Pulsed Power

Abstract-Many approaches to system-level modeling of lithium-ion battery cells subjected to nominal discharge rates of 1 to 100 C do not adequately apply to ultra-high pulsed power, low duty cycle applications operating at rates of 400 to 1500 C, such as demanded by electromagnetic launchers. These approaches use several empirical operating voltage vs. battery capacity data curves over the full operating voltage range at discharge rates close to the rates at which the model is expected to be accurate. To obtain this same data at ultra-high rates would risk thermal runaway, fire, and loss of the cell. An alternate method is developed capable of modeling high rate as well as low and high duty-cycle discharges, while requiring experimental data that is of low risk for high rate cells. The method applies to low discharge rates as well, but verification is not presented here. In this method, the operating voltage vs. capacity data curves are replaced by one open-circuit voltage vs. energy consumed data curve and an equivalent series resistance vs. temperature and open-circuit voltage data surface. The method is then implemented using the Modelica modeling language to accurately model a SAFT VL5U cell operating over a temperature range of 10 to 70 degrees Celsius, with thermal properties of the cell being gathered empirically.

The electrical characteristics and design features of a low inductance, compact, 500 kV, 500 J, 10 Hz repetition rate, Marx generator are discussed. While benefiting from the large energy density of mica capacitors, 4 mica capacitors were utilized in parallel per stage, keeping the parasitic inductance per stage low. Including the sparkgap switches, a stage inductance of 55 nH was measured, which translates with 100 nF capacitance per stage to ~ 18.5 Ω characteristic Marx impedance. Using solely inductors, ~ 1 mH each, as charging elements instead of resistors enabled charging the Marx within less than 100 ms with little charging losses. The pulse width of the Marx into a matched resistive load is about 200 ns with 50 ns rise-time. Repetitive HPM generation with the Marx directly driving a small Vircator has been verified. The Marx is fitted into a tube with 30 cm diameter and a total length of 0.7 m. We discuss the Marx operation at up to 21 kV charging voltage per stage, with repetition rates of up to 10 Hz in burst mode primarily into resistive loads. A lumped circuit description of the Marx is also given, closely matching the experimental results.

Air-core Tesla transformer combined with semiconductor devices can generate repetitive high-voltage pulses effectively. Air-core Tesla transformer of spiral type is suitable for repetitive operation since its primary voltage is relatively low. Based on the double resonance circuit of air-core Tesla transformer, the expressions of secondary voltage, primary current, and the maximum rise-rate of primary current are deduced. The effects of tuning characteristic on the output voltage and energy efficiency are simulated, and further verified by experiments. An air-core Tesla transformer prototype of spiral type is developed. To achieve repetitive operation, a resonant charging and discharging circuit based on air-core Tesla transformer is designed. The repetitive system based on this prototype can generate microsecond pulses with an average peak voltage of-140 kV at 300 Hz repetition rate. In repetitive mode, the tuning ratio is recommended to range in 1.0-2.0 to achieve high energy efficiency. The output voltage could be higher by increasing the charging voltage or tuning ratio.

High-voltage transformers can be built with coaxial transmission lines. This paper describes a transformer design that uses the coaxial screen as primary winding and the inner conductor as secondary. An advantage of transmission line transformers is that the insulation problem is solved and the construction can be kept simple; the coupling between the primary and secondary coils is high even though the transformer uses an air core. The air core brings another advantage: the capacity to store large quantities of magnetic energy. The combination of a high coupling factor and large energy storage capacity makes this transformer ideal for charging high-voltage capacitors fast. The winding type for the transformer is alternating Archimedean spirals. Here, we present a magnetic field analysis of the transformer's primary, secondary, and mutual inductance using a finite-element solver. We compare the measured magnetic flux density versus the calculated value. The step-up winding ratio of the transformer influences the coupling factor marginally if the construction has an even number of spiral layers for each set of windings. However, the result from the finite-element solver predicts a drop in coupling factor if the step-up transformer construction has an odd number of spiral layers. The copper conductors used in the transformer resemble isotropic copper pipes.

Beer was inoculated with Saccharomyces cerevisiae, Lactobacillus plantarum, Bacillus subtilis, and Salmonella Choleraesuis prior to pulsed electric fields (PEF) treatment at different levels of inlet temperature (<= 4 °C pre-cooled and <= 14.7 °C ambient), alcohol (3.5 and 0.5%). and carbonation (degassed and carbonated). PEF was applied at the electric field strengths of 35-45, 35, and 35-40 kV/cm, with respective treatment times of 402-2296, 765, and 612-765 micro-s, and corresponding energy densities of 530-2339, 707. and 707-739 kJ/l to investigate its germicidal efficacy with regard to beer processing temperature (PT). alcohol content, and carbonation. In pre-cooled and ambient-temperature PEF-processed beer, reductions in microbial count of 4.0 (PT <= 40.7 °C) and up to 8.4 log(10) (PT <= 68.7 °C) were achieved, respectively (P<0.05); inactivation using ambient-temperature PEF processing was comparable to thermal pasteurization applied at 76 °C for 30 s (up to 8.3 log(10) reduction in count (P >= 0.05)). Electric field strength and treatment time were fitted using a response surface model indicating higher PEF resistances of B. subtilis and S. Choleraesuis in beer (P<0.05) while energy density and processing temperature gradients fitted for these microorganisms could allow optimization of PEF beer treatment. No difference in microbial inactivation due to alcohol and carbonation levels was obtained, except for higher reductions (P<0.05) of L. plantarum in 3.5% beer and of S. Choleraesuis in carbonated beer.

