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Articles 1 - 30 of 76
Full-Text Articles in Physics
Lithium Tetraborate As A Neutron Scintillation Detector: A Review, Elena Echeverria, John W. Mcclory, Lauren Samson, Katherine Shene, Juan A. Colon Santana, Yaroslav V. Burak, Volodymyr T. Adamiv, Ihor M. Teslyuk, Lu Wang, Wai-Ning Mei, Kyle A. Nelson, Douglas S. Mcgregor, Peter A. Dowben, Carolina C. Ilie, James C. Petrosky, Archit Dhingra
Lithium Tetraborate As A Neutron Scintillation Detector: A Review, Elena Echeverria, John W. Mcclory, Lauren Samson, Katherine Shene, Juan A. Colon Santana, Yaroslav V. Burak, Volodymyr T. Adamiv, Ihor M. Teslyuk, Lu Wang, Wai-Ning Mei, Kyle A. Nelson, Douglas S. Mcgregor, Peter A. Dowben, Carolina C. Ilie, James C. Petrosky, Archit Dhingra
Faculty Publications
The electronic structure and translucent nature of lithium tetraborate (Li2B4O7) render it promising as a scintillator medium for neutron detection applications. The inherently large neutron capture cross-section due to 10B and 6Li isotopes and the ease with which Li2B4O7 can be enriched with these isotopes, combined with the facile inclusion of rare earth dopants (occupying the Li+ sites), are expected to improve the luminescent properties, as well as the neutron detection efficiency, of Li2B4O7. The electronic structure of both doped …
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra, Ashwin P. Rao, Phillip R. Jenkins, John D. Auxier Ii, Michael B. Shattan, Anil Patnaik
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra, Ashwin P. Rao, Phillip R. Jenkins, John D. Auxier Ii, Michael B. Shattan, Anil Patnaik
Faculty Publications
This work investigates and applies machine learning paradigms seldom seen in analytical spectroscopy for quantification of gallium in cerium matrices via processing of laser-plasma spectra. Ensemble regressions, support vector machine regressions, Gaussian kernel regressions, and artificial neural network techniques are trained and tested on cerium-gallium pellet spectra. A thorough hyperparameter optimization experiment is conducted initially to determine the best design features for each model. The optimized models are evaluated for sensitivity and precision using the limit of detection (LoD) and root mean-squared error of prediction (RMSEP) metrics, respectively. Gaussian kernel regression yields the superlative predictive model with an RMSEP of …
Reinvigorating A Technical Countering Weapons Of Mass Destruction Distance Learning Graduate Certificate Program, James C. Petrosky, Gaiven Varshney, Jeremy Slagley, Sara Shaghaghi
Reinvigorating A Technical Countering Weapons Of Mass Destruction Distance Learning Graduate Certificate Program, James C. Petrosky, Gaiven Varshney, Jeremy Slagley, Sara Shaghaghi
Faculty Publications
Current Countering Weapons of Mass Destruction (CWMD) demands can be divided broadly into policy and science. The science of chemical, biological, and radiological/nuclear weapons informs the limits of development, production, employment, operation, detection, risk characterization, human and material protection, and medical intervention. In short, the science of weapons of mass destruction (WMD) should precede and inform the development of policy. It is to this end that the Air Force Institute of Technology (AFIT) CWMD program was re-established, providing a technical educational option for practitioners to understand the science behind a very technically challenging subject.
