http://digital.library.wisc.edu/1793/6478 Search the Channel search http://minds.wisconsin.edu/simple-search http://digital.library.wisc.edu/1793/6520 Title: Wavelength-Agile Rayleigh Scattering by use of an Atomic Vapor Cell <br/> <br/>Authors: Pertzborn, Amanda Jo <br/> <br/>Abstract: A wavelength-agile technique using an atomic vapor cell is developed and applied to the measurement of Rayleigh scattering. The atomic vapor cell displays a steep change in refractive index as a function of wavelength, thereby creating a wavelength scan over a narrow spectral range. This scan can be utilized for high resolution spectral measurements. For example, a short pulse duration laser was input into the cell and the resulting wavelength-agile scan was used to resolve a single iodine absorption feature. These measurements revealed that the atomic vapor cell distorts the input pulse shape and therefore this technique must be used with care. A wavelength-agile scan of the Rayleigh scattering spectrum was created using the atomic vapor cell; the resolved Rayleigh scattering spectrum can be compared to theory to obtain the temperature, pressure, and velocity of the scattering medium. The overall goal of this research was to direct light scattered by the gas in a vortex tube into the atomic vapor cell in order to create a wavelength-agile Rayleigh scattering spectrum. The temperature, pressure, and velocity at the scattering location would be resolved from the results of this time-of-flight technique. In this research only the scattering in a fiber was measured due to experimental difficulties. The results of this measurement indicate that this wavelength-agile Rayleigh scattering technique is difficult. Rayleigh scattering is extremely weak and therefore difficult to measure while the atomic vapor cell distorts the light passing through it. <br/> <br/>Description: Pages: 198 Fri, 29 Oct 2004 22:58:59 GMT http://digital.library.wisc.edu/1793/6518 Title: High Spectral Resolution Emission Thermometry for Combustion Applications <br/> <br/>Authors: Myers, Adam M. <br/> <br/>Abstract: Several spectroscopic emission methods were investigated for the determination of combustion gas temperature. Spectroscopic simulations based on the HITRAN database were performed to aid in sensor design and data reduction. Four sensors were created, and limited testing was performed on three of the sensors. The first sensor was based on a tunable spectroscopic filter being used to resolve the spectrum of the water emission band near 2.6 μm. The measured water spectrum was compared to simulations to determine the temperature in a gas turbine combustor at Wright-Patterson Air Force Base. The second sensor is based on H2O emission in the ν1 + ν3 bands. Two emission lines located at 1404 nm and 1405 nm were used in a ratiometric manner to determine gas temperature. A third channel near these lines was used to subtract background emission. Testing of this sensor was delayed due to lower than expected light detection levels. The third sensor is based on CO2 emission from 4.2 μm to 4.4 μm. This region of the CO2 spectrum possesses the unique property of being optically dense over the engine operating range. The emissivity of this feature is unity, thus the slope of the feature can be compared to the Planck curve to determine temperature. This sensor was tested using an optically accessible engine based on the GM Triptane block. The fourth sensor is based on a commercial optical spectrum analyzer (OSA). An OSA uses a scanning grating to direct light onto a detector. It is able to accurately resolve the wavelength and power of incoming light. The measured data is compared to simulations to determine gas temperature. Testing of the OSA sensor was performed on a hydrogen- oxygen flame and on a high-pressure, high-temperature test cell. A high-pressure, high-temperature (HPHT) test cell was investigated and built to test a variety of sensors. The HPHT test cell consists of a heated, sealed quartz cell with a known quantity of the species under investigation inside of it. The cell is located in a pressurized vessel to keep the quartz cell from breaking. Windows on both ends of the pressure vessel allow for the testing of both emissions and laser-based sensors. The HTHP cell was tested with a commercial optical spectrum analyzer. <br/> <br/>Description: Under the supervision of Assistant Professor Scott T. Sanders, Pages: 104 Fri, 29 Oct 2004 22:58:59 GMT http://digital.library.wisc.edu/1793/6516 Title: Application of Supercontinuum Generation to Practical Absorption Spectroscopy <br/> <br/>Authors: Filipa, Jonathan A. <br/> <br/>Abstract: Supercontinuum light generation was used as a means to generate broadband light for spectroscopic measurements. The generated broadband light was used to measure carbon monoxide (CO) absorption in a sealed laboratory test cell. This investigation served as a proof of concept for optical system development that in the future can be applied towards making combustion measurements. Some of the basic concepts underlying supercontinuum generation are reviewed and the advantages and disadvantages of this broadband light generation technique are discussed. Particularly, interference brought on by the propagation of broadband light is reviewed and methods to deal with it are discussed. The distinction between high and low quality light for making spectroscopic measurements is detailed and CO absorption measurements were made using both types of light. From reviewing the results, it was found that high quality light is superior to low quality light for making high-speed spectroscopic measurements. <br/> <br/>Description: Under the supervision of Assistant Professor Scott T. Sanders, Pages: 92 Fri, 29 Oct 2004 22:58:59 GMT http://digital.library.wisc.edu/1793/6514 Title: Development of a Spatially Resolved Optical Technique to Measure Temperature using Two-Photon Absorption of Xenon <br/> <br/>Authors: Bednar, Natalie J. <br/> <br/>Abstract: A new spatially resolved optical technique to measure temperature was developed using two-photon absorption of xenon. This experiment excited the 256 nm two-photon transition of xenon by focusing the excitation source into a test cell at room temperature. Two-photon absorption only occurs at the focus of a laser beam; therefore a point measurement technique was possible. The spatial resolution for this experiment was approximately 0.6 mm; however, this technique enables higher resolution depending on the focus of the laser beam. Two-photon absorbance versus xenon number density was determined experimentally and used to validate a theoretical model created in MATLAB. This technique was designed primarily for two non-reacting flows: the vortex tube and the pulse tube. A case study for measurement in a vortex tube was presented; however, applying this technique to a pulse tube will be similar. <br/> <br/>Description: Under the supervision of Assistant Professor Scott T. Sanders, Pages: 95 Fri, 29 Oct 2004 22:58:59 GMT