Pulsed Power

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 9 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. 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.

tal data from gas-filled cylindrical liner z-pinch experiments are presented. The current discharge from the MAGPIE pulsed-power device at Imperial College London (1.4MA,240ns) is applied to a thin walled (80µm) Al tube with a static gas-fill inside (initial gas density 10-5 g/cc). The system is used to drive cylindrically converging strong shock waves (U s = 20km/s) into different gases. Axial diagnostics include interferometry, optical streak photography and time gated, spatially resolved optical spectroscopy. The experimental geometry is nominally uniform along the diagnostic line of sight and in addition the shock waves show a high degree of azimuthal symmetry. This allows determination of the radial dependence of axially averaged plasma parameters (n e ,T e ). The spectroscopy diagnostic is used to determine the temperature profile across the shock (in the precursor and post-shock regions) in different noble gases. Comparisons are made between experimental temperature and electron density profiles and the 1D radiation-MHD code HELIOS-CR. In addition, varying degrees of shock stability are seen in different noble gases. These observations will be briefly compared to cooling function calculations and analytical stability models.

Tout d'abord louanges et remerciements à Dieu pour m'avoir donné le courage et la force de terminer ce modeste travail. Je tiens à remercier mon directeur de thèse, M. Miloud KACHI, pour ses multiples conseils, suggestions et pour toutes les heures qu'il a consacrées à établir cette recherche. J'aimerais également lui dire à quel point j'ai apprécié sa grande générosité, disponibilité et ses qualités d'écoute et de compréhension. Cela a été un grand privilège pour moi d'avoir coopérer avec Monsieur le Professeur Lucien DASCALESCU du laboratoire d'étude aérodynamique IUT d'Angoulême de l'université de Poitier. Je tiens à lui adresser mes chaleureux remerciements pour ses remarques et conseils pertinents. Mes remerciements s'adressent également à Messieurs Karim MEDLES et Thami ZEGHLOUL pour toute leur aide, leur précieux conseils et leurs encouragements continus qu'il m'a prodigué durant la réalisation de cette thèse et leur confiance à mon égard. Je suis reconnaissant à Messieurs: Marian-Bogdan NEAGOE et Gontran RICHARD, doctorants à l'IUT d'Angoulême, pour leurs aides précieuses à la réalisation des manips. J'adresse tous mes remerciements à Professeur Ahcene LEMZADMI pour avoir accepté de présider mon jury. Mes remerciements vont également à Messieurs : Lazhar HEROUS, Noureddine ZOUZOU et Mokdad REMADNIA qui m'ont fait l'honneur d'examiner, évaluer et juger cette thèse. Mes remerciements s'adressent aussi à tous les membres de l'Institut PPRIME, de l'IUT d'Angoulême, de l'Université de Sidi-Bel-Abbès et de l'Université de Guelma, qui ont été proches de moi ces trois dernières années.

The use of pulse light to inactivate microbes has recently attracted interest of many researchers. Consequently, there are various reports on the efficacy and advantages of pulsed light in microbial inactivation; and also the potentiality of pulsed light systems being adopted for industrial use in this regards. Here, we review some of the works done in relation to microbial inactivation with pulse light, with emphasis on the role played by pulse light parameters such as fluence, spectral range, pulse power, pulse width, pulse frequency, etc. We focussed in particular on factors that make pulsed light systems more effective than their continuous wave counterpart and also proffer suggestions on possible areas for improvement in future study. The use of pulsed lasers in inactivating microbes was briefly appraised. Also, prospects and challenges in the use of pulsed light for inactivation were highlighted.

This paper presents an optimal design procedure for pulse transformers fed by power converters for supplying pulsed current magnets in particle accelerators. Usually their volume must be minimized because of limited space available in the accelerator tunnel. Analytical and numerical models are presented as well as an experimental validation and a real case study where the design tool is exploited to derive a wide variety of solutions depending on the pulse transformers location with respect to the magnet position.

