Pulsed Power

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.

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.

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.

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.

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.

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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.

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquidmixture, and for material processing.

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.

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.

— 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 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.

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.

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.

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.

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.

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.

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 /spl mu/F. Two different storage times have been considered: 2 /spl mu/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.

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.

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.

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.

The characteristics of a pulsed high-current generator has been studied for applications in extreme ultraviolet (EUV) generation. The objective is to clarify the electrical response of the generator circuit to the dynamic behavior of the discharge load. The experiments were carried out by driving a capillary discharge, where the plasma behavior is monitored by using high-speed camera and photodiodes. The generator performance is monitored by voltage and current probes. From the diagnostic results, the behavior of the last magnetic switch has become clear and the electrical efficiency of the generator system is obtained. The energy deposited in the capillary is calculated to be 4.5 J and the temporary plasma impedance at the peak current is observed to be 40 mΩ.

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.

Many accelerators at Sandia National Laboratories utilize the Rimfire gas switch for high voltage, high power switching. In addition, there are many multichannel closing switches used in pulsed power applications. This paper presents a brief overview of a study of the multichanneling section of the Rimfire switch. The effects of multichanneling and a method to force multichanneling are presented.

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.

... 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. ...

Pulsed power applications are widespread, ranging from microscopic devices up to systems that are major installations and cost many millions of dollars. This paper describes some of the approaches used for the larger systems that have been built and discusses their engineering challenges. Basic energy storage approaches include electrostatic (capacitors), magnetic (inductors), inertial (flywheels), electrochemical (batteries), and fuel or explosives. Systems based on these approaches each have their own requirements and challenges but also have many common components. An example of one potential future largescale opportunity-launch to space-is given and the need to develop more competitive economic approaches is discussed.

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquidmixture, and for material processing.

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 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.

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 Explosively-Formed Fuse (EFF) is a high-power opening switch that uses an explosive charge to interrupt current flow in an aluminum conductor . As such we expected the foil's resistance to increase with increasing current density by Joule heating. Yet an analysis of a large number of experiments clearly showed the opposite was true; there was a strong negative correlation between the peak resistance and current density. In the paper we analyze various possible causes including thermal softening of the metal, magnetic loading of the explosive and electric breakdown or conduction in the product gases at the higher applied fields. Our analysis suggests that magnetic loading is responsible for the degradation.

We report for the first time on the comparative use of pulsed-plasma gas-discharge (PPGD) and pulsed UV light (PUV) for the novel destruction of the waterborne enteroparasite Cryptosporidium parvum. It also describes the first cyto-, geno-and ecotoxicological assays undertaken to assess the safety of water decontaminated using PPGD and PUV. During PPGD treatments, the application of high voltage pulses (16 kV, 10 pps) to gas-injected water (N 2 or O 2 , flow rate 2.5 L/min) resulted in the formation of a plasma that generated free radicals, ultraviolet light, acoustic shock waves and electric fields that killed ca. 4 log C. parvum oocysts in 32 min exposure. Findings showed that PPGD-treated water produced significant cytotoxic properties (as determined by MTT and neutral red assays), genotoxic properties (as determined by comet and Ames assays), and ecotoxic properties (as determined by Microtox™, Thamnotox™ and Daphnotox™ assays) that are representative of different trophic levels in aquatic environment (p b 0.05). Depending in part on the type of injected gas used, PPGD-treated water became either alkaline (pH ≤ 8.58, using O 2 ) or acidic (pH ≥ 3.21, using N 2 ) and contained varying levels of reactive free radicals such as ozone (0.8 mg/L) and/or dissociated nitric and nitrous acid that contributed to the observed disinfection and toxicity. Chemical analysis of PPGD-treated water revealed increasing levels of electrode metals that were present at ≤30 times the tolerated respective values for EU drinking water. PUV-treated water did not exhibit any toxicity and was shown to be far superior to that of PPGD for killing C. parvum oocysts taking only 90 s of pulsing [UV dose of 6.29 μJ/cm 2 ] to produce a 4-log reduction compared to a similar reduction level achieved after 32 min PPGD treatment as determined by combined in vitro CaCo-2 cell culture-qPCR.

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.

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. Nomenclature Pd = Power density I pk = Peak current E = Voltage V = Volume of reactant (blasting media)

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.

In the PIM pulsed power machine a 1.5 MV, 100 ns duration pulse is generated by a 10 Ohm water Blumlein. A prepulse reduction system based on a gas switch has been designed and built by Titan PSD. This has been fitted and reduced the prepulse to less than 3 kV. Prepulse of this order is necessary to drive the focused ebeam diodes used for flash radiography. Details of the prepulse reduction system, the experimental data obtained and comparison with computer models of the machine will be presented. Figure 1. The PIM IVA pulsed power machine

A closing plasma switch triggered by the formation of a continuous laser spark between two electrodes has been developed and tested. The plasma channel is formed by focusing a Nd-YAG laser beam into a line focus using an axicon. The holdoff/minimum triggerable voltage ratio exceeds 1000. A model of the optical intensity distribution in the line focus is presented and compared with experimental results on plasma formation.

