross-sectional area and rail width, but the differences in mechanical performance among the three geometries are not significant, and the advantage of rails with larger moments of inertia for a given cross-sectional area is limited. The inductance gradient of the flat railgun is larger than those of the others, and the concave railgun has the smallest; consequently, the concave railgun is the least efficient. Compared with the flat and concave rails, the current density of the convex rail is smaller at the bore-side rail surface, but greater at the contact interface, especially at the trailing edge of the armature. [ABSTRACT FROM PUBLISHER]

By electrically isolating sections from the breech to the muzzle of a specially designed metal gun barrel (steel), the boundary conditions used in the 1984 paper by Kerrisk are changed. The result allows a metal gun barrel to be located close to the current-carrying rails while still maintaining high inductance per unit length ( $L^\prime $ ). Descriptions of two designs of two-rail open air railguns that use this result for an efficient gun are presented. Each current-carrying rail is supported by its own steel barrel section. For each case, a thermal management system is included. The open gun bore is directly exposed to the atmosphere or a gas ambient if a dielectric enclosure is used, along the gun’s entire length. [ABSTRACT FROM PUBLISHER]

By applying the principle of inverse current commutation with semiconductor (ICCOS) devices in a slow transfer of energy through capacitive hybrid (STRETCH) meat grinder system, a novel circuit topology called STRETCH meat grinder with ICCOS was proposed by the Tsinghua University in 2013. It can not only raise the amplitude of the opening current, but also reduce the cost of the STRETCH meat grinder circuit obviously by replacing the integrated gate-commutated thyristor (IGCT) with thyristor. This paper discusses the overall design, system implementation, and testing results of a STRETCH meat grinder with ICCOS system with roughly 1-kJ inductive energy. The load is a spiral coil with 1.4- \textm\Omega resistance and 1.4- \mu \textH inductance. With closed-loop control strategy, the system detects the charging current of the inductors. When it reaches the designated value, the triggering signal for ICCOS is delivered and after the predefined delay time, the triggering signal for discharging the voltage on the pulse-forming capacitor is delivered. The current of the inductors and the load are measured by Rogowski coils. The opening current is 1 kA and the maximum load current is close to 4 kA. All the voltages on the switches are lower than 1 kV. The experimental results are consistent with the simulated ones, which verified the correctness of the theoretical analysis and proved the applicability of the STRETCH meat grinder with ICCOS for larger energy level. [ABSTRACT FROM PUBLISHER]

Structural parameters directly affect the energy density and the total resistance of the inductors used in inductive pulse power supply (IPPS). This paper elaborates the relationship between the structural parameters and electrical performances of the inductors used in IPPS and set up the inductors for the experiment in slow transfer of energy through capacitive hybrid meat grinder circuit using air-core flat spirals of strip coil. Then we compile a program that can obtain the structural parameters of the inductors that have the highest energy density under the condition of given charging and discharging currents as well as inductances in the primary and secondary sides. The calculation results of the program are analyzed and verified by the measured values of the real inductors. At the end, on the condition of a constant current density, we put forward a rule that along with the increase in the system energy, the energy density of the IPPS became higher and the resistance of the inductors became lower. [ABSTRACT FROM PUBLISHER]

This paper performs the inductance and phase coupling analysis of a tubular permanent magnet machine with transverse flux configuration for electromagnetic launch (EML) applications. Self-inductance and mutual inductance are calculated by employing a frozen permeability finite element technique, and the results are validated by measurement on a prototype machine. The analysis of phase coupling problem is then undertaken, and it has been shown that the tubular transverse flux machine has the merit of magnetic decoupling between phases, and thus shows a brilliant prospect in EML applications. The influence of armature reaction on the inductance is also investigated, and it indicates that at higher current, the inductance fluctuates once instead of twice within one electrical cycle, which is quite different from that in conventional machines. [ABSTRACT FROM PUBLISHER]

