Measurement of keV-neutron capture cross sections and capture gamma-ray spectra of Er-167

The neutron capture cross sections and capture gamma-ray spectra of Er-167 were measured in the neutron energy region of 10 to 90 keV and at 550 keV. Using a neutron time-of-flight method with a 1.5-ns pulsed neutron source b y the Li-7(p, n)Be-7 reaction, the measurement was performed by detecting p rompt gamma rays from an enriched capture sample with a large anti-Compton NaI(T1) spectrometer. A pulse-height weighting technique was applied to obs erved capture gamma-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using th e standard capture cross sections of Au-197. The present results were compa red with the evaluated values of ENDF/B-VI and the previous measurement. Th e present measurement at 550 keV was the first one. The capture gamma-ray s pectra were obtained by unfolding the observed capture gamma-ray pulse-heig ht spectra. An anomalous shoulder was clearly observed around 3MeV in the g amma-ray spectra and the energy position of the shoulder was consistent wit h the systematics obtained in our previous work. The multiplicities of the observed gamma rays were derived from the gamma-ray spectra.