Inductive Pulsed Power Generator Research Articles

Observation of the development of pulsed discharge inside a bubble under water using ICCD cameras

The development of discharge inside a bubble in water is observed using high-speed gated ICCD cameras. A tungsten wire is inserted into a glass tube, which is immersed in water. Argon gas is injected into the glass tube through a solenoid valve to generate bubbles at the tip of the glass tube. The pulsed high voltage is generated using an inductive energy storage system pulsed power generator driven by a SI-thyristor. Two ICCD cameras with optical axes perpendicular to each other are used to take two orthogonal images, and an ICCD camera that is capable of taking 12 consecutive photographs used to evaluate the propagation velocity of the discharge. The discharge propagates into the bubble from the tip of the wire in the glass tube. Then, the discharge propagates along the bubble surface. The propagation velocity is almost independent of water conductivity and 2.7–3.6 × 105 m/s. The average maximum length of the discharge propagation decreases from approximately 8.9 to 5.4 mm with increasing water conductivity from 7 to 1000 μS/cm. Indigo carmine, a commonly used organic dye, was used as the chemical probe of the active species produced by the discharge inside the bubble. The amounts of indigo carmine decomposition with 120 min of treatment is 0.24–0.26 μmol and independent of water conductivity. Meanwhile, the energy efficiency for the indigo carmine decomposition in water decreases from 18 to 7.3 μmol/Wh with increasing water conductivity from 7 to 1000 μS/cm. The amount of hydrogen peroxide production by the treatment increases from 2.0 to 3.1 μmol with increasing the conductivity. These results show that the amount of active species consumed in loss reactions such as their recombination increases with decreasing length of discharge propagation.

Decomposition process of volatile organic compounds dissolved into water by pulsed discharge inside bubble

Decomposition process of volatile organic compound dissolved into water by discharge plasma inside bubble is investigated. The experiment is conducted on decomposition of dichloromethane (DCM). Argon or oxygen gas is injected into the water through a vertically positioned glass tube, in which high-voltage wire electrode is placed to generate plasmas at low applied voltage. The nanosecond pulsed high voltage generated by an inductive energy storage system pulsed power generator is applied to the tungsten wire to generate streamer discharge. Total organic carbon decreases and chloride ion concentration increases by the discharge treatment. To clarify the decomposition process, DCM and indigo carmine (IC) mixed solution is employed as specimen. The amount of IC decomposition decreases with increasing the DCM concentration. On the other hands, the amount of DCM decomposition is almost independent of IC concentration. These results show that DCM is quickly volatilized into the bubble, which is decomposed by hydroxyl radical produced by the discharge in gas phase inside bubble.

Demonstration of a 1 MJ XRAM Generator Supplying a Medium Caliber Railgun

The electric power supply for an electromagnetic launcher has to provide energy in the mega-joule range within an acceleration time which only lasts for milliseconds. Today’s giga-watt pulsed power generators are based on large capacitor banks and are therefore unsuitable for most mobile applications. Thus, power supply research focuses on size reduction by means of alternative technologies like inductive storage. The XRAM topology, where several inductors are charged in a series and discharged in a parallel connection, is a concept for inductive current multiplication. This technique requires simultaneous switching of closing and opening switches and was realized by using thyristors turned off by a counter-current pulse (inverse current commutation with semiconductor devices - ICCOS). At the French-German Research Institute of Saint-Louis (ISL), several aspects of this technology have been investigated and several demonstrators for different energies have been developed. Nowadays, the development of inductive pulsed power generators advances towards energy levels relevant for future applications. This paper presents the development of a 1 MJ XRAM generator which demonstrates the suitability of this technology by supplying the medium-caliber ISL railgun RAFIRA during dynamic experiments. The results of the latest experiment are reported, where the XRAM generator was charged to 842 kJ. A current of 40 kA was successfully interrupted by the ICCOS opening switches and an 80 g brush projectile was accelerated to 1120 m/s. The railgun current was switched off at the time of the projectile’s bore-exit, thus approximating a rectangular current pulse shape. Experimental results are compared to outcomes achieved with capacitor banks as railgun power supply.

Modular Toroidal Copper Coil for the Investigation of Inductive Pulsed Power Generators in the MJ-Range

Inductive pulsed power generators apply coils as powerful short time energy storage, which is an standard mean to deliver pulses of high power to loads like electromagnetic accelerators. This article deals with the design, simulation, construction, electrical characterization and a pulsed stress test of a modular toroidal coil. The coil was made from 180 D-shaped copper discs and has an approximate inductance of 1 mH ( $f > 50$ Hz) and frequency dependent resistance according to 3.88 m $\Omega$ $\cdot \sqrt{f}$ + 5 m $\Omega$ . Its height, diameter and weight is 0.4 m, 1 m and 1 ton respectively. It is designed to store more than 1 MJ of energy and was successfully tested up to 1.25 MJ. The coil satisfies our requirements for an inductive pulse power generator for EM Launch applications. Further skin effect optimizations will be considered in the future.

