Diagnosing the temperatures and densities of plasmas is critical to the understanding of a wide variety of phenomena. Everything from equations of state for warm dense matter (WDM) found in Jovian planets and inertial confinement fusion (ICF) to turbulent and dissipative processes in laser-produced plasmas, rely on accurate and precise measurements of temperature and density. This work presents improvements on two distinct techniques for measuring temperatures and densities in plasmas: x-ray Thomson scattering (XRTS), and Langmuir probes (LPs). At the OMEGA laser facility, experiments on warm dense matter were performed by firing lasers at an ablator foil and driving a planar shock into cryogenically cooled liquid deuterium. XRTS in the collective scattering regime was implemented to probe the matter, measuring densities of n_e ~ 4.3 x 10²³ cm^-3, temperatures of T_e ~ 12 eV and ionizations of Z ~ 1.0. Through an extension to XRTS theory for inhomogeneous systems, it was possible to extract an additional parameter, the length scale of the shock, whose value of ? ~ 1.33 nm was consistent with the predicted mean free path, and therefore the thickness of the shock. A unique triple Langmuir probe prototype was designed and tested at the Gregori group's lab at the University of Oxford. This probe was designed for a high temporal resolution of ~ 200 MHz for probing laser-produced shocks. The probes were used to measure the shock formed from ablating carbon rods in an argon gas fill. The probe yielded plasma parameters of n_e ~ 1.0 x 10¹⁷ cm^-3 , and T^e ~ 1.5 eV, consistent with measurements from interferometry and emission spectroscopy.

No description available.

No description available.

Estudamos o conceito de energia na teoria física a nível histórico e a nível de ensino-aprendizagem, isto é, do ponto de vista de sua criação, representação conceitual, matemática e experimental, na constituição de seu significado na teoria científica e na linguagem comum. Como um exercício preliminar, analisamos alguns dados sobre o ensino de conceitos de física na exposição científica do IFUSP \"Ondas, Campos e Partículas\", de 1989 a 1990, e, em 1991, com o nome de \"Do Caleidoscópio ao Carrossel\", no prédio da Engenharia Mecânica (Escola Politécnica). A exposição apresenta fenômenos das teorias da física nos campos da mecânica, eletricidade e magnetismo, termodinâmica e ótica, fenômenos que implicam ações em escalas macroscópicas e a nível atômico. Descrevemos uma entrevista de 13 minutos com quatro alunos de 1o grau que visitaram a exposição com monitoramento. Durante a situação da entrevista, que chamamos de pedagógica, esses alunos constróem o conceito de energia. Essa entrevista é analisada em termos dos contextos fenomenológico e epistemológico, contidos na exposição, ainda que os monitores que acompanharam a visita não falassem em energia. Descrevemos também uma entrevista com um monitor sobre ensino e aprendizagem. Enfocamos o conceito de \"conhecimento prévio do aluno como requisito para ensino\", e analisamos usando o conceito de zona de desenvolvimento proximal (ZDP) de Vygotsky. Usamos a moldura de Vygotsky (VY 1896/1934) na análise da entrevista com os alunos, que é um exemplo de como considerar a ZDP. Ela não visa avaliação, e nem apenas coleta de dados. Propomos o desenvolvimento de entrevistas pedagógicas para já se constituir uma situação de ensino-aprendizagem, como uma interação desejável, dialógica, onde a ZDP, isto é, a capacidade do aluno \"vir a saber\", seja desenvolvida. A análise da emergência do conceito de energia no caso estudado da entrevista com alunos é feita com a perspectiva de sistemas dinâmicos, dada a natureza complexa dos fenômenos estudados. A História e Filosofia das Teorias Científicas são usadas como ferramenta heurística para identificar correlação na constituição do espaço de significação. Concluíremos que, se os monitores não enfocavam diretamente o conceito de energia e os alunos aprendiam mesmo assim, é porque a exposição é um bom contexto onde a entrevista pedagógica pode ser utilizada como instrumento de ensino, Por fim, falamos da necessidade de um treinamento para monitores, onde sua formação inclua estudos históricos e epistemológicos e uma preparação