Compact Pulsed Power Sources Research Articles

A portable flash x-ray generator powered by an explosive driven ferroelectric generator.

In order to develop a portable flash x-ray source, a compact explosive pulsed power source based on an explosive-driven ferroelectric generator (EDFEG) is investigated numerically and experimentally in this paper. The EDFEG is used as a primary power supply to charge a pulse capacitor, and then the capacitor outputs high current through an inductor and an electrical exploding opening switch (EEOS). Finally, a high voltage fast pulse is generated on a diode, which generates x rays. A circuit model was built to analyze the performance of this compact pulsed power source. A portable flash x-ray generator prototype was constructed in our laboratory. The typical experimental results illustrated that after metal wires of the EEOS exploded, a high-voltage fast pulse with a peak value of 180kV, a rise time of 2.8ns, and a pulse width of 30ns was generated on the x-ray diode. Meanwhile, an x-ray pulse with a pulse width of 19ns, a focus of about 1mm, and a dose of 100 mR at 15cm was obtained.

40 year anniversary of the RADAN systems – compact pulsed power sources for various investigations

This article includes a brief overview of the compact RADAN-series subgigawatt pulsed voltage sources and describes their capabilities in various electrophysical researches. We present the results obtained in the experiments at nano- and subnanosecond time scales on the formation of the voltage pulses with a special shape, electron beams emission in air gaps and by the cold cathodes in vacuum, as well as generation of electromagnetic radiation. Particular attention is paid to the promising application of the RADAN systems.

Effect of Temperature on Breakdown Characteristics of Propylene Carbonate Under Microsecond Pulse

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.

Experimental Study on Microsecond Pulse Breakdown Characteristics of Propylene Carbonate Modified by Al Nanoparticles

Liquid dielectrics are very important and useful in pulsed power systems, due to their unique characteristics of large energy storage densities, ease of circulation, and low cost. They are applicable to power systems which have complex geometries. Propylene carbonate (PC), as a kind of polar liquids, shows bright prospects in compact pulsed power sources because of its great permittivity, high electrical breakdown stress, and broad environmental operating ability. In this paper, a dielectric breakdown experiments were conducted with a microsecond pulsed power source and a test cell with spherical electrodes. The breakdown properties of PC and PC-based nanofluids (NFs) were investigated by changing the increasing rate of the charging voltage. Besides, the influence of nanoparticles on the dielectric breakdown characteristics of PC was analyzed. Results show that with a slow increasing rate of the charging voltage, the introduction of nanoparticles greatly improved the breakdown stability of PC; while with a fast increasing rate of the charging voltage, NFs exhibited much larger mean breakdown voltage. We also demonstrated that the improvement effect of NFs' dielectric performance could be explained by the energy band theory very well.

Abnormal Polarity Effects of Streamer Discharge in Propylene Carbonate under Microsecond Pulses**Supported by the National Natural Science Foundation of China under Grant No 51677190, and the Hunan Provincial Natural Science Foundation of China under Grant No 2017JJ1005.

Propylene carbonate (PC) has a great potential to be used as an energy storage medium in the compact pulsed power sources due to its high dielectric constant and large resistivity. We investigate both the positive and negative breakdown characteristics of PC. The streamer patterns are obtained by ultra-high-speed cameras. The experimental results show that the positive breakdown voltage of PC is about 135% higher than the negative one, which is abnormal compared with the common liquid. The shape of the positive streamer is filamentary and branchy, while the negative streamer is tree-like and less branched. According to these experimental results, a charge layer structure model at the interface between the metal electrode and liquid is presented. It is suggested that the abnormal polarity effect basically arises from the electric field strength difference in the interface between both electrodes and PC. What is more, the recombination radiation and photoionization also play an important role in the whole discharge process.

