Decays of the Three Top Contributors to the Reactor ν[over ¯]_{e} High-Energy Spectrum, ^{92}Rb, ^{96gs}Y, and ^{142}Cs, Studied with Total Absorption Spectroscopy.
We report total absorption spectroscopy measurements of ^{92}Rb, ^{96gs}Y, and ^{142}Cs β decays, which are the most important contributors to the high energy ν[over ¯]_{e} spectral shape in nuclear reactors. These three β decays contribute 43% of the ν[over ¯]_{e} flux near 5.5 MeV emitted by nuclear reactors. This ν[over ¯]_{e} energy is particularly interesting due to spectral features recently observed in several experiments including the Daya Bay, Double Chooz, and RENO Collaborations. Measurements were conducted at Oak Ridge National Laboratory by means of proton-induced fission of ^{238}U with on-line mass separation of fission fragments and the Modular Total Absorption Spectrometer. We observe a β-decay pattern that is similar to recent measurements of ^{92}Rb, with a ground-state to ground-state β feeding of 91(3)%. We verify the ^{96gs}Y ground-state to ground-state β feeding of 95.5(20)%. Our measurements substantially modify the β-decay feedings of ^{142}Cs, reducing the β feeding to ^{142}Ba states below 2 MeV by 32% when compared with the latest evaluations. Our results increase the discrepancy between the observed and the expected reactor ν[over ¯]_{e} flux between 5 and 7 MeV, the maximum excess increases from ∼10% to ∼12%.
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
B C
BC
Rasco
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Heavy Ion Laboratory, University of Warsaw, PL-02-093 Warsaw, Poland.
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Wolińska-Cichocka
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.|Faculty of Physics, University of Warsaw, PL-02-093 Warsaw, Poland.
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A
Fijałkowska
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Rykaczewski
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Faculty of Physics, University of Warsaw, PL-02-093 Warsaw, Poland.
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Karny
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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Grzywacz
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.|CIRE Bredesen Center, University of Tennessee, Knoxville, Tennessee 37966, USA.
K C
KC
Goetz
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
C J
CJ
Gross
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Stracener
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 USA.
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Zganjar
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Nuclear Engineering, University of California, Berkeley, Berkeley California 94720, USA.
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Batchelder
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 USA.
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Blackmon
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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Brewer
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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Go
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
B
B
Heffron
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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T
King
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J T
JT
Matta
JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Faculty of Physics, University of Warsaw, PL-02-093 Warsaw, Poland.
K
K
Miernik
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
C D
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Nesaraja
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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Paulauskas
Department of Physics, Tennessee Technological University, Cookeville, Tennessee 38505, USA.
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MM
Rajabali
Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
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EH
Wang
Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, USA.
J A
JA
Winger
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37966, USA.
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Y
Xiao
Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
C J
CJ
Zachary