A method for implementing collision welding at moderate to small length scales has been developed. The flyer, instead of being driven by chemical explosives (explosive welding) or magnetic forces (magnetic pulse welding), is launched toward the target by the pressure created from the electrically driven rapid vaporization of a thin metallic conductor. Mechanical impulse is developed from 0.0762 mm thick aluminum foils, which are vaporized using capacitor bank discharge with nominal charging voltage of 5.5 kV and peak current on the order of 100 kA delivered with rise times of about 12 μs. Welding couples of copper–titanium, copper–steel, aluminum–copper, aluminum–magnesium and titanium–steel have been successfully created with the same input parameters such as foil geometry, input energy and standoff distance. Instrumented peel tests, lap shear tests and optical and scanning electron microscopy reveal a wide spectrum of both strengths and interface structures. Copper–titanium and copper–steel welds are strong and have characteristic wavy interfaces with little intermetallics or void formation. The other combinations are seen to have brittle interfaces with intermetallics and defects, with the collision welding parameters used presently. For the titanium–steel system, a thin nickel interlayer is introduced and all the layers are welded in a single experiment. Peel strength of the weld was observed to be quadrupled. Peak velocities of up to 560 m/s were obtained for titanium flyer sheets.

— A 700-kA gas switch with graphite electrodes for pulsed power supply module has been developed. This paper describes the design, construction, and testing of the high-current gas switch and its trigger system. The two-electrode gas switch is selected, which suffers high peak and fast rise time currents. The trigger generator based on resonant charging of a pulse transformer is constructed to trigger the gas spark. An electrodynamic force model of switch electrodes is established. The electrodynamic force of connecting wires is also calculated. By comparison of the mechanical strengths of polyformaldehyde, epoxy, and fiber-reinforced plastic (FRP) rods, where FRP rods are selected as switch rods, the experimental results show that the mechanical strength of the switch increases by 200%. Extensive electric testing has proven the operating parameters of the switch and its trigger system. The experimental results show that the measured discharge current waveform is demonstrated to be over a 700-kA peak current and a 500-µs pulsewidth. The transfer charge per shot is more than 500 C. Index Terms— Electrodynamic force, gas switch, graphite electrodes, pulse transformer, pulsed power supply (PPS), trigger system.

This paper details the testing of a commercially available gate turn-off thyristor (GTO) for application in inductivestore 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.

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A pulsed-power generator using inductive adder technology is proposed for the case of a discharge gap. The merit of this generator is to merge the pulsed-voltage and pulsed-current adders via the dual secondary windings with special circuit. For the nonlinear impedance in any discharge gap, the standalone voltage-pulse and current-pulse can be outputted successively by this generator. The proposed generator is especially useful for the common resolution of implementing pulse discharge at less cost. As an application example, a compact trigger prototype was developed to compatibly use in the gas-insulated and vacuum switches. Experiments achieved good results that the triggered switches showed stable performance and long life. If the basic circuit of this proposed generator is regarded as a pulsed-generating unit, a certain number of such units connected in parallel can be expected to form a general device with generating greater breakdown-voltage and sustained-current pulses for discharge gaps.

Growing interest in battery performance and cost reduction for hybrid and electric vehicles has restimulated interest in the United States in the use of high-power batteries as a potential source of pulsed power. Recent progress in high-powerdensity lithium-ion batteries and high-power semiconducting switches has suggested that a battery-inductor-based pulsed power system could become a viable option to pulsed alternators for electromagnetic (EM) launchers and other pulsed loads in the megajoule range. Approximate system sizing and a parametric study are presented, showing the effects of battery and inductor parameters on the overall efficiency and system size for a conceptual 2-MJ muzzle energy EM launch system utilizing the STRETCH circuit topology. The results show the relationship between potential increases in future component performance on overall system size reduction and efficiency.

Little research is done in field of Linear Reluctance Accelerators (coilguns) owing to their notorious inefficiency, difficulties in modeling their behavior, as well as little interest in them in lieu of seemingly better alternatives such as railguns, has stifled much of the advancement of the field. Here, a study and re-examination of Dr. William Slades’s 2005 paper “A Simple Unified Physical Model for a Reluctance Accelerator” was performed to continue further research suggestions mentioned within the paper. In our experimentation, the Slade accelerator was rebuilt using high saturation armatures, thin walled barrels, and a more powerful capacitor bank. We carried out our experiment using armatures of vanadium permendur, electrical iron, and 12L14 steel. Tektronix oscilloscope interface software was implemented to measure coil voltage, current, and armature exit velocities, and compared our results to Slade’s results and modeling equations. Results compiled establish a reasonable set of guidelines for designing these devices to achieve maximum efficiency.