Enhanced dielectric breakdown performances of propylene carbonate modified by nano-particles under microsecond pulses

Propylene carbonate shows appealing prospects as an energy storage medium in the compact pulsed power sources because of its large permittivity, high dielectric strength, and broad operating temperature range. In this paper, TiO2 nano-particles coated with γ-aminopropyltriethoxylsilane coupling agent are homogeneously dispersed into propylene carbonate and these nano-fluids (NFs) exhibit substantially larger breakdown voltages than those of pure propylene carbonate. It is proposed that interfaces between nano-fillers and propylene carbonate matrix may provide myriad trap sites for charge carriers. The charge carriers can be easily captured at the interfaces between NFs and the electrode, resulting in an increased barrier height and suppressed charge carriers injection, and in the bulk of NFs, the charge carriers' mean free path can be greatly shortened by the scattering effect. As a result, in order for charge carriers acquiring enough energy to generate a region of low density (the bubble) and initiate breakdown in NFs, much higher applied field is needed.

Effect of BaTiO3 nano-particles on breakdown performance of propylene carbonate.

As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 10(9) Ω m, and low freezing temperature (-49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

Microwave emission from an AXIAL-Virtual Cathode Oscillator driven by a compact pulsed power source

For the generation of microwaves, Electron beam devices operating in vacuum are most widely used. For pulsed and high power microwave generation, Virtual cathode oscillators (VIRCATORs) are said to be simple in operation and construction. They are generally driven by a pulsed power source which gives high input powers to the Vircator connected as load. Vircator, depending upon its efficiency, converts the electrical input power to the microwave power. We are presenting the results of an axial Vircator operating in 2×10−4 mbar vacuum and is driven by a compact pulsed power source. The energy source and pulse compression is realized in very user friendly approach to run the system. The radiating system presently runs at relatively low powers but has the scope of reaching to high power by a logical improvement. A study of effect of collapsing diode impedance, of the vacuum field emission diode of the Vircator, on the microwave emission is presented in the paper. We are also presenting the microwave emission measurement conducted in the given system. Effect of vacuum is also studied to the extent of present experimental limits.

紧凑型X-pinch装置探头标定

紧凑型X-pinch装置探头标定

紧凑型爆炸脉冲电源

紧凑型爆炸脉冲电源

The science and technology of electric launch

In addition to its continued research focus on the fundamental physics and engineering challenges in developing electric launchers for specific military weapons and applications, the US is exploring the technology for a number of exciting military and civilian launch applications. These efforts include compact pulsed power sources, power conditioning, armatures, integrated launch packages (armature/sabot/projectile), electromagnetic and electrothermochemical launchers, advanced materials and diagnostics, technology and systems integration, and modeling and simulation. Important advances have been achieved in the understanding and technological applications of electric launchers. These are discussed in the context of specific applications to future ground combat vehicles, the launch of aircraft from carriers and the launch of spacecraft.

The science and technology of electric launch: a US perspective

The US continues its focused research on the fundamental physics and engineering challenges in developing electric launchers for specific military applications. These efforts include compact pulsed power sources, power conditioning, armatures, integrated (armature/sabot/projectile) launch packages, electromagnetic and electrothermochemical launchers, advanced materials and diagnostics and technology and systems integration modeling and simulation. Important advances have been achieved in the understanding and technological applications of electric launchers. These are discussed in the context of specific applications to future ground combat vehicles.

Inductive energy technology for pulsed intense X-ray sources

Defense Special Weapons Agency (DSWA) has been developing inductive energy storage technology (IES) for applications requiring short pulses of X-rays with peak radiation power in the terawatt range. The purpose of this program is to develop more compact and affordable pulsed power sources and power flow technology needed for efficient conversion of the electromagnetic energy into radiation. Performance characteristics of present generators and power conditioning for future pulsed power IES designs are discussed. Because of the complex physics governing the interaction among the power conditioning, power flow, and load performance, DSWA supports studies of power flow to the load that converts the electromagnetic energy to X-ray radiation. Experiments performed at high power levels and resulting improvements in performance are reported.