This master thesis concerns the modeling of the pedestal in the fusion plasma device DTT and its dependence on several plasma parameters. The modeling was performed using the Europed code which is based on the EPED model. Several parameters were found to have a significant impact on the pedestal predictions. This included the plasma current, toroidal magnetic field and the density at the pedestal top. It was also found that the relative position between the temperature pedestal and density pedestal as well as one of the coefficients in the EPED model had a large impact on the pedestal predictions. Of these, the coefficient in the EPED model and the relative position shift are expected to impart the greatest uncertainty in the pedestal predictions performed. The reason for this is that there is currently no reliable method for estimating these parameters beforehand of an experiment. In the span of this work it was also found that restrictions on the safety factor in the core could have large impacts on the pedestal predictions.

Evolution of measured profiles of densities, temperatures and velocities in the edge pedestal region between successive ELM (edge-localized mode) events are analyzed and interpreted in terms of the constraints imposed by particle, momentum and energy balance in order to gain insights regarding the underlying evolution of transport processes in the edge pedestal between ELMs in a series of DIII-D discharges. The data from successive inter-ELM periods during an otherwise steady-state phase of the discharges were combined into a composite inter-ELM period for the purpose of increasing the number of data points in the analysis. These composite periods were partitioned into sequential intervals to examine inter-ELM transport evolution. The GTEDGE integrated modeling code was used to calculate and interpret plasma transport and properties during each interval using particle, momentum, and energy balance. Variation of diffusive and non-diffusive (pinch) particle, momentum, and energy transport over the inter-ELM period are examined for discharges with plasma currents from 0.5 to 1.5 MA and inter-ELM periods from 50 to 220 ms. Diffusive transport is dominant for ρ< 0.925, while non-diffusive and diffusive transport are very large and nearly balancing in the sharp gradient region 0.925 <ρ <1.0. Transport effects of ion orbit loss are significant for ρ > 0.95, and are taken into account. During the inter-ELM period, diffusive transport increases slightly more than non-diffusive transport, increasing total outward transport. Both diffusive and non-diffusive transport have a strong inverse correlation with plasma current. Weakening the electromagnetic pinch may increase outward particle transport, and enable control over the rebuilding of the edge pedestal between ELMs.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Complete real time testing of a telemetry tracking system typically requires the use of a cooperative target operating under conditions specially set up to simulate actual flight scenarios. This is a very expensive, time-consuming process and does not necessarily exercise all of the functions and capabilities available in new digital antenna controllers. This paper introduces Radar Environment Simulator technology and its application to testing of telemetry tracking systems. Measured results are shown, demonstrating that operational environment simulation is a valuable approach to quickly and effectively characterize the real time operation of a telemetry tracking system.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper takes one through the processes followed by a designer when responding to a specification for an earth terminal. The orbital parameters of Low-Earth Orbiting and Medium-Earth Orbiting (LEO and MEO) satellites that affect autotracking and pointing of an antenna are presented. The do’s and don’ts of specifying (or over specifying) the antenna feed and pedestal size are discussed. The axis velocity and acceleration rates required of a Y over X and El over AZ type pedestal are developed as a function of satellite altitude, radio frequency of operation, and ground antenna terminal diameter. Decision criteria are presented leading to requiring a tilt mechanism or a third axis to cover direct and near overhead passes using an El over Az pedestal. Finally, the expressions transforming Y over X configuration position angles to azimuth and elevation axis position angles are presented.

Recently, with the escalating demands for optical communications, the need for bandwidth in optical communication network has increased. The technology breakthrough indry fiber fabrication opens the possibility for fiber bandwidth form 1.3 to 1.6 £gm. Cr4+:YAG double-clad crystal fiber (DCF) grown by the co-drawing laser-heated pedestal growth method has a strong spontaneous emission spectum form 1.3 to 1.6 £gm. Such fiber is therefore, eminently suitable for optical coherence tomography (OCT), broadband optical amplifier, amplifier spontaneous emission (ASE) light source, and tunable solid-state laser applications. In this thesis, multilayer dielectric thin films were directly deposited by E-gun coating onto the end faces of the Cr4+:YAG DCF. To improve the thin-film quality, to increase transmittance of laser output, and to design for the high power laser. For broadband optical amplifier in dual-pump and double-pass scheme, a 3.0-dB gross gain, a 3.0-dB insertion loss, and a 0-dB net gain at 1.4-£gm signal wavelength have been successfully developed with HR coating onto one of the Cr4+:YAG DCF end faces. In addition, we have successfully developed the Cr4+:YAG DCF laser by direct HR coatings onto fiber end faces and increase transmittance of laser output. A record-low threshold of 31.2 mW with a slope efficiency of 7.5% was achieved at room temperature.

No description available.

