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Item A practical method for determining pit depths using X-ray attenuation in EDX spectra(2015-04) Avci, Recep; Davis, Bret H.; Wolfenden, Mark L.; Kellerman, Laura R.; Lucas, Kilean; Martin, Joshua; Deliorman, MuhammedinA practical method has been developed for rapidly determining the depth of a corrosion micro-pit from the path lengths of X rays passing through the walls of the pit on their way to an X-ray detector. The method takes advantage of the attenuation of the Bremsstrahlung and characteristic X-ray radiation accompanying each X-ray spectrum, and the results are verified independently using AFM and the special pit geometry surrounding MnS inclusions in 1018 carbon steel. The method has general validity and is especially valuable in those cases where the pit depth-to-width ratio is too steep to measure using the conventional methods.Item Determination of Landau free-energy parameters by dielectric measurements in the ferroelectric TSCC(1981-05) Bornarel, J.; Schmidt, V. HugoThe authors measured the adiabatic dielectric permittivity epsilon b of tris-sarcosine calcium chloride (TSCC) at 400 Hz near the ferroelectric transition for DC bias fields up to 5000 V cm-1. They found epsilon infinity =4.2+or-0.2, Curie-Weiss constant C+=38.3+or-0.3K, T0=129.4+or-0.1K, and Landau coefficients A=(2.95+or-0.2)*109 V m A-1 s-1 K-1 and B=(3.5+or-0.1)*1015 V m5 A-3 s-3. They observed evidence of an internal bias field as reported previously by others.Item Anomalies of hypersound velocity and attenuation in ferroelectric tris-sarcosine calcium chloride (TSCC) for small-angle and right-angle Brillouinscattering and Brillouin backscattering(1986-07) Wang, J. T.; Schmidt, V. HugoThe Brillouin spectra of ferroelectric tris-sarcosine calcium chloride have been observed using small-angle and right-angle scattering and also backscattering. For different-frequency phonons along the same direction, analogous anomalies in the sound velocity and the attenuation are seen. The smallest angle we have achieved is 7.48°. The temperature and frequency dependences of the sound velocity are discussed. The fact that the linewidth maximum for [001] phonons occurs somewhat below Tc seems to indicate that the anomalies are due to piezoelectric coupling induced by spontaneous polarization below Tc. For [010] phonons the elementary relaxation times which relate to the energy are estimated as τE0=5.25×10−13 sec above Tc and τE0=3.32×10−12 sec below Tc. The phonon attenuations are also estimated and compared with the observed ones. For the [001] phonons the elementary relaxation time is estimated as τ0=5.25×10−14 sec, in good agreement with the value obtained from right-angle Brillouin scattering.Item Anti-stokes generation in a continuous-wave raman laser(Montana State University - Bozeman, College of Letters & Science, 2008) Murphy, Sytil Kathleen; Chairperson, Graduate Committee: John L. CarlstenThe continuous-wave Raman laser system differs from other Raman systems in that it uses cavity enhancement to augment the pump laser source rather than a high-power pulsed laser source. Through interactions of the pump laser with the Raman active medium, all Raman systems can produce both red-shifted, Stokes, emission and blue-shifted, anti-Stokes, emission. Previous, continuous-wave Raman laser systems have focused on the Stokes emission. This dissertation presents theory and data on the anti-Stokes emission. Specifically, it investigates the anti-Stokes mode structure and the emitted power as a function of input pump power, detuning, pressure, and mode combination. In order to be able to compare theory to data, the existing semi-classical CW Raman laser theory is extended to include the possibility that the spatial mode of any of the three fields (pump, Stokes, or anti-Stokes) is not the fundamental spatial mode. Numerical simulations of this theory are used to understand the behavior of the CW Raman system. All the data is compared to the theory, with varying degrees of success. The pump laser used in this research is a frequency-doubled Nd:YAG at 532 nm and the Raman active medium is H 2. This combination results in Stokes and anti- Stokes wavelengths of 683 nm and 435 nm, respectively. Five methods were found in this research for increasing the amount of anti-Stokes emitted: increasing the input pump power, detuning from gain line-center of the Stokes emission, increasing the reflectivity of the cavity mirrors at the anti-Stokes wavelength, switching to a higher-order spatial mode, and decreasing the H 2 pressure within the Raman cavity. In general, it was found that the higher-order anti-Stokes modes did not agree with a single theoretical spatial mode. Superpositions were formed of multiple theoretical spatial modes giving intensity distribution across the profile similar to the measured profile. Three theoretical spatial mode symmetries were investigated: rectangular, cylindrical, and elliptical. Also measured was the Raman gain as a function of pressure. The accepted theory for the Raman linewidth was found to be slightly off.