Neutron Capture Reactions on Gadolinium Isotopes

Gadolinium;Neutron Capture;Cross Section;Resonance Parameters;Level Density;Photon Strength Function

Baramsai, Bayarbadrakh ; Gary E. Mitchell, Committee Chair,Undraa Agvaanluvsan, Committee Co-Chair,Mohamed A. Bourham, Committee Member,John H. Kelley, Committee Member,Christoper R. Gould, Committee Member,Baramsai, Bayarbadrakh ; Gary E. Mitchell ; Committee Chair ; Undraa Agvaanluvsan ; Committee Co-Chair ; Mohamed A. Bourham ; Committee Member ; John H. Kelley ; Committee Member ; Christoper R. Gould ; Committee Member

University:North Carolina State University

关键词: Gadolinium;    Neutron Capture;    Cross Section;    Resonance Parameters;    Level Density;    Photon Strength Function;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/3707/etd.pdf?sequence=1&isAllowed=y

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【 摘 要 】

The neutron capture reaction on 155Gd, 156Gd and 158Gd isotopes has been studiedwith the DANCE calorimeter at Los Alamos Neutron Science Center.The highly segmented calorimeter provided detailed multiplicity distributions ofthe capture gamma-rays. With this information the spins of the neutron capture resonances havebeen determined. The new technique based on the statistical pattern recognition methodallowed the determination of almost all spins of 155Gd s-wave resonances. The generalizedmethod was tested for s- and p-wave resonances in 94Mo and 95Mo isotopes. The resultswere compared with previous resonance data as well as results from other methods.The 155Gd(n,gamma)156Gd cross section has been measured for the incident neutronsenergy range from 1 eV to 10 keV. The results are in good agreement with other experiments.Neutron resonances parameters were obtained using the multilevel R-matrix code SAMMY.The fitted radiation and neutron widths were compared with the nuclear datalibrary ENDF/B-VII.0 and with a recent experiment at RPI.With the new spin assignments and resonance parameters, level spacings and neutronstrength functions were determined for s-wave resonances in 155Gd.The Monte Carlo code DICEBOX was used to simulate the gamma-decay of the compoundnuclei 156Gd, 157Gd and 159Gd. The DANCE detector response was taken intoaccount with a GEANT4 simulation. The simulated and experimental spectra were comparedto determine suitable model parameters for the photon strength functions (PSFs)and the level density (LD). The shape of the photon strength function which gave the bestagreement with the DANCE spectra contained four low-lying Lorentzian resonances, twofor the scissors mode and two for the M1 spin flip mode.