Orientador: Aruy Marotta / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T20:43:05Z (GMT). No. of bitstreams: 1 Bubliyeuski_DzmitryAlexandrovich_D.pdf: 2691341 bytes, checksum: 7b8e0d82f84d333a723eb14e64832cf3 (MD5) Previous issue date: 2008 / Resumo: Uma nova técnica de diagnóstico, denominada termo-espectroscópica, foi introduzida neste trabalho para estudo da interação do arco elétrico com o catodo frio de cobre numa instalação coaxial magnética, com catodo não-refrigerado, operando em gases plasmagênicos ar e nitrogênio. A técnica foi aplicada ao estudo da velocidade de rotação da mancha do arco e da densidade efetiva de corrente na mancha. Estes parâmetros têm estreita relação com o fenômeno da erosão de eletrodos frios. A nova técnica combina a técnica óptico-espectroscópica e a técnica térmica, e se baseia na teoria térmica da erosão. Por espectroscopia, registra-se a evolução temporal da intensidade da linha de emissão do vapor de cobre. Pelo método térmico, registra-se a evolução da temperatura da superfície do eletrodo. A técnica permite um grande aumento na sensibilidade de detecção do ponto de transição do regime de micro para macroerosão, através da observação do abrupto aumento da intensidade da linha espectral do cobre. Observamos que para o regime de microerosão, a velocidade é sempre maior, e a dispersão da velocidade sempre menor que na macroerosão. Esse fato confirma a existência de uma força de arraste superficial ao movimento do arco, que pode ser proporcionada pela fusão do eletrodo, por jatos catódicos e/ou por óxidos na superfície do eletrodo. A densidade de corrente na mancha apresenta um grande crescimento para valores baixos do campo magnético e certa saturação para altos valores. Para o ar foi observada uma forte influência dos óxidos na mobilidade da mancha, que é significativamente maior do que com nitrogênio. A diferença entre medidas obtidas no ar e nitrogênio é atribuída ao processo de decomposição de óxidos na superfície, que afeta a determinação correta do ponto de transição. O estudo experimental realizado nesta tese permite uma melhor compreensão dos fenômenos que ocorrem em manchas de arcos elétricos de eletrodos frios / Abstract: In the present work a new diagnostic technique, named thermo-spectroscopic one, was introduced for study of the interaction of the electric arc with a cold copper electrode using the coaxial magnetic installation with non-refrigerated cathode operated in air and nitrogen. The technique was applied to the measurement of the arc spot rotation velocity and the effective spot current density. These parameters have a direct relation with the phenomenon of the cold electrode erosion. The new technique combines the optic-spectroscopic method and the thermal method, and is based on the erosion thermophysical theory. Using spectroscopy, the temporal evolution of the intensity of the copper vapor emission line was registered. Via the thermal method, the evolution of the electrode surface temperature was recorded. By the observation of the abrupt increase of the copper spectral line intensity, the new technique permits a significative increase in the sensibility of the detection of the transition from the microerosion process to the macroerosion one. It was observed that the arc velocity for the microerosion regime is always higher and the velocity dispersion is always lesser then the ones for the macroerosion regime. This fact confirms the existence of the surface drag force to the arc movement, which can be provided by the electrode fusion process, by cathode jets and/or by oxides formed on the electrode surface. The arc spot current density presents a high growth for the low values of the magnetic field and certain saturation for the high values ones. For the air, a strong influence of oxides on the spot mobility was observed, that is more significant then the one for the nitrogen. The difference between the measurements for the air and the nitrogen is attributed to the oxide decomposition process on the electrode surface that affects the correct transition point determination. The experimental study, carried out in this thesis, allows a better understanding of the phenomenon taking place in cold electrode arc spots / Doutorado / Física de Plasmas e Descargas Elétricas / Doutor em Ciências