In this paper, circuit simulation was chosen as the main methodology to analyze the characteristics of an electromagnetic (EM) rail launcher (or EM railgun) system, and a complex simulation model was proposed, which was not merely built on the static electrical parameters. Moreover, practical physical processes contributed to the system have also been taken into consideration and expressed as electrical parameters. Thus, the description of a relatively complex system could be realized by a comparatively simple manner, and the simulation result is more accurate and reliable compared with the traditional circuit simulation ones with the static electrical parameters. A circuit simulation model of an EM launch system based on PSpice software was built, in consideration of multifactor effects, such as current skin effect, contact pressure, and contact resistance on the contact surface of the armature and the barrel, velocity skin effect, friction drag, and temperature coefficient of electrical resistivity. Simulations were made based on the proposed model as well as the traditional one. Last but not the least, a comparison between the simulation results and the experimental ones was made to verify the accuracy and effectivity of the improved model. [ABSTRACT FROM PUBLISHER]

After preliminary tests using a small 25 mm-caliber electromagnetic launcher, a larger mid-caliber launcher has been designed and fabricated. The launcher has a rectangular bore of 40 mm $\times $ 50 mm, where the rails are separated by 50 mm from each other and are 5.6 m long. To deliver an electrical current to the launcher, a new 4.8-MJ pulsed power supply (PPS) consisting of eight 600-kJ segments has been constructed. The 600-kJ segment is a basic building block of PPS operated independently. It contains a controller, a charger, a safety circuit, and six 100-kJ unit modules. Each unit module in the segment is composed of a 100 kJ capacitor bank, a thyristor switch, a crowbar diode, and a pulse-forming inductor. The modules in a segment are charged to the same voltage, but they are designed to have different triggering times to make a flexible shape of current waveform. The electrical parameters of the PPS were determined through the discharges of the unit modules and those of the rails were measured by launch experiments or short circuit tests at the ends of the rails. Launch experiments have been done using several current waveforms. The current of 1 MA in a few milliseconds accelerated the armatures of several hundred grams in mass to velocities near 2 km/s. In this paper, the design and basic performance of the constructed PPS and the electromagnetic launcher are presented. [ABSTRACT FROM PUBLISHER]

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

The Precision High Energy-Density Liner Implosion Experiment (PHELIX) is a pulsed power driver capable of delivering multimegampere currents to cylindrical loads. The PHELIX hardware includes novel design features to provide a high-energy conversion efficiency of approximately 10-MA output current per megajoule of stored energy. This is achieved by a rail-gap switched low-inductance Marx design (resistively damped) driving a multifilar air-core pulse transformer. The Marx output cables form the toroidal transformer that is an integral part of the disc line and removable load cassette assembly. The transformer and disc line uses conformal insulation methods and does not require replacement; after each shot, the transformer is completely reusable. Load cassettes can be easily exchanged to facilitate experimental variation. PHELIX is self-contained within its own transport container and Faraday cage that can be moved from the maintenance building to the Los Alamos Neutron Science Center 800-MeV proton accelerator facility to perform multipulse proton radiography. This paper details the electrical and mechanical design of the Marx and multifilar transformer assemblies as well as presenting the operational performance achieved to date. [ABSTRACT FROM PUBLISHER]

Modern accelerator driven experiments like linear colliders or spallation sources are supplied by RF amplifiers using klystrons. The cathode voltage for these klystrons can be generated by long pulse modulators generating highly accurate voltage pulses in the length of milliseconds. Conventional designs using pulse transformers become huge for long pulses. The series-parallel resonant converter (SPRC) topology avoids this drawback as the transformer is operating at high frequencies. This paper presents a comprehensive design approach for SPRC modules, which is based on an optimization procedure containing an electrical model of the resonant circuit and a thermal model of the semiconductors. In addition, an insulation and a leakage design procedure and a thermal model of the transformer are also presented. Finally, this procedure provides the optimal design parameters of the resonant circuit elements. With these parameters, a global optimizer chooses the optimum amount of modules connected in series and/or in parallel to fulfill the given restrictions. The efficiency of a basic SPRC-module is 94.7% with a pulsed power density of 4.63 kW/l. [ABSTRACT FROM PUBLISHER]

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

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]

This paper presents the design formulas for the calculation of the leakage inductance and stray capacitance of a toroidal core transformer. An analytical approach is utilized to calculate the leakage inductance and the turn-to-turn stray capacitance based on stored magnetic energy and electric energy, respectively. In addition, the effect of frequency on the leakage inductance is studied and some modifications are applied to the calculation method to consider the skin effect. The obtained results are validated by 3-D finite element simulations. In addition, the measurements for a prototype transformer are presented as a comparison with the calculated and simulated results. The results show that the presented formulas for the toroidal core transformers have a good accuracy. [ABSTRACT FROM AUTHOR]

