Radiative thermal neutron-capture cross sections for the W-180(n, gamma) reaction and determination of the neutron-separation energy
Abstract
Prompt thermal neutron-capture partial gamma-ray production cross sections were measured for the first time for the W-180(n, gamma) reaction using a cold guided-neutron beam at the Budapest Research Reactor. Absolute W-181 gamma-ray cross sections were internally standardized using well-known comparator gamma-ray cross sections belonging to the other tungsten isotopes present in the 11.35% enriched W-180 sample.
Transitions were assigned to levels in W-181 based largely upon information available in the literature. The total radiative thermal neutron-capture cross section sigma(0) was determined from the sum of direct prompt gamma-ray cross sections populating the ground state and a modeled contribution accounting for ground-state feeding from the quasicontinuum.
In this work, we find sigma(0) = 21.67(77) b. A new measurement of the cross section for the 5/2(-) metastable isomer at 365.6 keV, sigma(5/2)-((181)Wm, 14.6 mu s) = 19.96(55) b, is also determined.
Additionally, primary gamma rays, observed for the first time in the W-180(n, gamma) reaction, provide the most precise determination for the W-181 neutron-separation energy, S-n = 6669.02(16) keV.