PLASMA PHYSICS

Author: EGUILIOR DIAZ SONSOLES.
Year: 2004.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS UCM.

Summary: We conducted analysis perturbativos transport channel density and temperature electronics. The channel electron density we determine the coefficients of transportation for plasmas ECRH of estelerátor TJ-II by analyzing the evolution of the profiles of electron density. The analysis has been adjusted both the diffusion coefficient and the speed convecting by certain expressions that contain a number of parameters, and these have been identified through a process of least squares, so as to obtain the best possible adjustment to the density profile pilot over time. In these studies the term particle essential for determining diffusion and convection without ambigà ¼ age, has been obtained from the results of the code EIRENE. We have also conducted studies in the channel temperature electronics for the purpose of determining the diffusion coefficient of heat and power deposition profiles in estelarátor TJ-II. This would have conducted experiments modulating at different frequencies (Hz to tens of kHz) microwaves used to heat the plasma. In experiments with high frequency modulation, we have obtained the deposition profile of power, while the low frequency was obtained diffusion coefficient of heat using the Fourier transform. In these calculations include the power deposition profile previously estimated as a new ingredient. Further experiments have been performed on and off a girotrón results allow us to obtain radial profiles of the coefficient of heat transport and deposition profile power through technical adjustment by least squares. In the analysis of the heat transport experiments have emerged results indicate that studies are required link between transportation and heating through ECRH. To this end we have obtained equations Langevirn dela interaction cuasi-lineal between waves and particles using unambiguous equivalence between them and Fokker-Planck equation. These can be solved numerically to obtain the evolution in the space of moments of a particle test immersed in a magnetic field. The equations we have gained are relativists and valid for any kind of wave. These equations will be very useful to study the dynamics of microscopic particles in the actual geometry of the device and will enable us to, for example, obtain an estimate of radial flow out particles induced by the ECRH and radial electric field to maintain the status ambiopolar plasma.

Author: MUÑOZ SERRANO ENCARNACIÓN.
Year: 2004.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In this paper, the behavior of a spot in a cathodic arc plasma at atmospheric pressure has been studied from a dynamic, later applied to the particular case of a cathode-refractory W and pure graphite. It has been necessary in the first place, conducting a proper modeling of the cathodic region, which has incorporated the evaporation of cathodic particles of material, giving vital parameters such as current density and total density total energy flow on the surface cathodic. Thus, it is possible to obtain the evolution in time of the temperature distribution in the cathode, which together with the phenomenon of thermal ablation cathodic material that undergoes a change of phase, it allows to study the dynamics of the spot on the surface cathodic . Based on an initial crater where it is assumed located the spot cathodic, has obtained a judgment autoconsistente for calculating the maximum radius of the crater, and there was the possibility that the spot moves or not seems so natural for development numerical model. The theoretical modeling has been complemented by the pilot study spot on the surface of a graphite cathode. Exploration of the surface of the cathode through an electron microscope and a rugosímetro allow obtaining the radius of the crater formed in that area. Moreover, the dynamics of cathodic spot for different values of potential inter-electródico has been estudiad using a digital camcorder. Experimental observations confirm the theoretical results obtained.

Author: ÁLVAREZ MOLINA RAFAEL.
Year: 2004.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The objective of this thesis is the characterization by means of spectroscopic. Microwave plasma produced by the torch injection axial TIA called by its initials in French. This characterization has been done radially, ie for all positions inside plasma, which presents some difficulty since the TIA produces a plasma of just 1 mm in diameter. It has been necessary to develop a method for characterizing radio especially suitable for thin plasmas, consistent with the design of an experimental device and the proper development of a method of treating experimental data including technical investment Abel. The TIA is a versatile plasma that has been successfully used by our group in different applications. One is the atomic emission spectrometry, which uses helium gas plasmógeno, plasma occurs in contact with air and used high values of gas flow. Another is the destruction of waste, which are used both helium as argon, with the plasma inside a reactor for waste treatment patented by our group, and in conditions of low gas flow plasmógeno. The aim of this thesis has been the characterization of these plasmas. For the helium used in plasma spectrometry were obtained radial distributions of its main parameters for different conditions of power incident and flow of gas. It used either as a direct spectroscopic model colisional-radiativo (CFR) desarrolladopreviamentepor our group. It also estudióel effect of the interaction of other species present in the discharge, or by entering from the air that surrounds it, or by mixing with gas plasmógeno of atomic gases (Ar) or molecular (N2 and 02). Having regard to the usefulness of the CFR helium plasma, in this thesis has desarrolladoun CFR for the argon plasma. Using both models combined with measures espectroscópicasdirectas, proceeded to obtain the main parameters of helium and argon plasma used in the destruction of waste.