Pulsed power is a technology that is suited to drive electrical loads requiring very large power pulses in short bursts (high-peak power). Certain applications require technology that can be deployed in small spaces under stressful environments, e.g., on a ship, vehicle, or aircraft. In 2001, the U.S. Department of Defense (DoD) launched a long-range (five-year) Multidisciplinary University Research Initiative (MURI) to study fundamental issues for compact Manuscript

A pseudospark-based high repetition rate pulse generator, together with a resonant charging power supply is presented. The pulse generator was developed for research applications that include transient plasma ignition. The design incorporates a lumped element Blumlein pulse-forming network that is switched by a commercial pseudospark into an output pulse transformer with a METGLAS core. The Blumlein is charged up to 30 kV by a resonant capacitor charger, based on a fly-back transformer and high-power insulated gate bipolar transistor (IGBT) switch module. The output voltage of the charger is controlled by the on-time of the IGBT. Pulses with duration of 50 ns can be generated at a 2.6-kHz maximum repetition rate. Pulses with amplitude up to 90 kV can be delivered into a 200-load.

methods for cable insulation. In this study, a high frequency measurement technique to characterize the semi-conducting screens in medium voltage cross-linked polyethylene ( ) XLPE cables has been developed. The frequency ranges from 30 kHz to 500 MHz. The influence of the experimental set-up, sample preparation methods, pressure and temperature are investigated. A dielectric function is developed for the semiconducting screens and this is incorporated into a high frequency model for the cable. The propagation characteristics obtained from the high frequency cable model are compared with those obtained from measurements made on the same cables.

High current intense electron beams were investigated earlier for Flash X-rays and nuclear electromagnetic pulse generation. Starting with moderate parameters of 200 kV, 6 kA, 60 ns pulsed electron beam source from a system named Kilo Ampere Linear Injector (KALI-75) our latest development is KALI-30 GW system rated for 1 MV, 30 kA, 80 ns. First repetitive pulse LINAC without spark gap switching was developed as Linear Induction Accelerator (LIA-200) for technology demonstrations at 100 Hz. Also a repetitive Marx generator coupled reflex triode system to operate at 10 Hz. Next to this series of development LIA-400 has been developed to a capacity of 400 kV, 4 kA, 100 ns, 300 Hz. To make these pulse power systems applicable for big LINAC projects like nToF studies or ADS program, a high current electron gun has also been developed to give 100 A, 2 ns,10 Hz pulses.

Present paper describes the design and test results of indigenously developed electron beam pulsed accelerator, which is a kilo ampere linear injector: KALI-5000 having ratings of 1 MV, 80 kA, 100 ns, 80GW. It comprises of Marx generator, Blumlein pulse forming line (PFL) and relativistic electron beam diode. It is a single shot system. In view of numerous industrial and strategic applications of electron beam accelerators, BARC is actively pursuing the design and development of various kinds of accelerators viz. 10 MeV RF accelerators, 0.5 -3 MeV DC accelerator and 0.2-1 MeV pulsed electron accelerator. This paper presents the subsystem details of KALI-5000 and recent experimental results with electron beam emission.

The COBRA pulsedpower generator, with a nominal peak current of 1.1 MA and a minimum zero-topeak rise-time of about 100ns, is being used to study the early phases of wire-array z-pinch development with a variety of diagnostics. Here we present the results of applying point-projection x-ray radiography to make accurate, high-resolution spatial and temporal measurements of the plasma density distributions in tungsten (W) wire-array z-pinch implosions. Density measurements are quantified by comparing x-ray transmission recorded on photographic films to transmission through W calibration steps of known thicknesses. Plasma density distributions as a function of time are presented for the coronal (10 18 -10 20 /cm 3 ), ablation (<10 18 /cm 3 ) and on-axis (<10 19 /cm 3 ) plasmas during the pre-stagnation phases of z-pinch dynamics (70-170 ns after the start of the current pulse). With this data set the time dependence of ablation velocity and corresponding mass ablation rate are addressed.

Broadband, high resolution X-pinch radiography has been demonstrated as a method to view the instability induced small scale structure that develops in near solid density regions of both insulated and non-insulated cylindrical metallic liners. In experiments carried out on a 1-1.2 MA 100-200 ns rise time pulsed power generator, μm scale features were imaged in initially 16 μm thick Al foil cylindrical liners. Better resolution and contrast were obtained using an X-ray sensitive film than with image plate detectors because of the properties of the X-pinch X-ray source. We also discuss configuration variations that were made to the simple cylindrical liner geometry that appeared to maintain validity of the small-scale structure measurements while improving measurement quality.