Efficient, Dual-Particle Directional Detection System Using A Rotating Scatter Mask, Robert Olesen, Bryan V. Egner, Darren E. Holland, Valerie Martin, James E. Bevins, Larry W. Burggraf, Buckley E. O'Day Iii
Efficient, Dual-Particle Directional Detection System Using A Rotating Scatter Mask, Robert Olesen, Bryan V. Egner, Darren E. Holland, Valerie Martin, James E. Bevins, Larry W. Burggraf, Buckley E. O'Day Iii
AFIT Patents
A directional radiation detection system and an omnidirectional radiation detector. The omnidirectional radiation detector detects radiation comprising at least one of: (i) gamma rays; and (ii) neutron particles. A radiation scatter mask (RSM) of the radiation detection system includes a rotating sleeve received over the omnidirectional radiation detector and rotating about a longitudinal axis. The RSM further includes: (i) a fin extending longitudinally from one side of the rotating sleeve; and (ii) a wall extending from the rotating sleeve and spaced apart from the fin having an upper end distally positioned on the rotating sleeve spaced apart or next to …
Rotating Scatter Mask For Directional Radiation Detection And Imaging, Darren Holland, Robert Olesen, Larry Burggraf, Buckley O'Day, James E. Bevins
Rotating Scatter Mask For Directional Radiation Detection And Imaging, Darren Holland, Robert Olesen, Larry Burggraf, Buckley O'Day, James E. Bevins
AFIT Patents
A radiation imaging system images a distributed source of radiation from an unknown direction by rotating a scatter mask around a central axis. The scatter mask has a pixelated outer surface of tangentially oriented, flat geometric surfaces that are spherically varying in radial dimension that corresponds to a discrete amount of attenuation. Rotation position of the scatter mask is tracked as a function of time. Radiation counts from gamma and/or neutron radiation are received from at least one radiation detector that is positioned at or near the central axis. A rotation-angle dependent detector response curve (DRC) is generated based on …
Neutron Pulse-Time Extension Through Conversion To Positronium, Shawn T. Mctaggart
Neutron Pulse-Time Extension Through Conversion To Positronium, Shawn T. Mctaggart
Theses and Dissertations
Laser-Plasma interactions have strong potential as future neutron sources. Measuring the neutron rate is difficult due to several issues: the very short duration of the laser pulse and subsequent fusion events (on the order of a few picoseconds), the corresponding short duration of the neutron pulse, and the simultaneous emission of other ionizing particles such as protons and electrons. A system was designed to measure neutron emission by imposing a delay from the emission of other radiation by conversion of the neutrons into ortho-positronium (o-Ps), the triplet state of positronium. This lifetime extension enables more sensitive and selective detection of …
Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory
Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory
Faculty Publications
Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain …
Source Term Estimation Of Atmospheric Pollutants Using An Ensemble Of Hysplit Concentration Simulations, Casey L. Zoellick
Source Term Estimation Of Atmospheric Pollutants Using An Ensemble Of Hysplit Concentration Simulations, Casey L. Zoellick
Theses and Dissertations
In support of Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring and nuclear event detection, this study works toward source term estimation (STE) of dispersive pollutants using a novel method|an ensemble of forward trajectory concentration simulations using a meteorology-coupled dispersion model. Traditionally a mathematically and physically rigorous problem, STE of a plume of atmospheric pollutants can be solved in a variety of ways depending on what is known regarding the emission, but little has been studied on the sensitivity between the horizontal resolution of the meteorology data in relation to the dispersion model and the results derived from known concentrations at multiple locations. …
Modeling High-Altitude Nuclear Detonations Using Existing Ionospheric Models, Sophia G. Schwalbe
Modeling High-Altitude Nuclear Detonations Using Existing Ionospheric Models, Sophia G. Schwalbe
Theses and Dissertations
One threat to the United States is a nuclear weapon being detonated at high altitude over the country. The resulting electromagnetic pulse (EMP) could devastate the nation. Despite its destructive nature, the response of the ionosphere to such an event is poorly understood. This study assesses if existing ionospheric models, which are used to nowcast and forecast ionospheric changes, can be used to model the response to a high-altitude nuclear detonation (HAND). After comparing five ionosphere models, the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) was selected and modified to incorporate an array of F10.7 indices to serve as a proxy for …
Pulse Height Spectra Analysis Of A Neutron Energy Tuning Assembly, Jason R. Stickney
Pulse Height Spectra Analysis Of A Neutron Energy Tuning Assembly, Jason R. Stickney
Theses and Dissertations
