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1
Dupriez, Pascal. "Advanced high-power pulsed fibre laser systems and their applications". Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/65498/.
Texto completo da fonteResumo:
In this thesis, I report experimental studies towards power scaling of ultrashort fibre-based sources designed for applications including high average power femtosecond pulse generation and nonlinear frequency conversion. While the power produced by rare-earth doped fibre lasers operating in continuous-wave has dramatically increased within a few years to exceed the kilowatt level, pulsed fibre sources have been limited to tens of watts due to the onset of nonlinearities in fibre amplifiers. Therefore the aim is to manage fibre nonlinearities to achieve specific output properties at high average power. An innovative aspect of this work lies in the remarkable combination of telecom-grade semiconductor laser sources and high-power Yb-doped fibre amplifier technologies to produce short pulses at very high average power. Fibre nonlinear effects are often detrimental to the performance of fibre systems but can also provide an attractive tool to generate new useful wavelengths. The final part of this thesis describes efficient white light generation produced by a microstructure fibre pumped by the previously described green fibre source. Furthermore, I investigated a novel fibre source configuration for guide star application. The source I developed produced 1W at 589 nm through frequency doubling of 1178 nm radiation produced by pulsed Raman amplification in an Yb-doped fibre amplifier.
2
Kumar, Rajesh. "High power Tesla driven miniature plasma opening switch". Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/5478.
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The plasma opening switch (POS) is used in pulsed power systems where a very fast opening and high current switch is required. Plasma is injected into the switch, which carries a large conduction current, before it opens in a process that lasts for a few nanosecond and transfers the current to a parallel-connected load at a much increased voltage and with a much shorter rise time. The conduction and opening times of the switch are dependent on plasma parameters such as the distribution, speed and species, all of which are determined by the plasma source. Most of the earlier reported work involves large dimension POSs and a correspondingly high input current (more than 100 kA) and uses carbon plasma. One main objective of the present research was to achieve a low input current (20 kA) and miniaturised POS by using hydrogen plasma rather than carbon plasma on account of its lower mass. A cable gun was selected for producing the plasma, since although this produces both hydrogen and carbon plasma these arise different times during its operation. For the present application a Tesla transformer was used in preference to a Marx generator to produce an initial high voltage pulse for the system, on the basis of its simpler design and cost effectiveness. This transformer together with an associated water PFL (pulse forming line) and pressurised switch was capable of producing a load current in excess of 20 kA with a rise time of 53 ns, which was fed through the POS to the final load. Special diagnostics arrangements were necessary to measure the fast high current and voltage pulse a in nonintrusive way. Faraday cups and a high speed camera were used to measure the plasma parameters. The overall system built (i.e. including the POS) is capable of producing a 22 kA current with a rise time of 5 ns, and of generating a power of more than 10 GW. Much of the work detailed in the thesis has already been presented in peer reviewed journals and at prestigious international conferences.
3
Talebi, Rafsanjan Salman. "Advanced high-speed flywheel energy storage systems for pulsed power application". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3163.
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4
Price, Jonathan Hugh Vaughan. "The development of high power, pulsed fiber laser systems and their applications". Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15475/.
Texto completo da fonteResumo:
Rare-earth doped silica fibers have been used for many years to create continuous-wave lasers, and Er-doped fiber amplifiers are now widely used in telecommunications. In addition, cladding pumped fiber allows the efficient conversion of multimode radiation from high power, low cost, broad-stripe semiconductor laser diodes into the single-mode emission of fiber lasers. With its broad gain bandwidth and high optical conversion efficiency, Yb-doped silica fiber represents an attractive medium for the generation and amplification of high energy ultrashort optical pulses. However, these potential advantages of Yb-doped silica fiber as a gain and nonlinear medium for mode-locked lasers and ultrashort pulse amplifiers have been less well studied, and it was not until 1999 that significant research interest first appeared in Yb-fiber chirp pulse amplifier (CPA) systems. This thesis describes the development of the first practical and stable, femtosecond, Yb-fiber oscillator, and of an Yb-fiber amplifier based CPA system (pulses ~10 μJ, <500 fs). Novel aspects of the system include the use of a high extinction ratio Electro-Optic modulator for pulse selection, and the development of a compact chirped-fiber-Bragg-grating (CFBG) pulse stretcher that provides both 2nd and 3rd order chirp compensation. Recently published theoretical results have demonstrated that the asymptotic solution for ultrashort pulses in a high gain fiber amplifier is a linearly chirped pulse, which can therefore be recompressed with a standard grating compressor. This thesis reports the first experimental comparison of nonlinear pulse evolution towards the asymptotic form using a cascaded amplifier system. The "direct amplification" system was constructed by removing the CPA stretcher grating, which also enabled the use of a less dispersive and more compact compressor. Further system development should lead to the generation of ultrashort pulses at high average power levels and >100 kHz repetition rates. Holey fiber (HF) is a recently developed technology that uses rings of air holes around a solid core to confine the optical field by average-index effects. Fibers are highly suitable for applications using nonlinear optics because of the tightly confined mode and long interaction lengths. The increased mode confinement possible using HF means that small-core, high air-fill fraction HF are an attractive nonlinear medium. Furthermore, the high index contrast in such fibers can create a strong (anomalous) waveguide contribution to the dispersion, and such HFs can have anomalous dispersion at wavelengths <1.3 μm, where conventional fiber has normal dispersion. Therefore HFs can support solitons in new wavelength bands. This thesis reports the first demonstration of linear dispersion compensation, soliton transmission, and visible continuum generation seeded by a 1.06 μm Yb-fiber source. In addition, an experimental study is reported that used HF seeded from a Ti:Sapphire laser to generate continuum in distinct transverse spatial modes of a HF. Numerical simulations suggested that the observed enhancement in UV generation from a higher order mode could be due to differences in the dispersion profiles of the fundamental and higher order transverse modes. Finally, the development of a novel source of <200 fs pulses, continuously tuneable in wavelength from 1.06-1.33 μm, based on the soliton self-frequency-shift principle, is described. The source was constructed from a diode-pumped Yb-doped HF amplifier, and the Yb-fiber oscillator described above. The diode pump power controlled the output wavelength.
5
Piper, Andy. "The development of high power, pulsed fiber laser systems and their applications". Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/42427/.
Texto completo da fonteResumo:
Due to the recent renewal in interest in fiber laser technology, continuous wave (c.w.) laser technology using rare-earth doped silica fibers has developed rapidly in the past few years. In the late 80s, Erbium Doped Fiber Amplifiers were commercialised and became widely used in the telecommunications industry. Yb-doped silica fiber is particularly attractive as its broad gain bandwidth and high optical efficiency make it a preferred choice for both pulsed and c.w. high power fiber laser and amplifier applications. With the advent of cladding pump technology, low cost, high power broad-stripe semiconductor laser diodes with multimoded radiation could be efficiently used to produce high power Yb-doped silica fiber lasers with either single (~ 1 kW) or multimode (~ 10 kW) emission. Finally, the development and demonstration of a novel gain switched laser diode operating at 1 µm is reported. Using this gain switched laser diode as a seed source; the output gain switched pulses were compressed to 20 ps using a fiber compressor and thereafter amplified to achieve an output average power of 11.1 W at 1 GHz repetition rate using an YDFA cascade. Additional novel work was carried out later where a linearly dispersive CFBG was used to compress the pulses to 16.6 ps. These pulses were later amplified to average powers of 321 W at 1 GHz. This we believe is the highest output power ever achieved for a short pulse fiber laser system.
6
Sözer, Esin Bengisu Kirkici Hulya. "Gaseous discharges and their applications as high power plasma switches". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Thesis/Sozer_Esin_45.pdf.
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7
Benwell, Andrew L. "Flashover prevention on polystyrene high voltage insulators in a vacuum". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5018.
Texto completo da fonteResumo:
Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 18, 2008) Includes bibliographical references.
8
Patil, Sandeep Kesharsingh. "Modeling and simulations of diphasic composites for development of high energy density dielectrics". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Patil_09007dcc804e35ca.pdf.
Texto completo da fonteResumo:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2008) Includes bibliographical references.
9
Adamonis, Jonas. "High power Nd:YAG laser for pumping of OPCPA systems". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093516-33211.
