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The neutron capture cross sections and the capture γ-ray spectra of 117,119Sn were measured in an energy region from 15 to 100 keV and around 550 keV. A neutron time-of-flight method was adopted with a ns-pulsed neutron source based on the 7Li(p,n)7Be reaction and with a large anti-Compton NaI(Tl) spectrometer. A pulse-height weighting technique was applied to the observed capture γ-ray pulse-height spectra to obtain the capture yields. Using the standard capture cross sections of 197Au, the capture cross sections of 117,119Sn were derived with the errors less than 5%. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. The present results for the capture cross sections are compared with the previous experimental values and the evaluated values of JENDL-3.3, and ENDF/B-VI.8 and VII.0.

The capture cross sections and capture γ-ray spectra of 91,92Zr were measured in an incident neutron energy region from 15 to 100keV and at 550keV. A neutron time-of-flight method was adopted with a 1.5-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 γ-ray pulse-height spectra to obtain capture yields. Using the standard capture cross sections of 197Au, the capture cross sections of 91,92Zr were derived with the errors from 5 to 9%. The present results were compared with other measurements and the evaluated values in JENDL-3.3 and ENDF/B-VI. The JENDL-3.3 evaluations for 91Zr were in agreement with the present results, but those for 92Zr largely deviated from the present results. The capture γ-ray spectra of 91,92Zr were obtained by unfolding the observed capture γ-ray pulse-height spectra. The multiplicities of observed γ rays were derived from the γ-ray spectra.

A compact 4π Ge spectrometer was designed for the measurement of neutron capture cross sections of minor actinides. It consists of two EUROBALL clusters and four clover detectors with BGO shields surrounding a sample as close as possible so as to absorb a few γ-rays of high energy emitted after the neutron capture reaction with reasonable efficiency. This feature opens up the possibility to discriminate the desired nuclide from other impurities based on the measurement of excitation energy and determine the cross section accurately. Overall performances such as total detection efficiencies for 3 cascade γ-rays as well as monochromatic γ-rays were simulated using Geant4. It turned out we could achieve the peak detection efficiency as large as 0.9% for 3 cascade γ-rays, which is almost an order of magnitude larger than the value of the Gammasphere.

The capture cross sections and capture γ-ray spectra of 209Bi were measured in a neutron energy region from 5 to 80keV and at 520 keV, using pulsed keV neutrons from the 7Li(p, n)7Be reaction and a time-of-flight method. The capture γrays from a bismuth or standard gold sample were detected with a large anti-Compton NaI(Tl) spectrometer. The capture yield of the bismuth or gold sample was obtained by applying a pulse-height weighting technique to the corresponding capture y-ray pulse-height spectrum. The derived capture cross sections from 5 to 80 keV were in good agreement with recent measurements, but that at 520 keV was about half of previous measurements. This large discrepancy at 520 keV was ascribed to the incorrect background-subtraction in the previous measurements from a comparison between the present and previous capture γray spectra. Strong transitions from the capture states to low lying states of 210Bi were observed in the present γray spectra. The multiplicities of observed y rays were obtai...

First, the nucleosynthesis in the universe was reviewed. In particular, the neutron capture nucleosyntheses in the Big-Bang and the s- and r-processes were reviewed in detail. It was pointed out that keV-neutron capture cross sections were important for the study on the neutron capture nucleosynthesis. Second, our measurement of keV-neutron capture cross sections was explained briefly, and the results on 7 Li, 12 C, and 16 O were shown and compared with previous experimental values and the predicted values from the 1/ v law and the thermal neutron capture cross sections. The results at 30 keV on 12 C and 16 O were much larger than the 1/ v predictions, while the result at 30 keV on 7 Li was in good agreement with the 1/ v prediction. The large values for 12 C and 16 O were ascribed to the non-resonant p-wave neutron capture from the analysis of observed capture γ-ray spectra and the neutron energy dependence of derived partial capture cross sections. As for 7 Li, the good agreement was ascribed to the peculiarity of bound states of its residual nucleus, which strongly suppresses the non-resonant p-wave neutron capture. Finally, it was shown that the non-resonant p-wave neutron capture is predominant in the neutron capture nucleosynthesis of light nuclei in the universe.