A compact Pulsed Power system, which is reported in this paper, is designed for conducting Relativistic-Electron-Beam characterization experiments in the spacecharge limited flow. The experiments are conducted for various cathode materials like graphite and velvet and also for various anode transparencies and geometries by making them of thin foil as well as of mesh. The reported Pulsed power system is made very compact as well as portable by using solid dielectric pulsed forming line. The system consists of a tesla transformer, which is of helical secondary and cylindrical-sheet single-turn primary. Tesla charges a pulse forming line made of cascade of 50ohm transmission lines, which are of high wattage as well as high voltage ratings under pulsed operation. The net impedance of this cable cascade is such that it is matched for a designed diode as load. The impedance of designed diode is 13.5 ohm and is designed to operate at 250kV and hence almost 18.5kA current levels for 100ns pulse duration. Related design details as well as all the diagnostics, used for measurement of current, voltage and other parameters of interest, are reported and finally the results are compiled in this paper.

Abstract—In compact pulsed power conditioning systems,
a high electric energy density of its capacitors is of interest.
Commercially available capacitors are normally designed for long
storage time and long lifetime. The performance of capacitors in
terms of energy density capability can be improved by overstress
or overcharge, that is, charging to a significantly higher energy
density than specified. This paper explores the limits of overstressing
commercially available capacitors for short time spans.
The selected capacitors have a nominal dc voltage in the range of
2.5–10 kV and a capacitance in the range of 0.015–0.12 F. Two
different storage times have been considered: 2 s and 20 ms.
A high-voltage test setup was constructed. For the short storage
time, it was possible to overstress the energy density as compared
to nominal values with a factor of 26 and for the long storage
time with a factor of 14 for the best performing capacitor. Other
capacitors behaved significantly poorer, especially for the long
storage time.

This paper describes an induction voltage adder (IVA) being designed by Titan Pulse Sciences Division (TPSD) for AWE Aldermaston, UK. This IVA will be used to power the radiography sources in AWE's planned three-axis Hydrodynamic Research Facility (HRF). TPSD will provide the IVAs and AWE will provide the radiographic diodes. The full IVA will in its initial configuration deliver a 14 MV, 110 kA, 50-60 ns pulse first to a large area diode and then to a developmental radiographic diode. The HRF IVA has been designed utilizing two-conductor water dielectric pulse forming lines (pfls) with laser triggered gas switches and can be reconfigured to power a range of radiographic diodes with peak powers from 1.5 to 3.9 TW and peak voltages from 8 to 16.8 MV. LSP simulations of the vacuum region aided by parapotential theory have explored and optimized the coupling of the different IVA configurations to various diodes.

This paper presents the chest worn pulse
oximeter with integrated universal software radio peripheral
(USRP) with the global positioning systems (GPS) disciplined
clock transceiver from the National Instruments. It
illustrates the respiratory cardio monitoring using the
flexible reflective pulse oximeter with ECG. The gathered
cardio respiratory data assessed by the microcontroller and
the output is sent through to the remote monitor display by
means of wireless system. The device also incorporates an
early warning feature to alert then both the user and also the
person being monitored. The GPS device is included for
tracking and to determine the present location of the client
in case of an emergency situation. The output is then
transmitted and also displayed to a web based server via
radio frequency (RF). A complete hardware prototype model
is designed, developed, tested, and implemented thus
validated the proposed scheme. The statistical assessment
method is then integrated where the parameters gathered
are evaluated.

Electro-magnetic acoustic transducers (EMATs) are intended as non-contact and non-destructive ultrasound transducers for metallic material. The transmitted intensities from EMATS are modest, particularly at notable lift off distances. Some time ago a concept for a ''coil only EMAT'' was presented, without static magnetic field. In this contribution, such compact ''coil only EMATs'' with effective areas of 1-5 cm 2 were driven to excessive power levels at MHz frequencies, using pulsed power technologies. RF induction currents of 10 kA and tens of Megawatts are applied. With increasing power the electroacoustic conversion efficiency also increases. The total effect is of second order or quadratic, therefore non-linear and progressive, and yields strong ultrasound signals up to kW/cm 2 at MHz frequencies in the metal. Even at considerable lift off distances (cm) the ultrasound can be readily detected. Test materials are aluminum, ferromagnetic steel and stainless steel (non-ferromagnetic). Thereby, most metal types are represented. The technique is compared experimentally with other non-contact methods: laser pulse induced ultrasound and spark induced ultrasound, both damaging to the test object's surface. At small lift off distances, the intensity from this EMAT concept clearly outperforms the laser pulses or heavy spark impacts.

A high-voltage transmission-line pulse transformer has been constructed based on modern cable technology. The transformer has been successfully tested for output powers of 0.5 GW. The high-voltage cable is equipped with a resistive layer (semicon) on the inner conductor and on the inside of the outer conductor. Semicon cables are commonly used in high-voltage transmission of electrical power. The pulse transformer was built using a coaxial semicon cable, with the inner conductor used as secondary winding and the screen as primary winding. Such a transmission-line transformer works in the same way as an ordinary transformer. The input is transformed to the desired output using a step-up or a step-down configuration.

