Low energy proton capture study of the [14]N(p,γ)[15]O reaction Public Deposited

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Last Modified
  • March 22, 2019
Creator
  • Daigle, Stephen Michael
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • The 14N(p, γ)15O reaction regulates the rate of energy production for stars slightly more massive than the sun throughout stable hydrogen burning on the main sequence. The 14N(p, γ)15O reaction rate also determines the luminosity for all stars after leaving the main sequence when their cores have exhausted hydrogen fuel, and later when they become red giant stars. The significant role that this reaction plays in stellar evolution has far-reaching consequences, from neutrino production in our Sun, to age estimates of globular clusters in our Galaxy. The weak cross section and inherent coincidence summing in the 15O γ-ray decay scheme make a precision measurement of the astrophysical S-factor especially challenging, particularly for the ground-state transition. The present study, performed in the Laboratory for Experimental Nuclear Astrophysics (LENA), was aimed at measuring the ground-state transition at low energy by utilizing a new 24-element, position-sensitive, NaI(Tl) detector array. Because the array is highly segmented, the 14N(p, γ)15O S-factor was evaluated for transitions to the ground, 5.18, 6.18, and 6.79MeV states without the need for coincidence summing corrections. Additionally, the positionsensitivity of the detector was exploited to measure the angular correlation of the two-photon cascades. Software cuts were made to the data in order to identify single and coincident γ-ray events and a fraction fit analysis technique was used to extract the characteristic 15O peaks from the composite γ-ray spectrum. The results from the current work demonstrated a new approach to measuring weak nuclear cross sections near astrophysically relevant energies that, with refinements, has broader applications in γ-ray spectroscopy.
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DOI
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  • In Copyright
Advisor
  • Champagne, Arthur
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill
Graduation year
  • 2013
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