Physics Commons^™

Characterization Of The Cylinderical Split Internal-Loop Photobioreactor With Scenedesmus Microalgae: Advanced Culturing, Modeling, And Hydrodynamics, Laith S. Sabri

Doctoral Dissertations

"Microalgae are fast growing photoynthetic microorganisms and it have very wide range of industrial applications such as biofuels and wastewater treatment. These cells can be grown in a wide variety of systems ranging from open culture systems (e.g., ponds) to closed culture systems of photobioreactor (e.g., airlift). The open culture systems exist in the external environment, and hence, are not intrinsically controllable. However, the microalgae production in enclosed photobioreactors faces prohibitively high production costs with special difficulty in reactor design and scale-up. The light availability and utilization efficiency in the photobioreactor in terms of design and scale-up consider as the …

Correlation Between Delay Time And Measured Concentration And Concentration Uncertainty By Neutron Activation Analysis, James Thomas Seman

Doctoral Dissertations

"For the last several decades, it has been apparent that new methods of identifying explosives can help investigators trace their origins. One way to identify an explosive is through the use of taggants: materials added to a product that encodes information about the product such as when it was manufactured.

This research investigates the survivability of a new identification taggant called the Nuclear Barcode that overcomes some of the downfalls that have been identified in prior taggants. The Nuclear Barcode encodes information as a unique combination of concentrations of rare earths (Ho, Eu, Sm, Lu, and Dy) and precious metals …

Design And Characterization Of Multi-Spectral Underwater Beam-Port For Pool-Type Research Reactors, Meshari Mesfer Alqahtani

Doctoral Dissertations

“The beam-port is a cardinal facility at research reactors necessary for dry irradiation, testing and measurement experiments. The Missouri University of Science and Technology Reactor (MSTR) is one such reactor with a beam-port. Installation of additional beam-port in such reactor facilities can be prohibitive. A novel remedy to this is an underwater beam-port for pool-type reactors. The design and characterization of a conceptual underwater multi-spectral beam-port for neutron and gamma fluxes were completed for the MSTR. The neutron spectra from the MSTR were simulated using the Monte Carlo N-particle (MCNP). The determined neutron spectra were experimentally validated using SAND-II. The …

Search For The Decays Of 113ba, Yongchi Xiao

Doctoral Dissertations

The search for new alpha-emitters in the region above tin-100 was carried out in Japan Atomic Energy Agency (JAEA) tandem accelerator in Tokai, Japan. This work aimed to discover barium-113 produced via the fusion-evaporation reaction nickel-58(nickel-58,3n)barium-113 and observation through its alpha-decay chain from barium-113 to xenon-109 to tellurium-105 and tin-101. In the proof of principle experiment in March 2014, the alpha-decay chain of xenon-109 was observed with Double-sided Silicon Strip Detector (DSSD) and digital electronics at JAEA Recoil Mass Separator (RMS). The first discovery-oriented barium-113 experiment was carried out in December 2014 searching for its alpha-decay, ground-state to ground-state beta-decay …

Total Absorption Spectroscopy Of Neutron Rich Nuclei Across The N=50 Neutron Shell Closure, Kathleen Conner Goetz

Doctoral Dissertations

Decay spectroscopy of neutron rich nuclei near doubly magic 78^Ni [78-Nickel] is relevant to nuclear structure and astrophysics as well as reactor and neutrino physics. β-decay [beta-decay] calorimetry studies are essential to reconstruct the decay strength function and is used to overcome the problems arising from the high density of states leading to nuclear Pandemonium. The Modular Total Absorption Spectrometer, currently located in HRIBF at the Oak Ridge National Laboratory, collected data on 25 fission products of ²³⁸U [238-Uranium] during a run in March 2015. Analysis of the ^84,85,86Br [84, 85 and 86-Bromine] data from the …

Measurement Of Heavy Flavor Yield And Azimuthal Anisotropy At Forward Angles In Cu + Au Collisions At A Center-Of-Mass Collision Energy Per Nucleon Of 200 Gev, Brandon Kyle Schmoll

Doctoral Dissertations

Heavy flavor quarks are produced early in heavy ion collisions and will experience the full evolution of the Quark Gluon Plasma (QGP). Measurements at forward rapidity may be influenced as much, or more, by the cold nuclear matter effects as by the hot nuclear matter effects associated with a QGP. As the medium evolves, the initial spatial anisotropy of participants is converted to an azimuthal anisotropy in the momentum space of outgoing particles. Therefore, the momentum spectra modification and anisotropy parameters provide useful information about the heavy quark interaction with the bulk medium.

