Energy storage systems will likely be needed for future shipboard power systems that supply loads with high power variability such as pulsed power loads. The power generation in shipboard power systems may not be sufficient to satisfy the energy demands of the pulsed power load systems operating in conjunction with other ship service loads. Two fundamental items in evaluating the requirements of an energy storage system are the energy storage capacity and the ratings of the power conversion equipment that interfaces the energy device to the power system. The supply current of pulsed power load systems is aperiodic and cannot be described in terms of active power. Also, the RMS value and thus apparent power are only defined for periodic quantities. Therefore traditional methods of rating power equipment cannot be used. This thesis describes an approach to determine the ratings of an energy storage interface and the energy storage capacity of an energy storage device as a function of load and supply parameters. The results obtained using the proposed approach are validated with the results obtained from the simulation model of the generator supplying a pulsed power load in conjunction with an energy storage system. The energy storage system requirements for various pulsed power load profiles are obtained using the proposed approach. The method used for determining the ratings of an energy storage system utilizes an orthogonal decomposition of pulsed power load system supply current evaluated within a sliding window. The signals obtained from the decomposition are also useful in generating the control reference signals for the energy storage interface. Although the approach and methods are focused on a particular structure of the pulsed power load system, they may be generalized for use in any type of configuration of a pulsed power load system.

A slab-coupled optical fiber sensor (SCOS) falls into a narrow class of all-dielectric optical fiber electric field sensors, which makes it a perfect candidate for measurements of high electric fields in environments where presence of conductors is highly perturbing to the system under test. Its nonlinear response to high fields requires a new nonlinear calibration technique. A nonlinear calibration method is explained and demonstrated to successfully measure high electric fields, as well as high voltages with dynamic range up to 50 dB. Furthermore, a SCOS can be fitted into narrow spaces and make highly localized measurements due to its small size. This allows a SCOS to be integrated inside a standard high voltage coaxial cable, such as RG-218. Effects of partial discharge and arcing is minimized by development of a fabrication method to avoid introduction of impurities, especially air-bubbles, into the cable during SCOS insertion. Low perturbation of the measured voltage is shown by simulating the introduced voltage reflections to be on the order of –50 dB. It is also shown that a SCOS can be inserted into other cables without significant perturbation to the voltage. A complete high voltage and high electric field measurement system is built based on the high-voltage modifications of the SCOS technology. The coaxial SCOS is enhanced for robustness. Enhancements include packaging a SCOS into stronger ceramic trough, strengthening the fiber with kevlar reinforced furcation tubing and protecting the sensor with metal braces and protective shells. The interrogator is protected from electromagnetic interference with an RF-shielded box. Reduction in power losses introduced by the new PANDA-SCOS technology allows interrogator bandwidths to be increased up to 1.2 GHz. The whole measurement process is streamlined with dedicated software, developed specifically for high voltage and electric field measurements with support for the nonlinear calibration.

A slab-coupled optical fiber sensor (SCOS) falls into a narrow class of all-dielectric optical fiber electric field sensors, which makes it a perfect candidate for measurements of high electric fields in environments where presence of conductors is highly perturbing to the system under test. Its nonlinear response to high fields requires a new nonlinear calibration technique. A nonlinear calibration method is explained and demonstrated to successfully measure high electric fields, as well as high voltages with dynamic range up to 50 dB. Furthermore, a SCOS can be fitted into narrow spaces and make highly localized measurements due to its small size. This allows a SCOS to be integrated inside a standard high voltage coaxial cable, such as RG-218. Effects of partial discharge and arcing is minimized by development of a fabrication method to avoid introduction of impurities, especially air-bubbles, into the cable during SCOS insertion. Low perturbation of the measured voltage is shown by simulating the introduced voltage reflections to be on the order of −50 dB. It is also shown that a SCOS can be inserted into other cables without significant perturbation to the voltage.A complete high voltage and high electric field measurement system is built based on the high-voltage modifications of the SCOS technology. The coaxial SCOS is enhanced for robustness. Enhancements include packaging a SCOS into stronger ceramic trough, strengthening the fiber with kevlar reinforced furcation tubing and protecting the sensor with metal braces and protective shells. The interrogator is protected from electromagnetic interference with an RF-shielded box. Reduction in power losses introduced by the new PANDA-SCOS technology allows interrogator bandwidths to be increased up to 1.2 GHz. The whole measurement process is streamlined with dedicated software, developed specifically for high voltage and electric field measurements with support for the nonlinear calibration.