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

High synchronization accuracy can be obtained when saturable pulse transformer (SPT) with multisecondary windings is employed in the technology of multipulses synchronization. LC generator based on multisecondary windings SPT is presented in this paper. The operation principle of the proposed LC generator is introduced. Three important requirements for voltage multiplication are analyzed and simulated. Experimental studies are carried out, and the results show that: when the primary energy storage capacitor is charged to 335 V, the output voltage of the system can reach up to 48.2 kV. The voltage multiplication ratio is 2.9. It means that the output voltage is 2.9 times larger than the charging voltage on single main energy storage capacitor. The step up ratio of the whole generator is 143.9. The voltage multiplication ratio increases with the increase of the charging voltage. The generator is suitable to operate at high voltage situation. [ABSTRACT FROM AUTHOR]

Multipole field electromagnetic launcher (MFEL) is a new type of induction launcher that can produce radial magnetic field. This paper proposed different driving coil connection patterns of MFEL and analyzed their performance through experimental and simulation methods. To verify the conceptual feasibility, a small-size single stage capacitor-driven MFEL was built and tested for the first time. Powered by a 100 \muF capacitor bank charged to 3000 V, the launcher is able to accelerate a 50.4 g projectile to a velocity of 13.3 m/s. Characteristics of MFEL including inductance gradient, driving current, eddy current distribution, and magnetic field distribution were analyzed as well. [ABSTRACT FROM PUBLISHER]

SPHINX is a microsecond linear transformer driver located at Atomic Energy Comission (CEA) Gramat (France), which can deliver a current pulse of 6 MA within 800 ns in a Z -pinch load. Using the concept of the dynamic load current multiplier (DLCM), which was proposed by Chuvatin, we expect to increase the load current above 6 MA, while decreasing its rise time to \sim300 ns. The DLCM developed by the CEA Gramat and International Technologies for High Pulsed Power (ITHPP) is a compact system made up of concentric electrodes (autotransformer), a dynamic flux extruder (cylindrical wire array), a vacuum convolute (eight post-hole rods), and a closing switch (compact vacuum surface switch). The latter is a key component of the system, which is used to prevent the current from flowing into the load until the inductance builds up due to the implosion of the wire array. This paper presents the design and testing of the DLCM surface switch, resulting from both electrostatic simulations and experiments on the SPHINX generator. These studies, carried out either with or without load (open circuit), were valuable for a first experimental evaluation of the DLCM scheme in a microsecond regime and provided detailed information on the surface switch behavior. [ABSTRACT FROM AUTHOR]

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

This paper presents a gate unit with short-circuit protection for a 4.5-kV press-pack insulated gate bipolar transistor (IGBT) designed for pulsed applications and operated at a pulse current of 4 kA and the results of short-circuit tests performed with the mentioned switch and the gate unit. Initially, an overview of the gate unit, the implemented gate boosting as well as the two-stage turn-off and active clamping is given. An over-di/dt as well as an over-current detection using a printed circuit board (PCB) Rogowski coil is used in the gate drive to protect the IGBT during operation. Then, the design of the PCB Rogowski coil is introduced including partial element equivalent circuit simulations to predict the coil parameters. Measurements were made to verify these simulations. Afterward, two types of short-circuit tests were performed. First, the over-di/dt detection was tested by turn-on into a short circuit. The tests show that the over-di/dt detection reacts very fast. The IGBT was always able to turn off the short-circuit current. The maximum short-circuit current was 4.4 kA. Second, tests using an auxiliary switch were made to investigate the short-circuit events during pulse top. The IGBT was able to turn off a maximum short-circuit current of 8.7 kA. [ABSTRACT FROM AUTHOR]

Compensated pulsed alternator (CPA) is considered one of the most potential pulsed power supplies for electromagnetic railguns, due to its high energy density and power density. In this paper, a co-simulation method of a CPA powered railgun system is proposed. The railgun model was constructed on the Matlab/Simulink platform. In order to obtain a more accurate simulation result of the railgun launching process, the kinetic resistance is taken into account in the process of building the railgun model. The CPA model is set up in FLUX2-D so as to calculate the dynamic inductance of the alternator precisely. The coupling module between the two software packages is utilized to achieve the co-simulation of the CPA powered railgun system. The simulation results indicate that the optimum length (the displacement of the projectile exiting the muzzle while the current exactly reduces to zero) of the barrel has the relation with trigger moment of alternator. The muzzle velocity of the projectile would decrease when the trigger moment was delayed or the distance between the breech and the armature becomes farther. [ABSTRACT FROM PUBLISHER]