We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z (0), supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z (t) = B z (0) × [R(0)/R(t)] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z (t) and dB z /dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al., Phys. Rev. Lett. 113, 155004 (2014); P. F. Knapp et al., Phys. Plasmas, 22, 056312 (2015)]. Finally, we present some recent developments for designing and fabricating novel micro B-dot probes to measure B z (t) inside of an imploding liner. In one approach, the micro B-dot loops were fabricated on a printed circuit board (PCB). The PCB was then soldered to off-the-shelf 0.020inch-diameter semi-rigid coaxial cables, which were terminated with standard SMA connectors. These probes were recently tested using the COBRA pulsed power generator (0-1 MA in 100 ns) at Cornell University. In another approach, we are planning to use new multi-material 3D printing capabilities to fabricate novel micro B-dot packages. In the near future, we plan to 3D print these probes and then test them on the COBRA generator. With successful operation demonstrated at 1-MA, we will then make plans to use these probes on a 20-MA Z experiment. We would like to thank the MagLIF/ICF and the Dynamic Material Properties research groups at Sandia National Laboratories for many useful technical discussions regarding various aspects of magnetic flux compression on Z.

This paper introduces and describes the new Cornell Beam Research Accelerator, COBRA, the result of a three and one-half year collaboration. The flexible 4 to 5-MV, 100 to 250-kA, 46-ns pulse width accelerator is based on a four-cavity inductive voltage adder (IVA) design. In addition to being a mix of new and existing components, COBRA is unique in the sense that each cavity is driven by a single pulse forming line, and the IVA output polarity may be reversed by rotating the cavities 180° about their vertical axis. Our tests with negative high voltage on the inner MITL stalk indicate that the vacuum power flow has established reasonable azimuthal symmetry within about 2 ns (or 0.6 m) after the cavity output gap. Preliminary results with the accelerator, single cavity, and MITL are presented along with the design details and circuit model predictions

A relatively long-pulse width (0.1–1 μs) intense ion beam accelerator has been built for materials processing applications. An applied Br, magnetically insulated extraction ion diode with dielectric flashover ion source is installed directly onto the output of a 1.2 MV, 300-kJ Marx generator. The diode is designed with the aid of multidimensional particle-in-cell simulations. Initial operation of the accelerator at 0.4 MV indicates satisfactory performance without the need for additional pulse shaping. The effect of a plasma opening switch on diode behavior is considered.

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of either 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner&#39;s inner surface in the images. These images allow us to assess the stability of the liner&#39;s inn...

The rebuilt COBRA pulsed-power generator, which has a variable current-pulse waveform and amplitude (95-150-ns rise time and ∼1-MA peak current), has extended the range of the current-pulse parameters that can be used to study the X -pinches. X -pinches with 4-12 wires of several different wire materials (from Al to W) with diameters from 25 to 75 µm have been studied. The influence of the rate of the rise of current and the X -pinch wire mass on the X -pinch plasma formation and pinch implosion dynamics has been studied using a set of diagnostics with spatial and/or temporal resolution. Multiwire X -pinches were placed in the diode center, and/or two four-wire X -pinches were placed in one of the four parallel return-current circuits of the diode. The experiments showed that the most important factor determining the first X-ray burst timing is the linear mass density of the X -pinch wires, and an optimal value for obtaining a single high-energy X-ray burst was found. Radiographic images of the different test objects, wires in wire-array Z-pinches, and the X -pinches, themselves, were obtained using a micrometer-scale spatial resolution.

We present here the use of the continuum radiation from X-pinch-produced point x-ray sources for absorption spectroscopy as a new diagnostic to investigate the properties of aluminum plasmas created by pulsed power machines at 500 kA and 1 MA. This technique is being ...

Methods and apparatus for thermally altering the near surface characteristics of a material are described. In particular, a repetitively pulsed ion beam system comprising a high energy pulsed power source and an ion beam generator are described which are capable of producing single species high voltage ion beams (0.25-2.5 MeV) at 1-1000 kW average power and over extended operating cycles (10.sup.8). Irradiating materials with such high energy, repetitively pulsed ion beams can yield surface treatments including localized high temperature anneals to melting, both followed by rapid thermal quenching to ambient temperatures to achieve both novel and heretofore commercially unachievable physical characteristics in a near surface layer of material.

A 10-MVA-scale resonant oscillator, powered by a pulse-forming network and switched with a pair of commutating mercury ignitrons, was developed for the MST reversed-field pinch plasma-confinement experiment. A novel feature of this circuit is its commutation mechanism, wherein each turning on of one ignitron causes a reverse voltage transient that turns off the other. Two of these oscillators are used in oscillating-field current-drive tests, in which they are capable of nearly 1MW net input power to the plasma, with resonant frequencies of a few 100 Hz for pulse durations of a few tens of ms, being precharged for immediate full amplitude. We describe the circuit and its operation, and discuss features that allow reliable, high-current commutation of the ignitrons and exploit their low switching impedance.