Texto completo da fonteResumo:
This thesis was aimed to develop, investigate and optimize high power Nd:YAG laser system for OPCPA (Optical Parametric Chirped Pulse Amplifiers) pump. The particular attention is paid for the temporal characteristics of the Nd:YAG amplifies output pulse. Employment of Fabry-Perоt etalons in the cavities of two-stage Nd:YAG regenerative amplifier enables for amplified pulse stretching from 60 fs to ~ 100 ps pulse widths. The modulation of amplified pulse envelope is minimal when ration of thickness of the etalons is around 2. Envelope modulation can be controlled by changing the reflectivity of etalons. In order to improve amplified pulse contrast, we for the first time to our knowledge implemented second order intensity dependent filter, based on the effect of fundamental pulse polarization rotation in unbalanced second harmonic generators. By using this method, the contrast of the output pulses was improved by >102 times. We also demonstrated that Gaussian pulses from the output of Nd: YAG amplifiers can be transformed into flat–top pulses by using cascade second harmonic generation processes. The developed high output energy Nd:YAG amplifiers system for OPCPA pumping is optically synchronized with pulses of Yb:KGW oscillator and features two 532 nm outputs with pulse parameters: a) Gaussian pulse profile, ~ 300 mJ energy, 75 ps pulsewidth; b) hiper- Gaussian pulse profile, ~100 mJ energy, pulse width 100-150 ps.Disertacija yra skirta sukurti, ištirti ir optimizuoti didelės galios Nd: YAG lazerių sistemą efektyviam moduliuotos fazės signalų optinių parametrinių stiprintuvų kaupinimui. Ypatingas dėmesys yra skiriamas Nd:YAG stiprintuvų išvadinių impulsų laikinių parametrų formavimui. Pademonstravome, kad Fabry-Pero interferometrų panaudojimas Nd:YAG dvipakopio regeneracinio stiprintuvo rezonatoriuose leidžia stiprinamų impulsų trukmę padidinti nuo ~ 60 fs iki 100 ps. Tuo tarpu išvadinių impulsų laikinės plėtros mastas bei gaubtinės moduliacijos gylis gali būti valdomas keičiant etalonų atspindžio koeficientą, o jų gaubtinės moduliacijos vertė mažiausia, kai etalonų storio santykis artimas 2. Sustiprintų impulsų kontrasto gerinimui pirmą kartą pritaikėme netiesinį antros eilės filtrą, veikiantį fundamentinės spinduliuotės poliarizacijos sukimo, išderintame antros harmonikos generatoriuje, efekto pagrindu. Tokiu būdu Nd:YAG stiprintuvuose sustiprintų impulsų kontrasto vertė pagerinta apie 102 kartų. Taip pat pademonstruota, kad Nd: YAG stiprinimo sistemos išėjime naudojant pakopinius antros harmonikos generacijos procesus, Gauso formos impulsus galima transformuoti į hipergauso impulsus. Sukurta didelės išvadinės energijos pikosekundinė Nd:YAG stiprintuvų sistema yra optiškai sinchronizuota su užduodančio femtosekundinio Yb:KGW osciliatoriaus impulsais ir turi ~ 300 mJ , 75 ps trukmės Gauso impulsų bei 100 mJ, > 100 ps trukmės hipergauso laikinės formos impulsų išvadus.
10
He, Fei. "The development of high power fibre chirped pulse amplification systems". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/70913/.
Texto completo da fonteResumo:
With its broad gain bandwidth and high optical conversion efficiency, ytterbium (Yb)-doped silica fiber represents an attractive medium for the generation and amplification of ultrashort optical pulses. Research interest in Yb-doped fiber chirped pulse amplifier (CPA) systems first appeared in the late 1990s. However, the potential advantages and capabilities of Yb-doped fiber CPA systems were not fully studied during the early research. Further scaling of both the average power and the pulse energy have now become possible with the development of several key technologies that are associated with Yb-doped fiber CPA systems. Finally, the development of a novel fiber CPA system operating with strong selfphase-modulation (SPM) is described, which applied adaptive shaping of the spectral phase of the input pulses. The pre-compensation of both SPM induced phase distortion at high energies, and residual dispersion from mismatched stretcher/compressor technologies at low energies are investigated
11
Vaupel, Andreas. "High Energy, High Average Power, Picosecond Laser Systems to Drive Few-Cycle OPCPA". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5881.
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The invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA allows direct amplification of an almost-octave spanning bandwidth supporting few-cycle pulse durations at center wavelengths ranging from the visible to the mid-IR. The current record in peak power from a table-top OPCPA is 16 TW and the current record average power is 22 W. High energy, few-cycle pulses with stabilized carrier-envelope phase (CEP) are desired for applications such as high-harmonic generation (HHG) enabling attoscience and the generation keV-photon bursts. This dissertation conceptually, numerically and experimentally describes essential aspects of few-cycle OPCPA, and the associated pump beam generation. The main part of the conducted research was directed towards the few-cycle OPCPA facility developed in the Laser Plasma Laboratory at CREOL (University of Central Florida, USA) termed HERACLES. This facility was designed to generate few-cycle pulses in the visible with mJ-level pulse energy, W-level average power and more than 100 GW peak power. Major parts of the implementation of the HERACLES facility are presented. The pump generation beam of the HERACLES system has been improved in terms of pulse energy, average power and stability over the last years. It is based on diode-pumped, solid-state amplifiers with picosecond duration and experimental investigations are presented in detail. A robust system has been implemented producing mJ-level pulse energies with ~100 ps pulse duration at kHz repetition rates. Scaling of this system to high power (>30 W) and high peak power (50-MW-level) as well as ultra-high pulse energy (>160 mJ) is presented. The latter investigation resulted in the design of an ultra-high energy system for OPCPA pumping. Following this, a new OPCPA facility was designed termed PhaSTHEUS, which is anticipated to reach ultra-high intensities. Another research effort was conducted at CELIA (Univerist&"233; de Bordeaux 1, France) and aimed towards a previously unexplored operational regime of OPCPA with ultra-high repetition rates (10 MHz) and high average power. A supercontinuum seed beam generation has been established with an output ranging from 1.3 to 1.9 ?m and few ps duration. The pump beam generation has been implemented based on rod-type fiber amplifiers producing more than 37 W average power and 370 kW peak power. The utility of this system as an OPCPA pump laser is presented along with the OPA design. The discussed systems operate in radically different regimes in terms of peak power, average power, and repetition rate. The anticipated OPCPA systems with few-cycle duration enable a wide range of novel experimental studies in attoscience, ultrafast materials processing, filamentation, LIBS and coherent control.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
12
Dulgergil, Ebru. "Development Of A Pulsed Fiber Laser For Ladar System". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614635/index.pdf.
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In recent years laser technology has increasingly developed with the use of
fiber lasers and this has provided the possibility to implement different techniques in
the defense industry. LADAR is at the forefront of these techniques. Fiber lasers
constitute a perfect source for LADAR systems due to their excellent robustness,
compact size and high-power generation capability. In this study we will explore the
development of a pulsed fiber laser source for a LADAR system that can obtain high
resolution 3D images in eye-safe region.
A high power, all fiber integrated erbium system with strictly single mode
operation in eye-safe region based on MOPA (master oscillator power amplifier)
configuration with seed source and amplifier part was developed. Both the use of an
actively mode locked laser with erbium doped fiber and fiber coupled modulated
distributed feedback diode laser were investigated as seed sources for the amplifier
part. Both erbium doped single clad fiber and erbium-ytterbium doped double clad
gain fiber were used in this amplifier system. After amplification of the actively
mode locked laser, 12 W of average optical power was obtained through single
mode fiber with 1ns pulse duration at 10 MHz which corresponds to 1.2 kW peak
power. For the fiber coupled DFB diode laser, 9.5W average power was obtained
with around 8 ns duration pulses at 100 kHz and about 9.2 W average power was
also obtained with around 700 ps duration pulses at 1 MHz through strictly single
mode fiber at the output of the same amplifier system as was used in the actively
mode locked seed source. In both cases calculated peak power was around 10 kW
v
which is estimated as the highest peak power for an all fiber integrated system with
single mode operation.