Cr4+ doped Yttrium aluminum garnet (YAG) has a strong spontaneous emission that can generate near-infrared emission from 1.2 to 1.6 £gm. This broadband emission have aroused great interest in developing tunable wavelength lasers and amplified spontaneous emitter (ASE).In this dissertation, The valence states of Cr ions in Ca or Ca/Mg co-doped Cr:YAG single-crystal fibers are studied. The fibers were grown using the laser-heated pedestal growth (LHPG) method, followed by annealing treatments up to 1500 oC. The concentrations of the Cr3+ and Cr4+ ions in octahedral and tetrahedral sites in oxygen or nitrogen environments were characterized for the first time to our knowledge. Above 700 oC, migration of Cr4+ between octahedral and tetrahedral sites takes place, the ratio is about 4%; its relative stabilization energy was estimated. For Ca,Cr:YAG annealed in an oxygen or nitrogen environment, it was 0.25 and 0.3 eV, respectively. For Mg,Ca,Cr:YAG annealed in oxygen or nitrogen, it was 0.47 and 0.49 eV, respectively. For the Ca,Cr:YAG crystal fiber (Ca/Cr=113.1%) with oxygen annealing, about 35% and 2.5% of Ca ions took part in charge compensation for Cr4+ in the octahedral and tetrahedral sites, respectively. The density of oxygen vacancies depends on the concentration of Ca ions. The estimated ratios of the unreacted oxygen vacancies to total oxygen vacancies were about 63% and 88% for oxygen and nitrogen annealing, respectively. The main limitation on the concentration of Cr4+ in the tetrahedral site of YAG is the presence of unreacted oxygen vacancies. Furthermore, chromium ions tend to diffuse outward during the LHPG of YAG crystal fiber, in which the average Cr4+ ion concentration decreases significantly after each diameter-reduction step. The Cr4+ ions are replenished using an electron gun to deposit Cr2O3 and divalent-ion oxide (CaO or MgO) on the source rod circumference before growth. It was observed that Ca2+ has better efficiency to diffuse into the source rod more efficiently than Mg2+generating fewer defects and stacking faults. By CaO deposition and post growth annealing at 1350 oC under an oxygen environment, a 110% increase in Cr4+ concentration was obtained. The achieved Cr4+ concentration and the ratio of Cr4+ to total Cr were 1.76 10^18 cm^-3 and 5.5, respectively.

In order to meet the increasingly strict emissions targets required in modern civil aviation, lean burn combustors are being pursued as a means to reduce the environmental impact of gas-turbine engines. By adopting a lean air/fuel mixture NOx production may be reduced. The increase in proportional amount of high pressure air entering directly into the combustor reduces the amount available for cooling of the combustor liner tiles. A reduced mass of air places restrictions on the porosity of cooling arrays, requiring a departure from applications of pedestal and slotted film cooling typically used to cool double skin combustor liners. An alternative approach applied to lean burn combustors places impingement and effusion arrays on the cold and hot skins respectively for cooling of both sides of the hot liner skin. Although impingement cooling is well established as a means of promoting forced convection cooling, there are many areas on a liner tile where cooling behaviour is not well characterised. Additionally, film cooling reduces combustive efficiency and increases the production of NOx and CO, prompting interest in reducing its use in combustor cooling. The research for this thesis has focussed on investigations into current and proposed geometries to identify methods to enhance cold side cooling in lean burn applications. A fully modelled combustor liner tile has been used for investigation into the impact of structural and pressure blockages on cold side cooling performance of an impingementeffusion array using a transient liquid crystal technique to measure heat transfer performance. Research has found structural blockages can reduce heat transfer performance to ~60% of typical values, with crossflow development due to pressure blockage producing similar reductions in Nusselt values to ~70% of typical. A second investigation explored enhanced cooling geometries combining a distributed impingement feed over roughened channels of pedestals at variable height (H/D) and pitch (P/D). A newly proposed 'Shielded Impingement' concept combines full height pedestals, to protect impingement jets from developing crossflow, with quarter height pedestals for turbulence enhancement of crossflow cooling. The research has found that Shielded Impingement geometries displayed the strongest cooling performance of all tested designs due primarily to increased downstream Nusselt numbers. Pressure losses were comparable to short pedestal geometries, with little apparent effect of full height pedestals. Low pressure losses mean that application to extended channels in line with the full tile geometry is possible.