Asymmetric heavy ion collisions, such as Cu+Au, …

Remote Neutron Spectroscopy On Mars, Christopher Gayle Tate

Doctoral Dissertations

Remote neutron spectroscopy is an important technique in planetary science that allows for classification of the amount of light elements in a planetary regolith. It is especially suited for studying hydrogen abundances and elements with high thermal neutron absorption cross sections in the top ~1 meter of regolith. The Mars Science Laboratory rover Curiosity carries the first rover based neutron spectrometer Dynamic Albedo of Neutrons (DAN) in Gale crater, Mars. As the DAN instrument operates in passive mode, it is sensitive to neutrons produced through Galactic Cosmic Ray interactions and neutrons generated by the rover's Multi-Mission Radioisotope Thermoelectric Generator. In …

Jet-Hadron Correlations Relative To The Event Plane Pb--Pb Collisions At The Lhc In Alice, Joel Anthony Mazer

Doctoral Dissertations

In relativistic heavy ion collisions at the Large Hadron Collider (LHC), a hot, dense and strongly interacting medium known as the Quark Gluon Plasma (QGP) is produced. Quarks and gluons from incoming nuclei collide to produce partons at high momenta early in the collisions. By fragmenting into collimated sprays of hadrons, these partons form 'jets'. Within the framework of perturbative Quantum Chromodynamics (pQCD), jet production is well understood in pp collisions. We can use jets measured in pp interactions as a baseline reference for comparing to heavy ion collision systems to detect and study jet quenching. The jet quenching mechanism …

Production Of Electrons From Heavy Flavor Decays In Proton-Lead Collisions Measured With Alice At The Lhc, Rebecca Michelle Scott

Doctoral Dissertations

This dissertation presents a measurement of the yield and cross section of electrons from heavy flavor decays at central rapidity in proton-lead collisions measured by the ALICE (A Large Ion Collider Experiment) detector at the Large Hadron Collider. This analysis extends the transverse momentum reach of an earlier measurement in ALICE and the comparison is shown. The cross section of single electrons in proton-lead collisions is compared to the value expected in the absence of nuclear modification from proton-proton collisions. The cross section is well described by the perturbative Quantum Chromodynamics and no statistically significant alteration due to hot nuclear …

Improving Predictive Capabilities Of Classical Cascade Theory For Nonproliferation Analysis, David Allen Vermillion

Doctoral Dissertations

Uranium enrichment finds a direct and indispensable function in both peaceful and nonpeaceful nuclear applications. Today, over 99% of enriched uranium is produced by gas centrifuge technology. With the international dissemination of the Zippe archetypal design in 1960 followed by the widespread illicit centrifuge trafficking efforts of the A.Q. Khan network, traditional barriers to enrichment technologies are no longer as effective as they once were. Consequently, gas centrifuge technology is now regarded as a high-priority nuclear proliferation threat, and the international nonproliferation community seeks new avenues to effectively and efficiently respond to this emergent threat.

Effective response first requires an …

A Search For Double Beta Decay Of Xenon To Excited States Of Barium With Exo-200, Sereres Johnston

Doctoral Dissertations

This thesis presents searches for several modes of double beta decays of 136Xe to two low-lying excited levels of 136Ba. For each final level, both 2ν and 0ν double beta decay processes are considered. The data and general techniques developed by the EXO-200 collaboration are used, including a Machine Learning process to improve sensitivity in multivariate space. EXO-200 is an experimental program searching for 0νββ decay in a time projection chamber filled with 175 kg of liquid Xenon enriched to 80% 136Xe, functioning as both source and detector. Experimental searches of double beta decay with 136Xe and other isotopes are …

Beta-Delayed Neutron Data And Models For Scale, Kemper Dyar Talley

Doctoral Dissertations

Recent advancements in experimental and theoretical nuclear physics have yielded new data and models that more accurately describe the decay of fission products compared to historical data currently used for many applications. This work examines the effect of the adopting the Effective Density Model theory for beta-delayed neutron emission probability on calculations of delayed-neutron production and fission product nuclide concentrations after fission bursts as well as the total delayed neutron fraction in comparison with the Keepin 6-group model. We use ORIGEN within the SCALE code package for these calculations. We show quantitative changes to the isotopic concentrations for fallout nuclides …

