Neutron capture cross section measurements for 197Au from 4 to 80 keV at GELINA

Neutron capture cross section measurements for 197Au from 4 to 80 keV at GELINA

Massimi, C.; Becker, B.; Dupont, E.; Kopecky, S.; Lampoudis, C.; Massarczyk, R.; Moxon, M.; Pronyaev, V.; Schillebeeckx, P.; Sirakov, I.; Volev, K.; Wynants, R.


Neutron induced capture cross section measurements for 197Au have been performed in the energy region between 4 keV and 80 keV. The experiments have been carried out at the time-of-flight facility GELINA. The prompt capture gamma-rays were detected by two C6D6 liquid scintillators, placed at 12.5 m distance from the neutron source. The shape of the neutron flux was measured with a 10B-loaded double Frisch-gridded ionization chamber based on the 10B(n,alpha) reaction. The total energy detection principle in combination with the pulse height weighting technique was applied. The data have been normalized to the well-isolated and saturated 197Au resonance at 4.9 eV. Special procedures have been applied to reduce bias effects due to the weighting function, normalization, dead time and background corrections. Uncertainties due to normalization, neutron flux and weighting function are 1.0 %. An additional uncertainty of 0.5 % results from the correction for self-shielding and multiple interactions, which have been verified by experiment. Resonance fluctuations have been studied by additional measurements at a 30 m flight path station. The results reported in this work deviate systematically by more than 5% from the cross section that is recommended as a reference for astrophysical applications. They are about 2% lower compared to a standard evaluation of the 197Au(n,gamma) cross section that was based on a least squares fit of experimental data available in the literature prior to this work and are fully consistent with the latest average capture cross section obtained in a quasi-Maxwellian spectrum at 25 keV.

Keywords: neutron capture; neutron resonances; neutron cross section