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,

Recently industrial applications of ozone have increased in widely different areas including oxidation, sterilization, deodorization, bleaching and others. Ozone generation has been attained using ultra violet irradiation, electrolysis and electrical discharges. The electrical discharge technique includes silent discharge, surface discharge, pulse corona discharge and superimposed silent and surface discharges. In this study, high concentration ozone was produced by using a pulsed streamer discharge under atmospheric pressure of oxygen. A magnetic pulse compressor (MPC) which has a maximum output voltage of 60 kV, a maximum pulse repetition rate of 500 pulses per second (pps) and a pulse duration of about 130 ns was used as a pulsed power source. A spiral copper wire (1 mm in diameter, 10 mm pitch) wound on PVC tubes (26 mm and 30 mm in outside diameters) formed the central electrode in a coaxial geometry. A copper cylinder of 60 mm in internal diameter formed the outer electrode. The ozone production characteristics of three reactors having different dimensions of the gap spacing (15 mm and 17 mm) and length (500 mm and 1000 mm) were investigated. An oxygen flow rate in the range of 1 to 3 l/min at atmospheric pressure was used. It has been found that the dependence of ozone concentration on energy density (J/l) was almost the same for the three different reactors. Typically a production yield of ozone of 100 g/kWh at 30 g/m 3 was attained.

Burst RF fields (BRFFs) were applied to Chinese Hamster Ovary (CHO) cells, and the cell response to the BRFF of two different frequencies, 20 kHz and 50 MHz, was investigated by means of the fluorescent microscopy. The field strength and duration of the BRFF were fixed at 1 kV/cm, and 100 µs, respectively. Cells were placed in a 100 µm-gap electrode plated on the slide glass for a microscopy. Acridine orange (AO), which mainly reacts to DNA, was used as the fluorescent dye. From the experiment, the BRFF of 20 kHz initiates the increase in the permeability of cell membrane. In contrast, the BRFF of 50 MHz does not act on cell membrane but causes degeneration of DNA or RNA. We have experimentally demonstrated that the burst RF fields with only a small electric field of 1 kV/cm cause not only membrane reaction but also intracellular effects.

ABSTRACT The limiting crossed magnetic fields in SF6 due to E×B Townsend discharges are evaluated directly from a Monte-Carlo simulation technique. The validity of the effective reduced electric field concept, EREF, is also investigated at the corresponding limiting crossed fields together with the electron mean energies and collision frequencies

The limiting equivalent electric fields in N2+SF6 binary gas mixtures due to Townsend discharges are evaluated directly from a Monte-Carlo simulation when the mixture is subjected to orthogonal electric and magnetic fields. Along with the limiting equivalent electric fields, transverse and perpendicular drift velocities, electron mean energies and collision frequencies are also determined within the scope of the Monte-Carlo simulation. The equivalent reduced electric field (EREF) concept for the corresponding limiting electric fields is also investigated for the calculated mean energy levels and collision frequencies. The EREF values are found to be in good agreement with the previously published limiting electric field data.

Recent performance and reliability upgrades to the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility second axis induction cells have impacted various cell mechanical components. To attain a higher level of performance and reliability, key mechanical elements comprising the induction cells were redesigned. These elements include the oil-vacuum insulator assembly, cathode cap, oil and vacuum region cell extension hardware, induction cores' insulating material and configuration, and the high voltage drive plate. While developing these upgrades, other enhancements, unrelated to the electrical performance, were implemented as well. These enhancements include the solenoid assembly oilwater interface, the oil plumbing and ventilation, and the vacuum bellows assembly. Mechanical processes were also developed to attain high assembly quality during the cell refurbishment process. This paper presents and discusses each mechanical attribute associated with these upgrades of the DARHT second axis induction cells.

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 precooled 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 μs, 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 b 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 b 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 b 0.05) of L. plantarum in 3.5% beer and of S. Choleraesuis in carbonated beer.

Recent research efforts at TTU include the testing of a rapidly charged, rep-rated Marx generator driving a reflex triode vircator [1]. As expected, the burning of the cathode material (ordinary cloth velvet), was the primary failure mechanism during repetitive operation. In an effort to achieve a repetitive vircator (>10 Hz), we are exploring a low-cost, all-metal cathode. The cathode is made from aluminum with a patterned surface. A typical pattern is composed of peaks and troughs with dimensions on the order of tens of microns. The pattern is achieved with a simple, low-cost chemical etching process. Results include current, voltage, and microwave waveforms from two solid metal cathodes and a cloth velvet cathode.