Sub-barrier Photofission Measurements in 238U and 232Th Public Deposited

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Last Modified
  • March 20, 2019
Creator
  • Silano, Jack
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • A study of photofission of $^{232}$Th and $^{238}$U was performed using quasi-monoenergetic, linearly-polarized $\\gamma$-ray beams from the High Intensity $\\gamma$-ray source at TUNL. The prompt photofission neutron polarization asymmetries, neutron multiplicities and the photofission cross sections were measured in the sub-barrier energy range of 4.3-6.3 MeV. This data set constitutes the lowest energy measurements of those observables to date. Large polarization asymmetries are observed in both nuclei, consistent with the only other measurement of this kind made at a higher energy range. Over the newly probed energy range the asymmetries, multiplicities and cross sections all vary smoothly, revealing no new resonant fission processes. The present cross sections are consistent with a triple-humped $^{232}$Th fission barrier and a double-humped $^{238}$U fission barrier. Previous experimental evidence of a third minimum in the $^{238}$U fission barrier has been identified as an accelerator-induced background. Applications of the present data will also be discussed.
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Rights statement
  • In Copyright
Advisor
  • Karwowski, Hugon
  • Drut, Joaquin
  • Clegg, Thomas
  • Ahmed, Mohammad
  • Parikh, Nalin
  • Henning, Reyco
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2016
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