The development of such a fiber system with high power capability, compact
size and free of misalignment is expected to be useful for LADAR application as
well as other areas such as eye surgery, 3D silicon processing or any other material
processing applications.
13
Yagci, Mahmut Emre. "Development Of A Picosecond Pulsed Mode-locked Fiber Laser". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615773/index.pdf.
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Fiber lasers represent the state-of-the-art in laser technology and hold great promise for a
wide range of applications because they have a minimum of exposed optical interfaces,
very high efficiency, and are capable of exceptional beam quality. In the near future, the
most important markets such as micromachining, automotive, biomedical and military
applications will begin to use this technology. The scope of this thesis is to design and
develop a short picosecond pulsed fiber laser using rare-earth doped fiber as a gain
medium. The proposed master oscillator power amplifier (MOPA) will be used to generate
pulses with high repetition rates.
In this study, first we explain the basic theoretical background of nonlinear optics and fiber
laser. Then, the numerical simulation will be introduced to explain how the laser system
design and optimization. The simulation is based on nonlinear Schrödinger equation with the method of split-step evaluation. The brief theoretical background and simulation results of the laser system will be shown. Finally, the experimental study of the developmental fiber laser system that comprises an oscillator, preamplifier and power amplifier will be discussed.
14
Marwali, Mohammad Nanda Rahmana. "Digital control of pulse width modulated inverters for high performance uninterruptible power supplies". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1100484647.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xviii, 224 p.; also includes graphics. Includes bibliographical references (p. 199-211).
15
Kadja, Tchamie. "Chip Scale Tunable Nanosecond Pulsed Electric Field Generator for Electroporation". University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1556028923379642.
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16
Nami, Alireza. "A new multilevel converter configuration for high power and high quality applications". Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/33216/1/Alireza_Nami_Thesis.pdf.
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The Queensland University of Technology (QUT) allows the presentation of theses for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of ten published /submitted papers and book chapters of which nine have been published and one is under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of investigating multilevel topologies for high quality and high power applications, with specific emphasis on renewable energy systems. The rapid evolution of renewable energy within the last several years has resulted in the design of efficient power converters suitable for medium and high-power applications such as wind turbine and photovoltaic (PV) systems. Today, the industrial trend is moving away from heavy and bulky passive components to power converter systems that use more and more semiconductor elements controlled by powerful processor systems. However, it is hard to connect the traditional converters to the high and medium voltage grids, as a single power switch cannot stand at high voltage. For these reasons, a new family of multilevel inverters has appeared as a solution for working with higher voltage levels. Besides this important feature, multilevel converters have the capability to generate stepped waveforms. Consequently, in comparison with conventional two-level inverters, they present lower switching losses, lower voltage stress across loads, lower electromagnetic interference (EMI) and higher quality output waveforms. These properties enable the connection of renewable energy sources directly to the grid without using expensive, bulky, heavy line transformers. Additionally, they minimize the size of the passive filter and increase the durability of electrical devices. However, multilevel converters have only been utilised in very particular applications, mainly due to the structural limitations, high cost and complexity of the multilevel converter system and control. New developments in the fields of power semiconductor switches and processors will favor the multilevel converters for many other fields of application. The main application for the multilevel converter presented in this work is the front-end power converter in renewable energy systems. Diode-clamped and cascade converters are the most common type of multilevel converters widely used in different renewable energy system applications. However, some drawbacks – such as capacitor voltage imbalance, number of components, and complexity of the control system – still exist, and these are investigated in the framework of this thesis. Various simulations using software simulation tools are undertaken and are used to study different cases. The feasibility of the developments is underlined with a series of experimental results. This thesis is divided into two main sections. The first section focuses on solving the capacitor voltage imbalance for a wide range of applications, and on decreasing the complexity of the control strategy on the inverter side. The idea of using sharing switches at the output structure of the DC-DC front-end converters is proposed to balance the series DC link capacitors. A new family of multioutput DC-DC converters is proposed for renewable energy systems connected to the DC link voltage of diode-clamped converters. The main objective of this type of converter is the sharing of the total output voltage into several series voltage levels using sharing switches. This solves the problems associated with capacitor voltage imbalance in diode-clamped multilevel converters. These converters adjust the variable and unregulated DC voltage generated by renewable energy systems (such as PV) to the desirable series multiple voltage levels at the inverter DC side. A multi-output boost (MOB) converter, with one inductor and series output voltage, is presented. This converter is suitable for renewable energy systems based on diode-clamped converters because it boosts the low output voltage and provides the series capacitor at the output side. A simple control strategy using cross voltage control with internal current loop is presented to obtain the desired voltage levels at the output voltage. The proposed topology and control strategy are validated by simulation and hardware results. Using the idea of voltage sharing switches, the circuit structure of different topologies of multi-output DC-DC converters – or multi-output voltage sharing (MOVS) converters – have been proposed. In order to verify the feasibility of this topology and its application, steady state and dynamic analyses have been carried out. Simulation and experiments using the proposed control strategy have verified the mathematical analysis. The second part of this thesis addresses the second problem of multilevel converters: the need to improve their quality with minimum cost and complexity. This is related to utilising asymmetrical multilevel topologies instead of conventional multilevel converters; this can increase the quality of output waveforms with a minimum number of components. It also allows for a reduction in the cost and complexity of systems while maintaining the same output quality, or for an increase in the quality while maintaining the same cost and complexity. Therefore, the asymmetrical configuration for two common types of multilevel converters – diode-clamped and cascade converters – is investigated. Also, as well as addressing the maximisation of the output voltage resolution, some technical issues – such as adjacent switching vectors – should be taken into account in asymmetrical multilevel configurations to keep the total harmonic distortion (THD) and switching losses to a minimum. Thus, the asymmetrical diode-clamped converter is proposed. An appropriate asymmetrical DC link arrangement is presented for four-level diode-clamped converters by keeping adjacent switching vectors. In this way, five-level inverter performance is achieved for the same level of complexity of the four-level inverter. Dealing with the capacitor voltage imbalance problem in asymmetrical diodeclamped converters has inspired the proposal for two different DC-DC topologies with a suitable control strategy. A Triple-Output Boost (TOB) converter and a Boost 3-Output Voltage Sharing (Boost-3OVS) converter connected to the four-level diode-clamped converter are proposed to arrange the proposed asymmetrical DC link for the high modulation indices and unity power factor. Cascade converters have shown their abilities and strengths in medium and high power applications. Using asymmetrical H-bridge inverters, more voltage levels can be generated in output voltage with the same number of components as the symmetrical converters. The concept of cascading multilevel H-bridge cells is used to propose a fifteen-level cascade inverter using a four-level H-bridge symmetrical diode-clamped converter, cascaded with classical two-level Hbridge inverters. A DC voltage ratio of cells is presented to obtain maximum voltage levels on output voltage, with adjacent switching vectors between all possible voltage levels; this can minimize the switching losses. This structure can save five isolated DC sources and twelve switches in comparison to conventional cascade converters with series two-level H bridge inverters. To increase the quality in presented hybrid topology with minimum number of components, a new cascade inverter is verified by cascading an asymmetrical four-level H-bridge diode-clamped inverter. An inverter with nineteen-level performance was achieved. This synthesizes more voltage levels with lower voltage and current THD, rather than using a symmetrical diode-clamped inverter with the same configuration and equivalent number of power components. Two different predictive current control methods for the switching states selection are proposed to minimise either losses or THD of voltage in hybrid converters. High voltage spikes at switching time in experimental results and investigation of a diode-clamped inverter structure raised another problem associated with high-level high voltage multilevel converters. Power switching components with fast switching, combined with hard switched-converters, produce high di/dt during turn off time. Thus, stray inductance of interconnections becomes an important issue and raises overvoltage and EMI issues correlated to the number of components. Planar busbar is a good candidate to reduce interconnection inductance in high power inverters compared with cables. The effect of different transient current loops on busbar physical structure of the high-voltage highlevel diode-clamped converters is highlighted. Design considerations of proper planar busbar are also presented to optimise the overall design of diode-clamped converters.
17
Degnon, Mawuena. "Étude des commutateurs semi-conducteurs à ouverture destinés à des applications de puissance pulsée avec des tensions de sortie allant jusqu'à 500 kV". Electronic Thesis or Diss., Pau, 2024. https://theses.hal.science/tel-04685830.
