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| Title: | Neutron Capture Reactions on Gadolinium Isotopes |
| Authors: | Baramsai, Bayarbadrakh |
| Advisors: | 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 |
| Keywords: | Gadolinium
Neutron Capture
Cross Section
Resonance Parameters
Level Density
Photon Strength Function |
| Issue Date: | 2-Feb-2010 |
| Degree: | PhD |
| Discipline: | Physics |
| Abstract: | The neutron capture reaction on 155Gd, 156Gd and 158Gd isotopes has been studied
with the DANCE calorimeter at Los Alamos Neutron Science Center.
The highly segmented calorimeter provided detailed multiplicity distributions of
the capture gamma-rays. With this information the spins of the neutron capture resonances have
been determined. The new technique based on the statistical pattern recognition method
allowed the determination of almost all spins of 155Gd s-wave resonances. The generalized
method was tested for s- and p-wave resonances in 94Mo and 95Mo isotopes. The results
were 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 neutrons
energy 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 data
library ENDF/B-VII.0 and with a recent experiment at RPI.
With the new spin assignments and resonance parameters, level spacings and neutron
strength functions were determined for s-wave resonances in 155Gd.
The Monte Carlo code DICEBOX was used to simulate the gamma-decay of the compound
nuclei 156Gd, 157Gd and 159Gd. The DANCE detector response was taken into
account with a GEANT4 simulation. The simulated and experimental spectra were compared
to 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 best
agreement with the DANCE spectra contained four low-lying Lorentzian resonances, two
for the scissors mode and two for the M1 spin flip mode. |
| URI: | http://www.lib.ncsu.edu/resolver/1840.16/3707 |
| Appears in Collections: | Dissertations
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