para suprir a deficiência que detetamos na exposição, isto é, a de não abordar os conceitos na sua forma matematizada. A pesquisa das condições para aprendizagem na Exposição Científica e em Entrevista se desenvolve com instrumentos próprios: um sistema de análise em vídeo foi construído para pesquisar a linguagem usada na interação entre professor e aluno. Objetivamos estabelecer condições propícias para interações dialógicas. Como resultado secundário, foi adquirida certa familiaridade em trabalhar com o vídeo como instrumento para, ao mesmo tempo, mostrar e desenvolver aquisição do conhecimento científico de conceitos de física. / We have studied the concept of energy in Physics in the historical and the Teaching-Learning contexts, i.e., from the point of view of its creation, its mathematical and experimental conceptual representation, of its scientific and ordinary meaning constitution. As a preliminary exercise, we analysed some data about the Physics concepts teaching at the \"Waves, Fields and Particles\" Science Exhibition Center located at that time, in the Engineering Building of the University of São Paulo. The content of the Exhibition was regular demonstrations of phenomena delineated by classical theories of Mechanics, Eletromagnetism, Thermodynamics and some topics in Modern Physics. An interpretation of the exhibition could be in terms of the concept of energy and its transformations, as was shown by an interview with four visiting students described here. During this interview set, which we named pedagogical, these students constructed the concept of energy. This interview is analysed in terms of phenomenological and epistemological implications in the exhibition. A monitor thinking about teaching and learning has also been situated out of an interview. This monitor considers the pupil\'s previous subject matter knowledge as a requirement for teaching. By means of the ZDP (zone of proximal development), we are warned by Vygotsky against the extreme pre-requisites, which can limit the learning. We also make use of Vygotsky\'s concept in the analysis of the interview with students. The interview described in the first part of this work is a ZDP application example. It neither aims evaluation nor just data gathering. It will be developed to be a teaching-learning instrument. We believe this is possible, for it will be an interaction where the ZDP or the pupil\'s ability to \"come to know\" is to be considered. The case study of the emergence of the concept of energy from the interview with pupils is analysed within the framework of dynamic systems given the complex nature of the considered phenomena. The interview was set out in the field of the interactions where information are exchanged between the interviewer and the group and between the peer to peer interaction. The meaning of the concept of energy in Physics was related to the context of the exhibition where the concept was implicitly present. We came to the conclusion that this science exhibition, where the pedagogical interview can be utilized as a tool for teaching, has a good context for learning, once the students showed to have learned even though the docents hadn\'t focused the concept of energy directly. Then we commented about the need of a monitor\'s training, where historical and epistemological studies should be included. This training should also account for the exhibition\'s detected deficiency in approaching the scientific concepts in their mathematical formulation. The research for the emergence of learning in the scientific exhibition center and in interviews is developed by proper tools: a video analysis system is devised to search for the most efficient language in the interaction between teacher and pupil, or in any other teaching-learning situations. Our aim is to establish propitious settings for dialogical interactions in the attempt of dealing with the Vygotsky\'s cognitive \"proximal zone of development\", which is important when we consider the \"process\" of learning a complex concept. As a parallel outcome, we got some familiarity with video recording and analysis as an instrument for both developing and showing the student\'s acquisition of scientific knowledge of physical concepts.

