THERMONUCLEAR FUSION

Author: SALVADOR HERNÁNDEZ MAX.
Year: 2004.
University: POLITÉCNICA DE MADRID [www.upm.es].
Place of defense: E.T.S. INGENIEROS INDUSTRIALES.
Place of preparation: E.T.S.I INDUSTRIALES.

Summary: In recent years, with the increase in the total cost of exploration, drilling, extraction and transportation of fossil fuels and their derivatives, nuclear fusion offers mankind a great opportunity for their maintenance and development, pursuing a very powerful and clean energy as it is. Materials Physics is a major research area involved in the effort nuclear fusion, its main goal is to generate enough knowledge on three low activation materials: ferritic steels / martensílicos, alloys vanadio-cromo-titanio and composed of silicon carbide, which are considered as the main candidates for structural materials in the reaction chambers. This is an important area-not only for the safety of the plantations but also to increase the life of the nuclear reactor with appropriate materials that can be satisfactorily functional and economic exploitation. The Silicon carbide (SiC) is considered one of the major constituent materials for a nuclear fusion reactor. We have developed a physical model mecánico-cuántico semi-empírico tight bindign to obtain, for first principles, the eight energies of formation of defects in the elementary or native silicon carbide: vacant carbon and silicon (VC-VSi) antiposiciones carbon and silicon (AC-ASi), and four interstitial tetrahedral: interstitial carbon carbon coordinated and coordinated silicon (CTC-CTSi); coordinated interstitial silicon carbon and silicon (SiTC-SiTSi) with the advantage of the amounts Bloch, with a significant pattern of molecular dynamics, to manage, in this first part of our investigation, boxes of static simulations of: 64 and 216 atoms with the defect implemented. We calibrated our model tight binding regard to the code ab-initio VASP using the Density Functional Theory (DFT) and Approximation of the Local Density (LDA), gaining a major parameter is the enthalpy of formation of the composite SiC (? HSiC), in addition to various estequiometrías that depend on the important role that has the potential chemical (u). We have also developed our research with two other physical models: (DINMOL) at the University of Cagilari, which uses the potential classic Tersoff and this ab-initio VASP, to get well, the eight energies of formation of defects, and we have compared our results with other models ab-initio and potential Tersoff, with a major evaluation of the results of these investigators and our own results. We have established a weighted average repulsive to our potential peer F (R) (FCC = 0.50) for carbon and (FSiSi = 0.28) for silicon, in addition to establishing a network parameter of 4,295 Angstroms. With this approach, we have developed the second part of our research is to obtain the diffusion coefficients and the energies of migration of interstitial carbon and silicon, in addition to establishing the mechanisms for disseminating the defects that it is better known as kick-out. We have compared our results with those in the dissemination of simulations using interstitial potential Tersoff and demonstrated that, using this potential classic, there is no outreach to those simulations delos intersiciales using the potential of Tersoff and demonstrated that applying and 8 ste pot 42b ncial classic, there is no genetic interstitial diffusion (or vacancies) in the glass of SiC. Our results in the spread also presents a good agreement with experimental data, and concluded that we now have a powerful computational tool that uses the molecular dynamics mecánico-cuántica semi-empírica (tight binding) applied to a material biátomico as it is composed of Silicon Carbide.

Author: FUENTES LÓPEZ CÁNDIDA.
Year: 2006.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS UCM.

Summary: It has developed a system of warming neutral beam injection (NBI) for the magnetic confinement device TJ-II, which is generated and injected beam hydrogen atoms accelerated to energies of 40 keV and power between 700 and 1500 kW . TJ-II is the first fusion device with helical axis which makes use of an injection system neutral. The high degree of helicity of TJ-II gives its geometric structure heavily dimensional character that significantly increases the complexity of the heating system in two areas under consideration in this report: * The plasma has a cross section in the form of Jewish rotate around the central coil, so that the magnetic axis follows a propeller radio 0.28 m. For this reason, special attention has been given in this report to establish and optimize geometry injection to ensure adequate absorption in the plasma beam. * Some areas of the vacuum chamber of TJ-II are exposed to the direct interaction with the beam of neutral. The detailed analysis of the distribution of thermal loads within the vacuum chamber of TH-II, the design of appropriate protection and study of the thermal evolution of such protection has been an important element of the work program thesis. To do so, they had to adapt computational codes used in other experimental fusion devices by providing it with its three-dimensional, which characterizes the tJ-II. Given the particular importance of optimizing and controlling the parameters of injection, another of the main motivations of this Doctoral Thesis has been the development of diagnostics, specifically tailored to the needs of TJ-II, capable demonitorizar the most relevant parameters on efficiency the injection system. Thus, a measurement system with thermocouple temperature at the edge of the beam, which detect immediately possible inhomogeneidades beam misalignment or in the direction of injection. In addition, it has developed a diagnosis based on termografia infrared, which obtains the distribution map of neutral beam power that sets it apart from other fusion devices, allows for characterization and optimization in-situ beam after its transmission through the duct. All tasks carried out over the conduct of this Doctoral Thesis have served to optimize experimental transmission beam neutral and therefore increase the power injected into TJ-II. In short, will go into operation a second line of neutral injection, in which the criteria of operation and optimization deducted from this experience and will be installed replicas of diagnostics developed for the line of injection under consideration so far.