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Dans les systèmes de hautes puissances pulsées, le stockage inductif présente un avantage indéniable vis-à-vis du stockage capacitif du fait de sa plus forte densité d’énergie. L’exploitation de cet avantage nécessite toutefois l'utilisation d'un interrupteur à ouverture pour générer l'impulsion de tension. En outre, compte tenu de la demande croissante de générateurs impulsionnels fiables, en particulier pour les applications industrielles, il devient indispensable de recourir aux composants semi-conducteurs. La diode SOS (Semiconductor Opening Switch), développée dans les années 1990 à l'Institute of Electrophysics en Russie, est un candidat idéal pour la commutation état solide à ouverture, de par sa capacité à générer des impulsions de haute puissance de manière fiable et répétitive, tout en offrant une longue durée de vie et un fonctionnement exempt de maintenance. Cependant, le manque de fabricants de diodes SOS limite leur utilisation à grande échelle. Par conséquent, cette thèse se concentre sur l’étude de diodes disponibles dans le commerce (OTS : Off-The-Shelf) capables de commuter rapidement des courants élevés et de générer des tensions nanosecondes pouvant atteindre 500 kV. Plusieurs types de diodes, incluant les diodes de redressement, à avalanche, à temps de récupération rapide et de suppression de tension transitoire (TVS) ont été étudiés en tant qu’interrupteurs à ouverture, en comparaison avec les diodes SOS de référence. Pour mener à bien cette étude, des bancs d’essai à basse, moyenne et haute énergie (respectivement 25 mJ, 10 J et 40 J) ont été mis au point. Afin d’augmenter leur efficacité énergétique, ces bancs utilisent un circuit basé sur un élément magnétique unique : un transformateur impulsionnel saturable. Plusieurs noyaux magnétiques nanocristallins ont été examinés sur le banc de 10 J dans le but d’optimiser les performances du transformateur. Parmi les diodes étudiées sur les bancs de 25 mJ et 10 J, les diodes TVS et les diodes de redressement ont émergé du lot, démontrant des performances de temps de commutation de l'ordre de la nanoseconde et de tensions générées de plusieurs kilovolts. Enfin, un prototype de générateur de hautes puissances pulsées de 40 J (GO-SSOS) basé sur un interrupteur OTS composé de diodes de redressement a été développé. Le rendement énergétique du système varie de 35% à 70% selon la valeur de la charge, et la puissance crête obtenue est supérieure à 300 MW. Sur une charge de 1 kΩ, l'impulsion de tension générée atteint une amplitude de 500 kV avec un temps de montée de 36 ns et une largeur à mi-hauteur de 80 ns. La reproductibilité des impulsions à une fréquence de répétition de 60 Hz est démontrée, ainsi qu’une application de génération de décharges couronnes. Les travaux prouvent la fiabilité des diodes OTS en mode SOS, ne révélant aucune dégradation après quelques milliers d'impulsions générées. Ils ouvrent également la voie à l’utilisation de cette technologie pour des applications industrielles telles que la stérilisation par faisceau d’électronsIn pulsed power systems, inductive energy storage has an advantage over capacitive storage because of its higher energy density. Exploiting this advantage requires the use of an opening switch to generate the voltage pulse. Moreover, the growing need for reliable pulsed power generators, particularly for industrial applications, strongly supports the adoption of solid-state solutions. The Semiconductor Opening Switch (SOS) diode developed in the 1990s at the Institute of Electrophysics in Russia is an ideal candidate for solid-state opening switching because of its ability to reliably generate high-power pulses at high repetition rates while offering long lifetime and maintenance-free operation. However, the lack of SOS diode manufacturers prevents their widespread use. This thesis is therefore devoted to the study of off-the-shelf (OTS) diodes capable of rapidly switching high currents and generating nanosecond voltages of up to 500 kV. The research includes the investigation of various diode types including rectifier, avalanche, fast recovery, and transient voltage suppression (TVS) diodes as opening switches in comparison with state-of-the-art SOS diodes. Low, medium, and high-energy (25 mJ, 10 J, and 40 J respectively) test benches are developed for the experiments. Their circuits use a single magnetic element – a saturable pulse transformer – resulting in high energy efficiency. Several nanocrystalline cores are examined for optimum transformer performance at an energy of 10 J. Among the diodes investigated at 25 mJ and 10 J energy, the TVS and rectifying diodes stand out particularly promising with nanosecond switching time and generated voltages in the kilovolt range. Finally, a 40 J pulsed power generator prototype (GO-SSOS) based on an OTS opening switch consisting of rectifier diodes is developed. The GO-SSOS achieves a peak power of more than 300 MW with an energy efficiency ranging from 35% to 70% depending on the load value. Across a 1 kΩ load, the voltage pulse generated reaches 500 kV amplitude with a rise time of 36 ns and a pulse width of 80 ns. The system shows high reproducibility at a repetition rate of 60 Hz and is used to demonstrate a corona discharge application. The work proves the reliability of the OTS diodes in SOS mode, revealing no degradation after thousands of pulses. It also offers the prospect of using this technology in industrial applications such as electron-beam sterilization
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Stan, Nikola. "Complete Measurement System for Measuring High Voltage and Electrical Field Using Slab-Coupled Optical Fiber Sensors". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7053.
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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.
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Nguyen, Dat. "Dynamic feedback pulse shaping for high power chirped pulse amplification system". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5826.
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The topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic pulse shaping approaches. The experimental research addresses the topic of parabolic pulse generation in two distinct ways. First, pulse shaping technique involving a time domain approach is presented, that results in stretched pulses with parabolic profiles with temporal duration of 15 ns. After pulse is shaped into a parabolic intensity profile, the pulse is compressed with DCF fiber spool by 100 times to 80 ps duration at FWHM. A different approach of pulse shaping in frequency domain is performed, in which a spectral processor based on Liquid Crystal on Silicon technology is used. The pulse is stretched to 1.5 ns before intensity mask is applied, resulting in a parabolic intensity profile. Due to frequency to time mapping, its temporal profile is also parabolic. After pulse shaping, the pulse is compressed with a bulk compressor, and subsequently analyzed with a Frequency Resolved Optical Gating (FROG). The spectral content of the compressed pulse is feedback to the spectral processor and used to adjust the spectral phase mask applied on the pulse. The resultant pulse after pulse shaping with feedback mechanism is a Fourier transform, sub-picosecond ultrashort pulse with 5 times increase in peak power. The appendices in this dissertation provide additional material used for the realization of the main research focus of the dissertation. Specification and characterization of major components of equipment and devices used in the experiment are present. The description of Matlab algorithms that was used to calculate required signals for pulse shaping are shown. A brief description of the Labview code used to control the spectral processor will also be illustrated.Ph.D.
Doctorate
Physics
Sciences
Physics
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Ghasemi, Negareh. "Improving ultrasound excitation systems using a flexible power supply with adjustable voltage and frequency to drive piezoelectric transducers". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61091/1/Negareh_Ghasemi_Thesis.pdf.
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The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications.
To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis.
Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2.
An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4.
To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis.
According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.
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Takayanagi, Jun, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida e Toshio Goto. "Generation of high-power femtosecond pulse and octave-spanning ultrabroad supercontinuum using all-fiber system". IEEE, 2005. http://hdl.handle.net/2237/6770.
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Kim, Kyungbum. "ALL-SEMICONDUCTOR HIGH POWER MODE-LOCKED LASER SYSTEM". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2482.
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The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.Ph.D.
Optics and Photonics
Optics
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Murray, Paul R. "High peak power, pulsed, planar waveguide CO2 lasers". Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1225.
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Alexander, Eric Douglas. "Pulsed-Power Busbar Design for High-Powered Applications". Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71329.