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.

The neutron capture cross sections of 161Dy and 162Dy have been measured in the neutron energy region from 10 to 90 keV using the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology. 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 incident neutron spectrum on a capture sample was measured by means of a TOF method with a 6Li-glass detector. Capture γ-rays were detected with a large anti-Compton Nal(Tl) spectrometer, employing a TOF method. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained by using the standard capture cross sections of 197Au. The present results were compared with the previous measurements and the evaluated values of ENDF/B-VI.

Folding model potentials of 12C and 16O are obtained for neutrons, using a nucleon-density distribution and the effective nucleon-nucleon interaction DDM3 Y. These folded potentials, instead of a phenomenological optical potential, are applied to the calculation for the direct capture of low-energy neutrons on 12C and 16O. As a result, it is concluded that an observation of the neutron direct capture would be very useful to acquire the information on the nucleon-density distribution near the nuclear surface.

The capture γ rays from the broad 53-keV and the narrow 35-keV p-wave neutron resonances of 23Na were measured using a large anti-Compton HPGe γ-ray spectrometer. A neutron time-of-flight method wa...

The neutron capture cross sections and capture γ-ray spectra of 140 Ce and 141 Pr were measured in the neutron energy region of 10 to 100 keV and at 550 keV. Prompt γ rays from a capture sample were detected with a large anti-Compton Nal(Tl) spectrometer, employing a neutron time-of-flight method with a 1.5- ns pulsed neutron source by the 7Li(p, n)7Be reaction. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of 197Au. The present results were compared with evaluated values in JENDL-3.2 and previous measurements. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous bump was observed around 1.5 MeV in each γ-ray spectrum of 140Ce and 141Pr, and its energy position was consistent with the systematics obtained in our previous work. The multiplicities of the observed...

The neutron capture cross sections and capture γ-ray spectra of 167Er were measured in the neutron energy region of 10 to 90keV and at 550 keV. Using a neutron time-of-flight method with a 1.5-ns pulsed neutron source by the 7Li(p, n)7Be reaction, the measurement was performed by detecting prompt γ rays from an enriched capture sample with a large anti-Compton Nal(Tl) spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of 197Au. The present results were compared with the evaluated values of ENDF/B-VI and the previous measurement. The present measurement at 550 keV was the first one. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was clearly observed around 3 MeV in the γ-ray spectra and the energy position of the shoulder was consistent w...

The neutron capture cross sections and capture γ-ray spectra of 147,148,149,150,152,154Sm were measured in the neutron energy region of 10 to 90 keV and at 550 keV. A neutron time-of-flight method was adopted with a 1.5-ns pulsed neutron source by the 7Li(p, n)7Be reaction and with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained with the error of about 5% by using the standard capture cross sections of 197Au. The present results were compared with the evaluated values of JENDL-3.2 and previous measurements. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was clearly observed around 3 MeV in the γ-ray spectra of 150,152,154Sm, and the energy position of the shoulder was consistent with the systematics obtained in our previous work.

The neutron capture cross sections and capture γ-ray spectra of 143,145,146Nd were measured in the neutron energy region of 10 to 90 keV and at 550 keV. A neutron time-of-flight method was adopted with a 1.5-ns pulsed neutron source by the 7Li(p, n)7Be reaction and with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained with the error of about 5% by using the standard capture cross sections of 197Au. The evaluated values of JENDL-3.2 and previous measurements were compared with the present results. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was observed around 2 MeV in the γ-ray spectra of 145,146Nd, and the energy position of the shoulder was consistent with the systematics obtained in our previous work.