A prototype blasting power system suitable for excavation on the moon's surface was constructed and tested in the Space Research Institute (SRI) facilities. Such a system incorporates the use of electrically powered plasma blasting via a blasting probe and comprises a capacitor bank which is charged with a power supply at a relatively low rate (e.g. a few seconds) and then discharged at a very high rate (power pulse of tens of microseconds), generating a shock wave on a sample solid substance causing its fracture. After successfully testing the blasting power system and blasting probes, breaking specimens with masses of up to 850kg, 2-D and 3-D numerical simulations were carried out in order to correlate the experimental data of several samples of concrete cylinders. It is possible with a non-linear hydro-code numerical approach to simulate the rapid discharge into high peak power transient loads which eventually break the specimens.

A prototype blasting power system suitable for excavation on the moon's surface was constructed and tested in the Space Research Institute (SRI) facilities. Such a system incorporates the use of electrically powered plasma blasting via a blasting probe and comprises a capacitor bank which is charged with a power supply at a relatively low rate (e.g. a few seconds) and then discharged at a very high rate (power pulse of tens of microseconds), generating a shock wave on a sample solid substance causing its fracture. After successfully testing the blasting power system and blasting probes, breaking specimens with masses of up to 850kg, 2-D and 3-D numerical simulations were carried out in order to correlate the experimental data of several samples of concrete cylinders. It is possible with a non-linear hydro-code numerical approach to simulate the rapid discharge into high peak power transient loads which eventually break the specimens.

A repetitive inductive 700-MW high-voltage pulse generator that delivers a 150-ns square pulse with 20-ns rise time at 150 kV has been constructed. The pulse generator has a 1:10 air core transformer connected to a 25-Ω pulse forming line (PFL). The transformer and the PFL are both constructed using highvoltage cables. The closing switch of the PFL is a spark gap that is in a water tank together with the cable endings of the PFL and transformer. The electric field at the cable endings is refractively graded by the high permittivity of the surrounding water. The PFL is charged in 2.5 µs to 170 kV, and the electric field in the closing switch of the PFL reaches 33 kV/mm until the threshold voltage is exceeded. The efficiency of the pulse generator is 40%. The authors believe that this concept can be up-scaled to a 25-GW generator operating at 500 kV. An electric circuit simulation of a 25-GW pulse generator and an electrostatic simulation for a refractive cable ending are presented.

More and more attention has been attached to atmospheric-pressure air diffuse plasma due to its enormous potential applications. In this paper, we designed a large-scale, cylindrical diffuse-plasma chamber using wire electrodes and a repetitive nanosecond pulse generator. The plasma chamber can be completely exposed in the open air without any barrier dielectric, and the length of cylindrical plasma chamber was extensible. Using optical and electrical measurements, we investigated the effects of electrode distance, electrode length, pulse repetition frequency, and electrode angle on the uniformity of discharge space. Four discharge regions were distinguished based on different spectral characteristics. Additionally, it was found that the discharge uniformity was improved as the electrode distance decreases, but remained almost constant with the variations of electrode length and pulse repetition frequency. Both of the plasma uniformity and the power density increased significantly as the electrode angle reduced.

In Electromagnetic Forming (EMF) process a sheet metal is situated close enough to a working
coil. By discharging the initiallycharged capacitor bank through the coil the workpiece is repelled.
This repulsion force originates from the interaction of two magnetic fields; consequently sheet
metal forming can be achieved when the workpiece strikes the die.The output of an EMF system
strongly depends on the characteristics of the workpiece and electrical parameters. Displacement
of the workpiece influences the behavior of the system and the frequency of the applied current
affects the performance of the system. Geometrical characteristics of the workpiece which
determine the mass and effective area of the workpiece have also considerable effect. The
objective of this paper is to study the effect of these parameters on the output of an EMF system.
Simulations based on Finite Element Method (FEM) are used to study the (EMF) process and
investigate the performance of the system by changing effective parameters. Based on carried
out simulations the best configuration of a sheet metal forming system is suggested, which
enhances the efficiency of the system and the desired output is achievable.

In this communication a tabletop version of medium energy Plasma Focus is presented. It was designed for xray and neutron based applications, has a 5.6 µF bank formed by 8 capacitors, operates at 30 kV, delivers 250 kA in a quarter-period of 1.3 µs, and produces 3 10 7 neutrons per pulse at a repetition rate of 1 Hz. The hard xray output of this device is used for introspective imaging of metallic pieces, whereas the neutron yield is used for substance interrogation. A simplified model for the design engineering of this device is discussed, providing both the expected neutron yield and the x-ray characteristic energy. The hard x-ray output characteristics are evaluated from the acceleration voltage induced in the pinch, which is around 100 kV. Experiments conducted to validate the model are presented, showing a good agreement between the theoretical results and the experimental data.

