Gamma-Ray Emission Spectra as a Constraint on Calculations of ^234,236,238U Neutron-Capture Cross Sections

Conference · Thu May 28 00:00:00 EDT 2015

OSTI ID:1183397

Ullmann, John Leonard ^[1]; Kawano, Toshihiko ^[1]; Bredeweg, Todd Allen ^[1]; Baramsai, Bayarbadrakh ^[1]; Couture, Aaron Joseph ^[1]; Haight, Robert Cameron ^[1]; Jandel, Marian ^[1]; Mosby, Shea Morgan ^[1]; O'Donnell, John M. ^[1]; Rundberg, Robert S. ^[1]; Vieira, David J. ^[1]; Wilhelmy, Jerry B. ^[1]; Becker, John A. ^[2]; Wu, Ching-Yen ^[2]; Krticka, Milan ^[3]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Charles Univ., Prague (Czech Republic)

Neutron capture cross sections in the “continuum” region (>≈1 keV) and gamma-emission spectra are of importance to basic science and many applied fields. Careful measurements have been made on most common stable nuclides, but physicists must rely on calculations (or “surrogate” reactions) for rare or unstable nuclides. Calculations must be benchmarked against measurements (cross sections, gamma-ray spectra, and <Γ_γ>). Gamma-ray spectrum measurements from resolved resonances were made with 1 - 2 mg/cm² thick targets; cross sections at >1 keV were measured using thicker targets. The results show that the shape of capture cross section vs neutron energy is not sensitive to the form of the strength function (although the magnitude is); the generalized Lorentzian E1 strength function is not sufficient to describe the shape of observed gamma-ray spectra; MGLO + “Oslo M1” parameters produces quantitative agreement with the measured ²³⁸U(n,γ) cross section; additional strength at low energies (~ 3 MeV) -- likely M1-- is required; and careful study of complementary results on low-lying giant resonance strength is needed to consistently describe observations.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE/LANL
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1183397
• Report Number(s): LA-UR-15-23962; TRN: US1600156
• Resource Relation: Conference: 5. Workshop on Nuclear Level Density and Gamma Strength, Oslo (Norway), 18-22 May 2015; Related Information: PowerPoint presentation
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
URANIUM 238 TARGET
URANIUM 236 TARGET
URANIUM 234 TARGET
NEUTRON REACTIONS
CROSS SECTIONS
EMISSION SPECTRA
GAMMA RADIATION
GAMMA SPECTRA
KEV RANGE
INTERMEDIATE NEUTRONS
STRENGTH FUNCTIONS
CAPTURE
GIANT RESONANCE
LIMITING VALUES
MEV RANGE
SHAPE
E1-TRANSITIONS
M1-TRANSITIONS
LEVEL WIDTHS
EXCITATION FUNCTIONS
URANIUM 235
URANIUM 237
URANIUM 239