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The use of high-powered electrical energy systems requires an efficient and capable
means to move electrical energy from one location to another while reducing energy
losses. This paper describes the design and construction process of a high-powered
busbar system that is to be implemented in pulsed-power applications. In order to
obtain a robust system capable of handling in excess of 25kJ, both mechanical and
electrical analyses were performed to verify a capable design. The following methodology
describes how the Lorentz force was balanced with mechanical forces during the
design process and then validated after construction was completed using the fundamental
Maxwell equations and computer simulations. Main focuses include handling
of EMF, high current density concentrations, and overall mechanical stability of the
system and how these effects determine the physical design and implementation. In
the end, a repeatable methodology is presented in the form of a design process that
can be implemented in any system given the design criteria.Master of Science
25
Böhlmark, Johan. "Fundamentals of High Power Impulse Magnetron Sputtering". Doctoral thesis, Linköpings universitet, Plasma och beläggningsfysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7359.
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In plasma assisted thin film growth, control over the energy and direction of the incoming species is desired. If the growth species are ionized this can be achieved by the use of a substrate bias or a magnetic field. Ions may be accelerated by an applied potential, whereas neutral particles may not. Thin films grown by ionized physical vapor deposition (I-PVD) have lately shown promising results regarding film structure and adhesion. High power impulse magnetron sputtering (HIPIMS) is a relatively newly developed technique, which relies on the creation of a dense plasma in front of the sputtering target to produce a large fraction of ions of the sputtered material. In HIPIMS, high power pulses with a length of ~100 μs are applied to a conventional planar magnetron. The highly energetic nature of the discharge, which involves power densities of several kW/cm2, creates a dense plasma in front of the target, which allows for a large fraction of the sputtered material to be ionized. The work presented in this thesis involves plasma analysis using electrostatic probes, optical emission spectroscopy (OES), magnetic probes, energy resolved mass spectrometry, and other fundamental observation techniques. These techniques used together are powerful plasma analysis tools, and used together give a good overview of the plasma properties is achieved. from the erosion zone of the magnetron. The peak plasma density during the active cycle of the discharge exceeds 1019 electrons/m3. The expanding plasma is reflected by the chamber wall back into the center part of the chamber, resulting in a second density peak several hundreds of μs after the pulse is turned off. Optical emission spectroscopy (OES) measurements of the plasma indicate that the degree of ionization of sputtered Ti is very high, over 90 % in the peak of the pulse. Even at relatively low applied target power (~200 W/cm2 peak power) the recorded spectrum is totally dominated by radiation from ions. The recorded HIPIMS spectra were compared to a spectrum taken from a DC magnetron discharge, showing a completely different appearance. Magnetic field measurements performed with a coil type probe show significant deformation in the magnetic field of the magnetrons during the pulse. Spatially resolved measurements show evidence of a dense azimuthally E×B drifting current. Circulating currents mainly flow within 2 away cm from the target surface in an early part of the pulse, to later diffuse axially into the chamber and decrease in intensity. We record peak current densities of the E×B drift to be of the order of 105 A/m2. A mass spectrometry (MS) study of the plasma reveals that the HIPIMS discharge contains a larger fraction of highly energetic ions as compared to the continuous DC discharge. Especially ions of the target material are more energetic. Time resolved studies show broad distributions of ion energies in the early stage of the discharge, which quickly narrows down after pulse switch-off. Ti ions with energies up to 100 eV are detected. The time average plasma contains mainly low energy Ar ions, but during the active phase of the discharge, the plasma is highly metallic. Shortly after pulse switch-on, the peak value of the Ti1+/Ar1+ ratio is over 2. The HIPIMS discharge also contains a significant amount of doubly charged ions.
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Enache, Mugurel Catalin. "Numerical modelling and optical measurements for pulsed power systems". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/33116.
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This thesis illustrates a typical situation in which theoretical considerations and predictions are used to enhance the value of an experimental investigation. The body of the thesis is in two main parts, the first of which considers the two-dimensional modelling of representative pulsed-power systems while the second describes a number of valuable experimental tools that were developed for use in investigating the experimental behaviour of such systems.
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Duvoor, Prashanth. "Energy storage system requirements for shipboard power systems supplying pulsed power loads". Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11082007-170421.
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Rasch, Joel. "Probe measurements in a pulsed high power sputtering magnetron". Thesis, KTH, Rymd- och plasmafysik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91546.
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Miran, Seyed Mehdi. "Switches for pulsed-power conditioning in high energy applications". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/10616.
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This dissertation presents theoretical and experimental results from a research program that was aimed at finding practical ways of transferring energy to various loads, mainly from an inductive energy store fluxed by a primary store such as a capacitor bank. The main obj ecti ves of the work were to investigate and develop high power opening and closing switches, together with the transfer circuits needed to generate the fast (less than lOOns duration) high energy, pulses required in many applications. The study was to include a feasibility study of the use of the Plasma Erosion Opening Switch (PEOS) in such a system. To produce the large fast pulses required, an opening switch is required that: * Carry a current of the order of several kA during the inductor storage time. It should also be able to interrupt this current and to withstand the high voltage it will experience as the current is subsequently transferred to a load. * Conduct for as long as possible (up to one quarter period of the current waveform), to maximise the inductively stored energy which can be transferred to xhe load when the switch opens. * Open to an impedance that is large compared to the load impedance . This ensures that most of the inductively stored energy is transferred to the load. Open sufficiently rapidly to produce the required sharp pulse of voltage. In pulsed-power applications, energy is usually supplied from slow and relatively inexpensive power sources such as a capacitor bank, or an explosive flux-compression generator, which deliver large quantities of energy in the lO-lOO time range. Although no single switch is currently available which has such a long conduction time, together with a nanosecond opening time, the PEOS is a potential candidate. To overcome its short conduction time, while still obtaining an opening time of less than lOOns, the PEOS is used together with an additional slower stage or stages of switching. The key to this method is that each successive switching stage produces a considerably increased voltage. Various different types of switch were investigated and these are described in the thesis. Particular consideration is paid to the performance of the PEOS, as the final conditioning stage. Exploding foils are also investigated, together with a novel Automatic Exploding Foil Change-Over Switch, since an exploding foil opening switch is needed to condition the output of the capacitor bank before the PEOS. The initial resistance of the PEOS is very low, and the change-over switch is required to ensure that the current transfer takes place when the voltage across the fuse approaches its peak value. An important part of the investigation was to develop a mathematical model of the PEOS, as a part of the power condi tioning circuit, in order to simulate the system for different load conditions. The thesis explains the design, operation and performance characteristics of the various pulsed-power components, such as capacitor banks, closing and opening switches, pulse transformer, the vacuum system required for a PEOS, and high voltage and current measurement techniques.
30
Gunnarsson, Rickard. "Titanium oxide nanoparticle production using high power pulsed plasmas". Licentiate thesis, Linköpings universitet, Plasma och beläggningsfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128622.
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This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions. The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.
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Zabihi, Sasan. "Flexible high voltage pulsed power supply for plasma applications". Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48137/1/Sasan_Zabihi_Sheykhrajeh_Thesis.pdf.
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Demands for delivering high instantaneous power in a compressed form (pulse shape) have widely increased during recent decades. The flexible shapes with variable pulse specifications offered by pulsed power have made it a practical and effective supply method for an extensive range of applications. In particular, the release of basic subatomic particles (i.e. electron, proton and neutron) in an atom (ionization process) and the synthesizing of molecules to form ions or other molecules are among those reactions that necessitate large amount of instantaneous power. In addition to the decomposition process, there have recently been requests for pulsed power in other areas such as in the combination of molecules (i.e. fusion, material joining), gessoes radiations (i.e. electron beams, laser, and radar), explosions (i.e. concrete recycling), wastewater, exhausted gas, and material surface treatments. These pulses are widely employed in the silent discharge process in all types of materials (including gas, fluid and solid); in some cases, to form the plasma and consequently accelerate the associated process.
Due to this fast growing demand for pulsed power in industrial and environmental applications, the exigency of having more efficient and flexible pulse modulators is now receiving greater consideration. Sensitive applications, such as plasma fusion and laser guns also require more precisely produced repetitive pulses with a higher quality. Many research studies are being conducted in different areas that need a flexible pulse modulator to vary pulse features to investigate the influence of these variations on the application. In addition, there is the need to prevent the waste of a considerable amount of energy caused by the arc phenomena that frequently occur after the plasma process. The control over power flow during the supply process is a critical skill that enables the pulse supply to halt the supply process at any stage.