The fast pulsed electric discharge current drives all physical processes in the plasma focus device; in turn all physical processes in the focus affect the current waveform. Thus the discharge current waveform is the most important indicator of plasma focus performance. This underlies the importance of properly measuring, processing and interpreting the discharge current waveform. This paper reports the measurement of fast pulsed discharge current by the Rogowski coil, in two different modes: the current transformer, “I” mode, and current derivative, “Idot” mode. The processing and interpretation of recorded current waveform to obtain useful information about the physical processes in the plasma focus device are discussed. The current transformer with a large number of turns and a sub-1 Ohm terminator has good high frequency response, necessary for the sharp current dip region when dI/dt exceeds 2 × 1011 A/s. However the signal is “noisy” in the current dip region. Several methods to extract the current dip from the noise are discussed and examples of how low pass filters affect the signals are shown. The dI/dt coil, the Rogowski coil in “Idot” mode, with a few turns terminated by 50-Ohm is also described. Integrating the 1 GSa/s digital waveform does remove the high frequency noise components, yet the extracted waveform shows sharp angular features indicative of the retention of short-time features. This makes the dI/dt coil superior to the current transformer. A 7-turn coil is tested against the Lee Model code and found to be suitable to measure the plasma focus discharge current.

Flux Compression generators are widely used to achieve extreme high power pulses. In this method, after generation of current pulses flowing through an inductor, the chemical energy of an explosive is used to increase the power of the output voltage pulse applied to the load. During the transferring energy of the explosive to the output electrical pulse, the critical issue is to achieve the change of the inductance in a fast and controlled way. The current gain of such systems is strongly dependent on the time variation of the changeable inductance. The rate of the output current increase is approximately proportional to the rate of inductance reduction. This rate is determined by mass of explosive and dimensions of the detonation cylinder. There is no unique mathematical function by which the inductance transits from its initial value (L 0 ) to its final value (L f ), different functions can be realized by changing the physical dimensioning and design of FCG.

This frontier study investigated the timely development of pulsed ultraviolet light (PUV) and pulsed-plasma gas discharge (PPGD) technologies for the destruction of harmful Cryptosporidium oocysts and other problematical microorganisms in water. This constitutes the first study to report on the use of these pulsed power electrotechnologies (PPET) for the destruction of chlorine resistant Cryptosporidium oocysts, which have caused waterborne illness outbreaks worldwide. By accumulating energy over relatively long time periods, and by dissipating this energy in ultrashort pulses, the energy remains constant thus offering a radically new approach to energy delivery that have been shown to be orders of magnitude more efficient compared to using conventional decontamination approaches. Critical inter-related factors affecting the effective and repeatable decontamination performance of PUV and PPGD were identified during this study. The PUV approach proved superior to the PPGD system for treating similar artificially spiked samples in water, which is a positive finding considering the fact that commensurate toxicological investigations carried out in this study revealed that PPGD-treated water produced unwanted toxic end-points. This innovative,

The fast pulsed electric discharge current drives all physical processes in the plasma focus device; in turn all physical processes in the focus affect the current waveform. Thus the discharge current waveform is the most important indicator of plasma focus performance. This underlies the importance of properly measuring, processing and interpreting the discharge current waveform. This paper reports the measurement of fast pulsed discharge current by the Rogowski coil, in two different modes: the current transformer, "I" mode, and current derivative, "Idot" mode. The processing and interpretation of recorded current waveform to obtain useful information about the physical processes in the plasma focus device are discussed. The current transformer with a large number of turns and a sub-1 Ohm terminator has good high frequency response, necessary for the sharp current dip region when dI/dt exceeds 2×10 11 A/s. However the signal is "noisy" in the current dip region. Several methods to extract the current dip from the noise are discussed and examples of how low pass filters affect the signals are shown. The dI/dt coil, the Rogowski coil in "Idot" mode, with a few turns terminated by 50-Ohm is also described.

High-power lasers can be used to induce ionization of gases and thereby enable rapid triggering of electrical discharge devices, potentially faster than any devices based on mechanical or solid-state switching. With diffractive optical elements ͑DOEs͒ the laser light can conveniently be directed to positions within the gas so that an electrical discharge between two high-voltage electrodes is triggered reliably and rapidly. Here we report on two different types of DOE used for creating an electrical discharge in pure argon for potential high-voltage applications. One is the diffractive equivalent of a conventional axicon that yields an extended, and continuous, high-intensity focal region between the electrodes. The other is a multiple-focal-distance kinoform-a DOE that is designed to produce a linear array of 20 discrete foci, with high peak intensities, between the electrodes. We show that DOEs enable efficient, rapid switching and may provide increased flexibility in the design of novel electrode configurations.

