Optical Metamaterial Design, Fabrication And Test,
2011
Air Force Institute of Technology
Optical Metamaterial Design, Fabrication And Test, Jack P. Lombardi
Theses and Dissertations
Metamaterials, materials that make use of naturally occurring materials and designed structures to create materials with special properties not found in nature, are a fascinating new area of research, combining the fields of physics, microfabrication, and material science. This work will focus on the development of metamaterials operating in the visible and infrared which will be constructed and tested for basic optical properties. Possible applications for these materials will not be investigated. The this work will go into the fabrication and test of layered metal-dielectric structures, called layered metamaterials, as these structures hold potential for applications in advanced optical systems. …
Characterization Of A Boron Carbide Heterojunction Neutron Detector,
2011
Air Force Institute of Technology
Characterization Of A Boron Carbide Heterojunction Neutron Detector, James E. Bevins
Theses and Dissertations
New methods for neutron detection have become an important area of research in support of national security objectives. In support of this effort, p-type B5C on n-type Si heterojunction diodes have been built and tested. This research sought to optimize the boron carbide (BC) diode by coupling the nuclear physics modeling capability of GEANT4 and TRIM with the semiconductor device simulation tools. Through an iterative modeling process of controllable parameters, optimal device construction was determined such detection efficiency and charge collection were optimized. This allows an estimation of expected charge collection and efficiency given a set of operating …
Changes To Electrical Conductivity In Irradiated Carbon Nanocomposites,
2011
Air Force Institute of Technology
Changes To Electrical Conductivity In Irradiated Carbon Nanocomposites, Nickolas A. Duncan
Theses and Dissertations
Carbon nanotubes (CNT) and carbon nanofibers (CNF) are two nanoparticles incorporated in a polymer to create a composite material. These composites are two potential lightweight materials for use as replacements for aluminum structures on satellite systems. Both composite materials have a low resistivity that is consistent with conductive materials. However, the CNT composite is substantially more conductive than the CNF composite. The CNT and CNF composites were irradiated with electrons and neutrons to fluence levels of and. No changes were observed in the resistivity of the CNF composites following neutron and electron irradiation. A 3.7% increase in resistivity was observed …
Diffusion Of Rubidium Vapor Through Hollow-Core Fibers For Gas-Phase Fiber Lasers,
2011
Air Force Institute of Technology
Diffusion Of Rubidium Vapor Through Hollow-Core Fibers For Gas-Phase Fiber Lasers, Eric M. Guild
Theses and Dissertations
This work examines the diffusion of rubidium through a small diameter tube alone and in the presence of noble gases. A fluid dynamics analysis is investigated to aid in choosing a method for transferring atomic rubidium vapor that is reliable and efficient. Solutions to the time dependant ordinary differential equation describing the experimental flow properties of the system reveal more precise outcomes than previously practiced routines. Resolved viscosities and Poiseuille flow theory velocity profile distributions are characterized for noble gas carriers of the rubidium vapor. Applying Reynolds Numbers to the flow experiments provides pressure differential boundaries that are employed in …
Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy,
2011
Air Force Institute of Technology
Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy, Jacob L. Harley
Theses and Dissertations
A Telops Hyper-Cam midwave infrared (1.5 − 5.5μm) imaging Fourier-transform spectrometer (IFTS) was used to estimate industrial smokestack total effluent mass flow rates by combining spectrally-determined species concentrations with flow rates estimated via analysis of sequential images in the raw interferogram cube. Strong emissions from H2O, CO2, CO, SO2, and NO were observed in the spectrum. A previously established plume radiative transfer model was used to estimate gas concentrations, and a simple temporal cross-correlation analysis of sequential imagery enabled an estimation of the flow velocity. Final effluent mass flow rates for CO2 and …
Tof-Sims For Rapid Nuclear Forensics Evaluation Of Uranium Oxide Particles,
2011