Inductive pulse power supplies are of interest because their energy densities are one order of magnitude higher than those of capacitive power supplies, based on the same power-output capacity. The Institute of Advanced Technology puts forward an inductive pulse power topology called the slow transfer of energy through capacitive hybrid (STRETCH) meat grinder. In this topology, an active switch is used to cut off the charging current. Limited by the current turning off ability of integrated gated commuted thyristor, it may encounter difficulties in extending to higher-energy systems. Other than that, the cost of the system is very high. In this paper, the principle of the STRETCH meat grinder is presented. Then, the STRETCH meat grinder with inverse current commutation with semiconductor devices (ICCOS), which is proposed by the Institute of Saint Louis, is presented. The process of ICCOS in the STRETCH meat grinder is illustrated in detail. Finally, simulations are made based on Simplorer 8 to explain how ICCOS works clearly. A preliminary discussion of how to design ICCOS is also presented. We conclude that the STRETCH meat grinder with ICCOS removes the limitations of the original one and has potential applications for high-energy systems in future and can cut down the cost greatly. [ABSTRACT FROM PUBLISHER]

Electromagnetic railgun is one of the most important new concept weapons. Some key parameters of a rectangular caliber railgun system—the thickness of the armature d0 , the width of the caliber X, the height of the caliber Y, the minimum length of the rail L, the amplitude of current I, and the pulsewidth of current t0—are studied in this paper. By introducing the current carrier margin coefficient named \alpha , the ratio of armature thickness to railgun caliber width named \beta, and the ratio of caliber height to caliber width named \gamma, equations of some key parameters of the rectangular caliber railgun system are proposed. Based on analysis of the armature's electric heating capacity and mass, 0.7 is an appropriate value for \alpha. Based on analysis of parameters of railguns, \beta = 1/3 and \gamma \leq 1 are appropriate for small and medium calibers, and \beta < 1/3 and \gamma = 1 are appropriate for large calibers. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate a water treatment method that sprays waste water droplets into a pulsed discharge space. For this method, it is important to apply pulsed voltages with a short pulse width and a fast rise to the electrode to realize high energy efficiency. An inductive energy storage (IES) circuit using a semiconductor opening switch (SOS) outputs pulsed voltages similar to the above-mentioned voltage. We report the characteristics of the water treatment using the IES circuit. The capacitance and inductance in the IES circuit are varied. An increase in the inductance in the secondary circuit of the pulse transformer, results in the formation of pulsed voltages with a longer pulse width; thus, the ratio of the thermal loss to the discharge energy becomes high. However, the energy transfer efficiency improves. Additionally, we vary the maximum current of the SOS, keeping the pulse width constant, by adjusting the capacitance and the inductance. As a result, when the current in the SOS increased, pulsed voltages with a higher peak and a shaper rise are obtained. Further, the pulse width of the voltage and the energy transfer efficiency are not affected by the current in the SOS. Hence, the energy density of the discharge is higher. The increase in the secondary inductance and the forward current increased the energy efficiency of the water treatment system owing to the increase in the energy transfer efficiency and the discharge energy density. [ABSTRACT FROM PUBLISHER]

This paper describes a low cost, easy-to-implement circuit for triggering ignitrons in plasma physics experiments and other pulsed power applications. Using insulated gate bipolar transistors (IGBTs) for rapid switching, the circuit delivers >200~A peak current from a 0.1-\muF capacitor to the ignitron trigger pin with a rise time of \sim0.6~\mus. The trigger circuit is isolated from the ignitron by a pulse transformer. Details of the circuit design and practical considerations for working with IGBTs are discussed. Sources of inductance in the system are identified, and leakage inductance associated with the pulse transformer is shown to be the primary factor limiting the pulse rise time. [ABSTRACT FROM PUBLISHER]

The main purpose of this paper is the determination of plasma equilibrium parameters, as well as current density and safety factor profiles, in IR-T1 tokamak. For this purpose, a diamagnetic loop with its compensation coil and an array of magnetic probes were designed, constructed, and installed on the outer surface of the IR-T1 chamber, and then, the poloidal beta and poloidal and radial magnetic fields were measured. Moreover, a few approximate values of the internal inductance for different possible profiles of the plasma current density were also calculated. Then, from these two techniques results, the plasma horizontal displacement was determined. In addition, from the results, the current density and q-profiles were obtained. [ABSTRACT FROM PUBLISHER]