An energy tuning assembly (ETA) was previously designed and built for the purpose of irradiating samples with a combination of a thermonuclear and a prompt fission neutron spectrum. Initial research was performed to characterize the performance of the ETA at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron using 33 MeV deuteron breakup on tantalum as the neutron source. This research analyzes detector responses collected from three EJ-309 detectors used to characterize the ETA generated neutron field. A signal processing chain was developed to reduce the full waveform data into a pulse height spectrum. The primary goal was to develop a …
Characterization Of The Effects Of Heavy Charged Particle Exposure On The Radiation Resistant Bacterium Deinococcus Radiodurans, Todd A. Bryant
Characterization Of The Effects Of Heavy Charged Particle Exposure On The Radiation Resistant Bacterium Deinococcus Radiodurans, Todd A. Bryant
Theses and Dissertations
Although not an extremophile, Deinococcus radiodurans has proven to have exceptional resistance to ionizing radiation, specifically via gamma and X-ray photons. To date, no known experiments have bombarded the bacterium with charged particles larger than hydrogen. This study explored the effects on the organism’s ability to survive high linear energy transfer heavy-charged particle exposures of oxygen ions. It also investigated the effects of low linear energy transfer ultraviolet radiation on various mutants. Two uvrB mutants were created to ascertain the importance of the gene in single-strand break repair following gamma irradiation and two recF mutants were created to explore the …
Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry
Characterization Of Silicon Ion Exposure On Deinococcus Radiodurans, Richard F. Daughtry
Theses and Dissertations
Deinococcus radiodurans is a robust bacterium that is known for its extraordinary resistance to ionizing radiation. In general, many of the investigations of this bacterium's resistance have revolved around low linear energy transfer radiation, such as gamma and electron radiation. This study explored Deinococcus radiodurans's ability to survive high linear energy transfer radiation, specifically proton and neutron radiation. Deinococcus radiodurans was dehydrated to reduce the effects of low linear energy transfer radiation. The bacteria were exposed to both neutron and proton radiation of varying amounts and rehydrated. The resulting colonies were counted and compared to colonies of non-irradiated control samples …
Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore
Using An Astrophysical Model To Characterize Nuclear Dust, Anita N. Dunsmore
Theses and Dissertations
Dust clouds resulting from nuclear explosions are complex phenomena, and knowledge on how they form is lacking. Noting the similarities between supernovae and nuclear explosions led to the concept of modeling a nuclear dust cloud using a supernova simulation. MOCASSIN uses a Monte Carlo approach to model photons traveling through a dust cloud, allowing the cloud's characteristics to be discovered by comparing an observed spectrum to a calculated one and then changing input values to make the spectra match. Data files describing two nuclear fireballs of varying yields were created and analyzed using MOCASSIN, but yielded zero energy spectra. After …
In-Beam Γ-Ray Spectroscopy Studies Of Medium-Spin States In The Odd-Odd Nucleus 186Re, David A. Matters, F. G. Kondev, N. Aoi, Y. Ayyad, A. P. Byrne, M. P. Carpenter, J. Carroll, C. J. Chiara, P. M. Davidson, G. D. Dracoulis, Y. D. Fang, C. R. Hoffmann, R. O. Hughes, E. Ideguchi, R. V. F. Janssens, S. Kanaya, B. P. Kay, T. Kibedi, G. J. Lane, T. Lauritsen, John W. Mcclory, P. Nieminen, S. Noji, A. Odahara, H. J. Ong, A. E. Stuchbery, D. T. Tran, H. Watanabe, A. N. Wilson, Y. Yamamoto, S. Zhu
In-Beam Γ-Ray Spectroscopy Studies Of Medium-Spin States In The Odd-Odd Nucleus 186Re, David A. Matters, F. G. Kondev, N. Aoi, Y. Ayyad, A. P. Byrne, M. P. Carpenter, J. Carroll, C. J. Chiara, P. M. Davidson, G. D. Dracoulis, Y. D. Fang, C. R. Hoffmann, R. O. Hughes, E. Ideguchi, R. V. F. Janssens, S. Kanaya, B. P. Kay, T. Kibedi, G. J. Lane, T. Lauritsen, John W. Mcclory, P. Nieminen, S. Noji, A. Odahara, H. J. Ong, A. E. Stuchbery, D. T. Tran, H. Watanabe, A. N. Wilson, Y. Yamamoto, S. Zhu
Faculty Publications
Excited states in 186Re with spins up to J=12ℏ were investigated in two separate experiments using 186W(d,2n) reactions at beam energies of 12.5 and 14.5 MeV. Two- and threefold γ-ray coincidence data were collected using the CAESAR and CAGRA spectrometers, respectively, each composed of Compton-suppressed high-purity germanium detectors. Analysis of the data revealed rotational bands built on several two-quasiparticle intrinsic states, including a long-lived Kπ=(8+) isomer. Configuration assignments were supported by an analysis of in-band properties, such as |gK−gR| values. The excitation energies of the observed intrinsic states were compared with results from multi-quasiparticle blocking …
Characterization Of Neutron And Proton Exposure On The Radiation Resistant Bacterium, Deinococcus Radiodurans, Ronald C. Lenker
