Measurement of the Sm-151(n, gamma) cross section from 0.6 eV to 1 MeV via the neutron time-of-flight technique at the CERN n_TOF facility

Abstract

The Sm-151(n,gamma) cross section was measured with the time-of-flight technique from 0.6 eV up to 1 MeV relative to the Au standard with an overall uncertainty of typically 6%. Neutrons were produced by spallation at the innovative n_TOF facility at CERN; the gamma rays from capture events were detected with organic C6D6 scintillators. Experimental setup and data analysis procedures are described with emphasis on the corrections for detection efficiency, background subtraction, and neutron flux determination. At low energies, resonances could be resolved up to about 1 keV, yielding a resonance integral of 3575 +/- 210 b, an average s-wave resonance spacing of <D-0>=1.49 +/- 0.07 eV, and a neutron strength function of <S-0>=(3.87 +/- 0.33)x10(-4). Maxwellian-averaged capture cross sections are reported for thermal energies between 5 and 100 keV. These results are of relevance for nuclear structure studies, nuclear astrophysics, and nuclear technology. The new value of the Maxwellian-averaged cross section at kT=30 keV is 3.08 +/- 0.15 b, considerably larger than previous theoretical estimates, and provides better constraints for the thermodynamic conditions during the occurrence of the slow neutron capture process in low-mass stars during their asymptotic giant branch phase.