Neste trabalho foram produzidos Interferômetros Mach-Zehnder (IMZ) a partir de guias de onda do tipo pedestal com filmes finos de Bi&#8322;O&#8323;-WO&#8323;-TeO&#8322; (BWT) como camada de núcleo para aplicações em sensores ópticos integrados. A influência dos parâmetros e dos materiais utilizados nas etapas de processo foi verificada. Os valores de índice de refração efetivo e coeficiente de absorção em função do comprimento de onda foram obtidos para os filmes finos BWT. Os guias de onda pedestais foram caracterizados por Microscopia Eletrônica de Varredura, medidas de perda por propagação e perfis de campo próximo em 633 nm e 1050 nm. Os valores mínimos obtidos nas perdas por propagação foram de ~1,5 dB/cm em 633 nm e 3,0 dB/cm em 1050 nm. As medidas de perfis de campo próximo mostraram que guias de onda com larguras superiores a 7 m apresentaram comportamento multimodo. Foram obtidos IMZs que apresentaram guiamento de luz por toda a estrutura, com comportamento multimodo. Sensores ópticos de pressão e temperatura foram produzidos. A fabricação de diafragmas através do processo de corrosão úmida do silício é apresentada no sensor de pressão. Sensores ópticos de temperatura foram produzidos com filamentos metálicos. As cavidades ópticas não foram obtidas nesse sensor. A potência de luz na saída dos sensores de temperatura foi medida em função da diferença de potencial aplicada no filamento metálico. Os resultados apresentados mostram que guias de onda do tipo pedestal produzidos com núcleo de BWT são promissores para aplicações em sensores ópticos integrados. / In this work Mach-Zehnder Interferometers (MZI) were produced from the pedestal-type waveguides with Bi&#8322;O&#8323;-WO&#8323;-TeO&#8322; (BWT) thin films as the core layer for applications in integrated optical sensors. The influence of the parameters and materials used in the process steps was verified. The values of the effective refractive index and absorption coefficient as a function of wavelength were obtained for the BWT thin films. The pedestal waveguides were characterized by Scanning Electron Microscopy, by propagation loss measurements and near-field profiles at 633 nm and 1050 nm. The minimum values obtained by propagation losses were ~ 1.5 dB/cm at 633 nm and 3.0 dB/cm at 1050 nm. The measures of near-field profiles showed that waveguides with widths larger than 7 m presented multimode behavior. The MZIs obtained presented guiding light through the structure, with multimode behavior. Optical pressure sensors and temperature sensors were produced. The production of diaphragms using the wet etching process of silicon is presented on the pressure sensor. Optical temperature sensors were made with metallic filaments. Optical cavities were not obtained in this sensor. The light power in the output of the temperature sensors was measured as the voltage applied to the metal filament. The results show that the waveguides produced with pedestal-type and BWT thin films as core layer are promising for applications in integrated optical sensors.

Neste trabalho foram produzidos Interferômetros Mach-Zehnder (IMZ) a partir de guias de onda do tipo pedestal com filmes finos de Bi&#8322;O&#8323;-WO&#8323;-TeO&#8322; (BWT) como camada de núcleo para aplicações em sensores ópticos integrados. A influência dos parâmetros e dos materiais utilizados nas etapas de processo foi verificada. Os valores de índice de refração efetivo e coeficiente de absorção em função do comprimento de onda foram obtidos para os filmes finos BWT. Os guias de onda pedestais foram caracterizados por Microscopia Eletrônica de Varredura, medidas de perda por propagação e perfis de campo próximo em 633 nm e 1050 nm. Os valores mínimos obtidos nas perdas por propagação foram de ~1,5 dB/cm em 633 nm e 3,0 dB/cm em 1050 nm. As medidas de perfis de campo próximo mostraram que guias de onda com larguras superiores a 7 m apresentaram comportamento multimodo. Foram obtidos IMZs que apresentaram guiamento de luz por toda a estrutura, com comportamento multimodo. Sensores ópticos de pressão e temperatura foram produzidos. A fabricação de diafragmas através do processo de corrosão úmida do silício é apresentada no sensor de pressão. Sensores ópticos de temperatura foram produzidos com filamentos metálicos. As cavidades ópticas não foram obtidas nesse sensor. A potência de luz na saída dos sensores de temperatura foi medida em função da diferença de potencial aplicada no filamento metálico. Os resultados apresentados mostram que guias de onda do tipo pedestal produzidos com núcleo de BWT são promissores para aplicações em sensores ópticos integrados. / In this work Mach-Zehnder Interferometers (MZI) were produced from the pedestal-type waveguides with Bi&#8322;O&#8323;-WO&#8323;-TeO&#8322; (BWT) thin films as the core layer for applications in integrated optical sensors. The influence of the parameters and materials used in the process steps was verified. The values of the effective refractive index and absorption coefficient as a function of wavelength were obtained for the BWT thin films. The pedestal waveguides were characterized by Scanning Electron Microscopy, by propagation loss measurements and near-field profiles at 633 nm and 1050 nm. The minimum values obtained by propagation losses were ~ 1.5 dB/cm at 633 nm and 3.0 dB/cm at 1050 nm. The measures of near-field profiles showed that waveguides with widths larger than 7 m presented multimode behavior. The MZIs obtained presented guiding light through the structure, with multimode behavior. Optical pressure sensors and temperature sensors were produced. The production of diaphragms using the wet etching process of silicon is presented on the pressure sensor. Optical temperature sensors were made with metallic filaments. Optical cavities were not obtained in this sensor. The light power in the output of the temperature sensors was measured as the voltage applied to the metal filament. The results show that the waveguides produced with pedestal-type and BWT thin films as core layer are promising for applications in integrated optical sensors.