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Articles 1 - 8 of 8
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Development Of A Magnetic Confinement Attachment For Enhanced Signal In Handheld Laser Induced Breakdown Spectroscopy Soil Analysis, Alfred C. Anderson
Development Of A Magnetic Confinement Attachment For Enhanced Signal In Handheld Laser Induced Breakdown Spectroscopy Soil Analysis, Alfred C. Anderson
Theses and Dissertations
Field techniques for characterizing low levels of heavy elements of less than 100 parts per million in soils tend to be unreliable because of the relatively weak signal of these elements and the large, variable background inherent to analyzing soils with minimal sample preparation. To enhance the detection and analysis capability of a handheld laser-induced breakdown spectroscopy (LIBS) instrument, this work investigates the effects of a unique magnetic confinement apparatus on signal intensities, focusing on five iron lines as well as those from actinides in 11 soil samples. The proposed magnetic confinement apparatus achieved over 0.8 T but did not …
Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont
Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont
Theses and Dissertations
An energy tuning assembly was developed to spectrally shape the National Ignition Facility deuterium-tritium fusion neutron source to a notional thermonuclear and prompt fission neutron spectrum to fulfill neutron source capability gaps. The experimental neutron environment was characterized with activation dosimetry, neutronics and covariance models, and unfolded to determine the as-fielded neutron spectrum. The first energy tuning assembly was demonstrated to create synthetic spectrally accurate post-detonation fission products, enhancing U.S. technical nuclear forensics capabilities. ATHENA, a second-generation energy tuning assembly, was also optimized to meet similar objectives, but the new platform neutron fluence efficiency was increased by a factor of …
Correlated Positron-Electron Orbital (Cpeo): A Novel Method That Models Positron-Electron Correlation In Virtual Ps At The Mean-Field Level, Kevin E. Blaine
Correlated Positron-Electron Orbital (Cpeo): A Novel Method That Models Positron-Electron Correlation In Virtual Ps At The Mean-Field Level, Kevin E. Blaine
Theses and Dissertations
The Correlated Positronic-Electronic Orbital (CPEO) method was developed and implemented to capture correlation effects at between the positron and electron in the modeling of systems that involve a bound positron. Methods that effectively model these systems require many hundred basis functions and use a mean field approach as the beginning step. CPEO builds an orbital for virtual Positronium (Ps) that contains a positron in a bound state along with an accompanying electron to the larger system. Assigning the virtual Ps orbital allows for the two particle variational optimization in conjunction with the other particles that compose the whole system. This …
Data Driven Investigation Into The Off-Axis Brdf To Develop An Algorithm To Classify Anisotropicity, Anne W. Werkley
Data Driven Investigation Into The Off-Axis Brdf To Develop An Algorithm To Classify Anisotropicity, Anne W. Werkley
Theses and Dissertations
The Bi-directional Reflectance Distribution Function (BRDF) is used to describe reflectances of materials by calculating the ratio of the reflected radiance to the incident irradiance. While it was found that isotropic BRDF microfacet models maintained symmetry about ɸs = π, such symmetry was not maintained about the θs = θi axis, except for close to the specular peak. This led to development of a novel data-driven metric for how isotropic a BRDF measurement is. Research efforts centered around developing an algorithm that could determine material anisotropy without having to fit to models. The algorithm developed here successfully …
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Theses and Dissertations
One of the first fabricated metasurface optical devices, the in-plane V-antenna lenses, were plagued by a fundamental transmission limit (<25 >). Two distinct sets of Out-of-Plane phase elements were designed with improved transmission (~60 ). These were fabricated as beamsteerers and characterized in terms of their Bidirectional Transmittance Distribution Function measured as a function of scatter angle. Experimental data from the beamsteerers was analyzed via simulations using a finite element method (FEM). The measurements showed the designed beamsteering, but also a strong zero-order diffraction not present in the simulations, which motivated this study to understand what was causing these differences. …
Ab Initio Spectroscopy Of Natural And Artificial Fire Contaminants For V/W Band Frequency Signal Absorbance, Matthew B. Husk
Ab Initio Spectroscopy Of Natural And Artificial Fire Contaminants For V/W Band Frequency Signal Absorbance, Matthew B. Husk
Theses and Dissertations
The rotation and vibration spectral properties including frequencies and intensities for highly concentrated molecules present in wildland and artificial fires have been studied. These properties were used to determine absorption and its effect in a link budget analysis. Absorption in link budget analyses is commonly accounted for via line-by-line methodology aided by HITRAN documented intensities. Limited, if any, customization of spectral properties is available with HITRAN and other spectral databases. Ab initio calculations with different atomic basis sets were employed to obtain structures, dipole moments, rotational-vibrational frequencies and intensities, as well as various coupling parameters. Anharmonic corrections to the vibrational …
Lithium Compound Characterization Via Laser Induced Breakdown Spectroscopy And Raman Spectroscopy, James T. Stofel
Lithium Compound Characterization Via Laser Induced Breakdown Spectroscopy And Raman Spectroscopy, James T. Stofel
Theses and Dissertations
Industries such as lithium-ion battery producers and the nuclear industry community seek to produce and store lithium in pure chemical forms. However, these lithium compounds are reactive with the atmosphere and quickly degrade into less desirable forms. Therefore, industry desires a fast and effective quality control approach to quantify the ingrowth of these secondary lithium chemical forms. This research presents a novel approach using Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy in tandem to enhance lithium compound characterization beyond what is achieved by either technique alone. The resulting spectral data are aggregated using data fusion and analyzed using chemometrics for …
Error Reduction For The Determination Of Transverse Moduli Of Single-Strand Carbon Fibers Via Atomic Force Microscopy, Joshua D. Frey
Error Reduction For The Determination Of Transverse Moduli Of Single-Strand Carbon Fibers Via Atomic Force Microscopy, Joshua D. Frey
Theses and Dissertations
The transverse modulus of single strand carbon fibers is measured using PeakForce Atomic Force Microscopy - Quantitative Nanomechanical Measurement to less than 5 percent error for 11 types of carbon fiber with longitudinal moduli between 924-231 GPA, including export-controlled fibers. Statistical methods are employed to improve the quality of data to exclude outliers within an measurement and within the sample set. A positive linear correlation between the longitudinal and transverse modulus with an R2=0.76 is found. Pitch-based fibers exhibit lower measurement error than PAN-based fibers, while PAN fibers exhibited no apparent modulus correlation when the Pitch fibers are …