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Title: Near-barrier photofission in Th 232 and U 238

Here a study of photofission of $$^{232}\mathrm{Th}$$ and $$^{238}\mathrm{U}$$ was performed by using quasimonoenergetic, linearly polarized $${\gamma}$$-ray beams from the High Intensity $${\gamma}$$-ray Source at Triangle Universities Nuclear Laboratory. The prompt-photofission neutron polarization asymmetries, neutron multiplicities, and the photofission cross sections were measured in the near-barrier energy range of 4.3 to 6.0 MeV. This data set constitutes the lowest energy measurements of those observables to date using quasimonoenergetic photons. Large polarization asymmetries are observed in both nuclei, consistent with the $E1$ excitation as observed by another measurement of this kind made in a higher-energy range. Previous experimental evidence of a deep third minimum in the $$^{238}\mathrm{U}$$ fission barrier has been identified as an accelerator-induced background.
Authors:
 [1] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division; Triangle Universities Nuclear Lab., Durham, NC (United States); Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Physics and Astronomy
  2. Triangle Universities Nuclear Lab., Durham, NC (United States); Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
LLNL-JRNL-754505
Journal ID: ISSN 2469-9985; 941284
Grant/Contract Number:
AC52-07NA27344; FG02-97ER41033; FG02-97ER41041
Type:
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 98; Journal Issue: 5; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of North Carolina, Chapel Hill, NC (United States); Triangle Universities Nuclear Lab., Durham, NC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; fission; photonuclear reactions; polarization phenomena
OSTI Identifier:
1489469
Alternate Identifier(s):
OSTI ID: 1482760

Silano, J. A., and Karwowski, H. J.. Near-barrier photofission in Th232 and U238. United States: N. p., Web. doi:10.1103/PhysRevC.98.054609.
Silano, J. A., & Karwowski, H. J.. Near-barrier photofission in Th232 and U238. United States. doi:10.1103/PhysRevC.98.054609.
Silano, J. A., and Karwowski, H. J.. 2018. "Near-barrier photofission in Th232 and U238". United States. doi:10.1103/PhysRevC.98.054609.
@article{osti_1489469,
title = {Near-barrier photofission in Th232 and U238},
author = {Silano, J. A. and Karwowski, H. J.},
abstractNote = {Here a study of photofission of $^{232}\mathrm{Th}$ and $^{238}\mathrm{U}$ was performed by using quasimonoenergetic, linearly polarized ${\gamma}$-ray beams from the High Intensity ${\gamma}$-ray Source at Triangle Universities Nuclear Laboratory. The prompt-photofission neutron polarization asymmetries, neutron multiplicities, and the photofission cross sections were measured in the near-barrier energy range of 4.3 to 6.0 MeV. This data set constitutes the lowest energy measurements of those observables to date using quasimonoenergetic photons. Large polarization asymmetries are observed in both nuclei, consistent with the $E1$ excitation as observed by another measurement of this kind made in a higher-energy range. Previous experimental evidence of a deep third minimum in the $^{238}\mathrm{U}$ fission barrier has been identified as an accelerator-induced background.},
doi = {10.1103/PhysRevC.98.054609},
journal = {Physical Review C},
number = 5,
volume = 98,
place = {United States},
year = {2018},
month = {11}
}

Works referenced in this record:

Event identification in 3He proportional counters using risetime discrimination
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