Other Astrophysics and Astronomy Commons^™

Measurement Of 18f(Alpha,P)21ne With The Array For Nuclear Astrophysics And Structure With Exotic Nuclei (Anasen), Keilah S. Davis

LSU Doctoral Dissertations

Certain (α,p) reactions on proton-rich nuclei are among the most important nuclear reactions occurring during Type I X-ray bursts, as well as being impactful in stellar explosions during the Asymptotic Giant Branch (AGB) phase and on accreting white dwarfs (WD). However, large uncertainties remain for reaction rates on some radioactive nuclei due to the lack of direct measurements. The Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) is a gas target and charged-particle detector designed for direct measurements of (α,p) reactions. ANASEN was redesigned with two hexagonal barrels of 100-µm-thick silicon strip surrounding the beam axis over a …

19ne Excited States In Explosive Nucleosynthesis, Khang Pham

LSU Doctoral Dissertations

Classical novae and Type I X-ray bursts are stellar explosions that occur in binary systems, where nuclear reactions involving ¹⁹Ne play a crucial role in nucleosynthesis. In novae, the destruction of ¹⁸F via the ¹⁸F(p,alpha)¹⁵O reaction significantly affects the amount of ¹⁸F remaining in the ejecta, directly influencing the detectability of predicted 511-keV gamma rays. However, discrepancies between observed and predicted ¹⁸F abundances highlight uncertainties in the reaction rates, primarily due to unknown properties of resonances in the compound nucleus ¹⁹Ne. In Type I X-ray bursts, the ¹⁵O(alpha,gamma)¹⁹Ne reaction …

Measuring Cosmic Rays With Muon Detectors (Quarknet), Aiden Burton, Jack W. Maseberg

SACAD: Scholarly Activities

We report measurement of atmospheric muon particles originating from cosmic rays. Using four QuarkNet project scintillators in an unstacked geometry, we are counting muons in coincidence with each other. We are currently refurbishing a second detector apparatus and will soon be capable of measuring coincidence events for larger shower surface areas using a total of eight scintillators.

Three-Dimensional Spreading Of Magnetic Reconnection Between Non-Parallel Flux Ropes With A Guide Field, Regis John

Graduate Theses, Dissertations, and Problem Reports (ETD)

Magnetic reconnection is a fundamental plasma process that facilitates the rapid conversion of magnetic energy into particle acceleration, plasma flows, and heating. It plays a central role in explosive astrophysical events such as solar flares, where vast amounts of magnetic energy are released on short time scales. A key structure in many reconnection sites is the magnetic flux rope, a column of plasma carrying current threaded by helical magnetic fields, which is frequently involved in or generated by reconnection. Understanding how reconnection unfolds in such flux rope systems is critical for interpreting both space weather phenomena and laboratory plasma dynamics. …

Direct Measurement Of The 114cd(N, Gamma)115cd Cross Section In The 1 Ev To 300 Kev Energy Range, Kofi Tutu Addo Assumin-Gyimah

Theses and Dissertations

The large thermal cross section of cadmium makes it ideal for many practical applications where screening of thermal neutrons is desired. For example, in non-destructive assay techniques, or for astrophysical studies of the s-process. All such applications require precise knowledge of the neutron-capture cross section on cadmium. Although there are some data on neutron-capture cross sections particularly at thermal energies and at energies relevant for astrophysics, there is very little data at most other energies. Further, the evaluated cross sections from the ENDF and JENDL databases disagree at high energies. Therefore, there is a critical need for precise knowledge of …

Measurement Of Near-Threshold Proton Branching Ratios In 31s Important For Novae, Sudarsan Balakrishnan

LSU Doctoral Dissertations

Classical novae are stellar explosions that contribute to the nucleosynthesis of isotopes on the proton-rich side of the valley of stability up to ⁴⁰Ca. In ONe novae, the incompletely understood reaction rate of ³⁰P(p,γ)³¹S is known to strongly influence the production rate of several stable isotopes such as ³⁰Si, ³¹P, and ^32,33,34S. A precise measurement of this reaction rate has several potential implications towards matching astrophysical observables to the physical composition of the nova site -- the observed elemental abundance ratios of O/S and S/Al have been suggested as useful `thermometers' to gauge …

Measurements Of The 16c + 12c And 16c + 13c Fusion Cross Sections With Implications For Astrophysics, Ashley Ann Hood

LSU Doctoral Dissertations

The fusion of neutron-rich nuclei is of interest to nuclear astrophysics and nuclear structure. X-ray superbursts are powered by runaway thermonuclear burning deep inside of a neutron star, where heating from the pycnonuclear fusion of neutron-rich isotopes is an important heat source. Experimental measurements of fusion cross sections of neutron-rich isotopes have provided insights regarding nucleon transfer and nuclear structure properties affecting fusion. Recently, the ¹⁵C + ¹²C total fusion cross section was measured using a ¹⁵C beam produced by the in-flight beam production facility, which is part of the Argonne Tandem LINAC Accelerator System (ATLAS) at …

An Analysis Of Frenkel Defects And Backgrounds Modeling For Supercdms Dark Matter Searches, Matthew Stein

Physics Theses and Dissertations

Years of astrophysical observations suggest that dark matter comprises more than ~80 % of all matter in the universe. Particle physics theories favor a weakly-interacting particle that could be directly detected in terrestrial experiments. The Super Cryogenic Dark Matter Search (SuperCDMS) Collaboration operates world-leading experiments to directly detect dark matter interacting with ordinary matter. The SuperCDMS Soudan experiment searched for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei in low-temperature germanium detectors.

During the operation of the SuperCDMS Soudan experiment, ²¹⁰Pb sources were installed to study background rejection of the Ge detectors. Data from these sources …

Characterizing New Calibration Sources In Liquid Xenon Dark Matter Searches, Evan P. Bray, Rafael Lang, Sean Macmullin

The Summer Undergraduate Research Fellowship (SURF) Symposium

In order to use the XENON1T liquid xenon detector as a means for detecting dark matter, the response to nuclear and electronic recoils must be well calibrated. Electronic-recoil calibration of XENON1T will be done by using the noble gas radon-220 that emanates from a custom thorium-228 source to observe the electron recoils that its daughter elements induce in liquid xenon. A silicon PIN diode was constructed to ensure that the Th228 source does not contaminate the system with the long-lived isotopes Th228 (T1/2 of 1.9 y) or Radium-224 (T1/2 of 3.6 d). The PIN diode was fixed in a custom …

Light Vs. Quantum Gravity, Irving Martinez^*

COURI Symposium Abstracts, Spring 2012

No abstract provided.

Lunar Occultation Observer: A Nuclear Astrophysics All-Sky Survey Mission Concept, Riley Freelove

Von Braun Symposium Student Posters

No abstract provided.

Laboratory Astrophysics: Using Ebit Measurements To Interpret High Resolution Spectra From Celestial Sources, Carey Scott, Joshua Thompson, N. Hell, Greg V. Brown

STAR Program Research Presentations

Astrophysicists use radiation to investigate the physics controlling a variety of celestial sources, including stellar atmospheres, black holes, and binary systems. By measuring the spectrum of the emitted radiation, astrophysicists can determine a source’s temperature and composition. Accurate atomic data are needed for reliably interpreting these spectra. Here we present an overview of how LLNL’s EBIT facility is used to put the atomic data on sound footing for use by the high energy astrophysics community.