Characterization Of Neutron And Proton Exposure On The Radiation Resistant Bacterium, Deinococcus Radiodurans, Ronald C. Lenker
Theses and Dissertations
Deinococcus radiodurans is a robust bacterium that is known for its extraordinary resistance to ionizing radiation. In general, many of the investigations of this bacterium's resistance have revolved around low linear energy transfer radiation, such as gamma and electron radiation. This study explored Deinococcus radiodurans's ability to survive high linear energy transfer radiation, specifically proton and neutron radiation. Deinococcus radiodurans was dehydrated to reduce the effects of low linear energy transfer radiation. The bacteria were exposed to both neutron and proton radiation of varying amounts and rehydrated. The resulting colonies were counted and compared to colonies of non-irradiated control samples …
Modeling The White Sands Missile Range Fast Burst Reactor Using A Discrete Ordinates Code, Pentran, Taylor R. Schulmeister
Modeling The White Sands Missile Range Fast Burst Reactor Using A Discrete Ordinates Code, Pentran, Taylor R. Schulmeister
Theses and Dissertations
The goal of this research was to develop and characterize a deterministic model of a fast burst reactor (FBR) using a discrete ordinates neutral particle transport code, PENTRAN. The White Sands Missile Range FBR design was chosen for this research because this FBR is important to the DoD due to its short duration, high energy neutron flux which is representative of the neutron flux output created by a nuclear weapon. One, two, and three dimensional PENTRAN models of the FBR were developed and neutron transport based eigenvalue calculations were performed. These eigenvalue calculations were conducted using two different set of …
High Pressure Line Shapes Of The Rb D1 And D2 Lines For 4He And 3He Collisions, Wooddy S. Miller, Christopher A. Rice, Gordon D. Hager, Matthew D. Rotondaro, Hamid Berriche, Glen P. Perram
High Pressure Line Shapes Of The Rb D1 And D2 Lines For 4He And 3He Collisions, Wooddy S. Miller, Christopher A. Rice, Gordon D. Hager, Matthew D. Rotondaro, Hamid Berriche, Glen P. Perram
Faculty Publications
Line shapes for the Rb D1 (52S1/2 ↔ 52P1/2) and D2 (52S1/2 ↔ 52P3/2) transitions with 4He and 3He collisions at pressures of 500–15,000 Torr and temperatures of 333–533 K have been experimentally observed and compared to predictions from the Anderson–Talman theory. The ground X2Σ+1/2 and excited A2Π1/2, A2Π3/2, and B2Σ+1/2 potential energy surfaces required for the line shape predictions have been calculated using a one-electron …
New Transitions And Feeding Of The JΠ=(8+) Isomer In 186Re, David A. Matters, Nikolaos Fotiades, James J. Carroll, Christopher J. Chiara, John W. Mcclory, Toshihiko Kawano, Ronald O. Nelson, Matthew Devlin
New Transitions And Feeding Of The JΠ=(8+) Isomer In 186Re, David A. Matters, Nikolaos Fotiades, James J. Carroll, Christopher J. Chiara, John W. Mcclory, Toshihiko Kawano, Ronald O. Nelson, Matthew Devlin
Faculty Publications
The spallation neutron source at the Los Alamos Neutron Science Center Weapons Neutron Research facility was used to populate excited states in 186Re via (n,2nγ) reactions on an enriched 187Re target. Gamma rays were detected with the GErmanium Array for Neutron Induced Excitations spectrometer, a Compton-suppressed array of 18 HPGe detectors. Incident neutron energies were determined by the time-of-flight technique and used to obtain γ-ray excitation functions for the purpose of identifying γ rays by reaction channel. Analysis of the singles γ-ray spectrum gated on the neutron energy range 10≤En≤25MeV resulted in five transitions and one …
Electronic Characteristics Of Rare Earth Doped Gan Schottky Diodes, Aaron B. Blanning
Electronic Characteristics Of Rare Earth Doped Gan Schottky Diodes, Aaron B. Blanning
Theses and Dissertations
The Schottky barrier height (SBH) was measured on GaN based diodes with three different dopant types; Gd, Er and Yb. Two methods were used to determine the SBH. The first method was the Juergen Werner method to evaluate the I-V characteristics. The calculated SBH of the diodes using this method was 1.41 ± 0.20eV, 1.71 ± 0.25eV and 1.75 ± 0.28eV for the Gd-, Er- and Yb-doped diodes respectively. It was observed that using an ad-hoc effective Richardson constant value of 0.006Axcm-2xK-2 to calculate the SBH rendered results that were in no greater than 2% disagreement (neglecting …
Neutron Spectroscopy Using Lif Thin-Film Detectors, Michael A. Ford
Neutron Spectroscopy Using Lif Thin-Film Detectors, Michael A. Ford
Theses and Dissertations
A stacked array of segmented micro-structured semiconductor neutron detectors (MSNDs) has been fabricated to perform as a neutron spectrometer simultaneously capable of differentiating fast and thermal neutrons. The MSND devices consist of thin-film perforated diodes constructed from LiF powder back-filled into an etched silicon wafer. Geant4 simulations demonstrate than an eight-layer spectrometer consisting of alternating layers of MSND and hydrogenous moderator can successfully resolve neutron energies at a resolution dependent upon the number of layers and the thickness of the adjacent moderating materials. The simulated spectrometer response was compared to that obtained experimentally with mono-energetic neutrons from a D+D neutron …
