Thermal Neutron Capture onto the Stable Tungsten Isotopes

A.M. Hurst^1a, R.B. Firestone¹, B.W. Sleaford², N.C. Summers², Zs. Revay³, L. Szentmiklósi³, T. Belgya³, M.S. Basunia¹, R. Capote⁴, H. Choi⁵, D. Dashdorj^2,6, J. Escher², M. Krticka⁷ and A. Nichols⁴

¹ Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
² Lawrence Livermore National Laboratory, Livermore, CA 94551, USA
³ Institute of Isotopes and Surface Chemistry, H-1525, Budapest, Hungary
⁴ NAPC-Nuclear Data Section, International Atomic Energy Agency, A-1400 Vienna, Austria
⁵ Seoul National University, Seoul 151-742, Republic of Korea
⁶ North Carolina State University, Raleigh, NC 27695, USA
⁷ Charles University in Prague, Faculty of Mathematics and Physics, CZ-180 00 Prague 8, Czech Republic

^a e-mail: AMHurst@lbl.gov

Published online: 14 February 2012

Abstract

Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET γ-ray analysis software package for the compound tungsten systems ¹⁸³W, ¹⁸⁴W, and ¹⁸⁷W, prepared from isotopically-enriched samples of ¹⁸²W, ¹⁸³W, and ¹⁸⁶W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of γ-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.