Physics Commons^™

Testing A Novel Technique To Improve Aluminum-26 Accelerator Mass Spectrometry Measurements For Earth Science Applications, Meghan Sarah Janzen

Masters Theses

The measurement of cosmogenic ²⁶Al [aluminum-26] in geological samples by accelerator mass spectrometry (AMS) is typically conducted on Al₂O₃ [aluminum oxide] targets. However, Al₂O₃ is not an ideal source material because it does not form a prolific beam of Al^- [negative atomic aluminum ions] required for measuring low-levels of ²⁶Al. This thesis presents the performance of AlN [aluminum nitride], AlF₃ [aluminum fluoride] and mixed AlN + Al₂O₃ as novel alternative source materials for the analysis of ²⁶Al. A negative ion cesium sputtering source at the Holifield …

Evaluation Of Tagging Techniques Gamma-Decay Probabilities Using The Surrogate Method, Timothy Lee Reed

Masters Theses

A detailed analysis of the statistical and discrete [gamma]-decay tagging techniques was conducted using the absolute surrogate and surrogate ratio method (SRM) to obtain the 92Mo(n,[gamma]) cross section in an equivalent neutron energy range of 80 to 880 keV. Excited 93Mo and 95Mo nuclei were populated using (d,p) reactions on 92Mo and 94Mo targets, respectively. The absolute surrogate 92Mo(n,[gamma]) cross sections disagreed with evaluated neutron capture cross section data by as much as a factor of 4 using the statistical tagging approach, whereas the discrete [gamma]-decay tag absolute surrogate cross section disagreed with the evaluated neutron capture cross section by …

Characterization Of Heavy Ion Beams At The Heavy Ion Medical Accelerator In Chiba Using A Li-Drifted 5-Mm Silicon Detector, Alexander Lang

Nuclear Engineering Reports

Measurements were taken at the Heavy Ion Medical Accelerator in Chiba, Japan (HIMAC) to characterize accelerator beams to assist in the study of various tissue equivalent proportional counters (TEPCs) designed by Colorado State University (CSU), Oklahoma State University (OSU), and the National Aeronautics and Space Administration (NASA). There were four beams that were part of the HIMAC experiment:

• 290 MeV/nucleon carbon
• 150 MeV/nucleon helium
• 500 MeV/nucleon argon
• 500 MeV/nucleon iron

For the first time ever, a single, 5-mm lithium drifted silicon detector was used to characterize the beam and measure the spectrum of particles striking the TEPCs. If successful, this …

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 …

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 …

Higher-Order Corrections In Effective Theory Of Deformed Nuclei, Jialin Zhang

Masters Theses

The low-energy excitation bands of open-shell heavy nuclei have been accounted for by collective motion of the constituting nucleons. Macroscopically, heavy nuclei can be looked upon as deformed rotors undergoing surface vibration and rotation. Traditionally, deformed nuclei are described within the Bohr-Mottelson geometric model or the interacting boson model. An effective theory that exploits spontaneous symmetry breaking has recently been developed for axially deformed nuclei. It describes the rotational and vibrational degrees of freedom in terms of Nambu-Goldstone bosons and quadrupole phonons respectively, with a power counting based on their different energy scales. A systematic way to construct the rotationally …

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 …

A High-Energy Neutron Flux Spectra Measurement Method For The Spallation Neutron Source, Nicholas Patrick Luciano

Masters Theses

The goal of this work was to develop a foil activation method to measure high-energy (∼1-100 MeV) neutron flux spectra at the Spallation Neutron Source by researching the scientific literature, assembling an experimental apparatus, performing experiments, analyzing the results, and refining the technique based on experience. The primary motivation for this work is to provide a benchmark for the neutron source term used in target station and shielding simulations Two sets of foil irradiations were performed, one at the ARCS beamline and one at the POWGEN beamline. The gamma radiation of the foil activation products was measured with a high …