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD's hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept.

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD’s hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept. High-Voltage pulsed power systems used for Z-Pinch experimentation have in the past largely been based on Marx Generators. Marx generators deliver the voltage and current required for the Z-Pinch, but suffer from two significant drawbacks when applied to a flight system: they are very massive, consisting of high-voltage capacitor banks insulated in oil-filled tanks and they do not lend themselves to rapid pulsing. The overall goals of Phase 1 are to demonstrate the feasibility of the LTD concept for a Z-Pinch propulsion system and to learn techniques for d...

The University of Alabama in Huntsville (UAH) in partnership with the National Aeronautics and Space Administration at Marshall Space Flight Center is working to develop a pulsed power facility. The facility, known as Charger-1, is a 1-TW pulsed power machine. The hardware was originally DECADE Module 1 from L-3 Pulsed Sciences Division in San Leandro, CA. The DECADE program enabled the construction of several pulsed-power modules. Together, they were used for high-energy X-ray generation and weapons effects testing. The module at UAH is being outfitted for z-pinch propulsion system and nuclear energy production experiments. Its primary envisioned goal is to support the development of a Pulsed Fission-Fusion propulsion system with experimental data. This document is intended to update the nuclear and pulsed power communities as to the progress of the facility development. An overview of the facility and its status is presented.

The development of an autonomous RF radiation package for various applications is presented. This work is a coordinated effort to develop a tightly integrated unit, including the batteries, power supply, Marx generator, and plug and play antennas for various applications. ARC Technology has designed the Marx generator and its associated high voltage antennas for this effort. Previous work by ARC has demonstrated 75 mm diameter, 700 mm length diameter Marx generators capable of delivering 200 kV pulses into 50 Ω coaxial cable with sub-nanosecond risetimes, enabling it to drive an antenna and generate high power microwaves. This technology has been re-designed into a reduced length geometry and augmented by inductive charging to permit pulse repetition rates. The antenna is incorporated directly onto the Marx output for efficient energy transfer and for compactness. This package has demonstrated peak electric field strengths up to 4700 V/m at 10m. Texas Tech University has worked closely with ARC in developing a rapid charging power supply to meet stringent package constraints and still permit high pulse repetition rates. This system has already demonstrated the ability to charge a 50 nF capacitance up to 40 kV with a repetition frequency of 100 Hz, delivering an average power of 4 kW. This paper details the present status of the project, which will be completed in July, 2005. The cylindrical geometry of the final package has a diameter of 155 mm, a length of approximately 1500 mm without the antenna, and a mass of approximately 35 kg, depending upon the chosen antenna implementation. Results of preliminary tests are included.

An analysis is made of the current break process in microsecond plasma opening switches and their possible application in high-current generators. Necessary conditions are determined for generating megavolt pulses in the erosion mode of a plasma opening switch with the gap insulated by an external magnetic field. Under these conditions, efficient sharpening of high-power submegampere current pulses can be achieved. The possibility of using plasma opening switches operating at voltages of 5-6 MV to generate X-ray and gamma emission is discussed. The main operating and design parameters of a six-module plasma opening switch with a current pulse amplitude of 3.7 MA and voltage of 4-6 MV for use in the MOL generator, which is the prototype of one of the 24 modules of the projected Baikal multimegajoule generator, are estimated by using the available scalings.

At Plasma Liner Experiment, a set of 36 coaxial plasma guns are deployed quasi-uniformly over a 9 ft diameter spherical chamber and are used to form a high-Z spherically compressive plasma liner. Simulations indicate that for the concept to ultimately achieve optimal target density and temperature, a high degree of timing uniformity is required between all guns. To aid in quantifying and correcting gun-to-gun nonuniformities, a key diagnostic will consist of up to six fisheye-view CCD cameras positioned inside the main chamber such that each has all plasma guns within its view. The individual cameras can be triggered at different times to determine each plasma jet’s muzzle velocity and structure for different operating conditions. This camera array is currently under development, and the implementation needs and challenges for this camera array are discussed here. Additionally, we detail the analysis methodology for determining jet-to-jet uniformity deviations and how we can correct them, thereby improving overall liner uniformity.