Different pulse modulators which utilise different accumulation techniques including Marx Generators (MG), Magnetic Pulse Compressors (MPC), Pulse Forming Networks (PFN) and Multistage Blumlein Lines (MBL) are currently employed to supply a wide range of applications. Gas/Magnetic switching technologies (such as spark gap and hydrogen thyratron) have conventionally been used as switching devices in pulse modulator structures because of their high voltage ratings and considerably low rising times. However, they also suffer from serious drawbacks such as, their low efficiency, reliability and repetition rate, and also their short life span. Being bulky, heavy and expensive are the other disadvantages associated with these devices. Recently developed solid-state switching technology is an appropriate substitution for these switching devices due to the benefits they bring to the pulse supplies. Besides being compact, efficient, reasonable and reliable, and having a long life span, their high frequency switching skill allows repetitive operation of pulsed power supply. The main concerns in using solid-state transistors are the voltage rating and the rising time of available switches that, in some cases, cannot satisfy the application’s requirements. However, there are several power electronics configurations and techniques that make solid-state utilisation feasible for high voltage pulse generation. Therefore, the design and development of novel methods and topologies with higher efficiency and flexibility for pulsed power generators have been considered as the main scope of this research work. This aim is pursued through several innovative proposals that can be classified under the following two principal objectives.
• To innovate and develop novel solid-state based topologies for pulsed power generation
• To improve available technologies that have the potential to accommodate solid-state technology by revising, reconfiguring and adjusting their structure and control algorithms.
The quest to distinguish novel topologies for a proper pulsed power production was begun with a deep and through review of conventional pulse generators and useful power electronics topologies. As a result of this study, it appears that efficiency and flexibility are the most significant demands of plasma applications that have not been met by state-of-the-art methods. Many solid-state based configurations were considered and simulated in order to evaluate their potential to be utilised in the pulsed power area. Parts of this literature review are documented in Chapter 1 of this thesis.
Current source topologies demonstrate valuable advantages in supplying the loads with capacitive characteristics such as plasma applications. To investigate the influence of switching transients associated with solid-state devices on rise time of pulses, simulation based studies have been undertaken. A variable current source is considered to pump different current levels to a capacitive load, and it was evident that dissimilar dv/dts are produced at the output. Thereby, transient effects on pulse rising time are denied regarding the evidence acquired from this examination. A detailed report of this study is given in Chapter 6 of this thesis.
This study inspired the design of a solid-state based topology that take advantage of both current and voltage sources. A series of switch-resistor-capacitor units at the output splits the produced voltage to lower levels, so it can be shared by the switches. A smart but complicated switching strategy is also designed to discharge the residual energy after each supply cycle. To prevent reverse power flow and to reduce the complexity of the control algorithm in this system, the resistors in common paths of units are substituted with diode rectifiers (switch-diode-capacitor). This modification not only gives the feasibility of stopping the load supply process to the supplier at any stage (and consequently saving energy), but also enables the converter to operate in a two-stroke mode with asymmetrical capacitors. The components’ determination and exchanging energy calculations are accomplished with respect to application specifications and demands. Both topologies were simply modelled and simulation studies have been carried out with the simplified models. Experimental assessments were also executed on implemented hardware and the approaches verified the initial analysis. Reports on details of both converters are thoroughly discussed in Chapters 2 and 3 of the thesis.
Conventional MGs have been recently modified to use solid-state transistors (i.e. Insulated gate bipolar transistors) instead of magnetic/gas switching devices. Resistive insulators previously used in their structures are substituted by diode rectifiers to adjust MGs for a proper voltage sharing. However, despite utilizing solid-state technology in MGs configurations, further design and control amendments can still be made to achieve an improved performance with fewer components. Considering a number of charging techniques, resonant phenomenon is adopted in a proposal to charge the capacitors. In addition to charging the capacitors at twice the input voltage, triggering switches at the moment at which the conducted current through switches is zero significantly reduces the switching losses. Another configuration is also introduced in this research for Marx topology based on commutation circuits that use a current source to charge the capacitors. According to this design, diode-capacitor units, each including two Marx stages, are connected in cascade through solid-state devices and aggregate the voltages across the capacitors to produce a high voltage pulse. The polarity of voltage across one capacitor in each unit is reversed in an intermediate mode by connecting the commutation circuit to the capacitor. The insulation of input side from load side is provided in this topology by disconnecting the load from the current source during the supply process. Furthermore, the number of required fast switching devices in both designs is reduced to half of the number used in a conventional MG; they are replaced with slower switches (such as Thyristors) that need simpler driving modules. In addition, the contributing switches in discharging paths are decreased to half; this decrease leads to a reduction in conduction losses. Associated models are simulated, and hardware tests are performed to verify the validity of proposed topologies. Chapters 4, 5 and 7 of the thesis present all relevant analysis and approaches according to these topologies.
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Wu, Jian. "Data modeling for Shipboard Power System". Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-03252004-220340.
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Ji, Chao. "High performance resonant pulsed power supply for radio frequency applications". Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594395.
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In the past decade, there has been an increased demand to develop compact power supplies with high efficiency and high power density in order to revolutionise traditional approaches for high power radio frequency (RF) applications, such as long pulse modulators used for high energy physics acceleration experiments. Resonant technology has been considered to meet these challenges, due to its soft-switching characteristic at high operating frequency. The aim of this research project is to provide further knowledge in series resonant parallel loaded (SRPL) resonant converters for long pulse modulators, and to design advanced closed-loop control strategies for voltage pulse regulation. The proposed converter comprises three single phase SRPL resonant output stages, which guarantees a strong ability of overcoming the influence of tank unbalances and enables independent modulation procedures. A DQ modelling approach was utilized to analyse the converter. Based on it, a PI + repetitive control strategy was designed for voltage pulse regulation to obtain good dynamics and steady state performance. A combined frequency and phase shift modulation method was selected to control the converter so that soft-switching of semiconductor devices can be always achieved, even in the presence of large tank unbalances. Good correlation between simulation and experimental results has been demonstrated, which validates the converter circuit design, modelling approach, control strategy and modulation method
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Chen, Kang Kang. "High power pulsed ytterbium doped fibre lasers and their applications". Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/207735/.
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The aim of my project is to develop pulsed Ytterbium (Yb) doped fibre master oscillator power amplifier (MOPA) systems seeded by semiconductor lasers. I was principally focused on two specific projects aligned to sponsored programs of research within the ORC pulsed fibre laser group: the first project, TSB funded project LAMPS, aimed to develop an important class of next generation laser system capable of average output powers of more than 100 W when operating in both the nanosecond and picosecond regimes. The goal was to develop a fully fiberized, polarisation maintaining, single transverse mode system. The full project included the development of the necessary diode & micro-optic systems, fibre beam delivery technology and with application focused evaluations in collaboration with our industrial partners. The main project partners were BAE Systems, Selex, Ceram, Intense Photonics, ORC, Herriot Watt University, Power Photonics, OptoCap and Rofin Sinar. I contributed to the development of the single transverse mode Ytterbium (Yb)-doped fibre system and achieved the full target specifications of 100 W of output power with single mode and single polarisation operation in both the nanosecond and picosecond regimes. In addition, second harmonic generation pumped by the fundamental beam at 1.06 μm was also achieved. In order to transfer from picosecond pulses to nanosecond pulses it is only necessary to switch the seed laser, the power amplifier system remaining unchanged making for a highly flexible system. Both fundamental and second harmonic beam were successfully used to do material processing and various high power frequency conversion experiments (visible, broadband supercontinuum and mid-IR). The second project, called HEGAC (also funded by the TSB), was a collaboration with the University of Cambridge and SPI Lasers Ltd. The aim of the HEGAC project was to develop a high power nanosecond fibre laser with an active pulse shaping capability suitable for cutting metals. This project targeted mJ pulses with more than 100 W average power at the final output – with a 200 W stretch objective. We first achieved more than 310 W using a free space seeding and pumping configuration in our laboratories proving power scaling of our proposed approach. I subsequently rebuilt and improved this system and developed a fully- fiberized version (including all pump launches). The laser was capable of generating >100 W of output power and pulse energies up to 2.5 mJ. This project also involved spatial mode as well as temporal pulse shaping. Using a pair of axicon lenses the normal Gaussian beam profile was converted to a ring shaped profile as required and the system tested up to average powers of 100 W. In addition to the normal temporal pulse shapes required using our pulse shaping system (square, triangle and step), I also achieved high average power pulses with smooth shaped pulses (Parabolic and Gaussian) using an adaptive pulse shaping technique. The laser was transported and successfully used in materials processing experiments at Cambridge, proving the robustness of the design and implementation. I also did some novel experiments on high efficiency Raman conversion exploiting the square shaped pulses possible using this laser
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Ure, K. A. N. "The generation of short, tunable high power optical pulses". Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383874.