Review of Inductive Pulsed Power Generators for Railguns

This literature review addresses inductive pulsed power generators and their major components. Different inductive storage designs like solenoids, toroids and force-balanced coils are briefly presented and their advantages and disadvantages are mentioned. Special emphasis is given to inductive circuit topologies which have been investigated in railgun research such as the XRAM, meat grinder or pulse transformer topologies. One section deals with opening switches as they are indispensable for inductive storages and another one deals briefly with SMES for pulsed power applications. In the end, the most relevant inductor systems which were realized in respect to railgun research are summarized in a table, together with its main characteristics.

Design and Simulation of HTS Coils With a New Structure for an Inductive Pulsed Power Generator

Inductive pulsed power supplies (PPS) attract attention from several research institutions and scholars since the energy density of inductors is approximately one order of magnitude higher than that of capacitors. To effectively improve the output current of high-temperature superconductor (HTS) PPS and lower requirements for the switch, research studies have been done on STRETCH meat grinder circuit with HTS coils as an inductive module of XRAM. This paper mainly discusses the possibility of HTS coils applying to the STRETCH meat grinder as one of the fundamental research for PPS. With the characteristics of strong mechanical properties, high Ic, and low loss, HTS wire has become sufficiently available to build prototypes and practical instruments. This paper proposes a new coil winding structure that makes HTS coils applicable to the STRETCH meat grinder. Simulation results show that the transposition method can obtain a relative even current distribution in HTS parallel coils. By using the HTS magnet in the STRETCH meat grinder, maximum pulse current amplitude of 625 A can be obtained with a current multiplication factor of 5.2. Compared with the simulation results, experiments will be taken in the near future to verify the feasibility of the proposed coil structure and will be described in detail in further research work.

Influence of circuit parameter on ozone synthesis using inductive energy storage system pulsed power generator

An inductive energy storage system pulsed power generator using semiconductor opening switch (SOS) diodes was employed to drive a co-axial cylinder plasma reactor for ozone synthesis with high yield. Fast recovery diodes were used as SOS diodes in the inductive energy storage system pulsed power generator to produce short-pulse high-voltage with high-repetition rate. The high-voltage pulse was applied to a 1 mm diameter center wire electrode in the reactor. The copper cylinder of 19 mm inner diameter was used as outer electrode and was connected to a ground. Oxygen and dry air were used as source gases and were injected into the plasma reactor with 2 L/min. gas flow rate. The synthesized ozone concentration increased in proportion to pulsed voltages repetition rate under oxygen gas condition. The ozone yield of about 230 g/kWh was obtained in oxygen gas and was independent of circuit parameter. The ozone yield decreased from 230 to 100 g/kWh by changing the source gas from oxygen to dry air. The ozone yield depended on circuit parameters such as capacitance of the primary energy storage capacitor and inductance of the secondary energy storage inductor under dry air condition.

誘導性パルスパワー電源を用いたオゾン生成効率のパルス幅依存性

Nanosecond pulse voltages of several pulse widths were applied to a cylindrical plasma reactor for ozone synthesis with high energy yield. Nanoseconds pulse voltages were produced by inductive energy storage system pulsed power generators using semiconductor opening switch (SOS) diodes. First recovery diodes were used as SOS diodes in the inductive energy storage system to produce short-pulsed high voltage with high-repetition rate. The short pulse voltage of 9.5 ns width and 33 kV peak voltage was produced at charging voltage of 15 kV and was applied to a 1 mm diameter center wire electrode in the plasma reactor. The copper cylinder of 19 mm inner diameter was used as outer electrode and was connected to a ground. The ozone yield of 271 g/kWh was obtained using the 9.5 ns width pulse voltage at synthesized 412 ppm of ozone concentration. The yield 271 g/kWh was more than twice as much as the yield 114 g/kWh at 401 ppm using a 60 ns pulse voltage.

Energy Efficiency of Inductive Energy Storage System Pulsed Power Generator Using Fast Recovery Diode

Characteristics of inductive energy storage system pulsed power generator with semiconductor opening switch (SOS) diodes are investigated with focusing on an energy transfer efficiency from the generator to the resistive load. Fast recovery diodes VMI K100UF were used as SOS and were connected in series and/or in parallel to realize a large current and a high output voltage. The output voltage increases with increasing circuit inductance L and/or primary capacitor capacitance C. The reverse pumping time also increases with LC value and is saturated to 100 ns at LC=50×10-15 HF. The pulse width of the output voltage increases gradually with increasing value of the LC multiplication. The energy transfer efficiency of the generator to the resistive load has a maximum value of 71% at C=4nF and L=12.6μH when the load resistance is 122 Ω. This value is almost two times larger than 56 Ω of the surge impedance Zs=√L/C and much smaller than impedance of the SOS diodes after interrupting the circuit current. The maximum energy transfer efficiency decreases from 71 to 32% with decreasing LC value from 50×10-15 to 1.2×10-15 HF.