The electronic control, instrumentation and communication hardware is becoming more and more compact and faster in operation due to the increased use of large scale integration of semiconductor devices operating at higher speeds. The use of VLSI circuit based systems in various industrial and defence sectors is also increasing continuously. Since the operating threshold voltages and currents of these devices are very small they are very prone to electrical disturbance in their operation by the Electromagnetic Interference (EMI) signals. Their proper functioning is very important particularly in the case of systems used in mission mode, critical defence/industrial platforms. EMI can be generated within the electronic system/equipment itself or may result due to some external electromagnetic source. The high power Ultra Wide Band system is one such kind of external High Power Electromagnetic (HPEM) interference source which may cause malfunctioning/physical damage to the sensitive electronic systems. Hence it is necessary to test the susceptibility of electronics to such high power UWB based intentional EMI or IEMI sources. The sources for generating these transient EM fields may also be used in impulse radars and offensive applications to mal-operate/damage non-friendly electronics. The UWB system consists of a high voltage pulsed power source called pulser along with a high bandwidth (Ultra Wide Band) antenna to radiate the UWB signal. The pulse fed by the pulser to the antenna through a switch is of high voltage type (amplitude of few 10s of kV to about a MV) and has a sub-nanosecond rise time. Most of the UWB systems developed over the world have the switch employing gaseous dielectric switching media used at pressures above the atmospheric level to generate such a fast rise time voltage pulse. Use of gaseous switching media at sub-atmospheric pressures to achieve sub-ns rise time, short duration high voltage pulses required for the high power UWB applications is another possibility. This possibility has not been exploited till date. Hence it was decided to develop a pulser switch with gaseous switching media at sub-atmospheric pressures (up to 50 mbar) and achieve sub-ns rise time voltage pulses of up to 50 kV. The energy delivered out by the UWB system depends upon the pulser output energy per switching shot and the repetitive switching rate of the pulser. To achieve maximum energy output it is required to maximize either the energy per switching shot or the pulse repetition rate (PRR) of the pulser switch. The optimization of the pulser operation to achieve maximum pulser energy output in every switching shot has not been tried so far. In this work it was decided to analyze the circuit so as to achieve maximum pulser output energy per switching shot. Another objective of the study was to systematically characterize the pulser switch using various gases and gas mixtures as the switching media to evaluate the switch performance as a function of gas pressure and switch breakdown voltage. The effect of pulser and antenna performance parameters on the UWB system performance was also decided to be evaluated. Hence the present thesis work deals with the design, development, evaluation and performance optimization of a 50 kV, 25 MW UWB system based on Half Impulse Radiating Antenna (HIRA) fed by a coaxial capacitive pulser. The spark gap type self triggered pulser switch is designed to have a fixed gap spacing and variable gas pressure in order to vary the switch breakdown voltage. The switch is designed for operation with dry air, nitrogen, sulphur hexafluoride (SF6) and a mixture of different gases as the dielectric switching media with pressures of up to 5 bar above the atmospheric level and up to 50 mbar below the atmospheric level. Physical placement of the switch just above the coaxial pulser capacitor terminal offered a low inductance geometry. The rise time estimation of the switch has been carried out as a function of gas pressure and the switch arc inductance. These rise time values have been compared with the measured ones and a good agreement was found between the two. The rise time values indicate that an inverse relationship exists between the gas pressure and the rise time. The rise time was found to decrease at increased pressures. SF6 gas offered the minimum rise time out of all the gases/mixtures studied. The pulse repetition rate (PRR) of the UWB system depends upon the dielectric recovery of the gaseous switch and the charging time of the pulser capacitor. To estimate the PRR a circuit model has been proposed based on these parameters. The model shows an inverse relationship between the switch breakdown voltage (BDV) and the gas pressure with the PRR. The estimated PRR values were found to vary between 800 Hz