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Full-Text Articles in Physical Sciences and Mathematics
Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans
Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans
Theses and Dissertations
Multiplexed Compton Scatter Tomography (MCST) is explored as a method of nondestructively generating cross-sectional images of a sample's electron density. MCST is viable when access is available to only one side of the sample because it registers scattered gamma radiation. Multiplexing in scattered photon energy and in detector position allows simultaneous interrogation of many voxels with comparatively wide collimation. Primary components include a radioisotope source, fan beam collimators, and energy-discriminating detectors. The application of MCST to inspecting aluminum airframes for corrosion is considered. This application requires source gammas near 100 keV where the scattered gamma energy is severely broadened by …
Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday
Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday
Theses and Dissertations
Initial efforts to characterize the scattering dynamics of B + H2 focus on computing scattering matrix elements for the fine structure transition B (2P1/2) --> B (2P3/2) in collisions with H2, allowing for rotational excitation. Using a new application of the time dependent Channel Packet Method (CPM), reactant and product wave packets are prepared in the asymptotic limit on the B (2P1/2) and B (2P3/2) surfaces. They are propagated using the split operator method together wit a unitary transformation between the …
Kinetic Model Of A Space-Based, Br (4 2P1/2 → 4 2P3/2) Laser Pumped By Solar Photolysis Of Ibr, Barry N. Behnken
Kinetic Model Of A Space-Based, Br (4 2P1/2 → 4 2P3/2) Laser Pumped By Solar Photolysis Of Ibr, Barry N. Behnken
Theses and Dissertations
A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 2P1/2 → 4 2P3/2) transition under IBr photolysis-was developed, executed, and interpreted. In recognition of an evolving national interest in space-based laser development, the model presumed operation on a space station platform. Results indicate that a well-engineered IBr laser is capable of generating 1.2 kilowatts of continuous-wave (CW) power under a pumping concentration of 20,000 solar units. Such performance translates to an efficiency of roughly 0.29%, appreciably better than the 0.1% ascribed to the heretofore leading solar-pumped competitor. An extensive analysis …
Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil
Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil
Theses and Dissertations
This laboratory thesis investigated the applicability of reflectance spectroscopy as a tool to measure desorption rates by directly observing the change in trichloroethylene bound to surface sites. Diffuse reflectance spectroscopy holds the promise of being a faster technique with minimal sample preparation time. Reflectance spectroscopy's dependence on the surface of the sample is its greatest advantage, as well as its greatest disadvantage. Both high and low resolution scans were made of different soil samples contaminated by trichloroethylene. After the technique of spectral subtraction was used, potential TCE signals were observed from the dolomitic limestone sample. Unfortunately, due to the low …
Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts
Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts
Theses and Dissertations
The Multiplexed Compton Scatter Tomograph (MCST) uses single back-scattered photons to image electron density in aluminum. A source of error in this imaging technique is the presence of multiple scatters. This thesis studies the double scatter spectrum as an approximation of the multiple scatter spectrum. A deterministic code called Monte Carlo Double Scatter (MOCADS) was developed to investigate the double scatter spectrum. The code includes calculations of the Rayleigh scatter, Compton scatter, Doppler broadening effects of the spectrum, and polarization effects following the Compton scatter. The Doppler broadening portion of the code was validated by a deterministic code called Scatgram. …
Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath
Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath
Theses and Dissertations
Electrical characterization has been performed on ion-implanted p-type 4H-SiC to assess the activation efficiency and implantation-related damage recrystallization with the intention of developing an implantation/annealing scheme. Low doped (Na - Nd = 5x10(exp 15)/cu cm) epitaxial p-type layers grown by MOCVD were implanted with Al or B at doses ranging from 1x10(exp 13) to 1x10(exp 14)/sq cm at room temperature or 500 deg. C. The electrical technique of Temperature Dependent Hall Effect (TDHE) indicated that Al and B act as shallow acceptors 4H-SiC with ionization energies of ^252 and ^285 meV, respectively. The highest activation efficiency for Al and B …