A method for implementing collision welding at moderate to small length scales has been developed. The flyer, instead of being driven by chemical explosives (explosive welding) or magnetic forces (magnetic pulse welding), is launched toward the target by the pressure created from the electrically driven rapid vaporization of a thin metallic conductor. Mechanical impulse is developed from 0.0762 mm thick aluminum foils, which are vaporized using capacitor bank discharge with nominal charging voltage of 5.5 kV and peak current on the order of 100 kA delivered with rise times of about 12 µs. Welding couples of copper-titanium, copper-steel, aluminum-copper, aluminum-magnesium and titanium-steel have been successfully created with the same input parameters such as foil geometry, input energy and standoff distance. Instrumented peel tests, lap shear tests and optical and scanning electron microscopy reveal a wide spectrum of both strengths and interface structures. Copper-titanium and copper-steel welds are strong and have characteristic wavy interfaces with little intermetallics or void formation. The other combinations are seen to have brittle interfaces with intermetallics and defects, with the collision welding parameters used presently. For the titanium-steel system, a thin nickel interlayer is introduced and all the layers are welded in a single experiment. Peel strength of the weld was observed to be quadrupled. Peak velocities of up to 560 m/s were obtained for titanium flyer sheets.

The subcritical experiment (SCE) program was initiated after the 1992 moratorium on underground nuclear testing in support of stockpile stewardship . The dynamic material properties of plutonium are a major topic of exploration for the SCE program. In order to provide for a multilayered containment of plutonium, the SCEs are executed in the U1a underground tunnel complex at the Nevada Test Site (NTS). Cygnus is a new radiographic xray source developed for diagnostic support of the SCE Program at NTS.

In this paper, we review the suitability of diamond as a semiconductor material for high performance
electronic applications. The current status of the manufacture of synthetic
diamond is reviewed and assessed. In particular, we consider the quality of intrinsic
material now available and the challenges in making doped structures suitable for
practical devices. Two practical applications are considered in detail. First, the
development of high-voltage switches capable of switching voltages in excess of 10 kV.
Second, the development of diamond MESFETs for high-frequency and high-power
applications. Here device data are reported showing a current density of more than
30 mA mm- 1 along with small-signal RF measurements demonstrating gigahertz
operation. We conclude by considering the remaining challenges which will need to be
overcome if commercially attractive diamond electronic devices are to be manufactured.

One-dimensional CuO nanocrystals with spindly structure were successfully synthesized using pulsed wire explosion technique in deionized water. By modulating the exploding medium temperature spherical Cu nanoparticles and one-dimensional CuO nanocrystals can be selectively synthesized. At low temperature (1 C) the particle growth is governed by Ostwald ripening resulting in formation of equidimensional crystals (spherical). As the exploding temperature increases (60 C), oriented aggregation in a preferential direction resulted in unique spindly nanostructure. A possible crystal growth mechanism for these nanostructures with various morphologies at different exploding temperature is proposed. Particle growth by Ostwald ripening or orientated aggregation is highly dependent on exploding medium temperature. This technique uses pulsed power, hence the energy consumption is low and it does not produce any process byproducts. This study will provide a mean by which a most energy efficient and eco-friendly synthesis of one-dimensional CuO nanocrystals can be realized.

http://link.springer.com/content/pdf/10.1007%2Fs11051-012-1410-7.pdf

A robust through-silicon via technology is necessary for high-power, high-performance 3D-silicon applications. To study through-via interconnection reliability, modules consisting of a test chip, silicon carrier interposer with through-vias, and ceramic substrate were constructed. A socket assembly containing a microchannel water cooler was also constructed to apply pulsed power to via daisy chain test sites. Test results to date indicate that the interconnection reliability is limited by the solder bump portions of the interconnection, not the through-silicon via itself.

Planar wire array (PWA) experiments were performed on Michigan Accelerator for Inductive Z-pinch Experiments, the University of Michigan's low-impedance linear transformer driver (LTD)-driven generator (0.1 , 0.5–1 MA, and 100–200 ns), for the first time. It was demonstrated that Al wire arrays [both double PWA (DPWA) and single PWA (SPWA)] can be successfully imploded at LTD generator even at the relatively low current of 0.3–0.5 MA. In particular, implosion characteristics and radiative properties of PWAs of different load configurations [for DPWA from Al and stainless steel wires with different wire diameters, interwire gaps, and interplanar gaps (IPGs) and for Al SPWA of different array widths and number of wires] were studied. The major difference from the DPWA experiments on high-impedance Zebra accelerator was in the current rise time that was influenced by the load inductance and was increased up to about 150 ns during the first campaign (and was even longer in the second campaign). The implosion dynamics of DPWAs strongly depends on the critical load parameter, the aspect ratio (the ratio of the array width to IPG) as for Al DPWAs on high-impedance Zebra, but some differences were observed, for low-aspect ratio loads in particular. Analysis of X-ray images and spectroscopy indicates that K-shell Al plasmas from Al PWAs reached the electron temperatures up to more than 450 eV and densities up to 2 × 10 20 cm −3. Despite the low mass of the loads, opacity effects were observed in the most prominent K-shell Al lines almost in every shot. Index Terms— K-shell radiation, Linear Transformer Driver (LTD), planar wire array (PWA), plasma pinch, shadowgraphy images, X-ray spectra and images.

... Steve Best1, Martin E. Baltazar-Lopez2, Zachary M. Burell3, Henry W. Brandhorst, Jr.4 Space Research Institute, Auburn University, AL 36849-5320 USA ... The concrete was modeled using a porous EOS and a Drucker-Prager strength model. ...

