Measurement of keV-neutron capture cross sections and capture gamma-ray spectra of Ce-140 and Pr-141

The neutron capture cross sections and capture gamma -ray spectra of Ce-140 and Pr-141 were measured in the neutron energy region of 10 to 100 keV and at 550 keV. Prompt gamma rays from a capture sample were detected with a l arge anti-Compton NaI(TI) spectrometer, employing a neutron time-of-Right m ethod with a 1.5-ns pulsed neutron source by the Li-7(p, n)Be-7 reaction. A pulse-height weighting technique was applied to observed capture T-ray pul se-height spectra to extract capture yields. The capture cross sections wer e derived with the error of about 5% by using the standard capture cross se ctions of Au-197. The present results were compared with evaluated values i n JENDL-3.2 and previous measurements. The capture gamma -ray spectra were obtained by unfolding the observed capture gamma -ray pulse-height spectra. An anomalous bump was observed around 1.5 MeV in each gamma -ray spectrum of Ce-140 and Pr-141, and its energy position was consistent with the syste matics obtained in our previous work. The multiplicities of the observed ca pture gamma rays were derived from the gamma -ray spectra.