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Tasker, Douglas George. "Megabar isentropic compression experiments (ICE) using high explosive pulsed power (HEPP)". Thesis, Loughborough University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487678.
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In the shock physics community there is significant interest in the acquisition of accurate isentropic Equation of State (EOS) data at megabar pressures (i.e., at -50 GPa and above). A relatively new technique, called the Isentropic Compression Experiment or ICE, uses rapidly rising magnetic fields to compress materials to high stresses of the order of 50 GPa and above over a few hundred nanoseconds. This work was first performed on the Z-machine at the Sandia National Laboratory in Albuquerque, NM, USA. Using ICE, the Sandia researchers were able to obtain relatively accurate EOS data at large stresses in a planar geometry.
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Warnock, Dwight S. "Design and optimization of a 600-KJ railgun power". Thesis, Monterey, California. Naval Postgraduate School, 2003. http://hdl.handle.net/10945/6254.
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Approved for public release; Distribution is unlimitedThe purpose of this thesis is to explore the design options for a 1.2-m railgun power supply capable of accelerating a 150-g to 250-g projectile to 1000 m/s. In order to accomplish this task a MATLAB model will be constructed to conduct trade-off studies between various power supply configurations in an attempt to maximize the system performance. The final design shows that by distributing the system capacitance between four equal size banks and firing them sequentially the total system capacitance can be reduced by more than half. Because the capacitor banks are fired sequentially, the current pulse is length-ened resulting in more efficient use of the barrel. The final benefit of using a multiple-bank system is that the individual bank currents are reduced by a factor of four over the single-bank scenario. By reducing the bank currents solid-state switches are now an affordable option further improving the system performance. By applying a systematic approach to optimizing the power supply this study has shown that the energy required to accelerate a 172-g projectile to 1000 m/s can be reduced from 1.3 MJ in the single-bank scenario to 600 KJ by distributing the capacitance over four equal sized banks.
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Freegarde, Tim. "Spectroscopic applications of pulsed metal vapour lasers". Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:e3c6fbf2-5e85-4025-bd56-83012421353c.
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The remainder of this thesis considers the longitudinal coherence of the copper vapour laser, and describes the design and initial performance of a narrow bandwidth dye laser for use with a CVL. Careful construction of a grazing-incidence grating arrangement similar to that of Littman has resulted in a laser which is particularly simple to align and which promises ease of tuning over a wide range. Operation confined to a single longitudinal mode has been demonstrated, corresponding to single shot bandwidths below IGHz, but instabilities caused by vibration and uneven dye flow broaden the time-averaged width to around 3GHz. Suggested improvements have not yet been implemented.
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Fu, Dianbo. "Improved Resonant Converters with a Novel Control Strategy for High-Voltage Pulsed Power Supplies". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34432.
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The growing demand for high voltage, compact pulsed power supplies has gained great attention. It requires power supplies with high power density, low profile and high efficiency. In this thesis, topologies and techniques are investigated to meet and exceed these challenges.
Non-isolation type topologies have been used for this application. Due to the high voltage stress of the output, non-isolation topologies will suffer severe loss problems. Extremely low switching frequency will lead to massive magnetic volume. For non-isolation topologies, PWM converters can achieve soft switching to increase switching frequency. However, for this application, due to the large voltage regulation range and high voltage transformer nonidealities, it is difficult to optimize PWM converters. Secondary diode reverse recovery is another significant issue for PWM techniques.
Resonant converters can achieve ZCS or ZVS and result in very low switching loss, thus enabling power supplies to operate at high switching frequency. Furthermore, the PRC and LCC resonant converter can fully absorb the leakage inductance and parasitic capacitance. With a capacitive output filter, the secondary diode will achieve natural turn-off and overcome reverse recovery problems. With a three-level structure, low voltage MOSFETs can be applied for this application. Switching frequency is increased to 200 kHz.
In this paper, the power factor concept for resonant converters is proposed and analyzed. Based on this concept, a new methodology to measure the performance of resonant converters is presented. The optimal design guideline is provided.
A novel constant power factor control is proposed and studied. Based on this control scheme, the performance of the resonant converter will be improved significantly. Design trade-offs are analyzed and studied. The optimal design aiming to increase the power density is investigated. The parallel resonant converter is proven to be the optimum topology for this application. The power density of 31 W/inch3 can be achieved by using the PRC topology with the constant power factor control.Master of Science
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Figura, E. S. "Observations of Z-pinches driven by a high voltage, pulsed power source". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47434.
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Teh, Peh Siong. "High performance pulsed fiber laser systems for scientific & industrial applications". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/383623/.
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This thesis reports an investigation of the power scaling of pulsed fiber laser systems towards the hundreds of Watts regime whilst keeping the impact of fiber nonlinearities such as Stimulated Raman Scattering (SRS) at a manageable level. Two regimes of pulsed operation are investigated: the nanosecond pulse regime and the picosecond pulse regime. Some of the work reported in this thesis was carried out in collaboration with SPI Lasers and Institute for Manufacturing, University of Cambridge under the TSB funded SMART LASER programme. In the nanosecond regime, two kinds of MOPA configurations are investigated. In the first instance a high accuracy active pulse shaping technique is implemented. Using the combination of a fast electrical Arbitrary Waveform Generator (AWG) and an Electro-Optic Modulator (EOM), optical pulses can be shaped into various custom defined pulse shapes with high temporal resolution feature definition, allowing faster pulse rise and fall times than previously possible. This MOPA has the capability to generate a maximum average output power of ~70 W, pulse energy close to 1 mJ, all within a diffraction limited output beam. The second instance a fully-fiberized system capable of producing up to 45 W of average output power with a pulse energy of ~1 mJ was developed in collaboration with SPI Lasers Ltd. Unlike the first system, which uses an EOM for optical pulse shaping, an Acousto-Optic Modulator (AOM) is instead used to pre-shape the leading edge of the optical seed pulse in order to reduce the impact of nonlinear effects caused by the high peak powers otherwise associated with gain-saturation assisted reshaping of long nanosecond square input pulses, providing a cost-effective solution for the SMART Laser system. The successful development of the SMART Laser system allowed SPI Lasers Ltd to introduce a new product line, namely the G4 pulsed fiber laser system. Both types of fiber laser system were used in material processing experiments to investigate their performance and capabilities. Using a nanosecond fiber MOPA as a pump source, a synchronously pumped, tuneable, Raman fiber laser is demonstrated both in the near infrared (NIR) and visible regions. A continuous tuning range of 28nm in the NIR and 2.8nm in the visible region are achieved with efficiencies in the range of 12% to 18% respectively. The conversion efficiency can be increased further with the use of a feedback signal. Furthermore, with the presence of a feedback signal, the linewidth of the Raman Stokes lines in both visible and NIR regions shows a significant narrowing effect. This technique will allow the generation of wavelengths which are not easily generated with rare-earth doped fiber lasers and will be useful in the fields of spectroscopy, archaeology, biomedical and many more. Next, optical pulses in the picosecond regime are investigated. A gain-switching technique is used to generate a stable train of picosecond optical pulses from a semiconductor laser diode (SLD). Gain switching of different types of commercially available SLDs shows different temporal and spectral characteristics which are primarily influenced by the design of the specific chip used. The shortest pulse durations achieved through direct gain switching resulted in ~50 ps pulses; however these were far from transform-limited. However, an external FBG seeded gain switched SLDs was shown to be capable of producing transform-limited optical pulses. I show that a mode-locking mechanism is responsible for the short, transform limited optical pulses observed. This is the first demonstration of a mode locked SLD at the 1.06 μm waveband. With this technique, 18 ps optical pulses with pulse energy of 7.2 pJ and peak power of 400 mW were obtained. The single polarization, stable, picosecond optical pulses were fed into a chain of polarization maintaining fiber amplifiers to investigate the power scaling capability of this system. A maximum average output power of 513 W is demonstrated in a diffraction-limited output beam. The system operated at a repetition frequency of 215 MHz, corresponding to an estimated pulse energy of 2.4 μJ and a peak power of ~ 69 kW. At the maximum operating output power, the OSNR is measured to be well above 26 dB with a polarization extinction ratio (PER) of 17 dB. A pulse energy of 3.23 μJ is achieved from a similar system at a reduced operating frequency of 53 MHz and an average optical power of 200 W, corresponding to a pulse peak power of 107 kW. In both cases, further power scaling is limited by the SRS. These results represent the highest optical power demonstrated from a fiber MOPA producing tens of picosecond optical pulses.