and 5 kHz in the experimented range of the switch breakdown voltage. The PRR values have also been experimentally measured. There is a good match between the measured and the estimated values up to the switch BDV of 12.5 kV after which the difference is increased to about 20 %. The feed for the reflector of the HIRA antenna consists of a pair of coplanar conical transverse electromagnetic (TEM) feed plates as they have a better antenna aperture blockage performance. The angles of the TEM feed plates have been chosen using stereographic projections of the feed plates into the HIRA reflector. Each TEM feed plate of 200  characteristic impedance has been terminated by matched resistor. An analytical expression has been derived to optimize the pulser output voltage at which the energy output per switching shot of the UWB system is maximum. It was found that when the pulser output voltage i.e. the switch breakdown voltage is 75 % of the dc source voltage the output energy delivered is maximum. It was possible to achieve a maximum output energy of 10 J per switching shot for the designed 25 MW high power UWB system. The HIRA antenna has been analysed for the impedance profile for frequencies up to 3.5 GHz and was found to maintain a reflection performance better than -10 dB over the frequency range. The radiated field analysis of the antenna was carried out using an analytical model and numerically by using a commercially available software. It was found that as per the analytical model, the Figure of Merit (FoM) of the designed UWB system is 1.41 V for a normalized excitation feed pulse of 1 V and the 3 dB spectral content of the radiated field is between 180 MHz-1.8 GHz. The corresponding results using computer simulations of the UWB system indicate a slightly lesser FoM of 1.1. Higher FoM obtained using the analytical model is due to ignoring the antenna aperture blockage and the field diffraction effects over the TEM feed arms as well as from the rim of the reflector of the antenna. The radiated field amplitude and gain of the HIRA antenna were found to be a direct function of the frequency of the radiated signal. Higher gains and narrower beam width for the radiated field were observed with an increase in the frequency. The radiated field spectral waveform in the near field region was observed to have a notch at a particular frequency and its harmonics. The notch frequency was found to be a function of the propagation time difference called clear time. The effect of pulser rise time, antenna feed arm impedance and position on the radiated far field amplitude and wave shape was analysed. It was observed that with decrease in the pulser rise time from 700 ps to 100 ps, the radiated field amplitude increases by about 600 %. A matched termination impedance with position of 30of the TEM feed arms with respect to the vertical symmetry axis of the antenna provides a higher radiated field amplitude and lower post pulse oscillations in the radiated field waveform. The pulser switch was evaluated systematically for various performance parameters such as BDV, rise time, PRR, voltage recovery and jitter characteristics as a function of switch gas pressure, type of gaseous switching media and breakdown voltage at pressures above and below the atmospheric level. The switch BDV was found to be a linear function of pressure of the gas used i.e. dry air, nitrogen, sulphur hexafluoride (SF6) and a mixture of air and SF6. The measured rise times of all the gases were found to be in inverse proportion to the switch gas pressure. SF6 gas offered the best rise time and hence was found to be a good contender for achieving higher radiated field amplitudes and bandwidth. The voltage recovery characteristics of SF6 gas and air were experimentally studied as a function of the recovery time. It is found that both the gases have similar recovery characteristics having a distinct saturation plateau region. It was found that for a given recovery time SF6 recovers to a higher voltage than air and the recovery further improves for SF6 at increased pressures (between 0.5-2 bar). The effect of the number of switching shots on the jitter in the switch rise time was measured by operating the switch continuously at a PRR of 1 kHz and for total number shots up to 10.8 M. It was observed that the jitter increases by an order of magnitude after 10.8 M shots. This indicates that for the present switch design, the switch electrodes require maintenance (buffing, polishing, etc.) after every 3.5 M shots to maintain a reasonably low jitter. SF6 gas was characterized for a fixed source voltage to determine the effect of pressure on rise time in the sub atmospheric regime (up to 50 mbar). It was found that the rise time vs. pressure characteristics follows the Paschen’s curve