Photoneutron cross sections for samarium isotopes: Toward a unified understanding of(γ,n)and(n,γ)reactions in the rare earth region

Abstract

Photoneutron cross sections were measured for the seven stable samarium isotopes 144,147,148,149,150,152,154 Sm near the neutron threshold with quasi-monochromatic laser-Compton scattering γ rays. Our photoneutron cross sections are found to be low by 20%-37% relative to existing data. The photoneutron data are analyzed with the TALYS reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the E1 γ -ray strength. Using the γ -ray strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse (n,γ ) cross sections including the radioactive nucleus 151 Sm with a half-life of 90 yr. The radiative neutron capture cross section for 153 Sm with the half-life of 1.928 d is deduced with the γ -ray strength function method.

Photoneutron cross sections for neodymium isotopes: Toward a unified understanding of(γ,n)and(n,γ)reactions in the rare earth region

“…The energy spread of the LCS γ -ray beam with a low-energy tail was 1%-2% in full width at half maximum (see Figs. 4 and 5 of [3]). Details of the GEANT4 simulation will be given in a forthcoming paper [21], where also a more in-depth description of the experimental setup can be found.…”

“…Neutrons were detected with a high-efficiency 4π neutron detector consisting of 20 3 He proportional counters embedded in a polyethylene moderator of 36 × 36 × 50 cm 3 fully covered by additional 5-cm-thick polyethylene plates with 1-mm-thick cadmium for background neutron suppression. Neutrons were moderated in the polyethylene before being detected with three rings of 4, 8, and 8 3 He counters placed at distances of 3.8, 7.0, and 10.0 cm, respectively from the γ -ray beam axis.…”

“…Neutrons were moderated in the polyethylene before being detected with three rings of 4, 8, and 8 3 He counters placed at distances of 3.8, 7.0, and 10.0 cm, respectively from the γ -ray beam axis. The average neutron energy was determined by the so-called ring-ratio technique originally developed by Berman and Fultz [23].…”

“…A description of the experimental procedure and the data reduction is limited to a minimum in Sec. II, yielding a detailed description to the preceding paper [3]. The theoretical analysis of the photoneutron cross sections is given in Sec.…”

“…The neutron capture data are also of essential importance for nuclear transmutation of long-lived fission products known as nuclear waste in the field of nuclear engineering [2]. Following the preceding paper for samarium isotopes [3], this paper for neodymium isotopes constitutes the second part of our investigations in the rare earth region.…”