New Methods for the Determination of Total Radiative Thermal Neutron Capture Cross Sections
- Lawrence Berkeley National Laboratory, Berkeley CA 94720 (United States)
- Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Prague 8 (Czech Republic)
- Lawrence Livermore National Laboratory, L-414, 7000 East Avenue, Livermore, CA 94551 (United States)
- Institute of Isotope and Surface Chemistry, H-1525, Budapest (Hungary)
Precise gamma-ray thermal neutron capture cross sections have been measured at the Budapest Reactor for all elements with Z = 1-83,92 except for He and Pm. These measurements and additional data from the literature been compiled to generate the Evaluated Gamma-ray Activation File (EGAF), which is disseminated by LBNL and the IAEA. These data are nearly complete for most isotopes with Z<20 so the total radiative thermal neutron capture cross sections can be determined directly from the decay scheme. For light isotopes agreement with the recommended values is generally satisfactory although large discrepancies exist for {sup 11}B, {sup 12,13}C, {sup 15}N, {sup 28,30}Si, {sup 34}S, {sup 37}Cl, and {sup 40,41}K. Neutron capture decay data for heavier isotopes are typically incomplete due to the contribution of unresolved continuum transitions so only partial radiative thermal neutron capture cross sections can be determined. The contribution of the continuum to the neutron capture decay scheme arises from a large number of unresolved levels and transitions and can be calculated by assuming that the fluctuations in level densities and transition probabilities are statistical. We have calculated the continuum contribution to neutron capture decay for the palladium isotopes with the Monte Carlo code DICEBOX. These calculations were normalized to the experimental cross sections deexciting low excitation levels to determine the total radiative thermal neutron capture cross section. The resulting palladium cross sections values were determined with a precision comparable to the recommended values even when only one gamma-ray cross section was measured. The calculated and experimental level feedings could also be compared to determine spin and parity assignments for low-lying levels.
- OSTI ID:
- 21143158
- Journal Information:
- AIP Conference Proceedings, Vol. 1005, Issue 1; Conference: CNR 2007: 2007 international workshop on compound-nuclear reactions and related topics, Yosemite National Park, CA (United States), 22-26 Oct 2007; Other Information: DOI: 10.1063/1.2920738; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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