A modular linear transformer driver (LTD) is a novel fast-discharge high-pulsed power source for primarily stored energy. In LTDs, a large number of stages (or cavities) can be connected in series or in parallel conveniently to directly generate high power pulses of 50–200 ns with the required voltage or current. This paper introduces an LTD stage developed by us recently. This LTD stage consists of 14 bricks in parallel. Each brick contains two 40-nF capacitors and a compact multigap gas spark switch in series. The switch is a modification of our original version, and the diameter and the height of which have been reduced to 98 and 127 mm, respectively. The circuit model of this stage is established in PSPICE, and its output parameters are obtained through simulation. Driving a rough-matched resistive load of 0.27 \Omega, its output current peak is 300 kA with an overall rise time of about 110 ns at a charged voltage of the capacitors of about \pm90 kV, agreeing well with its simulation result. [ABSTRACT FROM PUBLISHER]

Pulse step modulation (PSM)-based high-voltage power supplies have played a significant role in fusion research. In many cases, multisecondary transformers are used for generation of tens of kilovolt range outputs with fast (microsecond-order) transient response. In this scheme, large numbers of isolated voltage sources are connected in series to generate the output. Isolated voltage sources can be achieved by a large number of separate transformers or by a single unit of multisecondary transformer. Naturally, a transformer having numbers of secondary windings (\sim40) on a single core is the preferred solution for PSM topology due to its space and cost consideration. For design and simulation analysis of such a power supply, the model of a multisecondary transformer poses special problem to any circuit analysis software. While many simulation software packages provide transformer models with limited number (3–6) of secondary windings, they still fail to predict the actual observed results from a manufactured unit. This paper discusses the difficulties in modeling, step by step with representative schemes of multisecondary transformer, and advantages/disadvantages of each scheme with simulation results. Finally, a model using flux-coupled cores as basic building blocks is proposed; this model is able to simulate actual transformers very close to its observed parameters in test and actual usage. [ABSTRACT FROM PUBLISHER]

This paper discusses the efficiency of energy transfer from an inductive energy store to a short-circuit load with a microsecond megaampere plasma opening switch (POS). A very simple electrotechnical technique for estimation of electron current loss is proposed, and its operability is proven. The applicability of the technique for analysis of experimental data is considered. The low rate of rise of the POS resistance along with considerable current loss causes weak pulse sharpening with a time shift of the current pulse and a decrease in its magnitude. [ABSTRACT FROM PUBLISHER]

To provide substantial reduction in the size and energy of high-energy-density experiments, we have designed, built, and operated a liner implosion system that is driven by a multiturn-primary, single-turn-secondary, current step-up toroidal transformer. The Precision High Energy-density Liner Implosion eXperiment (PHELIX) pulsed-power driver, which is currently under development at Los Alamos National Laboratory, Los Alamos, NM, can provide >400 kJ of capacitively stored energy and peak load currents of >5 MA to implode centimeter-size liners in 10–20 \mu\s, attaining speeds of 1–4 km/s. Diagnosis of scaled-down liner implosion experiments will be performed with the 800-MeV proton radiographic (pRad) system at Los Alamos Neutron Science Center (LANSCE); therefore, PHELIX is designed to be portable with a footprint of only 8 \times 25\ \ft^2. The multiframe, high-resolution imaging capability of pRad will be used to study hydrodynamic and material phenomena. Experiments with scaled-down electromagnetic railguns, pulsed high-field magnets, and magnetic flux compression are also under consideration. This paper discusses the overall PHELIX design concept and layout, and details of the electromechanical design needed to ensure repeatable operation. [ABSTRACT FROM AUTHOR]