Low-dielectric (k) films are one of the performance drivers for continued scaling of integrated circuit devices. These films are needed in microelectronic device interconnects to lower power consumption and minimize cross talk between metal lines that "interconnect" transistors. Low-k materials currently in production for the 45 and 65 nm node are most often organosilicate glasses (OSG) with dielectric constants near 2.8 and nominal porosities of 8-10%. The next generation of low-k materials will require k values 2.6 and below for the 45 nm device generation and beyond. The continuous decrease in device dimensions in ultra large scale integrated (ULSI) circuits have brought about the replacement of the silicon dioxide interconnect dielectric (ILD), which has a dielectric constant (k) of approximately 4.1, with low dielectric constant materials. Lowering the dielectric constant reduces the propagation delays, RC constant (R = the resistance of the metal lines; C = the line capacitance), and metal cross-talk between wires. In order to reduce the RC constants, a number of low-k materials have been studied for use as intermetal dielectrics. The k values of these dielectric materials can be lowered by replacing oxide films with carbon-based polymer films, incorporating hydrocarbon functional groups into oxide films (SiOCH films), or introducing porogens in the film during processing to create pores. However, additional integration issues such as damage to these materials caused by plasma etch, plasma ash, and wet etch processes are yet to be overcome. This dissertation reports the effects of plasma, temperature and chemical reactions on low-k SiOCH films. Plasma ash processes have been known to cause hydrophobic films to lose their hydrophobic methyl groups, rendering them to be hydrophilic. This allows the films to readily absorb moisture. Supercritical carbon dioxide (SC-CO2) can be used to transport silylating agents, hexamethyldisilazane (HMDS) and diethoxy-dimethlysilane (DEDMS), to functionalize the damaged surfaces of the ash-damaged films. The thermal stability of the low-k films after SC-CO2 treatment is also discussed by performing in-situ heat treatments on the films. UV curing has been shown to reduce the amount of pores while showing only a limited change dielectric constant. This work goes on to describe the effect of UV curing on low-k films after exposing the films to supercritical carbon dioxide (CO2) in combination with tetramethylorthosilicate (TMOS).

Orientador: Munemasa Machida / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica, Gleb Wataghin / Made available in DSpace on 2018-08-14T10:48:49Z (GMT). No. of bitstreams: 1 Nascimento_Fellypedo_M.pdf: 4493365 bytes, checksum: 50c2d66d1ba6fb6004585fe057e964e5 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho, foram feitas medidas simultâneas e três linhas e emissão e hidrogênio no tokamak NOVA-UNICAMP. A partir das medidas e brilho as emissões das linhas Ha , H b e Hg e fazendo uso de coeficientes que constam nas tabelas de Johnson e Hinnov, foi possível determinar temperaturas e densidades eletrônicas no plasma ao longo de descargas o tokamak. Para isto, foi utilizada, e aperfeiçoada, uma técnica desenvolvida num trabalho e doutoramento recente do nosso grupo, a qual faz uso do conceito de unicidade do tempo de confinamento de partículas. Os principais aprimoramentos realizados neste diagnóstico foram: utilização de três espectrômetros para medidas simultâneas das emissões e hidrogênio, instalação e fibras ópticas para coletar a luz emitida pelo plasma, adoção de um sistema de colimação para obter um certo grau e definição espacial nas medidas, uso de um maior número e valores e temperaturas na análise dos dados e desenvolvimento de um novo método (algorítimo) para obter os valores de temperaturas e densidades dos elétrons no plasma. As temperaturas e densidades eletrônicas médias obtidas ficaram em torno e 7,5 eV e 7,0 ·10 12cm-3, respectivamente. Estes valores estão entro do espera o para tais parâmetros na borda do tokamak NOVA-UNICAMP. Isto indica que este diagnóstico pode ser usado para monitorar ensidades e temperaturas e elétrons em plasmas gerados por tokamaks. Além isso, foram efetuados alguns experimentos com detectores multicanal e o gás hidrogênio foi trocado pelo hélio, na tentativa de mostrar a versatilidade do diagnóstico proposto. / Abstract: In this work, we have made simultaneous measurements of three hydrogen emission lines on our tokamak. From the measurements of absolute brightness of the Ha , H b e Hg lines an using data from Johnson an Hinnov table, was possible to determine electronic ensities an temperatures during the tokamak ischarges. For this,we have used, an refined, a technique developed in a recent PhD thesis in our work group. This technique uses the concept of particle confinement time uniqueness. The main upgrades made in this diagnostic were: the use of three spectrometers for simultaneous measurements of the hydrogen emissions, installation of optical fibers to collect the light emitte by the plasma, adoption of a collimation system for having some spatial definition of the measurements, use of a greater range of temperature values uring the data analysis and development of a new method (algorithm) for obtaining the electronic densities and temperatures in the plasma. The average temperature and density obtained was about 7.5 eV and 7.0 ·1012cm-3, respectively. The results obtained are in accordance with the expected values for these parameters at the edge of the NOVA-UNICAMP tokamak plasma. This indicates that this diagnostic can be used to monitor the electronic densities and temperatures in tokamak plasmas. Additionally, we have made experiments with multichannel detectors, and the hydrogen gas was replaced by helium, in an attempt to show the versatility of the proposed diagnostic. / Mestrado / Física / Mestre em Física

