Discovery of the origin of the enormous 88Zr neutron-capture cross section and quantifying its impact on applications

Abstract The probability for a radioactive 88 Zr nucleus (83.4 day half life) to absorb neutrons across resonance energies — its neutron-capture resonance integral — is the largest ever reported and implies that the neutron-capture cross section is orders of magnitude larger than previously thought at energies relevant to nuclear test diagnostics and nucleosynthesis applications. However, these applications require the shape of this cross section across a range of energies, not just this integral quantity. We measured the 88 Zr neutron total cross section from 0.0253 to 500 eV. Because the same resonances or other nuclear structure responsible for the neutron capture-cross section are reflected in the total cross section, we used these data to extract the former from the latter as a function of energy. Our data reveal a resonance at 0.171 eV and result in a thermal neutron-capture cross section of 771,000±31,000 barns, in good agreement with the recently published value. In contrast, the neutron-capture resonance integral extracted from our data, 15,210±670 barns, is a factor of 200 smaller than the recently reported value. We discuss the impact of this difference on applications.