The Plasma Liner Experiment (PLX) BETHE recently demonstrated formation of an imploding plasma liner via the merging of 36 discrete jets. Magnetized targets have been routinely formed by head on collision of two deuterium jets magnetized by the interaction with fields from external solenoids. These jets are formed by coaxial pulsed plasma accelerators. Our 3D simulation tool SPFMax has been validated against these experimental data, providing confidence to perform integrated simulations including plasma liner formation, magnetized target formation, and target compression. SPFMax is used to model the effects of plasma jet initial conditions on fusion yield in a reactor relevant parameter space.

Temperature Energy Equations Future work The Plasma Liner Experiment (PLX) BETHE has routinely demonstrated formation of an imploding plasma liner via the merging of 36 discrete jets. Magnetized targets are formed by head on collision of two hydrogen jets magnetized by the interaction with fields from external solenoids. Diagnostics on the plasma liner formation experiment include, but are not limited to, time gated imaging at stagnation, laser interferometry, and density gradient measurements using normalized Bremsstrahlung radiation. Three dimensional simulations using SPFMax of the 36 jet liner experiment produce synthetic diagnostic signatures that are compared directly with these experimental data. The merging of the plasma jets is nearly collisionless below a certain density when the ion/electron collisional mean free path is comparable or longer than the jet diameter. These effects are studied in SPFMax to study the role played in the imaging, interferometry, and density gradient of the stagnation region. • Identify causes for departure in PLX and SPFMax interferometry traces • Continue extrapolation to reactor relevant conditions and identify an ignition space using 3D model

• Two magnetized jets merging experiment is an effort to develop the magnetized targets gun for the target-liner integrated experiment in PLX (Plasma Liner Experiment) at Los Alamos National Laboratory. • The idea is to launch two magnetized plasma jets as precursor target jets in the PLX spherical chamber and 36 unmagnetized high Z plasma liner jets will spherically implode the target plasma. • It is important to characterize both target plasma and liner plasma jets to be able to access the overall performance of PJMIF reactor concept. • Two magnetized jets merging experiments have begun in January 2022 by Hyperjet. • The future scope of work is to identify if there are other dominant parameters to cause these peaks separation such as conductivity, temperature • If precursor jets are the natural phenomenon, then we would like to explore this as a preheating mechanism for the plasma ignition.

Weft insertion in weaving is an important subject, which has been studied by many research workers, for decades. A number of mechanisms have been invented, designed, manufactured, developed and employed for this purpose, although, only some of these systems have been commercialised. The present paper reports a magnetic weft inserting system, which was desi- gned and manufactured as a model on basis of electromagnetic force. Different features of the system and the parameters affecting in weft insertion are explained and discussed, also.

Applying series configuration of the insulated gate bipolar transistors (IGBTs) to the pulsed power supplies offers unique features such as compactness and long life time. In the high voltage pulsed power supplies, a large number of the IGBTs are required to be serially connected. Hence, the safe operating condition provision for the series IGBTs is an important and crucial issue. The effect of the voltage unbalancing factors becomes remarkable when the switches number in the series structure increases. There are passive and active methods to balance the voltage of the series IGBTs. In both of these methods, an amount of power must be dissipated to remove the effect of the voltage unbalancing factors. Consequently, the power loss is considerable when a large number of series devices are necessary. This paper proposes an effective power recovery system that recovers the power associated with the series stacking of the IGBTs. Using this proposal, the efficiency of the resulted series switch enhances considerably. The power recovery system can be implemented easily for any number of series IGBTs. It consists of a simple DC/DC converter and several interconnection diodes for power recovery procedure. Proper performance of the proposed structure is evaluated by the aid of simulations and experiments.

The series configuration of fast semiconductor switches seems to be the key component in the high-voltage and fast rising time pulse generation. In this approach, two important issues must be considered. The first is to provide a safe operating condition for the switches in transient intervals. The second is to design a gate drive system with the capability of driving a large number of discrete devices simultaneously. The aim of this paper is to obviate these two requirements. First, different factors affecting the unbalanced voltage sharing between the series switches are discussed. In this investigation, the switch-to-ground parasitic capacitance effect has been recognized as the major effect on the unbalanced voltage sharing in the transient interval. Two schemes for abating this effect are proposed. To solve the unbalanced voltage distribution, the structure with a snubber circuit in the clamp mode operation is suggested. This scheme can be used for any number of switches without destructively affecting their behavior. In addition, the output pulse with a fast rising time could be obtained by the proposed gate drive system. In order to evaluate the operation of the proposed structure, a stacked switch with the voltage capability of 36 kV is tested experimentally. The characteristics of the obtained pulse are the fast rising time (69.5 ns) with the dV/dt of 460 kv/µs and the wide range of the pulsewidth adjusting to 0.5-15 µs. In addition, the voltage variance of the switches level in the series structure is about 10%.