Les simulations hydrodynamiques pour la physique de haute densité d'énergie ainsi que pour la fusion par confinement inertiel exigent une description détaillée de flux d'énergie. Le mécanisme principal est le transport électronique, qui peut être un phénoméne non local qui doit être décrit avec des modèles de Fokker-Planck, stationnaires et simplifiés dans les codes hydrodynamiques à grande échelle. Mon travail thèse est consacré au développement d'un nouveau modèle de transport non local basé sur l'utilisation d'une méthode de fermeture entropique pour la résolution des premiers moments de l'équation de Fokker-Planck agrémentée d'un opérateur de collision dédié. Une telle fermeture permet une bonne résolution des fortes anisotropies de la fonction de distribution électronique dans les régimes où le développement d'instabilités électrostatiques à petite échelle le requiert. Ce modèle aux moments (M1) est comparé avec succès au modèle de Schurtz, Nicolaï et Busquet (SNB), référent dans le domaine du transport électronique non local. Ce modèle, basé sur l'hypothèse d'une faible anisotropie de la fonction de distribution sous-jacente induisant une relation de fermeture polynomiale (P1), utilise un opérateur de collision simplifié dont nous avons proposé une amélioration. Après avoir considéré plusieurs configurations typiques de transport de chaleur, nous avons montré que le modèle M1 ultidimensionnel peut prendre naturellement en compte des effets d'un plasmas magnétisés sur le transport électronique. De plus, ce modèle permet de calculer des fonctions de distribution utiles aux études cinétiques comme la stabilité du plasma dans la zone de transport. Nous confirmons avec notre modèle que le transport d'énergie électronique peut fortement modifier l'amortissement des ondes de Langmuir et des ondes acoustiques ; contrairement aux modèles non locaux simplifiés, M1 décrit les modifications de la fonction de distribution et l'amortissement des ondes du plasma. La structure du modèle permet également de prendre en compte naturellement des champs magnétiques autogénérés, qui jouent un rôle crucial dans des simulations multidimensionnelles. Ces champs magnétiques pourraient également être étudiés pour concentrer l'énergie dans les schémas d'ignition. Enfin, nous montrons que le modèle M1 reproduit les résultats de la théorie locale élaborée par Braginskii pour tous les niveau de magnétisation et propose de nouveaux résultats pour le régime non local. Ce travail constitue une première validation de l'utilisation des fermetures entropiques, dans les régimes de faibles anisotropies, qui va s'ajouter aux tests dans les régimes fortement anisotropes. / Hydrodynamic simulations in high-energy-density physics and inertial con nement fusion require a detailed description of energy uxes. The leading mechanism is the electron transport, which can be a nonlocal phenomenon that needs to be described with quasistationary and simplified Fokker-Planck models in large scale hydrodynamic codes. My thesis is dedicated to the development of a new nonlocal transport model based on a fast-moving-particles collision operator and on a first moment Fokker-Planck equation, simplified with an entropic closure relation. Such a closure enables a better description of the electron distribution function in the limit of high anisotropies, where small scale electrostatic instabilities could be excited. This new model, so called M1, is successfully compared with the well known nonlocal electron transport model proposed by Schurtz, Nicolaï and Busquet, using different collision operators, and with the reduced Fokker-Planck model, based on a small-anisotropies polynomial closure relation (P1). Several typical configurations of heat transport are considered. We show that the M1 entropic model may operate in two and three dimensions and is able to account for electron transport modifications in external magnetic fields. Moreover, our model enables to compute realistic electron distribution functions, which can be used for kinetic studies, as for the plasma stability in the transport zone. It is demonstrated that the electron energy transport may strongly modify damping of Langmuir and ion acoustic waves, while the simplified nonlocal transport models are not able to describe accurately the modifications of the distribution function and plasma wave damping. The structure of the M1 model allows to naturally take into account self-generated magnetic fields, which play a crucial role in multidimensional simulations. Moreover, magnetic fields could also be used for the focusing of energetic particles in alternative ignition schemes. The M1 model reproduces the results of the local transport theory in plasma, developed by Braginskii, in a broad range of degrees of magnetization and predicts new results in the nonlocal regime. This work constitutes a first validation of the entropic closure assumption in the weakly-anisotropic regime. It can be added to the existing tests, in the strongly-anisotropic regimes.