The problem with which this investigation is concerned is that of determining the steady-state and dynamic characteristics of the admittance of a metallic probe immersed in a laboratory plasma which has the low electron densities and low electron temperatures characteristic of the ionospheric plasma. The problem is separated into three related topics: the design and production of the laboratory plasma, the measurement of the steady-state properties of dc and very low frequency probe admittance, and the study of transient ion sheath effects on radio frequency probe admittance.

Electron densities and collision frequencies were obtained on a number of gases in a dc discharge at low pressures (0.70-2mm of Hg). These measurements were performed by microwave probing of a filament of the dc discharge placed coaxially in a resonant cavity operating in a TM₀₁₀ mode. The equipment and techniques for making the microwave measurements employing the resonant cavity are described. One of the main features of this investigation is the technique of differentiating the resonance signal of the loaded cavity in order to make accurate measurements of the resonant frequency and half-power point frequencies.

The circumgalactic medium (CGM) is thought to contain the massive reservoir of gas exchanged over the course of galactic evolution, including the fuel for future star formation and the remnants of a galaxy’s merger history. Models and observations suggest that the CGM has a very low density, and faint optical or UV emission from this gas is exceedingly difficult to detect. This thesis is a combination of simulations, instrumentation and observations aimed at ultimately understanding the distribution and kinematics of ionized gas in the CGM. We present a suite of small-box hydrodynamic simulations created to study the interaction between smooth gas inflow and supernovae-driven outflow at the disk-halo interface where the galactic disk transitions into the CGM. They track the fate and kinematic evolution of gas accreting onto the galactic disk and find evidence of partial mixing with the enriched outflow. We use equilibrium photoionization models to create mock surface brightness maps of Ha and OVI emission. These observables motivate the need for new instrumentation and in suit, we present the newly commissioned Circumgalactic Ha Spectrograph (CHaS): a custom integral field unit (IFU) spectrograph tailored to detect low-surface brightness optical emission in the low-redshift universe. CHaS is deployed in the focal plane of the MDM Observatory Hiltner 2.4-meter telescope, conducting wide-field (10' x 10') spectral imaging with a competitive survey speed proportional to the high instrument grasp. A microlens array segments the field of view into > 60,000 spectra with a spatial resolution of 2.6'' and a resolving power of R ~ 10,000. Accordingly, CHaS is capable of resolving structure on scales less than 1 kpc (at 10 Mpc) and distinguishing emission lines separated by less than 40 km/s. As designed, a 50-100h exposure with CHaS would be the deepest H-alpha image and velocity field ever obtained, reaching a surface brightness of a few mR on scales of a few arcmin. Shorter, hour-long integrations with CHaS reveal a detailed map of the denser interstellar medium and bright emission at the disk-halo interface. We present results for three early commissioning targets: NGC 4631, NGC 7331 and NGC 1068, including high-resolution velocity maps and detections of new extended emission line regions far into the halo. We report a previously unnoted ribbon of ionized gas around NGC 1068, extending tens of kpc from the galactic disk beyond the known outer filamentary structure. Ongoing observations will provide a deeper probe of ionized gas far into the CGM of many nearby galaxy targets, detecting faint extended emission and mapping the velocity of ionized gas beyond the disk.