with a value of pressure at which rise time is the lowest for a given source voltage. With increase in the source voltage the rise time was found to decrease. The HIRA based UWB radiating system was evaluated for radiated fields in the near and far field region for the temporal and spectral characteristics. It was found that for the source voltage of 25 kV, the FoM in the near and far field region are 29.4 kV and 28.9 kV respectively. The fields in the distant far field region have more oscillatory post pulses due to the effect of ground reflections and the low frequency dipole moment mismatch of the antenna. Since SF6 gas offered the best rise time of 193 ps at a voltage of 46 kV than the other gases tried, the radiated field is the highest (5.3 kV/m) with SF6 at a distance of 10 m offering a gain factor of 1.15. Dry air offered a radiated field gain factor of 0.83 which got improved by 33 % by just 30 % addition of SF6 gas into the air. The field amplitudes measured were in good agreement with those computed using the analytical model and the computer simulations and they follow the 1/R rule as a function of the far field distance, R in the bore sight direction. The measured radiation pattern of the UWB system showed a focussed and narrow radiated field beam at higher frequencies with a half field beam width (HFBW) of 8 at 2 GHz. The UWB system was measured to have dominant highest cut off frequency of 1.79 GHz with a band ratio and percentage band width of 9.56 and 162.11 % respectively. This confirmed that the developed system is of sub-hyper band radiator type. The UWB system developed through this work is having a better performance than some of the other systems developed elsewhere in the world, in terms of FoM (53 kV) and the PRR (> 1 kHz). The system can be further improved in terms of consistency (jitter) and intensity by use of a triggered switch and hydrogen gas at 100 bar pressure as the switching medium respectively. The profile of the TEM feed plates of the HIRA antenna may be further improved to have a better antenna aperture fill factor. Such multiple systems in an arrayed manner may be used either for higher power output/better agility of the radiated field beam. This system will be fully exploited for the applications of susceptibility evaluation of electronic circuits, non-friendly applications as well as impulse radars

Les céramiques sont couramment utilisées depuis les années 1960 comme matériaux constitutifs de blindages. En effet, grâce à leurs très bonnes propriétés physiques et mécaniques, elles permettent, pour un même niveau de protection, un gain de masse important par rapport aux blindages métalliques. Cependant, la microstructure d’une céramique peut avoir une forte influence sur sa résistance à l’impact. Le but de cette thèse est, à partir d’essais de caractérisation et en se basant sur l’utilisation de quatre nuances de carbure de silicium présentant des microstructures différentes, d’éclaircir les liens entre microstructure et performance à l’impact. Les campagnes expérimentales de compression dynamique et d’écaillage sont basées sur une utilisation innovante du moyen GEPI installé au CEA Gramat. Pour l’étude du comportement en compression dynamique des céramiques, il a permis d’utiliser la technique d’analyse lagrangienne et ainsi de remonter à l’évolution de la résistance des matériaux au cours du chargement. Pour les essais d’écaillage, il a permis, entre autres, une étude de la sensibilité à la vitesse de déformation de la résistance en traction dynamique. La caractérisation de la fragmentation dynamique est quant à elle basée sur des essais d’impact sur la tranche. Un essai innovant d’impact sur céramique préalablement fragmentée a également été dimensionné et réalisé. Ces différents essais expérimentaux ont permis de mettre en évidence et de comprendre l’influence de la microstructure du matériau sur son comportement face aux différents types de sollicitations. L’ensemble des résultats expérimentaux a été comparé à des simulations numériques permettant de valider les lois de comportement utilisées. Le modèle de fragmentation des matériaux fragiles DFH (Denoual-Forquin-Hild) a ainsi montré de très bonnes capacités à simuler le comportement des céramiques sous chargement de traction dynamique (écaillage et fragmentation) / Since the sixties, ceramics are commonly used as armour materials. Indeed, thanks to their interesting physical and mechanical properties, they allow a significant weight benefit in comparison to monolithic steel plate armours. However, the microstructure of the ceramic may have a strong influence on its penetration resistance. Based on characterisation tests and on the use of four silicon carbide grades, this work aims to highlight the links between the microstructure