Author: GARCIA OLAYA JERONIMO.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: SECCIO D'ENGINYERIA NUCLEAR.
Place of preparation: EDIFICI B4 Campus NORD.

Summary: The magnetically confined plasmas study is one of the most promising research fields in the present days due to the high perspectives of unlimited and clean energy that fusion has generated. In this framework, the stellarator devices play a significant role because of, unlike in the tokamak case, their continuum working regime, which will be an essential feature of the future fusion commercial reactor. Heat transport studies in stellarator devices are completely necessary since the main plasma properties (and therefore, the total fusion power generated) are absolutely dependent. Nowadays, the largest stellarator in the world is the Large Helical Device (LHD). There is also a stellarator device is Spain, TJ-II, which is located in the installations of CIEMAT in Madrid. In this thesis, turbulent and conductive heat transport is studied in both devices with the aim of comparing its formation and suppression. First of all, collisional transport, i.e. neoclassical transport, which is caused by the particle collisions, is studied by means of a new transport model implemented in the transport code PRETOR-Stellarator. This model is able to calculate heat diffusivities as well as the neoclassical electric field with reasonable accuracy without spending as much computational time as in the Monte Carlo techniques. It is deduced from the results that, for both TJ-II and LHD, neoclassical transport may be quite important in plasmas with low density and high temperatures, although higher levels of neoclassical transport are obtained in TJ-II. Both devices share the feature that in low collisional plasmas, a high positive neoclassical electric field with a high shear appears in the plasma core. This electric field can be responsible of the suppression of the turbulence heat transport. Some new turbulent heat transport models have been added to PRETOR-Stellarator in order to study this kind of transport. Both, LHD and TJ-II, share a common heat transport in the confinement region (plasma core), called drift wave electromagnetic transport, and which is due to the fluctuations of the magnetic field. Outside this region, turbulent heat transport in LHD has similar characteristic to that in tokamaks, whereas in TJ-II, turbulent transport is maintained. Turbulent heat transport reduction is a major issue in fusion research, since the capability of producing commercial fusion energy depends strongly on the low levels of turbulence of the plasma. The appearance of a neoclassical electric field in the plasma core and its interaction with turbulent transport has been studied. It is shown that this electric field is able to generate a rotation in the plasma which is able to suppress turbulent transport to neoclassical levels when density is low enough. These plasmas are called to have an internal transport barrier and have stepped electron temperature profiles with hollow electron density profiles. Finally, once electron heat transport in stellarators has been clarified, a comparison of the designs of the future commercial reactor based on both, stellarators and tokamaks, has been carried out. A stellarator commercial reactor, based on the design of the LHD, would have a 15.5 m major radius, 2.5 m minor radius, with a continuum working regime based on low temperatures and high densities. Main energy sinks are due to conductive-convective heat losses and radiation losses (in a 95% from Bremmstrahlung radiation). The fact that it has such a large major radius makes this design expensive and difficult to build. A tokamak fusion reactor would be smaller, however, the high temperatures achieved make cyclotron radiation losses to be very high, and a wall with a high reflection coefficient seems to be necessary.

Author: GARCIA OLAYA JERONIMO.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: SECCIO D'ENGINYERIA NUCLEAR.
Place of preparation: EDIFICI B4 Campus NORD.