This frontier study investigated the timely development of pulsed ultraviolet light (PUV) and pulsed-plasma gas discharge (PPGD) technologies for the destruction of harmful Cryptosporidium oocysts and other problematical microorganisms in water. This constitutes the first study to report on the use of these pulsed power electrotechnologies (PPET) for the destruction of chlorine resistant Cryptosporidium oocysts, which have caused waterborne illness outbreaks worldwide. By accumulating energy over relatively long time periods, and by dissipating this energy in ultrashort pulses, the energy remains constant thus offering a radically new approach to energy delivery that have been shown to be orders of magnitude more efficient compared to using conventional decontamination approaches. Critical inter-related factors affecting the effective and repeatable decontamination performance of PUV and PPGD were identified during this study. The PUV approach proved superior to the PPGD system for treating similar artificially spiked samples in water, which is a positive finding considering the fact that commensurate toxicological investigations carried out in this study revealed that PPGD-treated water produced unwanted toxic end-points. This innovative,

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II [1], features a 2.5-MeV injector and a 15.5-MeV, 2-kA, 1.6-microsecond accelerator consisting of 74 induction cells and drivers. Major induction cell components include high flux swing magnetic material (Metglas 2605SC) and a Mycalex TM insulator. The cell drivers are pulse forming networks (PFNs). The DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their operational parameters. These R&D efforts identified problems in the original cell design and means to upgrade the design, performance and reliability of the linear induction cells . Physical changes in the cell oil region, the cell vacuum region, and the cell drivers, together with different operational and maintenance procedures, have been implemented in the refurbished units resulting in greatly enhanced cell performance and reliability. All 74 cells have now been refurbished and tested for acceptance. This paper gives the results of those tests and the performance of the 26 refurbished cells in the Scaled Accelerator. . The accelerator is formed by a series of 74 identical cylindrically symmetric shaped cells. The cell accepts a HV pulse from the driver and delivers this pulse to the annular gap in the inner cylindrical surface (beam line). The inner conductor is surrounded by annular ferromagnetic cores to reduce loss current from the HV plate to ground. Each cell is 73" in diameter and weighs 16,000 lbs. Each cell is driven by 4 PFN Marx stages in series, . Between the top stage of the Marx and the grounded lid are a set of diodes and series resistors that clamp voltage reversal at the cell. Reversal occurs due to saturation of the Metglas cores late in the pulse. The flat top on the cell voltage is achieved by varying the number of turns on the inductor between each capacitor, a PFN section.

Generation and features of the radio frequency (rf) hollow cathode discharge (HCD) and its transition into the hollow cathode arc (HCA) are described. Rf linear hollow cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining hollow cathode and microwave plasmas, integrates features of both and provides more options to control plasma characteristics and consequently properties of deposited films. The rf hollow cathodes can be operated in both, PVD and PE CVD regimes, depending on process parameters. These regimes can even be combined within one process. New concepts of fused hollow cathode (FHC), microwave antenna (MWA) and Hybrid hollow electrode activated discharge (H-HEAD) cold atmospheric plasma sources are introduced. The FHC with its modular concept can be used for gas conversion, cleaning and for surface treatment of temperature-sensitive materials at ambient atmosphere. The H-HEAD cold atmospheric plasma source, capable of generating plasma plumes more than 15 cm long, enables treatment of 3-d and complex geometry objects even at low gas flows.

A method, system and apparatus for plasma blasting comprises a solid object having a borehole, a blast probe comprising a high voltage electrode and a ground electrode separated by a dielectric separator, wherein the high voltage electrode and the dielectric separator constitute an adjustable probe tip, and an adjustment unit coupled to the adjustable probe tip, wherein the adjustment unit is configured to selectively extend or retract the adjustable probe tip relative to the ground electrode and a blasting media, wherein at least a portion of the high voltage electrode and the ground electrode are submerged in the blast media. The blasting media comprises a thixotropic or electro-rheological fluid. The adjustable tip permits fine-tuning of the blast. The property of instantaneous high viscosity of thixotropic and electro-rheological fluids is advantageously used to seal the cavity containing the blasting probe thereby increasing the blasting pressure making the whole system more efficient.

We report on the DC and pulsed performance of nonpolar m-plane InGaN/GaN multiple-quantum-well light-emitting diode (LED) lamps. LED structures were grown on free-standing m-plane GaN substrates by metalorganic chemical vapor deposition. LEDs with an area of 300 Â 300 mm 2 were packaged into conventional epoxy-encapsulated lamps. The emission wavelength of the LEDs was 452 nm. A CW output power as high as 0.6 mW was achieved at a drive current of 20 mA, corresponding to an external quantum efficiency of 1.09%. Pulsed power measurement on the lamps yielded an output power of 23.5 mW at a drive current of 1 A for a duty cycle of 0.25%.

