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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.

In order to measure the neutron capture cross-section of minor actinides, we have proposed the use of a 4 π Ge spectrometer. A time-of-flight neutron beam line for the experiment has been constructed at the electron LINAC of Kyoto University Research Reactor Institute. The assembling of the 4 π Ge spectrometer is in progress. We are also developing a new data acquisition system based on a digital processing technique.

A new system to measure the γ -ray angular distributions of the C ( α , γ ) 12 O 16 reaction has been installed at the 3.2 MV Pelletron accelerator laboratory at Tokyo Institute of Technology. An intense 2.27 MeV α -beam with the pulse width of 1.9 ns was used to study the performance of the system. The γ -rays from the C ( α , γ ) 12 O 16 reaction were detected with three high-efficiency anti-Compton NaI(Tl) spectrometers, and they were well separated from neutron background from the C ( α , n ) 13 O 16 reaction using a time of flight method. The present study has demonstrated high sensitivity of the system to measure the γ -ray angular distributions of the C ( α , γ ) 12 O 16 reaction at low energy, and to determine both E1 and E2 cross-sections.

We have determined the σ E 2 / σ E 1 ratio of the 12 C( α , γ ) 16 O reaction at E c m = 1.39 MeV and at E c m = 1.58 MeV by measuring the angular distribution of the γ -ray feeding from the α -capturing state of 12 C to the ground state of 16 O.

JSNS, the Japanese Spallation Neutron Source, is a forthcoming 1MW spallation neutron source. Since it is highly intense and has low background, it will provide a unique opportunity to study neutron-induced nuclear reactions relevant to astrophysics with excellent sensitivity and accuracy. Details of the JSNS facility and a plan for an experimental study of cosmonuclear physics are presented.

The keV neutron capture cross section of 62 Ni was measured using an anti-Compton Nal(Tl) spectrometers.Prompt discrete γ -rays feeding from a neutron capture state of 62 Ni to low-lying excited states were observed. The Maxwellin-aver aged cross section at 30 keV is derived to be 37.5 mb, which is 2.9 times larger than the value used in the calculation of nucleosynthetic yields of massive stars. The observation of discrete γ -rays is crucial to unambiguously determine the small neutron cross section of 62 Ni.

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.

The neutron capture cross section of 62Ni has been measured in the energy range from 5.5 to 90 keV by employing a prompt discrete γ-ray detection method with the use of an anti-Compton NaI(Tl) spectrometer. The Maxwellian-averaged capture cross section at 30 keV is derived as being 37.0 ± 3.2 mbarn, 3 times larger than the value currently used for the nucleosynthetic yield estimations in massive stars. The result could provide crucial information for the long-standing problem of the largest overproduction of 62Ni. The intense discrete γ-ray feeding from a neutron capture state to the ground state of 63Ni was for the first time observed at stellar neutron energy. This observation and the neutron energy dependence of the total neutron capture cross section of 62Ni indicate clearly that the dominant capture process of 62Ni is a nonresonant direct s-wave capture process and not a p-wave capture process as previously predicted.

We have for the first time determined with high precision the energy spectrum of low-energy neutrons ( E n

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.

In the study of Self-Consistent Nuclear Energy System, the following 29 long-lived fission products (LLFPs) have been selected to be transmuted into stable or short-lived nuclides: 106Ru, 102Rh, 109Cd, 125Sb, 134Cs, 146,147Pm, 154,155Eu, 171Tm, 85Kr, 90Sr, 93mNb, 113mCd, 121mSn, 137Cs, 151Sm, 152Eu, 108mAg, 158Tb, 166mHo, 79Se, 93Zr, 94Nb, 99Tc, 107Pd, 126Sn, 129I, 135Cs. In the present study, the number of neutrons necessary for the transmutation of the 29 LLFPs with an FBR was evaluated, and the present status of the (n, γ) and (n,2n) cross section data of the 29 LLFPs in JENDL-3.2 and ENDF/B-VI was investigated. The main results of the present study are as follows: (1)only 0.25 neutron per fission is necessary for the transmutation of the 29 LLFPs with isotopic separation, whereas 6.8 neutrons are necessary with chemical separation, (2)the accuracy of the cross sections is 30 to 100% except for the (n, γ) cross sections of limited nuclides in limited incident neutron energy regions.

The neutron capture cross-sections of 164 Dy were measured in the neutron energy region of 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 7 Li(p,n) 7 Be reaction by bombarding a 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 6 Li-glass detector. Capture γ-rays were detected with a large anti-Compton NaI(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 197 Au. The present results were compared with the previous measurements and the evaluated values of ENDF/B-VI.