The physical processes that occur during the initial stages of nanosecond explosion of thin wires play an important role in the development of plasma for nanoparticle preparation. The transition of the wire material from the condensed state to conducting plasma has not yet been fully understood. In this paper, underwater electrical explosions of copper wires were investigated with pulsed voltage in the timescale of a few microseconds. A self-integrating Rogowski coil and a voltage divider were used for the measurements of the current and the voltage on the wire load, respectively. The current rise rate was adjusted by changing the circuit parameters, including the discharge voltage and circuit inductance, and the copper wire properties consisting of the length and the diameter. The effect of the current rise rate on the phase transitions involving melting from solid to liquid and vaporization from superheated liquid to the vapor–drop mixture was obtained by the analysis of the current and voltage waveforms of copper wire explosion. The energy of melting and vaporization was calculated based on experimental waveforms of current and voltage. In addition, the effect of applied voltage, circuit inductance, and the length and diameter of copper wire was acquired on the electrical explosion characteristics of copper wires. [ABSTRACT FROM PUBLISHER]

This paper presents the design and development of a repetitive Marx generator rated at 1 kJ, 300 kV, 12 kA, and 10 Hz and which is suitable to drive the load directly. Bipolar charging of a Marx generator scheme has been adopted to get the following: 1) faster rise time and 2) relatively low charging voltage. The faster rise time is due to the reduced number of spark gaps down to six for 12 in-series capacitors (0.15 \mu\F and 50 kV) of a six-stage bipolar-charging Marx generator. Interstage inductive charging further enhances the efficiency of the overall system as compared to resistive charging. The generator is characterized by an aqueous resistive load for both polarities at the output voltage. Output voltages of the same magnitude have been achieved for both polarities. The matched impedance is found to be 25 \Omega for which a suitable reflex triode is designed. Intense electron beams and high-power microwaves have been generated using this Marx generator and reflex triode system. Experimental results demonstrating the Marx generator and the reflex triode operation are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper details the testing of a commercially available gate turn-off thyristor (GTO) for application in inductive-store power supplies. GTOs have been used as a component of inductive-store systems directly and as part of compound switches. These GTOs are generally available commercially and typically have extensive datasheets. However, the inductive-store application differs significantly from conventional switching applications, which significantly reduces the utility of the datasheets; GTOs are typically used at 100–1000 Hz in a fairly continuous manner, whereas in an inductive-store system, a GTO may be conducting for a relatively long time before doing a single turn off. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel double-projectile railgun, which can launch two projectiles synchronously. This salvo performance can improve the hit rate and the destructive power on the target. The railgun has two barrels stacked in series and is powered by a pulse power. In order to verify its salvo performance, we conducted a 3-D eddy current electromagnetic field simulation with the finite-element numerical method. The simulation results showed that the self-inductance gradient (L^\prime) of each pair of rails is not always constant; the value depends on the armatures' position, particularly when the armatures are closer to the breech. Moreover, we found that, when the two armatures are at different positions, the values of the mutual-inductance gradient of the two pairs of rails (M12^{\prime}, M21^{ \prime}) are different (M12^{\prime} \neq M21^{\prime}). Subsequent circuit simulation of the launching process showed that the propulsive force acting on the armature in the front is less than that on the armature behind. We discovered that the configuration of the railgun will facilitate the synchronization during the launching process, even if the two armatures have different masses, move under different frictions, or start at different positions. We further tested a corresponding scale model of the railgun. The experiment led to the conclusion that the double-projectile railgun has good salvo performance. [ABSTRACT FROM AUTHOR]

The inductance gradient is one of the important parameters on the design and evaluation of railgun performance. The size, shape, and material of rails have effects on the inductance gradient. In 2-D analysis, the length of rails assumed to be infinite and then the effect of the armature ignored and a constant inductance gradient is obtained. In 3-D simulations, with assuming a fixed position for the armature (usually in the middle of rail), the inductance gradient can be determined. However, with the moving of the armature along rail length and the increasing of the current path, the applied force on the projectile will be different when it is constant and in the middle of the structure. Therefore, inductance gradient in the structure length will be changed. In this paper, with considering a railgun with copper rails with 1-m length, according to the input current and the resultant force of the aluminum armature in the rail length it was displaced in every step, the inductance gradient was determined. The results show that the amount of inductance gradient is not constant and will be increased with armature movement toward the muzzle. [ABSTRACT FROM AUTHOR]