Air Force Institute of Technology
Tof-Sims For Rapid Nuclear Forensics Evaluation Of Uranium Oxide Particles, Hannah E. Hocking
Theses and Dissertations
Because of nuclear proliferation concerns, nuclear material must be safeguarded, and peaceful intentions verified. The field of nuclear forensics addresses these concerns. While established nuclear forensic techniques exist, quicker, more accurate and less expensive methods are of interest for nonproliferation applications. Currently a host of different analytical techniques, requiring a week or longer, are employed to obtain isotopic ratios, chemical abundances and morphology for forensic particulate samples. Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is a candidate technology for rapid evaluation of these properties for small amounts of nuclear materials. After a thorough investigation, this study found TOF-SIMS to be particularly …
Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers,
2011
Air Force Institute of Technology
Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers, Bradley S. Jones
Theses and Dissertations
The properties of thin, cerium activated, yttrium aluminum garnet (YAG:Ce), scintillating fiber-shaped crystals were investigated for particle tracking and calorimetric applications such as Compton imaging of Special Nuclear Material from remote platforms at standoff ranges. Silicon photomultipliers (SiPMs) are relatively new, efficient, single photon sensitive, solid-state photodiode arrays which are well suited for the readout of scintillating fibers. Using SiPMs, the scintillation decay time profiles of six 400 micrometers YAG:Ce fiber crystals were measured under alpha and gamma irradiation. Interestingly, the observed decay times in the thin fibers were substantially slower than values for bulk single crystal YAG:Ce reported in …
Characterization Of Neutron-Induced Defects In Isotopically Enriched Lithium Tetraborate,
2011
Air Force Institute of Technology
Characterization Of Neutron-Induced Defects In Isotopically Enriched Lithium Tetraborate, Brant E. Kananen
Theses and Dissertations
Lithium Tetraborate (LTB) is assessed for use as a material for neutron detection. LTB isotopically enriched in either Li-6 or B-10 provides a medium that efficiently captures and transmutes neutrons into more readily detected forms of material or energy. Neutron detection is desirable to detect elicit movement of special nuclear material or nuclear weapons. Single crystals of LTB, Li-6 or B-10 enriched, were neutron irradiated, and electron paramagnetic resonance was used to detect point defects induced by the neutrons. Multiple defects were noted in the irradiated crystals. Two particular defects, perturbed lithium vacancies and lithium clusters are proposed as induced …
Investigation Of Gate Leakage Current In Nitrogen-Irradiated Algan/Gan Heterostructures,
2011
Air Force Institute of Technology
Investigation Of Gate Leakage Current In Nitrogen-Irradiated Algan/Gan Heterostructures, Rose E. May
Theses and Dissertations
Due to commercial and government interest in devices capable of functioning in high-power, high-frequency space applications, radiation tolerant AlGaN/GaN devices have been under study in recent years. Passivation of the AlGaN surface by (Si3N4) prevents electron trapping and enhances the 2DEG, but it also increases gate leakage currents, which can lead to device failure. This study sought information about current leakage mechanisms by introducing displacement damage close to the Si3N4/AlGaN interface. The effects of irradiation damage around the Si3N4/AlGaN interface on irradiation-induced leakage current were investigated for three …
Analysis Of Plasma Bubble Signatures In The Ionosphere,
2011
Air Force Institute of Technology
Analysis Of Plasma Bubble Signatures In The Ionosphere, Omar A. Nava
Theses and Dissertations
Plasma bubbles are large scale structures of depleted plasma density in Earth's ionosphere that disrupt radio and satellite communications, to include global navigation satellite systems. This study used the Ionospheric Forecast Model (IFM) to analyze affected look angles and total electron content (TEC) differences due to plasma bubbles of various sizes for 27 geophysical conditions consisting of different seasons and levels of solar and geomagnetic activity at 421 GPS ground stations worldwide. Overall, different geographic locations and plasma bubble configurations produced different affected look angle profiles. Bigger plasma bubbles, larger density depletion factors, higher levels of solar activity and the …