Summary: The magnetically confined plasmas study is one of the most promising research fields in the present days due to the high perspectives of unlimited and clean energy that fusion has generated. In this framework, the stellarator devices play a significant role because of, unlike in the tokamak case, their continuum working regime, which will be an essential feature of the future fusion commercial reactor. Heat transport studies in stellarator devices are completely necessary since the main plasma properties (and therefore, the total fusion power generated) are absolutely dependent. Nowadays, the largest stellarator in the world is the Large Helical Device (LHD). There is also a stellarator device is Spain, TJ-II, which is located in the installations of CIEMAT in Madrid. In this thesis, turbulent and conductive heat transport is studied in both devices with the aim of comparing its formation and suppression. First of all, collisional transport, i.e. neoclassical transport, which is caused by the particle collisions, is studied by means of a new transport model implemented in the transport code PRETOR-Stellarator. This model is able to calculate heat diffusivities as well as the neoclassical electric field with reasonable accuracy without spending as much computational time as in the Monte Carlo techniques. It is deduced from the results that, for both TJ-II and LHD, neoclassical transport may be quite important in plasmas with low density and high temperatures, although higher levels of neoclassical transport are obtained in TJ-II. Both devices share the feature that in low collisional plasmas, a high positive neoclassical electric field with a high shear appears in the plasma core. This electric field can be responsible of the suppression of the turbulence heat transport. Some new turbulent heat transport models have been added to PRETOR-Stellarator in order to study this kind of transport. Both, LHD and TJ-II, share a common heat transport in the confinement region (plasma core), called drift wave electromagnetic transport, and which is due to the fluctuations of the magnetic field. Outside this region, turbulent heat transport in LHD has similar characteristic to that in tokamaks, whereas in TJ-II, turbulent transport is maintained. Turbulent heat transport reduction is a major issue in fusion research, since the capability of producing commercial fusion energy depends strongly on the low levels of turbulence of the plasma. The appearance of a neoclassical electric field in the plasma core and its interaction with turbulent transport has been studied. It is shown that this electric field is able to generate a rotation in the plasma which is able to suppress turbulent transport to neoclassical levels when density is low enough. These plasmas are called to have an internal transport barrier and have stepped electron temperature profiles with hollow electron density profiles. Finally, once electron heat transport in stellarators has been clarified, a comparison of the designs of the future commercial reactor based on both, stellarators and tokamaks, has been carried out. A stellarator commercial reactor, based on the design of the LHD, would have a 15.5 m major radius, 2.5 m minor radius, with a continuum working regime based on low temperatures and high densities. Main energy sinks are due to conductive-convective heat losses and radiation losses (in a 95% from Bremmstrahlung radiation). The fact that it has such a large major radius makes this design expensive and difficult to build. A tokamak fusion reactor would be smaller, however, the high temperatures achieved make cyclotron radiation losses to be very high, and a wall with a high reflection coefficient seems to be necessary.

Author: TORRES CASTRO JESUS PEDRO.
Year: 2005.
University: CÓRDOBA [www.uco.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: We present a non-intrusive method of plasma diagnosis based on spectroscopic analysis of the various Stark broadening of the spectral lines of hydrogen Balmer series. This method has been called method of crossing lines simultaneously and can diagnose the electron density and temperature electronics. There will always be a historical study on the various theories and models Stark effect in plasmas, with application in a microwave discharge generated by atmospheric pressure. It uses the computational model of Gigosos-Cardeñosos (Gig-Card), which collects dela best way at present significant contributions to the Stark effect as a dynamic ion. There is also an experimental characterization of details of the profile line H-beta of the series Balmer not yet listed in a satisfactory manner in theoretical models, such as those relating to its asymmetry and the structure of the central valley of spectral profile. As a diagnostic technique, the method of crossing lines successfully implemented in different laboratory plasmas generated by microwaves at atmospheric pressure; argon plasma in surfatrón, argon plasma at TIA, plasma hilio at TIA. It is necessary to introduce extra careful hydrogen discharges for optimal observation of the spectral lines of the Balmer series. It also manages to explore a pure hydrogen plasma at atmospheric pressure at TIA. Finally, the method of crossing lines and models widening Stark apply to the photosphere of the Sun. The method of crossing-based Stark broadening of spectral lines compares well in the discharge of pure hydrogen at atmospheric pressure at TIA with other methods of diagnosis and analysis, as the so-called diagram Boltzaman amended, based on the theory of balance excitación- saturation in the plasma.

Author: YANGUAS GIL ANGEL.
Year: 2005.
University: SEVILLA [www.us.es].
Place of preparation: INSTITUTO DE CIENCIA DE MATERIALES DE SEVILLA (CSIC - UNVIERSIDAD DE SEVILLA).

Summary: The plasma-assisted deposition (PECVD) of thin films of silicon oxide silico and is a process of great interest because of their possible application in microelectronics materials as low dielectric constant or low-k. In such processes, the properties of materials are determined by the conditions of deposition, in which the plasma plays a key role in controlling the species that reach the surface of the subject. This thesis has been carried out experimental and theoretical study of blood and the thin films of SiOxCyHz obtained from mixtures Ar/O2/tetrametilsilano. From the experimental point of view, have been used techniques such as optical emission spectroscopy and mass spectrometry for the analysis of plasma, while the thin films have been characterized by FT-IR, XPS, and AFM. This last technique has been carried out a study of the influence that the time of deposition and scale of measurement have in the roughness of thin films. The results have been obtained in connection with the so-called theory of dynamic scaling. Moreover, it has conducted the simulation of discharges in Ar and O2 through a global model, which has involved the development of complex kinetic models of the species in the plasma of these gases. In the case of Ar, for the construction of this model has produced a new set of sections effective for different processes inelastic impact by mail. In addition, the deposition process has been simulated using simple models based on Monte Carlo techniques dynamics, through which it has become clear that the influence different parameters, such as the distribution function of particles incidents have at the time to determine the microstructure of the thin films obtained.