Physics Commons^™

Microscopic Description Of Nuclear Fission At Finite Temperature, Jordan David Mcdonnell

Doctoral Dissertations

While a predictive, microscopic theory of nuclear fission has been elusive, advances in computational techniques and in our understanding of nuclear structure are allowing us to make significant progress. Through nuclear energy density functional theory, we study the fission of thorium and uranium isotopes in detail. These nuclides have been thought to possess hyperdeformed isomers in the third minima of their potential energy surfaces, but microscopic theories tend to estimate either shallow or non- existent third minima in these nuclei. We seek an explanation in terms of neutron shell effects. We study how the fission pathways, the symmetry, and the …

Experimental Studies Of Nuclei Near Doubly Magic 100sn And 78ni, Lucia Cartegni

Doctoral Dissertations

The experimental study of exotic nuclei is very important for our understanding of nuclear structure. In this work the nuclei near doubly magic nuclei 100Sn and 78Ni were studied in two separate experiments. The first one was performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. This experiment searched for the alpha decay of 112Cs, in order to establish the proton separation energy of 104Sb. Although the alpha decay of 112Cs was not observed, the upper limit of the alpha branching ratio was set at 0.26%. The improved statistics enabled an improved half-lives measurement of …

Population Of Low-Lying Levels In The One-Neutron Halo Nucleus 11be Via The Neutron Transfer Reaction 10be(D,P), Kyle Thomas Schmitt

Doctoral Dissertations

Historically, measurements of differential cross-sections for the neutron transfer reaction (d, p) on stable targets have been an important tool for extracting spectroscopic information. In particular, it is possible to make orbital angular momentum assignments and extract spectroscopic factors for ground states and excited states by comparing measurements to cross sections calculated for pure single-particle states. In recent years, the advent of rare isotope beams have made it possible to apply this method to increasingly exotic nuclei. As nucleon separation energies decrease along the path to the proton and neutron drip lines, many new reaction channels are opened. Out of …

Analysis Of 26Al + P Elastic And Inelastic Scattering Reactions And Galactic Abundances Of 26Al, Stephen Todd Pittman

Doctoral Dissertations

²⁶Al(p,p)²⁶Al and ²⁶Al(p,p’)²⁶Al^* scattering reactions were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at the Oak Ridge National Laboratory (ORNL). The purpose of the elastic scattering study was to determine properties of previously uncharacterized ²⁷Si levels above the proton threshold in the energy range E(c.m.) ~ 0.5 - 1.5 MeV and to calculate reaction rates for the ²⁶Al(p,γ[gamma])²⁷Si reaction that destroys ²⁶Al. The inelastic scattering reaction was also evaluated to investigate the reaction that produces the metastable state of ²⁶Al at E(c.m.) = 228 keV, …

Radii And Neutron Correlations Of (6,8)He Within The Gamow Shell Model, Georgios Papadimitriou

Doctoral Dissertations

We study the spatial correlations between halo neutrons in ^6,8He within the complex-energy Gamow Shell Model (GSM). To this end, we calculate the neutron and proton radii, and two-neutron correlations in a large shell model space consisting of the 0p_3/2 resonance and non-resonant p-sd scattering continuum. We use schematic forces and the finite-range Modified Minnesota interaction.
The calculated charge radii, corrected for the core polarization and spin-orbit effects, are compared to the values extracted from measured atomic isotope shifts.
We find that the charge radius of ⁶He primarily depends on the two-neutron separation energy and the shell-model …

Energy Functional For Nuclear Masses, Michael Giovanni Bertolli

Doctoral Dissertations

An energy functional is formulated for mass calculations of nuclei across the nuclear chart with major-shell occupations as the relevant degrees of freedom. The functional is based on Hohenberg-Kohn theory. Motivation for its form comes from both phenomenology and relevant microscopic systems, such as the three-level Lipkin Model. A global fit of the 17-parameter functional to nuclear masses yields a root- mean-square deviation of χ[chi] = 1.31 MeV, on the order of other mass models. The construction of the energy functional includes the development of a systematic method for selecting and testing possible functional terms. Nuclear radii are computed within …

The Beta Decay Of 79,80,81zn And Nuclear Structure Around The N=50 Shell Closure, Stephen William Padgett

Doctoral Dissertations

This dissertation reports on new information in the [beta minus] decay of the neutron-rich nucleus 81Zn, which populates states in its daughter nucleus 81Ga. This includes new [gamma]-ray transitions in the daughter nucleus, 81Ga, as well as a [beta]-delayed neutron branching ratio. This isotope was produced at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory through the Isotope Separation Online technique. They are fission fragments from proton-induced fission on a uranium carbide target. These fission fragments are ionized and both mass and isotopically separated before arriving at the Low Energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS). The …