A Generalized Method For Fissile Material Characterization Using Short-Lived Fission Product Gamma Spectroscopy, Justin Richard Knowles

Doctoral Dissertations

Characterizing the fissile content of nuclear materials is of particular interest to the safeguards and nuclear forensics communities. Short-lived fission product gamma spectroscopy offers a significant reduction in analysis time and detection limits when compared to traditional non-destructive assay measurements. Through this work, a fully generalizable method that can be applied to variations in fissile compositions and neutron spectra was developed for the modeling and measurement of short-lived fission product gamma-rays. This method uses a 238-group neutron flux that was characterized for two pneumatic tube positions in the High Flux Isotope Reactor using flux monitor irradiations. This flux spectrum was …

Actinium-225 Production Via Proton Irradiation Of Thorium-232, Justin Reed Griswold

Doctoral Dissertations

High energy proton spallation reactions on natural thorium metal targets have been utilized to produce multi mCi [milliCurie] quantities of Actinium-225. Theoretical cross sections for actinium and thorium isotopes as well as for a select number of the fission products produced in these reactions were generated by the Monte Carlo radiation transport code PHITS to simulate the experimental data obtained from sixteen irradiations of thorium metal targets with 25-210 µA [microampere] proton beams ranging in energies from 77 to 192 MeV. Irradiations were conducted at Brookhaven National Laboratory (BNL) and Los Alamos National Laboratory (LANL), while target dissolution and processing …

Hadron Physics In Tests Of Fundamental Symmetries, Chien Yeah Seng

Doctoral Dissertations

Low energy precision tests of fundamental symmetries provide excellent probes for the Beyond Standard Model Physics. Theoretical interpretations of these experiments often involve the application of non-perturbative Quantum Chromodynamics in the study of hadronic matrix elements that may either serve as signals of new physics or Standard Model backgrounds. In this work I present a series of studies on different hadronic matrix elements using various low-energy effective approaches to Quantum Chromodynamics, and discuss the impact of these studies on our knowledge of Standard Model and Beyond Standard Model physics.

Fundamental Physics With Cold Neutron Beams, Kyle Brandon Grammer

Doctoral Dissertations

The neutron exhibits rich physics both as a tool for studying materials, particle and nuclear physics, as well as the object of experimental study. The neutron lifetime is an important input to Big Bang Nucleosynthesis models and is currently known only to approximately 0.3\% with the most precise measurements from two different experimental techniques in disagreement by more than 3$\sigma$ [sigma]. Parity violation has been the subject of study since its discovery in 1957. Parity violation experiments provide access to studying the hadronic weak interaction, which is otherwise suppressed by several orders of magnitude below that of the strong interaction. …

Methodology For Generating Simplified Cross Section Data Sets For Neutron Transport Calculations, Thomas Jay Harrison

Doctoral Dissertations

Neutron shielding problems involve radiation transport calculations over a wide range of energies. Fission neutrons have initial energy on the order of MeV, fusion neutrons have initial energy on the order of 10s of MeV, and space-origin neutrons have initial energy on the order of 100s of MeV or higher. Shielding calculations must track the neutrons from their initial energies until they are no longer of interest; for deep-penetration neutrons, this final energy can be on the order of eV before the neutron is no longer tracked. Thus, for deep-penetration space radiation shielding problems, the calculation may require tracking the …

Effective Field Theory Approach To Collective Motion In Atomic Nuclei, Eduardo Antonio Coello Perez

Doctoral Dissertations

Collective motion in heavy nuclei has been studied within collective and algebraic models, and within density functional theory. While they reproduce the energy spectra of these systems, their predictions for some electromagnetic transitions and moments do not lie within experimental uncertainty; in other words, these predictions are inconsistent with experimental data. An effective field theory approach to collective motion in heavy nuclei solves this long standing problem. Based on symmetry arguments only, the effective field theories, constructed as expansions in powers of a small parameter, consistently describe the energy spectra of nuclei exhibiting collective motion at low order in the …

On The Spin Evolution Of Isolated Pulsars, Oliver Quinn Hamil

Doctoral Dissertations

Neutron stars are the remnants of supernova explosions, and harbor the densest matter found in the universe. Because of their extreme physical characteristics, neutron stars make superb laboratories from which to study the nature of matter under conditions of extreme density that are not reproducible on Earth. The understanding of QCD matter is of fundamental importance to modern physics, and neutron stars provide a means of probing into the cold, dense region of the QCD phase diagram.