Analysis Of A Van De Graaff Generator For Emp Direct Current Survivability Testing, Robert J. Kress
Analysis Of A Van De Graaff Generator For Emp Direct Current Survivability Testing, Robert J. Kress
Theses and Dissertations
The direct current produced from the Van de Graaff (VDG) at the Air Force Research Laboratory (AFRL) has been measured and analyzed. The current pulse produced from the VDG is oscillatory. Experimental data show complete damping occurs after 8 oscillations and within 10-6 seconds. The spark gap distance and circuit resistance were varied to determine if the circuit could convert to an overdamped RLC circuit in order to reduce the oscillations. The data establishes that the VDG produces at least 3 full wave Fourier frequencies of: 3, 7, and 15 MHz ± 2.0 MHz, while the first oscillation had …
Cathodoluminescence And Thermoluminescence Of Undoped Ltb And Ltb:A (A = Cu, Ag, Mn), Zachary L. Hadfield
Cathodoluminescence And Thermoluminescence Of Undoped Ltb And Ltb:A (A = Cu, Ag, Mn), Zachary L. Hadfield
Theses and Dissertations
The Department of Defense is interested in lithium tetraborate (Li2B4O7) crystals for their possible use as a solid state neutron detection material. With large concentrations of 6Li and 10B, it has a high neutron capture cross section. Furthermore, the crystal fluoresces in the presence of ionizing radiation, making it an attractive candidate for a scintillating detection device. However, there is a lack of fundamental knowledge about the material characteristics, particularly with regard to its fluorescent spectrum. Cathodoluminescence measurements were conducted on undoped and doped samples of lithium tetraborate in order to characterize …
Modeling Radioactive Decay Chains With Branching Fraction Uncertainties, Timothy M. Higley
Modeling Radioactive Decay Chains With Branching Fraction Uncertainties, Timothy M. Higley
Theses and Dissertations
This thesis is a parameter study of the effects of branching fraction uncertainty from nuclear decay on isotope quantities at later times. Development of how to calculate and accurately draw random samples of branching fractions is done. Overall effects as well as isotope quantity uncertainty distributions are also explored. Isotope quantities are calculated using exponential moments methods with transmutation matrices. Uncertainty from both half-lives and branching fractions is carried through these calculations by Monte Carlo methods. Results of the study show that uncertainty from branching fractions dominates most isotopes present from neutron fission after approximately one month. Another result is …
Modeling Sodium Iodide Detector Response Using A Parametric Equations, Neeraj Sethi
Modeling Sodium Iodide Detector Response Using A Parametric Equations, Neeraj Sethi
Theses and Dissertations
This research utilizes the relationship between source location, background radiation and detector placement to quantify an expected detector response from a 3x3 Sodium Iodide gamma detector. A parametric equation is developed to calculate the detector response as a function of distance and source photon energy. Using MCNP particle current and pulse height tally functions, backscattering photons are quantified as a function of material thickness and energy distribution. Three configurations of source - detector - scattering medium were modeled in MCNP using the pulse height tally functions, integrated over a 70keV - 360keV energy window and plotted as a function of …
Solving Point-Reactor Kinetics Equations Using Exponential Moment Methods, Paul M. Thelen
Solving Point-Reactor Kinetics Equations Using Exponential Moment Methods, Paul M. Thelen
Theses and Dissertations
A robust method of solving the reactor point kinetic equations was designed using exponential moment methods. Although the method requires a relatively large number of calculations to complete, the accuracy ensured by each individual step calculation allows larger time steps to be used. The algorithm designed was verified to converge to the correct value as step size was reduced. Additionally, the algorithm can take steps much larger than the average neutron lifetime while maintaining some precision. An error control scheme was designed based on changes observed in the results as a function of time step size. The error control adaptively …
Electron Damage Effects On Carbon Nanotube Thin Films, Jeremy S. Best
Electron Damage Effects On Carbon Nanotube Thin Films, Jeremy S. Best
Theses and Dissertations
This research investigated the effects of electron damage on single walled carbon nanotube (CNT) thin films. CNT thin films were irradiated by electrons with energies of 500 keV and 1 MeV to determine what damage was created in the CNT thin film structure, how it affected conductivity, and what changes were evident in the Raman spectra.