Baryon Spectrum Analysis Using Dirac's Covariant Constraint Dynamics, Joshua Franklin Whitney

Doctoral Dissertations

We determine the energy spectrum of the baryons by treating each of them as a three-body system with the interacting forces coming from a set of two-body potentials that depend on both the distance between the quarks and the spin and orbital angular momentum coupling terms. We first review constraint dynamics for a relativistic two-body system in order to assemble the necessary two body framework for the three-body problem. We review the different types of covariant two-body interactions involved in constraint dynamics, including vector and scalar, and solve the problem of energy eigenstates using constraint dynamics. We use the Two …

Remote Sensing Of Sediments And Volatiles On The Martian Surface And Terrestrial Analog Sites, Craig James Hardgrove

Doctoral Dissertations

The role of water and volatiles in the solar system is of critical interest in planetary science. Evidence for the past action of water or direct observation of water on a planetary body can indicate the potential to harbor life and is critical to human exploration of the solar system. We study two very different remote sensing techniques that address the issue of identifying water-related processes on the surface of other planetary bodies, and in particular, Mars. The first technique, combined thermal infrared and visible imaging, has been used extensively on Mars for determining the thermal inertia of surface materials. …

Proton-Proton Correlation Functions As A Probe To Reaction, Micha A. Kilburn '95

Doctoral Dissertations

In an experiment at NSCL, proton-proton (p-p) correlation functions were measured in ⁴⁰Ca+⁴⁰Ca and ⁴⁸Ca+⁴⁸Ca reactions, both at E/A = 80 MeV. The High Resolution Array (HiRA) detected light particles with excellent energy (<200 keV) and angular (~0.2^o) resolution. The MSU 4pi Array covered 77% of the total 4pi solid angle and was used to determine the impact parameter for collisions using transverse energy (E_t) as the relevant observable.

Two-particle correlation functions are employed in this work to measure the space-time …

Open Heavy Flavor Measurement At Forward Angles For Cu+Cu Collisions At Center Of Mass Nn Collision Energy 200 Gev, Irakli Garishvili

Doctoral Dissertations

The main purpose of Relativistic Heavy Ion Collider (RHIC) program is to study the Quark-Gluon Plasma (QGP), a deconfined state of matter believed to be created in ultra-relativistic heavy ion collisions. Heavy quarks, expected to be produced during the earlier stages of heavy ion collisions, serve as an important probe of the QGP.‎

‎The following dissertation presents measurements of single muons resulting from the semileptonic decay of heavy flavor quarks in the rapidity range of $1.4 < \vert\eta\vert < 1.9$ for Cu+Cu nuclei collisions at $\sqrt{s_{NN}}=200$ GeV measured by the PHENIX experiment. Single muon spectra were measured for three different centrality classes (0 - 20 \% , 20 - 40 \%, 40 - 94 \%) within the $p_{T}$ range of 1.0 - 4.0 GeV/c.‎

‎To calculate single muon spectra, a full background estimate was statistically subtracted from inclusive spectra of muon candidate tracks reconstructed in the PHENIX muon …

Beta-Decay, Beta-Delayed Neutron Emission And Isomer Studies Around 78Ni, Mustafa Moiz Rajabali

Doctoral Dissertations

A study of nuclei with few nucleons outside the closed shell provides benchmarks for the nuclear shell model especially in this modern era of physics where exotic doubly magic nuclei can be tested. The subject of this thesis is to experimentally investigate the properties of nuclei near ⁷⁸Ni and to confront them with the predictions of modern large scale shell model calculations. In this regard, an experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL) to measure excited states in ^71-73Ni populated via the beta-decay of ^71-73Co. Data collected from this experiment lead to partial level …

The Applications Of The Tracer Particle Method To Multi-Dimensional Supernova Simulations, Ching-Tsai Lee

Doctoral Dissertations

A new tracer particle implementation has been developed for the 2D supernova code ”CHIMERA”. 2D supernova simulations have been performed for a wide range of progenitors, between 10 and 25 solar mass. In the case of the Heger12 model, we have obtained a successful explosion. Analysis of the tracer particle data generated by supernova simulations reveals the aspherical geometry of the ejecta. Using the hydrodynamic trajectories provided by the tracer particles, we have performed the nucleosynthesis calculations in the post processing approximation, including the effects of neutrino captures, to understand the nucleosynthesis consequences of these models.