Isolated pulsars are rotating neutron stars that emit beams of electromagnetic radiation into space which appear like lighthouses to observers on Earth. Observations …

Nucleosynthesis In Self-Consistent Core-Collapse Supernova Models Using Multidimensional Chimera Simulations, James Austin Harris

Doctoral Dissertations

Observations of nuclear abundances in core-collapse supernova (CCSN) ejecta, highlighted by γ-ray [gamma-ray] observations of the ⁴⁴Ti [titanium-44] spatial distribution in the nearby supernova remnants Cassiopeia A and SN 1987A, allow nucleosynthesis calculations to place powerful constraints on conditions deep in the interiors of supernovae and their progenitor stars. This ability to probe where direct observations cannot makes such calculations an invaluable tool for understanding the CCSN mechanism. Unfortunately, despite knowing for two decades that supernovae are intrinsically multi-dimensional events, discussions of CCSN nucleosynthesis have been predominantly based on spherically symmetric (1D) models, which employ a contrived energy source …

Event Localization In Bulk Scintillator Crystals Using Optical Coded Apertures, Joshua Brian Braverman

Doctoral Dissertations

Scintillation-based radiation detectors provide an effective method to detect radioactive materials. In medical physics, astrophysics, and national security technology oftentimes it is optimal to have the ability to localize a radioactive interaction in a scintillator to as small a region as possible within the crystal. Current methods rely on the ability to centroid a light spot as read onto a phototransducer (commonly a photomultiplier tube), and due to the typical width of the light spot when it reaches the phototransducer, the resolution is generally limited to several millimeters. One method to achieve a finer resolution is to use a segmented …

Computational Framework For Small Animal Spect Imaging: Simulation And Reconstruction, Sang Hyeb Lee

Doctoral Dissertations

Small animal Single Photon Emission Computed Tomography (SPECT) has been an invaluable asset in biomedical science since this non-invasive imaging technique allows the longitudinal studies of animal models of human diseases. However, the image degradation caused by non-stationary collimator-detector response and single photon emitting nature of SPECT makes it difficult to provide a quantitative measure of 3D radio-pharmaceutical distribution inside the patient. Moreover, this problem exacerbates when an intra-peritoneal X-ray contrast agent is injected into a mouse for low-energy radiotracers.

In this dissertation, we design and develop a complete computational framework for the entire SPECT scan procedure from the radio-pharmaceutical …

Beta Decay Of Neutron-Rich Isotopes Of Zinc And Gallium, Mohammad Faleh M. Al-Shudifat

Doctoral Dissertations

Beta-decays of neutron-rich nuclei near the doubly magic ⁷⁸Ni [78Ni] were studied at the Holifield Radioactive Ion Beam Facility. The half-life and the gamma-gamma coincidence spectra were used to study the nuclear structure. A new ^82,83Zn [82Zn, 83Zn] decay-scheme was built, where a 71±7% beta-delayed neutron branching ratio was assigned in ⁸²Zn [82Zn] decay. New gamma-ray lines and energy levels observed in ^82,83Ga [82Ga, 83Ga] beta-decay were used to update previously reported decay-schemes. The experimental results were compared to shell model calculations, which postulate the existence of Gamow-Teller transitions in these decays. The half-lives of 155±17 …

Measurement Of The Parity Violating Asymmetry In Elastic Electron Scattering Off 208pb, Jonathan W. Wexler

Doctoral Dissertations

The Lead Radius Experiment (PREX) was carried out in order to provide a model independent measurement of the RMS radius √ < r² >of the neutron distribution in the ²⁰⁸Pb nucleus. The parity-violating scattering asymmetry for longitudinally polarized 1.06 GeV electrons from an unpolarized ²⁰⁸Pb target was measured at Q² = 0.00880 GeV². This measurement was performed by the PREX collaboration in Hall A at Jefferson Laboratory in Newport News, VA, between March and June, 2010. The electron detectors used in this measurement were designed and fabricated by University of Massachusetts-Amherst and Smith College. The resulting …

A Study Of The Structure Of Light Tin Isotopes Via Single-Neutron Knockout Reactions, Andrew Franklin Ayres