Dependence of Initial Oxygen Concentration on Ozone Yield Using Inductive Energy Storage System Pulsed Power Generator

Dependence of initial oxygen concentration on ozone yield using streamer discharge reactor driven by an inductive energy storage system pulsed power generator is described in this paper. Fast recovery type diodes were employed as semiconductor opening switch to interrupt a circuit current within 100 ns. This rapid current change produced high-voltage short pulse between a secondary energy storage inductor. The repetitive high-voltage short pulse was applied to a 1 mm diameter center wire electrode placed in a cylindrical pulse corona reactor. The streamer discharge successfully occurred between the center wire electrode and an outer cylinder ground electrode of 2 cm inner diameter. The ozone was produced with the streamer discharge and increased with increasing pulse repetition rate. The ozone yield changed in proportion to initial oxygen concentration contained in the injected gas mixture at 800 ns forward pumping time of the current. However, the decrease of the ozone yield by decreasing oxygen concentration in the gas mixture at 180 ns forward pumping time of the current was lower than the decrease at 800 ns forward pumping time of the current. This dependence of the initial oxygen concentration on ozone yield at 180 ns forward pumping time is similar to that of dielectric barrier discharge reactor.

Production of an Atmospheric‐Pressure Glow Discharge Using an Inductive Energy Storage Pulsed Power Generator

AbstractSummary: An atmospheric‐pressure glow discharge has been generated using an inductive energy storage pulsed power generator. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges simultaneously at all tips of a needle‐array electrode in nitrogen. The large number of streamer discharges prevent glow‐to‐arc transitions caused by inhomogeneous thermalization. SOS diodes are used as an opening switch to shorten the rise time. Circuit parameters such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor are determined by experimental results using dummy resistive loads. The results show that circuit parameters adequate for producing atmospheric glow discharges are different from those for producing corona discharges. The energy transfer efficiency of the pulsed power generator has a maximum value of 75% at 193 Ω dummy load resistance. Voltage‐current characteristics of the glow discharge show two regions: constant voltage (normal glow) and an increasing voltage with discharge current (abnormal glow). The glow current is drastically decreased by eliminating the SOS diodes, in which case the charging voltage is directly applied to the electrode. Spatial‐ and time‐averaged electron densities in a positive column are estimated from calculations based on nitrogen swarm data. The electron density is estimated to be 1.8 × 1011 cm−3, which is much larger than 9.7 × 109 cm−3 in the case without the SOS diodes.Photographs of atmospheric pressure nitrogen glow discharge generated using a needle‐array electrode at a 1.0 cm gap length.imagePhotographs of atmospheric pressure nitrogen glow discharge generated using a needle‐array electrode at a 1.0 cm gap length.

High Voltage Generation from Inductive Pulsed Power Generator Using a Marx Circuit and an Exploding Wire

High voltage output up to 800 kV with voltage risetimes of 15 to 40 ns is successfully generated by a compact pulsed power generator (60×120×150 cm3) with an inductive energy storage system. This pulsed power generator consists of a Marx circuit, an inductor, and a thin and long exploding copper wire. The circuit parameters including an exploding wire are optimized for a high voltage generation, avoiding a re-strike of the wire. It is shown that the ratio of the energy in a storage inductor at the beginning of wire vaporization on the energy consumed during wire vaporization is essential in the production of a high voltage.

Inhomogeneity of currents in a wire array during its exploding phase

The current in a wire array during its exploding phase has been studied. The wire array consisting of many thin wires is used as a plasma source in a z-pinch X-ray radiation system. The current distribution in the exploding wire array plays an important role in producing an initial symmetrical plasma. In the present experiment, four tungsten wires of 0.1 mm in diameter were exploded in a vacuum. The experiment was carried out with an inductive voltage adder pulsed power generator providing a current of 160 kA at quarter period of 1.8 /spl mu/s The currents through and the voltage across the wires were measured simultaneously. It was found that the currents in the wires were inhomogeneous, especially after the wires became plasma. Once the currents became inhomogeneous, the inhomogeneity remained throughout the discharge. It was also studied how the dimensions of the wires affected the homogeneity of the currents. Wires of different lengths or different cross sectional areas resulted in strong inhomogeneities of the currents. The wires with shorter length or smaller cross-sectional area became plasmas earlier than other wires. Thus, the resistances of the wires were not equal. These differences in the resistance caused the inhomogeneity of the currents.