Cathodoluminescence Of Irradiated Hafnium Dioxide,
2011
Air Force Institute of Technology
Cathodoluminescence Of Irradiated Hafnium Dioxide, Emily A. Purcell
Theses and Dissertations
The purpose of this research is to understand the effect of radiation on HfO2 thin films, and to compare the quality of HfO2 thin films produced by both atomic layer deposition (ALD) and pulsed laser deposition (PLD); PLD samples had varying substrate temperatures during deposition (300°C, 500°C, and 750°C). The entirety of this research was conducted using cathodoluminescence (CL) as the examination method. The excitation source was a Kimball Physics EMG-12 electron gun. The photomultiplier tube contained a gallium arsenide photocathode. Measurements were made with beam energies ranging from 1 to 10 keV and beam currents ranging from …
Adaptive Imaging Methods Using A Rotating Modulation Collimator (Rmc),
2011
Air Force Institute of Technology
Adaptive Imaging Methods Using A Rotating Modulation Collimator (Rmc), Daniel T. Willcox
Theses and Dissertations
The Rotating Modulation Collimator (RMC) belongs to a larger class of radiation imaging systems that rely on either temporal or spatial modulation of incident radiation through collimation to map the location of the incident radiation source. The strengths of these detection systems include their low cost and simplicity. A major drawback is the collection time required for low radiation intensities due especially to the loss of radiation information resulting from collimation. One method of addressing this drawback for the RMC is by applying an adaptive imaging approach. As with most system design theory, there are inherent design tradeoffs for the …
An Analytical Model Of Nanometer Scale Viscoelastic Properties Of Polymer Surfaces Measured Using An Atomic Force Microscope,
2011
Air Force Institute of Technology
An Analytical Model Of Nanometer Scale Viscoelastic Properties Of Polymer Surfaces Measured Using An Atomic Force Microscope, Jacob B. Goldberg
Theses and Dissertations
The United States Air Force and the Department of Defense is increasingly interested in nanomaterials. To study these materials, one needs to measure the mechanics of materials on the nanoscale. Over the past few decades the atomic force microscope (AFM) has been used in various methods to establish local surface properties at the nanoscale. In particular, surface elasticity measurements are crucial to understanding nanoscale surface properties. Problems arise, however, when measuring soft surfaces such as polymers and biological specimens, because these materials have a more complex viscoelastic response. This research focuses on modeling an AFM dynamic nanoindentation experiment intended to …
Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate,
2011
Air Force Institute of Technology
Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate, Christina L. Dugan
Theses and Dissertations
Lithium tetraborate (Li2B4O7) crystals are being developed for possible use in solid state neutron detectors. The 6Li(n,α)3H and 10B(n,α)7Li reactions are the basis for neutron detection, and a Li2B4O7 crystal enriched with Mn should show improved efficiency for neutron detection. There is a lack of fundamental characterization information regarding this useful material, particularly with regard to its electronic configuration. Photoemission spectroscopy was used to determine the energy level structure of the Mn doped Li2B4O7 crystals. …
Directional Pair-Production Spectrometer Design For Airborne Stand-Off Detection Of Special Nuclear Material,
2011
Air Force Institute of Technology
Directional Pair-Production Spectrometer Design For Airborne Stand-Off Detection Of Special Nuclear Material, William L. Harrell
Theses and Dissertations
The purposes of this research are to experimentally and theoretically prove the concept of a directional pair-production spectrometer to detect and locate the tailings that are created when making Special Nuclear Material (SNM) at stand-off distances from a remotely piloted vehicle (RPV). A directional pair-production spectrometer uses the information garnered from the high energy gamma rays emitted by these SNM manufacturing tailings to perform pair-production spectroscopy and identify the isotope of interest. Through simultaneous operation as a Compton camera, the detection system will be able to measure rudimentary directional information from the medium energy gamma decays. The detector used for …
Understanding The Influence Of Turbulence In Imaging Fourier-Transform Spectrometry Of Smokestack Plumes,
