Made available in DSpace on 2014-10-09T12:55:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:00Z (GMT). No. of bitstreams: 0 / Neste trabalho foi desenvolvida a t¶ecnica de Espectroscopia de Plasma Induzido por Laser aplicada µa an¶alise de patrim^onio hist¶orico atrav¶es do estudo das moedas de Um Cruzeiro de 1945 e Mil R¶eis de 1939, utilizando um laser de Nd:YAG operando em modo de chaveamento Q. Foram determinadas as melhores condi»c~oes de energia do pulso laser e tempos de atraso entre o pulso e a aquisi»c~ao dos espectros e de integra»c~ao do sinal espectrosc¶opico para aplica»c~ao da t¶ecnica em patrim^onio hist¶orico. Para garantir a reprodutibilidade da t¶ecnica, a temperatura de excita»c~ao eletr^onica, a temperatura de ioniza»c~ao e a densidade eletr^onica do plasma foram determinadas. O dano causado µas moedas foi avaliado utilizando a t¶ecnica de Tomogra¯a por Coer^encia ¶ Optica. Utilizando o m¶etodo livre de calibra»c~ao, as concentra»c~oes elementares foram determinadas, por¶em a concentra»c~ao determinada para o Alum¶³nio, presente no material de forja, estava abaixo de seu valor nominal e do valor determinado atrav¶es da t¶ecnica de An¶alise por Ativa»c~ao Neutr^onica. Uma investiga»c~ao da fra»c~ao de ioniza»c~ao revelou que a fra»c~ao de ioniza»c~ao presente no plasma estava acima do valor esperado por ioniza»c~ao t¶ermica para as temperaturas atingidas, indicando a presen»ca de processos de ioniza»c~ao n~ao t¶ermicos, que in°uenciavam nas medidas do Alum¶³nio. Foi realizada uma corre»c~ao na concentra»c~ao do elemento, utilizando a fra»c~ao de ioniza»c~ao devido aos processos de ioniza»c~ao n~ao t¶ermicos, e os novos valores de concentra»c~ao determinados obtiveram uma grande concord^ancia com os valores nominal e determinados por An¶alise por Ativa»c~ao Neutr^onica. ii / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:53:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:35Z (GMT). No. of bitstreams: 0 / No presente trabalho foi realizada uma análise de dois padrões de aço inoxidável ferrítico submetidos à ação de lasers pulsados, um no regime de nanosegundos e outro no regime de femtosegundos. Foram determinadas as temperaturas e densidades do plasma formado a partir da análise espectroscópica da radiação emitida em diferentes faixas espectrais, por diferentes espécies e em diferentes janelas de integração no tempo. As temperaturas foram obtidas de duas formas, pelo método do gráfico de Boltzmann e pela razão entre duas linhas. Os resultados foram comparados com o intuito de verificar se o método da razão conseguia recuperar os resultados obtidos pela abordagem do gráfico de Boltzmann. Foi observada uma grande concordância entre os dois métodos no regime de femtosegundos, ao passo que no regime de nanosegundos a recuperação das temperaturas não foi tão satisfatória. A densidade eletrônica do plasma foi determinada a partir do alargamento Stark e verificou-se que o plasma gerado pelo laser de nanosegundos era mais denso que aquele gerado no regime de femtosegundos. As densidades determinadas sob diferentes janelas de integração do sinal no tempo foram também comparadas sendo que aquelas relativas aos estágios iniciais do plasma eram maiores que aquelas de estágios finais. Com a obtenção das temperaturas e das densidades foi possível caracterizar totalmente o plasma e compará-lo com outros plasmas naturais e artificiais. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

No description available.

No description available.

No description available.

No description available.