Three Dimensional Positron Annihilation Momentum Spectroscopy Of Lithium Tetraborate Crystals, Stefan B. Fagan-Kelly
Three Dimensional Positron Annihilation Momentum Spectroscopy Of Lithium Tetraborate Crystals, Stefan B. Fagan-Kelly
Theses and Dissertations
Previous endeavors in positron annihilation spectroscopy (PAS) at AFIT have resulted in the design and characterization of a second-generation three-dimensional positron annihilation momentum spectroscopy system (3DPAMSS) which combines two-dimensional angular correlation of annihilation radiation (2D ACAR) and coincident Doppler broadening of annihilation radiation (CDBAR) in order to measure electron momentum distributions in samples and thus characterize material defects. The focus of this particular research is to nondestructively measure negative defects in the crystal lattice of copper-doped, silver-doped, and undoped lithium tetraborate by 3DPAMSS spectroscopy using a Na-22 source and two high-purity germanium (HPGe) position-resolvable strip detectors. Lithium tetraborate is a …
Depth-Resolved Cathodoluminescence Of Tho2, Michael G. Lee
Depth-Resolved Cathodoluminescence Of Tho2, Michael G. Lee
Theses and Dissertations
Single crystal thorium dioxide (ThO2) samples were hydrothermally grown and studied using depth-resolved cathodoluminescence (CL) to characterize the surface and bulk electronic states. X-ray diffraction (XRD) measurements were collected to confirm that these crystals were ThO2 in the fluorite structure. Understanding the chemical and structural quality of ThO2 will aid in the fabrication of better neutron detectors as well as in the power production with thorium breeder reactors. Monte Carlo simulations predicted the expected energy-dependent electron interaction depths in the ThO2 crystals. CL was conducted with electron energy range of 1.5 - 12 keV, a …
Passive, Low Cost Neutron Detectors For Neutron Diagnostics At The National Ignition Facility, Nathaniel C. Loyd
Passive, Low Cost Neutron Detectors For Neutron Diagnostics At The National Ignition Facility, Nathaniel C. Loyd
Theses and Dissertations
Experimental validation of neutron fluence models of fusion events at the National Ignition Facility is necessary to predict radiation damage to measurement electronics. Due to programmatic and facility limitations, traditional neutron measurement techniques are not well suited for this application. Notably, a low cost and passive measurement technique that provides a permanent record is preferred. A detector was designed using gadolinium oxide contained within an aluminum reservoir. The reservoir is secured by a thin layer of Mylar and x-ray film, and vacuum sealed in a light tight package. In the presence of a thermal neutron flux, the gadolinium atoms absorb …
Neutron Shielding Effectiveness Of Multifunctional Composite Materials, Anthony D. Marchand
Neutron Shielding Effectiveness Of Multifunctional Composite Materials, Anthony D. Marchand
Theses and Dissertations
Composite materials offer a greater degree of flexibility in design and engineering of specialized space vehicle shielding applications compared to aluminum. A new design for shielding materials has been developed by including specific neutron absorbers and conductive materials into the composite structure. In this research, the neutron shielding capability of two types of custom-designed nanocomposite materials are compared to that of T6061 aluminum.