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Iachello, Marco. "Nonlinear oscillations in high power systems". Doctoral thesis, Università di Catania, 2015. http://hdl.handle.net/10761/3913.
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The main topic of this work is to investigate on nonlinear phenomena affecting high power systems and on the strategies adopted to model them. In the first chapter the attention is focused on two big areas of high power systems: power electronics and systems/devices used to sustain plasma fusion. Although it is common that System Engineers tend to associate high power systems with power electronics, it is worth noting that power systems related to nuclear fusion represent a challenging area rich in nonlinearities. Specifically, while nonlinear oscillations in power electronics are due to oscillations of electrical nature, the ones present in nuclear fusion can also refer to other physical quantities. We will refer to the latter taking into account macroscopic plasma instabilities affecting JET plasmas, and proposing both theoretical approaches and experimental ones to describe their dynamic. The former rely on nonlinear mathematical equations able to mimic the nonlinear behavior of the system under certain conditions while the latter are based on a physical realization of the system starting from its mathematical model.
High power systems related to power electronics are investigated in Chapter 2 where the importance of thermal modeling for the power electronics modules is pointed out and a new modeling strategy which starts from a distributed parameter analysis to obtain a lumped parameter model is introduced.
In this case, the proposed methodology is based on the assumption that the heat transfer problem can be assumed to be linear and the thermal impedances approaches can be therefore used. In this relevant case study nonlinearities in modeling high power systems can also be neglected under certain conditions. In particular, concerning high power modules, it is well-known how the geometry of the device and the proper choice of the cooling system can play a key role for these simplifications.
A data-driven approach based on neural networks to model plasma instabilities is presented in Chapter 3. This approach is introduced because physical models often require a deep knowledge of the system parameters that sometimes is difficult to obtain.
In Chapter 4 considerations and results on new identification methodologies based on parallel identification models for discrete-time systems are presented.
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Davari, Pooya. "High frequency high power converters for industrial applications". Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/62896/1/Pooya_Davari_Thesis.pdf.
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The main contribution of this project was to investigate power electronics technology in designing and developing high frequency high power converters for industrial applications. Therefore, the research was conducted at two levels; first at system level which mainly encapsulated the circuit topology and control scheme and second at application level which involves with real-world applications. Pursuing these objectives, varied topologies have been developed and proposed within this research. The main aim was to resolving solid-state switches limited power rating and operating speed while increasing the system flexibility considering the application characteristics. The developed new power converter configurations were applied to pulsed power and high power ultrasound applications for experimental validation.
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Hibbard, John Arthur 1959. "A HIGH VOLTAGE D.C. PULSE SYSTEM AND ASSOCIATED ATHERMAL, IN VITRO EXPERIMENTS (POWER, SHORT, SYNERGISM)". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275500.
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Brown, Martin. "High voltage soliton production in nonlinear transmission lines and other pulsed power applications". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364003.
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Hussein, Alaa Adnan. "Space debris mitigation in Low Earth Orbit (LEO) using high power pulsed lasers". Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/81287/.
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Mitigating space debris with lasers is investigated as a possible mechanism for contactless space debris deflection in Low Earth Orbit (LEO). This deflection mechanism can be carried out by irradiating the space debris surface with a high-power laser beam. The energy absorbed by the surface of the debris, from the laser beam, sublimates the irradiated surface, transforming it to gas from solid. The ablated material is formed into a plume of ejecta, which acts against the orbital debris if the laser is beamed in the right direction; it produces a small push or thrust that deflects the debris by reducing its orbital velocity, altitude and eventually its lifetime in orbit. This approach could also be used to push space debris away from operational satellites paths. Laser ablation depends mainly on understanding the physical properties of both, the laser beam and the space debris. The interaction process for three different commonly used spacecraft materials are illuminated by a laser beam and investigated both experimentally and by using theoretical models. Experimental results and theoretical verifications are employed to evaluate the feasibility of the ablation model and to understand its performance in producing an effective deflection of space debris. This was investigated using Nd3+ Glass laser pulses with three metals: nickel (Ni), aluminium (Al) and copper (Cu). The Nd3+ Glass laser operated at a wavelength of 1.06 μm that provided intensities just below the threshold for plasma formation. This interaction produces surface power intensities ranging between one GW/m2 to one TW/m2, which produces high order temperature gradients that cause non-equilibrium energy transport phenomenon. This phenomenon cannot be explained by classical theories. The results have been used for the enhancement of the ablation model. Additional enhancements included the temperature penetration in the target surface. The surface temperature transients of metals due to laser interaction have also been investigated, and heat transfer is simulated by utilising a kinetic particle model, which captures the dominant energy transport processes. This model of energy transport permits determination of the significant decline in temperature gradients and the non-equilibrium conditions that occur between the Fermi surface conduction electrons and lattice phonons. This results in an accurate temperature distribution calculation within the space debris. The laser pulse specification and the properties of the space debris material were specified for simulation. The kinetic model has been used to simulate the spatial temperature distribution growth in the space debris when illuminated with a 1.06 μm wavelength Nd3+ Glass laser. The evaporation physics are also incorporated into the kinetic model. The average mass flow rate has been evaluated. A critical difference has been discovered between the experimental results and the predicted results using the classical Fourier Theory. The experimental data of the target surface temperatures are compared with Fourier and electron Kinetic theories. The experimental results validate the theoretical results and model improvements. It also illustrated the inaccuracy of Fourier theory regarding its solution of steep energy gradients and its failure to illustrate the non-equilibrium energy transport state, which grows between electrons and lattice phonons. It was noticed that the electron Kinetic theory results provide sufficient agreement with the experimental results below the boiling point and give a much better model than Fourier theory above the boiling temperature. The enhancements have permitted the laser specifications and the performance of the ablation treatment to be characterised. The performance of orbital debris mitigation with pulsed lasers outperformed alternative techniques that can produce a small contactless push on space junk. This method avoids sending complicated spacecraft into orbits to take space debris away from Earth orbits. The laser power that is required to reduce the altitude and the orbital velocity of space debris were predicted and calculated theoretically. The performance has been assessed by its capability to move small debris, centimetre size, by at least a couple of m/s. The results confirmed the possible benefits of using lasers to mitigate space debris in LEO. Employing current technologies together with a high Technology Readiness Level (TRL), an affordable and compact laser system could be successfully constructed and attached to traditional artificial satellites as a space-based laser system. Such a system could demonstrate the method, synergies and techniques of laser ablation. Mission complexity and the extra mass are saved by the direct debris ablation process, which can operate at a relatively small distance compared to a ground-based laser system. The analysis thus confirms the feasibility of utilising space-based laser systems and the applicability of the model's experimental validation.
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Hochberg, Martin Christian [Verfasser]. "A high-voltage pulsed power modulator for fast-rising arbitrary waveforms / Martin Hochberg". Karlsruhe : KIT Scientific Publishing, 2020. http://d-nb.info/1205069860/34.
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Hochberg, Martin [Verfasser]. "A high-voltage pulsed power modulator for fast-rising arbitrary waveforms / Martin Hochberg". Karlsruhe : KIT Scientific Publishing, 2020. http://d-nb.info/1205069860/34.
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Kemp, Mark A. "Simulation and experimental study of the multichanneling rimfire gas switch". Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4281.
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Thesis (M.S.) University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 10, 2006) Includes bibliographical references.
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Lee, Jae Myoung. "Experimental and theoretical studies of the fabrication of nanoparticles using a high power pulsed laser /". Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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