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In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.

In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.

In the master´s thesis author deals with simulations of electromagnetic fields and their applications in the electric practice at the design of electromagnetic devices. The first part of thesis deals with 3 electromagnetic field simulation softwares, their comparison and selection of the best software for the practical part of the thesis. The second part contains the practical applications of electrostatic and electromagnetic field simulation of HT power supply.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / As a vehicle reenters or flies at hypersonic speed through the atmosphere, the surrounding air is shock heated and becomes weakly ionized. The plasma layer thus formed causes a communication problem known as ‘radio blackout’. At sufficiently dense plasma conditions, the plasma layer either reflects or attenuates radio wave communications to and from the vehicle. In this paper, we propose an electromagnetic field configuration as a method to allow communication through the plasma layer. Theoretical models show that this may address the blackout problem under a range of conditions. Preliminary experimental results are also presented.

São analisados os campos eletromagnéticos de baixa frequência devidos a limitadores magnéticos ergódicos e desviadores ergódicos e a densidade de potência absorvida em plasmas cilíndricos de tokamaks, considerando os efeitos da deriva diamagnetica e da rotação de plasma com velocidade paralela às linhas de campo magnético de equilíbrio. É considerado o tensor dielétrico de plasma frio colisional para esse modelo. Para a banda de frequências f < 30 kHz e modos com números poloidal/toroidal 31-1, para plasma com fator de segurança com crescimento monótono, e 21-1, para plasma com fator de segurança com um mínimo entre o centro e a borda do mesmo, a densidade de potência absorvida é negativa para frequências menores que a específica de deriva de elétrons e pode ser entendida como uma instabilidade. Esse modo pode ser estabilizado a medida que a frequência se aproxima do valor do mínimo do contínuo de Alfvén na região da superfície magnética racional considerada. Para os modos -311 e -2/1 a densidade de potência absorvida é positiva. A rotação de plasma com velocidade de f106 cm/s no centro do plasma não tem efeitos significativos sobre os resultados em comparação com a deriva diamagnética. Para a banda de frequências 30 7 f < 150 kHz podem ser excitadas ondas de Alfvén de deriva rápidas. A excitação dessas ondas depende da derivada do fator de segurança e das derivadas das frequências angulares diamagnêticas, nos casos de cisalhamento quase nulo e de cisalhamento negativo no centro do plasma, sendo a resistência de antena positiva e oscilatória com os valores dos máximos crescendo com a frequência. Ondas de Alfvén globais são excitadas no centro do plasma para modos poloidal/toroidal com sinais opostos (M/N<O) para plasmas com fator de segurança com crescimento monótono e fre- qüências menores que a mínima do contínuo de Alfvén. Os campos magnéticos do limitador magnético ergódico e do desviador ergódico comlsem a reação do plasma apresentam grandes diferenças. / Low frequency fields and power density absorption excited by ergodic magnetic lirniters and ergodic divertors are analyzed under the influence of the diamagrietic drift effect and the plasma rotation, whicli is parallel to the magnetic field, in the cylindrical plasma model of tokamaks. The dielectric tensor for that model is taken in the collisiorial cold plasma limit. For the frequency band f < 30 kHz the power density absorption for modes witli poloidal/toroidal numbers 31-1 in the plasma with monotonically growing safety factor and 21-1 for the plasma with safety factor with a minimum between the plasma core and the edge, is found to be negative for frequencies below a specific electron drift angular frequency and it can be understood as an instability. The unstable mode can be stabilized as the frequency approaclies tlie Alfvén continuum minimum at the position of the rational magnetic surface. For the modes -311 and -211 the power density absorption is positive. The plasma rotation with core velocity f106 cm/s has no effect in comparison with diamagnetic drift. For the frequency band 30 7 f < 150 kHz it is shown that fast drift Alfvén waves can be excited as eigenmodes. The excitation of these waves depends on the derivatives of the safety factor and the diamagnetic drift angular frequencies in the cases of flat or negative shear in the plasma core and the antenna resistance is positive and oscillatory with the maxima growing with the frequency. Global Alfvén wave resonances are excited at the plasma core for poloidal/toroidal mode numbers with opposite signs (M/N<O) for a monotonically growing safety factor and the frequencies below the minimum of the Alfvén continuum. The ergodic magnetic limiter and ergodic divertor magnetic fields with/witliout the plasma back reaction shows strong differences.

A Transparência Eletromagneticamente Induzida tem sido muito usada atualmente para implementação de memórias quânticas. Neste trabalho, estudamos este fenômeno, experimental e teoricamente, utilizando um sistema de dois níveis com degenerescências como modelo para o átomo. Tratamos o campo eletromagnético como quantizado e propomos um modelo linearizado para as flutuações que leva em consideração as forças quânticas de Langevin. Devido ao excesso de ruído de fase presente em nosso laser, a implementeção numérica do modelo levou em consideração apenas a autocorrelação de fase como fonte para o sinal de ruído observado. Este modelo mostrou um bom acordo qualitativo com os dados experimentais observados. Fizemos medidas de ruído de soma e subtração com o esquema de deteção balanceada, calculamos os coeficientes de correlação normalizado e mostramos que há regiões de correlação e anticorrelação que variam com a intensidade do feixe. Observamos também uma inversão de picos no sinal de soma não prevista pelo modelo à medida que diminuimos a intensidade. Esta inversão pode ser causada por contribuições das flutuações de amplitude do laser a baixas intensidades. / Electromagnetically Induced Transparency has attracted much attention recently as a source to implement quantum memories. In this work, we studied this phenomenon, both theoretically and experimentally, using a degenerate two-level system modeling the atoms. We quantize the electromagnetic field and propose a linearized model for fluctuations that takes into account the quantum Langevin forces. Because of the excess noise in the phase of our laser, the numerical implementation of the theoretical model takes into account only the phase autocorrelation term as a source for the observed noise. This model showed a good qualitative agreement with the experimental data. We made sum and subtraction noise measurements using the balanced detection scheme, we calculated the normalized correlation coefficient and we showed that there are regions of correlation and anticorrelation that change with laser intensity. We also observed a peak inversion of the sum signal as laser intensity becames smaller that was not predicted by the model with only phase noise. The cause for this inversion can be the contribution of laser amplitude noise at small intensities.

The DC magnetron sputtering system (MSS) is used in microelectronic industries, and is a key device in the thin film depositions manufacturing process. The major influence factors of the DC magnetron sputtering system operational performance such as operational time and target utilization, which are due to unsatisfactory interactions between electrons and electromagnetic field inside the sputter. This study hopes to improve an established DC MSS, by employing commercial finite element analysis software that will be calculated the flux density, and using three-dimensional equation of motion to estimate the behavior of electrons inside the sputter; furthermore, in the light of the influence electrons position and speed, proposed refinements that the magnetic field above the target is controlled to make the performance improvement. Results from a study showed that the operational trajectory of the electrons at different magnetic flux density levels on top of the target after an operational period, the proposed refinements can increase the sputtering efficiency by as much as 30%. Other than that, through the similarities and dissimilarities between the additional magnetic fields and the main magnetic flux direction, the target erosion profiles with the refinements are more evenly spread out; reduction in the target material consumptions can also be expected.