The Thesis "Videosequences and their use in teaching physics at the elementary school" provides a basic understanding of the issue of the use of audiovisual technology in an environment at the elementary school, focusing on the integration of video in teaching physics at the second stage. It describes the possibilities of video sources on the Internet and instructions for their preparation and to their own creation. The Thesis is also based on practical experiences that means the inclusion of specific movies in two selected topics in teaching physics.

Estudamos o conceito de energia na teoria física a nível histórico e a nível de ensino-aprendizagem, isto é, do ponto de vista de sua criação, representação conceitual, matemática e experimental, na constituição de seu significado na teoria científica e na linguagem comum. Como um exercício preliminar, analisamos alguns dados sobre o ensino de conceitos de física na exposição científica do IFUSP \"Ondas, Campos e Partículas\", de 1989 a 1990, e, em 1991, com o nome de \"Do Caleidoscópio ao Carrossel\", no prédio da Engenharia Mecânica (Escola Politécnica). A exposição apresenta fenômenos das teorias da física nos campos da mecânica, eletricidade e magnetismo, termodinâmica e ótica, fenômenos que implicam ações em escalas macroscópicas e a nível atômico. Descrevemos uma entrevista de 13 minutos com quatro alunos de 1o grau que visitaram a exposição com monitoramento. Durante a situação da entrevista, que chamamos de pedagógica, esses alunos constróem o conceito de energia. Essa entrevista é analisada em termos dos contextos fenomenológico e epistemológico, contidos na exposição, ainda que os monitores que acompanharam a visita não falassem em energia. Descrevemos também uma entrevista com um monitor sobre ensino e aprendizagem. Enfocamos o conceito de \"conhecimento prévio do aluno como requisito para ensino\", e analisamos usando o conceito de zona de desenvolvimento proximal (ZDP) de Vygotsky. Usamos a moldura de Vygotsky (VY 1896/1934) na análise da entrevista com os alunos, que é um exemplo de como considerar a ZDP. Ela não visa avaliação, e nem apenas coleta de dados. Propomos o desenvolvimento de entrevistas pedagógicas para já se constituir uma situação de ensino-aprendizagem, como uma interação desejável, dialógica, onde a ZDP, isto é, a capacidade do aluno \"vir a saber\", seja desenvolvida. A análise da emergência do conceito de energia no caso estudado da entrevista com alunos é feita com a perspectiva de sistemas dinâmicos, dada a natureza complexa dos fenômenos estudados. A História e Filosofia das Teorias Científicas são usadas como ferramenta heurística para identificar correlação na constituição do espaço de significação. Concluíremos que, se os monitores não enfocavam diretamente o conceito de energia e os alunos aprendiam mesmo assim, é porque a exposição é um bom contexto onde a entrevista pedagógica pode ser utilizada como instrumento de ensino, Por fim, falamos da necessidade de um treinamento para monitores, onde sua formação inclua estudos históricos e epistemológicos e uma preparação para suprir a deficiência que detetamos na exposição, isto é, a de não abordar os conceitos na sua forma matematizada. A pesquisa das condições para aprendizagem na Exposição Científica e em Entrevista se desenvolve com instrumentos próprios: um sistema de análise em vídeo foi construído para pesquisar a linguagem usada na interação entre professor e aluno. Objetivamos estabelecer condições propícias para interações dialógicas. Como resultado secundário, foi adquirida certa familiaridade em trabalhar com o vídeo como instrumento para, ao mesmo tempo, mostrar e desenvolver aquisição do conhecimento científico de conceitos de física. / We have studied the concept of energy in Physics in the historical and the Teaching-Learning contexts, i.e., from the point of view of its creation, its mathematical and experimental conceptual representation, of its scientific and ordinary meaning constitution. As a preliminary exercise, we analysed some data about the Physics concepts teaching at the \"Waves, Fields and Particles\" Science Exhibition Center located at that time, in the Engineering Building of the University of São Paulo. The content of the Exhibition was regular demonstrations of phenomena delineated by classical theories of Mechanics, Eletromagnetism, Thermodynamics and some topics in Modern Physics. An interpretation of the exhibition could be in terms of the concept of energy and its transformations, as was shown by an interview with four visiting students described here. During this interview set, which we named pedagogical, these students constructed the concept of energy. This interview is analysed in terms of phenomenological and epistemological implications in the exhibition. A monitor thinking about teaching and learning has also been situated out of an interview. This monitor considers the pupil\'s previous subject matter knowledge as a requirement for teaching. By means of the ZDP (zone of proximal development), we are warned by Vygotsky against the extreme pre-requisites, which can limit the learning. We also make use of Vygotsky\'s concept in the analysis of the interview with students. The interview described in the first part of this work is a ZDP application example. It neither aims evaluation nor just data gathering. It will be developed to be a teaching-learning instrument. We believe this is possible, for it will be an interaction where the ZDP or the pupil\'s ability to \"come to know\" is to be considered. The case study of the emergence of the concept of energy from the interview with pupils is analysed within the framework of dynamic systems given the complex nature of the considered phenomena. The interview was set out in the field of the interactions where information are exchanged between the interviewer and the group and between the peer to peer interaction. The meaning of the concept of energy in Physics was related to the context of the exhibition where the concept was implicitly present. We came to the conclusion that this science exhibition, where the pedagogical interview can be utilized as a tool for teaching, has a good context for learning, once the students showed to have learned even though the docents hadn\'t focused the concept of energy directly. Then we commented about the need of a monitor\'s training, where historical and epistemological studies should be included. This training should also account for the exhibition\'s detected deficiency in approaching the scientific concepts in their mathematical formulation. The research for the emergence of learning in the scientific exhibition center and in interviews is developed by proper tools: a video analysis system is devised to search for the most efficient language in the interaction between teacher and pupil, or in any other teaching-learning situations. Our aim is to establish propitious settings for dialogical interactions in the attempt of dealing with the Vygotsky\'s cognitive \"proximal zone of development\", which is important when we consider the \"process\" of learning a complex concept. As a parallel outcome, we got some familiarity with video recording and analysis as an instrument for both developing and showing the student\'s acquisition of scientific knowledge of physical concepts.

No description available.

No description available.