Cross section measurements of $^{155,157}$Gd(n,$\gamma$) induced by thermal and epithermal neutrons

TL;DR

This study measured neutron capture cross sections of $^{155}$Gd and $^{157}$Gd using time-of-flight at CERN, finding values slightly different from existing data and analyzing resonance structures up to 1 keV.

Contribution

First precise measurements of $^{155}$Gd and $^{157}$Gd neutron capture cross sections at CERN with resonance analysis extending up to 1 keV.

Findings

Capture cross sections at thermal energy: 62.2(2.2) kb for $^{155}$Gd and 239.8(9.3) kb for $^{157}$Gd.

Resonance parameters consistent with evaluations up to 180-300 eV.

Observed resonance-like structures above 300 eV characterized up to 1 keV.

Abstract

Neutron capture measurements on $^{155}$Gd and $^{157}$Gd were performed using the time-of-flight technique at the n\_TOF facility at CERN. Four samples in form of self-sustaining metallic discs isotopically enriched in $^{155}$Gd and $^{157}$Gd were used. The measurements were carried out at the experimental area (EAR1) at 185 m from the neutron source, with an array of 4 C$_6$D$_6$ liquid scintillation detectors. The capture cross sections of $^{155}$Gd and $^{157}$Gd at neutron kinetic energy of 0.0253 eV have been estimated to be 62.2(2.2) kb and 239.8(9.3) kb, respectively, thus up to 6\% different relative to the ones reported in the nuclear data libraries. A resonance shape analysis has been performed in the resolved resonance region up to 180 eV and 300 eV, respectively, in average resonance parameters have been found in good agreement with evaluations. Above these energies the observed resonance-like structures in the cross section have been tentatively characterised in terms of resonance energy and area up to 1 keV.