Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 99 Tc

The capture cross sections of 99Tc were measured in the incident neutron energy region from 8 to 90 keV and at 190, 330, and 540 keV. A neutron time-of-flight method was adopted with a ns-pulsed neutron source by the 7Li(p, n) 7Be reaction and with a large anti-Compton NaI(Tl) spectrometer. A pulse-height weighting technique was applied to observed capture gamma-ray pulse-height spectra to derive capture yields. Using the standard capture cross sections of 197Au, the capture cross sections of 99Tc were obtained with the error of about 5%. The present results were compared with other measurements and the evaluated values in JENDL-3.2 and 3.3 and ENDF/B-VI. Capture gamma-ray spectra were obtained by unfolding observed capture gamma-ray pulse-height spectra. A change of slopes was observed at 2.2 MeV in the spectra. The multiplicities of observed gamma rays were obtained from the gamma-ray spectra.