and the ballistic efficiency. Experimental compressive and spalling tests are based on the use of the GEPI device. For studying the compressive dynamic behaviour, it allows using the lagrangian analysis method and characterising the yield strength of the material. For studying the tensile dynamic behaviour, it allows assessing the strain-rate sensitivity of the spall strength. An analysis of the fragmentation process is performed based on Edge-On Impact tests. Moreover, an innovating impact test on fragmented ceramics has been designed and performed. The different experimental results allow a better understanding of the influence of the ceramic microstructure on its behaviour under the different loadings. All the experimental data have been compared to numerical results allowing validating the constitutive models. The DFH (Denoual-Forquin-Hild) damage model of brittle materials showed very good capacities to simulate the tensile dynamic behaviour of ceramics (spalling and fragmentation)

Ce projet de recherche s’inscrit dans le parcours international de la maitrise de Physique (option plasma) de l’Université de Montréal en collaboration avec l’Université Paul Sabatier de Toulouse (France). Il concerne la caractérisation des décharges électriques (Sparks) dans les liquides diélectriques et ses applications dans la synthèse de nanoparticules. L’objectif est d’amélioré la connaissance des conditions de formation des nanoparticules. Cela implique de caractériser l’ensemble du système expérimental et de développer sa métrologie d’une part, et d’autre part d’obtenir l’évolution des paramètres plasma lors de la synthèse. Dans un premier temps, sur le site du LAPLACE (UMR5213), Toulouse, il a fallu développer une alimentation électrique impulsionnelle destinée à réaliser des décharges dans les liquides. En se basant sur un dispositif existant qui fût amélioré, le fonctionnement a été caractérisé du point de vue électrique (courant - tension). L’application à la synthèse de nanoparticules a été ensuite abordée pour différentes conditions expérimentales, en considérant l’aspect énergétique (bilan d’énergie, caractéristiques de la décharge…). Les travaux se sont poursuivis à l’Université de Montréal, où un circuit électrique équivalent du système expérimental est réalisé afin de visualiser l’évolution temporelle des paramètres plasma (température et densité électronique) en fonction des paramètres électriques choisis. Aussi, la synthèse de nanoparticules de Co et Ni par la décharge a été évaluée et les nanoparticules formées sont caractérisées à l’aide du microscope électronique à Transmission de Polytechnique Montréal. / This research project is part of the international master's program in Physics (plasma option) between Université de Montréal and Université Paul Sabatier - Toulouse (France). It concerns the synthesis of nanoparticles by pulsed electrical discharges in liquids. The objective is to develop the synthesis process while improving the knowledge of the formation conditions of nanoparticles. This involves characterizing the entire experimental system and developing its metrology on the one hand, and on the other hand obtaining the evolution of plasma parameters during synthesis. Initially, at the LAPLACE lab (UMR5213), Toulouse, it was necessary to develop a pulsed electrical supply to produce discharges in liquids. Based on an existing device that, after being improved, the discharge process is characterized from the electrical point of view (current, voltage). The application of the device in the synthesis of nanoparticles was tested under different experimental conditions, considering the energy aspect (energy balance, characteristics of the discharge, etc.). The second part was conducted at Université de Montréal, where the synthesized nanoparticles are characterized using the transmission electron microscope of Polytechnique Montreal. Also, the electrical circuit equivalent to the experimental system was determined to visualize the time evolution of the plasma parameters (Temperature and Electron Density) based on the electrical characteristics.

This thesis deals with the aspects of methods for pulsed high-level EM quantities measurement. Methods for current and voltage measurement in pulsed power generator and power measurement in pulse microwave generator are discussed. New approaches to single-shot measurement methods application are proposed. The theoretical analysis of suitable sensor designs is performed. The magneto-optic measurement method has been experimentally realized. On the basis of experimental results a fiber-optic current sensor has been designed and theoretically analyzed. For identification and measurement of the free-space electromagnetic pulse a combined calorimetric sensor has been designed and built.