This dissertation is dedicated to my lovely and supportive wife, Eman Omar, my children, Omar and Maryam, my mother and my father, Mr. Taha Ghareeb. Without their patience, understanding, support, encouragement, and most of all love, the completion of this work would not have been possible. v ACKNOWLEDGMENTS This dissertation would not have been possible without the help, support, dedication and patience of my major advisor, Prof. Osama Mohammed, whom I consider myself fortunate to work with. I wish to express in words my deepest gratitude to Professor Osama Mohammed, for his guidance, encouragement, and support during my graduate study. Prof. Mohammed has always been an endless supply of ideas, guidance, suggestions and useful discussions for me. I am grateful for the chance he gave to me to work at the Energy Systems Research Laboratory, where I found all the equipment and facilities I needed to experimentally verify my results. This laboratory is where I was developed professionally in an environment where work and engineering ethics are highly respected. I do appreciate Professor Mohammed's many constructive suggestions and technical as well as personal help. I would like to thank my dissertation committee members Professor W. Kinzy Jones, Professor Sakhrat Khirzroev, Dr. Arif Sarwat and Dr. Mark Roberts for their insightful comments and constructive suggestions in the review of my research proposal and dissertation. I would like to acknowledge the research support provided from the office of Naval Research (ONR) throughout my years of research in Energy Systems Research Laboratory (ESRL). I also acknowledge the dissertation year fellowship (DYF) from FIU graduate school during the last year of my study. Although this doctoral dissertation is considered to be my personal accomplishment, I would like to acknowledge my colleagues in Energy Systems Research Laboratory for their creative support, encouragement, and collaborations during my graduate studies.

The main aim of this paper is to expose a simple and low cost device that allows to measure high frequency cur- rents. The Rogowski coil is a flux-to-voltage transducer for non-intrusive current measurement. Its use is usually asso- ciated to an external circuit for integrating ...

This paper describes a pulsed electron gun that can be used as an FEL, as an injector for electron linear accelerators or for rf power generation. It comprises a 1 to 5 MeV, 1 to 2 ns pulsed power supply feeding a single diode, photoexcited acceleration gap. Beam quality of a ~ 1nC charge in ~ 1 GV/m field was studied. Computations of the beam parameters as a function of electrode configuration and peak electron current are presented together with descriptions of the power supply, laser and beam diagnostics systems.

For developing high-quality and cost-efficient products, it is important to evaluate and compare system level performance for different configurations early in the development process. This paper will present the development and optimization for a steel frame system using a combined CAD/FEM program. In this study, a detailed steel frame model is designed and analysed. The issues to be improved are the vibrations of the outer parts of the bonnet. The negative effect consists in acoustical disturbance, mechanical stress, material fatigue and oscillations. 3D model is analysed through finite elements analysis method and confirm a higher displacement at frame's extremities caused by an unstable dynamic behaviour as an effect of different excitation sources (combustion engine, loading, unloading, general balance of the machine). To demonstrate the applicability of the developed models, results of computer simulations are presented.

Explosively formed fuse (EFF) devices are opening switches for high explosive pulsed power (HEPP) applications. Such switches have been operated at currents up to 25 MA, voltages up to 500 kV, and power over 3 TW in our large-scale HEPP systems. The switch consists of a conducting foil that is driven by high explosives into a dielectric die consisting of extrusion anvils and gaps that separate them. The switch develops resistance as the foil is extruded. We have conducted tests with many foils, and many die materials and patterns. We have also performed calculations using both 2-D hydrodynamic (hydro) and magneto-hydrodynamic (MHD) codes of switches with the different die patterns. Dies with more massive corners at each extrusion position develop resistance faster, and tend to have more pronounced features in the resulting R(t) curves. In addition, the explosive drive is important as is the shape and density of the anvil bottom. These data and calculations will be discussed, along with what we have learned from MHD calculations. To date, we have been unable to calculate accurate R(t) curves accurately from first principles with MHD codes, but have gained increased insight into performance.