The performance of a single inductive coil driver with six different turns of drive coils is analyzed and emulated with the emulation program in this paper. Under the condition that the integral projectile mass is 1.125 kg and the armature length is 300.0 mm, the maximum velocities of the projectile are 130.1, 134.1, and 132.8 m/s when the drive coil axial lengths are 50.0, 100.0, and 150.0 mm, respectively, and the drive coil radial thickness is 20.0 mm. By changing the drive coil radial thickness to 30.0 mm, the maximum velocities of the projectile are 112.5, 110.2, and 116.3 m/s when the drive coil axial lengths are 50.0, 100.0, and 150.0 mm, respectively. The result shows that only when the structural parameters of the drive coil and the armature are matched suitably that the maximum velocity of the projectile can be reached. This conclusion provides a reference for the engineering practice of the inductive coil driver. [ABSTRACT FROM AUTHOR]

Some intriguing advantages of permanent-magnet linear synchronous machines (PMLSMs), such as simple structure, high thrust, high efficiency, ease of maintenance, and controller feedback, make it possible to take the place of steam catapults in the future. The conventional PMLSM is renowned for its simple structure and high efficiency, whereby the high reactive power resulted from great leakage inductances during the long stator. Thus, great concern is paid to the section structure of the PMLSM. A sectioned permanent-magnet linear synchronous machine (SPMLSM) used in the EMALS is introduced in this paper, whose stator core is continuous but the armature winding is divided into two sectioned parts. First, the electromagnetic fields of the SPMLSM are investigated analytically. Then, the fields are computed by the finite-element method (FEM) and measured experimentally. Not only are the self-inductances and mutual inductances in one section studied but also the mutual inductances between the two sections. These inductances are then calculated by the FEM and measured experimentally. Good correlation among the results was obtained by these three methods. [ABSTRACT FROM AUTHOR]

An electromagnetic railgun (EMG) fed by a capacitor bank was developed to launch hypervelocity projectiles. The efficiency of the EMG will ultimately determine the scale of its use since it determines the size of the power source. In practice, it is difficult to calculate the energy loss in the EMG system in a simple way, because of complicated physical phenomena such as dynamic friction occurring during firing. In this paper, an expression of the friction in the EMG system is conceived and validated by the measured current and in-bore velocity of the armature. With the conceived expression, a full circuit model, including the effects of the friction in the EMG system, is derived and validated. The simulated current and velocity based on the model are in good agreement with the measurements. The efficiency and energy loss in our EMG system are calculated and analyzed with the full circuit model. The primary mechanisms of the energy loss attribute to the impedance of the rail and pulse formation network. [ABSTRACT FROM AUTHOR]

Compact high-voltage Marx generators have found wide ranging applications for driving resistive and capacitive loads. Parasitic or leakage capacitance in compact low-energy Marx systems has proved useful in driving resistive loads, but it can be detrimental when driving capacitive loads where it limits the efficiency of energy transfer to the load capacitance. In this paper, we show how manipulating network designs consisting of these parasitic elements along with internal and external components can optimize the performance of such systems. [ABSTRACT FROM PUBLISHER]

Solid-state modulators based on pulse transformers offer the advantage that, with the turns ratio of the transformer, the primary voltage could ideally be adapted to available switch technology, and a series connection of switches could be avoided. To increase the power level, several semiconductor switches must be connected in parallel, and a balancing between the different switches must be guaranteed. Here, the matrix transformer concept, which is based on multiple primary and/or secondary windings, as well as flux adding, offers superior performance with respect to the achievable rise times. However, the influence of the parasitic elements on the voltage and current distribution is quite involved. In this paper, the influence of the parasitic elements of the matrix transformer on the current balancing and on the winding voltages is investigated based on reluctance models. Additionally, the inherent current balancing of the matrix transformer for windings mounted on different cores is explained. Furthermore, the influence of parasitic load/transformer capacitances on the turnoff transient is discussed in detail. [ABSTRACT FROM PUBLISHER]

High-inductive helical magneto-cumulative generators (MCGs) of 50- and 80-mm diameters intended for a plasma focus (PF) powering are created in VNIIEF. High energy gain, efficient operation into loads to 50 nH, and the possibility of application in combination with the current opening switches are the distinctive features of the generators. Having small sizes and masses, these generators produce current pulses from 400 kA to 1 MA with the rise time of ∼0.5 μs powered with the energy less than 100 J. This paper presents results of experimental research during which the high stability of the MCG operation both on the current amplitude and operation time is shown. Results of the experiments on the PF powered from the MCG, operated in the regime of the magnetic flux extra compression, are presented. The yield of 1012 neutrons per pulse was recorded in the tests with the MCG-80 and PF with D-T mixture. [ABSTRACT FROM AUTHOR]