Two Plasma Focus devices were studied as pulsed sources of high-energy X-ray radiation. High-sensitivity, fast-response commercial radiographic film was used as X-ray detector. The relevant characteristics of the pulsed polyenergetic radiation are discussed in terms of its effective mean attenuation with the penetration distance on different metallic samples. The effective characteristic thickness for each metal was obtained. These results were then used to assess the spectral properties of the radiation pulses for each device as function of charging pressure and voltage. From them, effective energies of the X-rays belonging to the 80 -110 keV ranges were obtained.

When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2-kA, 18-MeV electron beam with more than 1500-ns current/energy "flat-top." In initial tests DARHT-II has already accelerated beams with current pulse lengths from 500-ns to 1200-ns fullwidth at half maximum (FWHM) with more than1.2-kA, 12.5-MeV peak current and energy. New experiments are planned with a ~1600-ns pulse length, but with reduced current and energy. These pulse lengths are all significantly longer than any other multi-MeV LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated absence of BBU, the pulse length was too short to determine whether ionhose instability would be present toward the end of a pulse longer than 1500-ns. The 1600-ns pulse experiments are designed to resolve these and other beam-dynamics issues with a long-pulse beam.

Photoconductive semiconductor switches (PCSS's), such as optically-triggered GaAs switches, have been developed for a variety of applications. Such switches exhibit unique properties as a consequence of lock-on, a phenomenon associated with the bistable switching of these devices. In this paper, lock-on is explained in terms of collective impact ionization. Furthermore, the effect of defects on the performance of these devices is investigated.

The fast pulsed electric discharge current drives all physical processes in the plasma focus device; in turn all physical processes in the focus affect the current waveform. Thus the discharge current waveform is the most important indicator of plasma focus performance. This underlies the importance of properly measuring, processing and interpreting the discharge current waveform. This paper reports the measurement of fast pulsed discharge current by the Rogowski coil, in two different modes: the current transformer, “I” mode, and current derivative, “Idot” mode. The processing and interpretation of recorded current waveform to obtain useful information about the physical processes in the plasma focus device are discussed. The current transformer with a large number of turns and a sub-1 Ohm terminator has good high frequency response, necessary for the sharp current dip region when dI/dt exceeds 2 × 1011 A/s. However the signal is “noisy” in the current dip region. Several methods to extract the current dip from the noise are discussed and examples of how low pass filters affect the signals are shown. The dI/dt coil, the Rogowski coil in “Idot” mode, with a few turns terminated by 50-Ohm is also described. Integrating the 1 GSa/s digital waveform does remove the high frequency noise components, yet the extracted waveform shows sharp angular features indicative of the retention of short-time features. This makes the dI/dt coil superior to the current transformer. A 7-turn coil is tested against the Lee Model code and found to be suitable to measure the plasma focus discharge current.

An ultra miniature device has been designed and constructed (nanofocus NF: 5nF, 5-10kV, 5-10kA, 60-250 mJ, 16 ns time to peak current). Sub-millimetric anode radii covered by coaxial insulators were used for experiments in hydrogen. Evidence of pinch was observed in electrical signals in discharges operating at 100 mJ. A single-frame image converter camera (4ns exposure) was used to obtain plasma images in the visible range. The dynamics observed from the photographs is consistent with: a) formation of a plasma sheath close to the insulator surface, b) the plasma sheath arrive over the anode, c) radial compression over the anode, and d) finally the plasma is detached from the anode in the axial direction. The total time since stage a) to d) was observed in ~30 ns. This ultra miniature device has a value for the "plasma energy density parameter" and for the "drive parameter" of the same order or higher than plasma focus devices operating at energies several orders of magnitude higher. X ray and neutron emission is being studied. Neutron yield of the order of 10 3 neutron per shot is expected for discharges operating in deuterium at 10kA.

Proposed ship-based long-range electromagnetic guns require input energies greater then 100 MJ, at peak powers in excess of 50 GW, and at average power in the tens of megawatts. This paper describes a conceptual pulsed-power system for driving these types of guns. A generic design was developed based on state-of-the-art power-supply, capacitor, and switching technologies. Results of modeling and parametric studies are presented, and key issues that impact system size and configuration are explored. An assessment is made of the feasibility of integrating this type of system into an electric-drive ship.

A pulsed discharge produced underwater has been an attractive method to treat waste water. For the optimization and realization of the water treatment system utilizing underwater pulsed discharge, modeling analysis could be one of the essential works. However, there is still no simulation work about the underwater pulsed discharge due to the lack of knowledge about its characteristic parameters such as electron temperature, electron density, and so on. In this paper, the temperature and the electron density in a pulsed discharge plasma produced underwater are measured and presented. A magnetic pulse compressor (MPC) was developed and used to create the electrical discharge in water. The developed MPC is all-solid state and is, therefore, a maintenance-free generator. To define the temperature and the electron density in an underwater pulsed discharge plasma, two kinds of spectroscopic measurements, called the line-pair method and Stark broadening, were carried out. According to the experimental results, the temperature and the electron density in the pulsed discharge plasma between point-plane electrodes immersed in water are determined to be 15 000 K and 10 18 /cm 3 , respectively.