Measurement of the keV-Neutron Capture Cross-Sections and Capture -Ray Spectra of 155Gd and 157Gd

The neutron capture cross-sections and the capture -ray spectra of 155Gd and 157Gd were measured at the 3-MeV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology in the energy range from 10 to 550 keV. Pulsed keV-neutrons were produced from the 7Li(p,n)7Be reaction by bombarding the lithium target with the 1.5-ns bunched proton beam from the Pelletron accelerator. The spectrum for the neutrons incident on a capture sample was measured by means of a time-of-flight method with a 6Li-glass detector. Capture - rays were detected with a large anti-Compton NaI(Tl) spectrometer by employing a time-of-flight method. A pulse-height weighting technique was applied to the observed capture -ray pulse-height spectra to derive the capture yields. The neutron capture cross-sections were determined relative to the standard capture cross-section of 197Au. The results were compared to other measurements and the evaluated values. The capture -ray spectra were obtained by unfolding the observed capture -ray pulse-height spectra.