<div>Laser-produced plasmas (LPP) have been used in a wide range of applications such as in pulsed laser deposition (PLD), extreme ultraviolet lithography (EUVL), laser-induced breakdown spectroscopy (LIBS), and many more. In the collision of two laser-produced plasmas, the two counter-streaming plasmas may face a degree of stagnation which influences the subsequent development of the compound plasma plume. The plume development of the stagnation layer can deviate quite noticeably from typical laser-plasma behavior. For instance, an enhanced degree of collisionality is expected, especially when the plasma collision transpires in a low pressure ambient. Colliding plasma can be intentionally implemented or conversely may occur naturally. In EUV lithography colliding plasma could service as an efficient EUV source with inherent debris mitigation. Conversely, colliding plasma could manifest in an inertial fusion energy (IFE) chamber leading to contamination, disrupting successful device operation.</div><div><br></div><div>Various techniques such as optical emission spectroscopy (OES), CCD plume imaging, laser-induced fluorescence (LIF), laser-induced incandescence (LII), and scanning electron microscopy (SEM) may be used to study laser-produced plasmas and their associated byproducts. These techniques will be used extensively throughout this work to aid in developing an understanding of the various physical and chemical phenomena occurring in these plasmas.</div><div><br></div><div><div>Chapter 1 provides introductory knowledge regarding LPPs with a specific exploration into colliding plasma and its relevance to a broad body of scientific knowledge. Additionally, the principles behind the various experimental techniques are capitulated.</div><div><br></div><div>Chapter 2 presents the laboratory facilities available at our Center for Materials Under eXtreme Environment (CMUXE) which can be used to study LPP. The various equipment (chambers, lasers, spectrograph, etc.) are discussed in detail.</div><div><br></div><div>Chapter 3 begins the series of substantive chapters which comprise the original research of this thesis. Here, the early formation (< 1 μs) of colliding carbon plasmas produced from the ablation of graphite is explored. The influence of plume hydrodynamics on the temporary lateral confinement of the stagnation layer is discussed with attention to the three different laser intensities studied. Additionally, species in the plasma were identified using OES and monochromatic plume imaging. A large increase in Swan emission from C2 dimers is observed in the stagnation layer, suggesting formation of C2 and/or re-excitation of C2 produced ab initio during laser ablation. Results were compared with HEIGHTS computational modeling to verify observations and to validate the code package for a new plasma regime.</div><div><br></div><div>Chapter 4 functions as a continuation from Chapter 3, looking into the intermediate time (1-10 μs) dynamics of colliding carbon plasma. To observe transient molecular species of carbon, C2 and C3, LIF was employed. By acquiring plume images through LIF, the various mechanisms by which C2 and C3 appear at different times in the plasma lifetime may be discerned. Using optical time-of-flight (OTOF), more information of carbon species populations may be determined to construct space-time contours which offer corroborative information regarding the spatiotemporal development of the stagnation layer.</div></div><div><br></div><div><div>Chapter 5 presents work on colliding Sn plasma for application as a EUV light source. The accumulation of material along the stagnation layer makes colliding plasmas a suitable preplasma in a dual pulse laser scheme. Dual-pulse EUV concepts call for the formation of a preplasma from the stagnation of two Sn plasmas. This preformed plasma is then subject to a second, pumping laser purposed to optimize the conversion efficiency (CE) of laser energy into EUV output. Characterization of the stagnation layer was obtained through optical emission spectroscopy while CE data is obtained using an absolutely calibrated EUV photodiode. HEIGHTS computational modeling then provides prediction of EUV emission upon using a CO2 laser for preplasma reheat.</div><div><br></div><div>Chapter 6 explores the collision between two dissimilar plasmas. Laser-produced plasma of Si and C are created in a manner which enables the two plasmas to collide. The ensuing development of the colliding plasma regime is then discussed in terms of relevant plume hydrodynamics. Analysis of the colliding regime is accomplished using fast-gated plume imaging and optical time-of-flight.</div><div><br></div><div>The final chapter, Chapter 7, provides a concise summary of the results presented in the preceding chapters. Additionally, recommended research directives are presented which are designed with consideration for the current facilities and capabilities at CMUXE.</div></div>