Reduction of the source size of gas-puff z-pinch plasmas using an inductive pulsed power system

A small scale inductive pulsed power (IPP) generator with copper wire fuses as an opening switch has been applied to an argon gas-puff z-pinch plasma which can be used as a point source for x-ray lithography. The IPP generator with fuses supplies a driving current of 60 kA in 400 ns to the z-pinch plasma. Without fuses, the generator serves as a conventional fast bank (FB) system which supplies z-pinch current of 60 kA in 4.5 μs. Characteristics of the z-pinch implosions in IPP and FB systems are investigated and compared. The result obtained shows that the intensity of soft x rays emitted from hot spots in both systems is decreased gradually with longer delay time, which is the time difference between energizing a gas-puff actuator and a primary current trigger. Dual axis pinhole imagery shows that the hot spot size is 0.8 mm in diameter in both systems. However, the average radial displacement of hot spots is 0.9 mm in the FB system and it is reduced to 0.4 mm in the IPP system. Optical framing camera images have confirmed that the radial distribution of hot spots is due to kink instability. The framing images also show that the imploding plasma in the FB system which has a pinch size of 2.2 mm in diameter can be further compressed to 1.3 mm. The IPP system can suppress the kink instability of pinch plasma and increases plasma column uniformity along the z axis. This suggests that the IPP system can improve the stability of the pinched plasma so as to minimize the end-on source size for x-ray lithography applications.

Gas-Puff Z-Pinch Plasmas Driven by Inductive Energy Storage Pulsed Power Generator

An inductive energy storage pulsed power generator is used as a power source of gas-puff z-pinch plasmas to investigate the effect of the steepened current rise on the intensity of soft X-rays and the spatial reproducibility of the hot spots. Furthermore, two kinds of electrodes, which are solid and mesh type, are used to investigate the influence of the incident gas distribution on the z-pinch plasmas. In the case of the solid electrode, the axial symmetry of the plasma column during pinching and the spatial reproducibility of the hot spots is improved not only by the steepened current rise but also the induced pulsed voltage. On the other hand, the improvement in the plasma column and the reproducibility due to the inductive pulsed power generator is unclear in the case of mesh electrode. In this experiment, the uniform gas distribution has priority over the current rise time and the induced pulsed voltage.

ヒューズを用いた誘導型パルスパワー電源の高繰り返し化

ヒューズを用いた誘導型パルスパワー電源の高繰り返し化

誘導型パルスパワー電源を用いたNO<sub>x</sub>除去

The discharge using pulse power with a short pulse width can produce a lot of electrons with high energy. This method has a possibility to remove poisonous gases with low energy consumption. In this paper, the inductive energy storage pulsed power generator, which can generate narrow and high voltage pulses (FWHM less than 100ns, output voltage of about 100kV), is used to remove NOx gas. It is found from spectrum measurement that this generator can produce high energy electrons, more than 10eV, in the discharge region at atmospherics pressure. The mixed gases of NO and N2 are used as a trial gas. The NO removal ratio of about 95% is achieved without producing NO2. These chemical phenomena are approximately explained by solving rate equations.

Parametric scaling study of a magnetically insulated thermionic vacuum switch

A parametric scaling study is performed on MINOS (magnetically insulated opening switch), a novel fast (/spl sim/100 ns) high-power opening switch concept based on a magnetically insulated thermionic vacuum diode. Principal scaling parameters are the switch dimensions, voltage, current, applied magnetic field, and switching time. The scaling range of interest covers voltages up to 100 kV and currents of several kA. Fundamental scaling properties are derived from models of space-charge flow and magnetic cutoff. The scaling is completed with empirical results from the experimental MX-1 switch operated in an inductive storage pulsed power generator. Results are presented in diagrams showing voltage, current, power, and efficiency relationships and their limitations. The scaling is illustrated by the design of a megawatt average power opening switch for pulsed power applications. Trade-offs in the engineering of this type of switch are discussed.

誘導型パルスパワー発生装置におけるヒューズ冷却水抵抗を考慮した出力電圧上昇法

誘導型パルスパワー発生装置におけるヒューズ冷却水抵抗を考慮した出力電圧上昇法

Plasma erosion opening switch using laser-produced plasma

In order to construct a practical inductive energy storage pulsed power generator, an opening switch which can repeatedly conduct a large current and then rapidly interrupt this current is necessary. Though the plasma erosion opening switch (PEOS) can interrupt a large current rapidly, the effective number of switch operations is limited because of the decrease of the carbon sprayed on the insulator with each shot. A PEOS using a laser-produced plasma, which can possibly be operated for hundreds of thousands of shots without maintenance, is proposed, and its operation as an opening switch is confirmed experimentally.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>