Helices in proteins have substantial permanent dipole moments arising from the nearly perfect alignment of the individual dipole moments of each peptide bond. Interaction with this helix "macrodipole" is thought to perturb the pKa values of basic or acidic residues at the helix termini. The goal of this project is to investigate the effect of the helix confonnation on the proton affinities ofbasic amino acids placed at theN- or Ctenninus of helical model peptides in the gas phase. Several series of model peptides having a basic residue, lysine (K) or 2,3- diaminopropionic acid (Dap ), located at either terminus were synthesized by solid phase peptide synthesis using conventional techniques or the amino acid fluoride approach. Proton affinities were determined for several basic amino acids and peptides using mass spectrometry by applying the extended Cooks' kinetic method. Favorable conformations and theoretical proton affinities were probed using computational chemistry. The proton affinities determined for Na-acetyl-(L)-lysine, Ac-AK, Ac-KA, and Ac-KAA are 236.8 ± 1.9 kcal mol-1 , 249.4 ± 2.0 kcal mol-1 , 241.5 ± 1.9 kcal mol-1 , and 244.4 ± 2.0 kcal mol-1 respectively. The large negative entropy changes for each of the peptides upon protonation ( -11.2 to - 21.7 cal mol-1 K- 1 ) are consistent with globular confmmations adopted by the protonated peptides due to extensive intramolecular hydrogen bonding. The measured proton affinities of the peptides increased with the size of the peptide as expected. However, the measured proton affinity of the peptide with C-terminal lysine, Ac-AK, is substantially higher than that of the con·esponding peptide with N-terrninal lysine, Ac-KA, contrary to expectations. Proton affinities determined for these compounds using computational chemistry are in reasonable agreement with experimental results. Additionally, proton affinities calculated for helical polyalanine and Aib (aaminoisobutytic acid) modified polyalanine peptides with C-terminal basic residues (Ac AnK and Ac-(AibA)n-Dap) are much larger than proton affinities calculated for the corresponding peptides with N-terminal basic residues. These results indicate that the helix dipole has a substantial effect on the basicity of residues at the helix termini.

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No description available.

Halo currents (HCs) in post-disruption plasmas can be large enough to exert significant electromagnetic loads on structures surrounding the plasma. These currents have axisymmetric and non-axisymmetric components, both of which pose threats to the vacuum vessel and other components. However, the non-axisymmetric forces can rotate, amplifying the displacements they cause when the rotation is close to the structures’ resonant frequencies. A new physically motivated scaling law has been developed that describes the rotation frequencies of these HCs and has been validated against measurements on HBT-EP, Alcator C-Mod, and other tokamaks. This scaling law can describe the time-evolution of the asymmetric HC rotation throughout disruptions on HBT-EP as well as the time-averaged rotation on C-Mod. The scaling law can also be modified to include the edge safety factor at the onset of rotation (𝒒_𝑜𝑛𝑠𝑒𝑡), which significantly improves its validity when applied to machines like C-Mod, where 𝒒_𝑜𝑛𝑠𝑒𝑡 changes frequently. The 𝒒_𝑜𝑛𝑠𝑒𝑡 dependence is explained by the relationship between the poloidal structure of the HC asymmetries and the MHD instabilities that drive them, which has been observed experimentally for the first time using a novel set of current sensing limiter tiles installed on HBT-EP. The 1/𝑎² and 𝒒_𝑜𝑛𝑠𝑒𝑡-dependence of the rotation suggest that the HCs predominantly rotate poloidally. This remains consistent with the toroidal rotation observed on HBT-EP and other tokamaks through the “Barber Pole Illusion” and the direction of rotation’s dependence on the direction of 𝐼_𝑝. This scaling law is used to make projections for next generation tokamaks like ITER and SPARC, which predicts that rotation will be resonant on ITER. However, resonant effects can still be avoided if the duration of the disruption is kept short enough to prevent two rotations from being completed.