2011
Air Force Institute of Technology
Understanding The Influence Of Turbulence In Imaging Fourier-Transform Spectrometry Of Smokestack Plumes, Jennifer L. Massman
Theses and Dissertations
An imaging Fourier-transform spectrometer (IFTS) was used to collect infrared hyper-spectral imagery of smokestack plume of a coal-burning power facility to assess the influence of turbulence on spectral retrieval of temperature (T) and pollutant concentrations (Ci). Radiance fluctuations due to plume turbulence introduced scene change artifacts (SCA) in the spectra. Time-averaging the spectra minimizes SCA magnitudes, but accurate T and Ci retrieval would require a priori knowledge of the statistical distribution of temperature and other stochastic flow field parameters. A method of quantile sorting in interferogram space that would allow the retrieval of the temperature distribution is …
Combating Biological Terrorism From Imported Food,
2011
Air Force Institute of Technology
Combating Biological Terrorism From Imported Food, Jeffrey S. Nelson
Theses and Dissertations
There is a threat that a terrorist or terrorist organization will use access to the US food supply to kill or sicken Americans by contaminating imported food products from Mexico. The food that Americans eat is coming more and more often from foreign countries such as Mexico. Foodborne diseases infect nearly fifty million people in the US each year, resulting in over three thousand deaths. There are many terrorist organizations that would like to deliberately contaminate American food. Drug cartels and terrorist organizations currently operate in Mexico, one of the leading food importers into the US. The purpose of this …
Integration Of A Worldwide Atmospheric Based Model With A Live Virtual Constructive Simulation Environment,
2011
Air Force Institute of Technology
Integration Of A Worldwide Atmospheric Based Model With A Live Virtual Constructive Simulation Environment, David B. Simmons
Theses and Dissertations
Yearly DoD spends millions of dollars on Modeling and Simulation tools in order to accomplish two fundamental tasks: make better decisions and develop better skills. Simulators that are based on realistic models enable the USAF to properly train, educate, and employ military forces. LEEDR is an atmospheric model based on worldwide historic weather data that is able to predict the extinction, absorption, and scattering of radiation across a broad range of the electromagnetic spectrum. Through this study LEEDR models the propagation of 1.0642 micron laser radiation at worldwide locations and through various environmental conditions. This modeled laser transmission output, based …
Branch Point Mitigation Of Thermal Blooming Phase Compensation Instability,
2011
Air Force Institute of Technology
Branch Point Mitigation Of Thermal Blooming Phase Compensation Instability, Mark F. Spencer
Theses and Dissertations
Thermal blooming can have a major impact on high-energy laser (HEL) beam propagation in the atmosphere. In theory, an adaptiveoptics (AO) system can mitigate the nonlinear optical effects induced by thermal blooming; however, when a single deformable mirror is used for phase-only compensation, analysis predicts the possibility of instability. This instability is appropriately termed phase compensation instability (PCI) and arises with the time-dependent development of spatial perturbations found within the HEL beam. These spatial perturbations act as local hot spots that produce negative-lens-like optical effects in the atmosphere. An AO system corrects for the hot spots by applying positive-lens-like phase …
Improving The Efficiency Of Photon Collection By Compton Rescue,
2011
Air Force Institute of Technology
Improving The Efficiency Of Photon Collection By Compton Rescue, Alexander W. Stevenson
Theses and Dissertations
A method to improve the efficiency of photon collection in thin planar HPGe detectors was investigated. The method involved implementing a second HPGe detector to collect Compton scattered photons from the primary detector and incorporating coincident interactions in the two detectors that sum to the full energy event into the energy spectrum. This method is termed Compton rescue because the Compton scattered photons make a partial energy deposition in the primary detector and are added back to the spectrum after being detected by the second detector. This research has implications on improving the efficiency of positron annihilation spectroscopy (PAS) techniques …