Doctoral Dissertations

The region around 100 Sn [100Sn] is important because of the close proximity to the N=Z=50 magic numbers, the rp process, and the proton drip-line. Alpha decay measurements show a reversal in the spin-parity assignments of the ground and first excited states in 101 Sn [101Sn] compared to 105 Te [105Te]. However, the lightest odd- mass tin isotope with a firm spin-parity assignment is 109 Sn [109Sn]. The d 5/2 [d5/2] and g 7/2 [g7/2] single-particle states above N=50 are near degenerate, evidenced by the excitation energy of the first excited state in 101 Sn at only 172 keV. The …

Neutron Polarimetry With Polarized 3he For The Npdgamma Experiment, Matthew Martin Musgrave

Doctoral Dissertations

Cold neutrons enable the study of the fundamental interactions of matter in low-energy, low-background experiments that complement the efforts of high-energy particle accelerators. Neutrons possess an intrinsic spin, and the polarization of a beam of neutrons defines the degree to which their spins are oriented in a given direction. The NPDGamma experiment uses a polarized beam of cold neutrons to make a high precision measurement, on the order of one part in 100 million, of the parity-violating asymmetry in the angular distribution of emitted gamma-rays from the capture of polarized neutrons on protons. This asymmetry is a result of the …

The Study Of Nuclear Structure Of Neutron-Rich 81ge And Its Contribution In The R-Process Via The Neutron Transfer Reaction 80ge(D,P), Sunghoon Ahn

Doctoral Dissertations

The study of low-lying levels of nuclei near closed shells not only elucidates the evolution of nuclear shell structure far from stability, but also affects estimates of heavy element nucleosynthesis in supernova explosions. Especially, the properties of the low-lying levels in ⁸¹Ge[Germanium 81] are important because the sensitivity study of the r-process pointed out that the properties of the nucleus can affect the final bundance pattern. Also, the spins and parities measurements of the states are essential to understand the shape coexistence in odd-mass N = 49 isotones.

This work describes the study of the odd-mass N = …

Investigation Of Time And Position Resolved Alpha Transducers For Multi-Modal Imaging With A D-T Neutron Generator, Joshua William Cates

Doctoral Dissertations

Deuterium-Tritium (D-T) neutron generators have been used as an active interrogation source for associated particle imaging (API) techniques. The D-T reaction yields a 14.1 MeV neutron and a 3.5 MeV alpha (or assoicated) particle, projected nearly back-to-back. The kinetics of the reaction allow the direction and initial time of the neutron to be determined utilizing position sensitive detectors for both the alpha and neutron. This information facilitates multi-modal fast neutron imaging of inspection objects and closed containers to infer the geometry within them and the presence of special nuclear material (SNM). Since position and time of interaction of the alpha …

Neutron Scintillation Detectors Based On Polymers Containing Lithium-6 For Radiation Portal Monitor Applications, Andrew Neil Mabe

Doctoral Dissertations

The work presented herein describes an investigation of four main types of thin film polymer scintillators containing ⁶Li [lithium-6] for neutron detection: polystyrene containing ⁶LiF [lithium-6 fluoride] and a preblended fluor mixture comprising 2,5-diphenyloxazole and 1,4-bis(5-phenyloxazol-2-yl)benzene; poly(styrene-co-lithium maleate) containing salicylic acid; poly[styrene-co-lithium maleate-co-2-phenyl-5-(4-vinylphenyl)oxazole]; and poly(styrene-co-lithium 4-vinylbenzoate). A variety of chemical and physical characterizations as well as optical and scintillation characterizations were performed to guide the development of optimized compositions of each type of polymer film. The scintillation performances of optimized compositions of each type of polymer film were calibrated using …

Secondary Light Particle Data Base Development Using A Thermodynamic Coalescence Model, Mahmoud Pourarsalan

Doctoral Dissertations

ABSTRACT

As heavy ions are transported through shielding and interact with shielding materials accurate values of total, elastic scattering, reactions cross sections and angular distributions of the emitted nucleons, light high energy particles such as deuteron, triton, helion, alpha particles and other heavy ions are required in order to design appropriate and adequate shielding to protect the human crews and instruments from ionizing radiations during long duration space missions. Double-differential (energy and angle) light energetic particle production cross sections must be known for ion energies from tens of MeV/nucleon to tens of GeV/nucleon for all emitted light energetic particles for …