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.

An NaI(Tl) spectrometer system has been installed to measure the cross section of a radiative neutron-capture reaction of a nucleus at an astrophysically relevant energy of between 10 and 500 keV. The system consists of two large anti-Compton NaI(Tl) spectrometers and a new data-taking system. The spectrometer can detect a discrete γ-ray emitted promptly from a neutron-capture state to its low-lying state, and the data-taking system can transfer events with much higher rates, about 30-times higher, compared to the existing system.

The capture cross sections and capture γ-ray spectra of 139 La were measured in a neutron energy region from 10 to 100keV and at 550keV. Pulsed keV neutrons were produced by the 7 Li(p,n) 7 Be reaction with a pulsed proton beam from a Pelletron accelerator. Capture γ-rays were detected with a large anti-Compton NaI(Tl) spectrometer by means of a time-of-flight method. A pulse-height weighting technique was applied to the observed capture γ-ray pulse-height spectra to obtain capture yields. Using the standard capture cross sections of 197 Au, the capture cross sections of 139 La were derived with uncertainties of about 5%. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. The present results were compared with previous measurements and evaluated values.

The cross sections of the neutron capture reaction on light nuclei, protons,12C and16O, were measured at astrophysically relevant energies between 10 and 300 keV. They are not only important for estimating yields of elements in the primordial nucleosynthesis, stellar nucleosynthesis of s-, r-, and p-processes, but also to study the role of meson exchange currents, the nuclear structure and the reaction mechanism. In the measurement, we used a prompt γ-ray detection method, combined with a pulsed neutron beam, and a recently developed Monte-Carlo code, TIME-MULTI, to correct for neutron multiple-scattering effects in a sample.

A γ-ray from a neutron-capture reaction on 127 I in an NaI(Tl) detector was observed in background measurement. The neutrons were considered to be produced by cosmic-ray muon captured by Pb, which was used for shielding the spectrometer against γ-ray background. The observed γ-ray yield of the reaction was compared with the value calculated by assuming that the fast neutrons produced in the Pb were thermalized while they passed through a plastic scintillation counter, which surrounded the NaI(Tl) detector, and these thermal neutrons were captured by 127 I in the detector. They agree with each other, supporting the present interpretation. The γ-ray energy from the capture state to the ground state in 128 I was different from the previously measured value using thermal neutrons; the difference could be due to a nonuniformity of the detector. The present result has important implications for developing a low-background γ-ray spectrometer for studying rare physical phenomena.

We confirm the simultaneous realization of burning or transmutation of radioactive nuclides and of net energy generation. An investigation of the neutron balance in a reactor core is carried out. It is numerically shown that the neutrons can burn all the transuranium elements (TRU's) produced in the core as fuel in the SCNES reactor. It is numerically found that the fission products (FP's) whose half-lives are longer than one year can be contained and transmuted into harmless nuclides in the core without losing the neutron balance. It is shown that isotope separation of the FP's is required to realize the SCNES. As an example, we investigate the required energy for a scheme of the atomic vapor laser isotope separation (AVLIS) of FP's. It is shown that, in principle, the energy required for the isotope separation is much lower than the generated fission energy. The SCNES is scientifically realized in principle.

TIME-MULTI, a time-introduced Monte Carlo estimation code for multiple neutron scattering events in a thick sample, was designed to extract accurate neutron-capture cross sections. In order to obtain the energy and time-of-flight spectra of a captured neutron, the neutron's history in the sample was simulated by a Monte Carlo method. The code was applied to the 1H(n, γ)D reaction with different sample thicknesses and was shown to give the correct capture cross section independent of the thickness.

A similarity was studied between the production/transmutation process of fission products in a fast reactor and that of the s-process nucleosynthesis in a star. A long-period burnup calculation of ...

We measured the $\ensuremath{\gamma}$-ray angular distribution from $^{12}\mathrm{C}$$(\ensuremath{\alpha},{\ensuremath{\gamma}}_{0})$$^{16}\mathrm{O}$ to the ground state of $^{16}\mathrm{O}$ using a pulsed $\ensuremath{\alpha}$ beam at ${E}_{\mathrm{eff}}=1.6$ and $1.4$ MeV. True events of $^{12}\mathrm{C}$$(\ensuremath{\alpha},{\ensuremath{\gamma}}_{0})$$^{16}\mathrm{O}$ were discriminated from background events with a time-of-flight method because of neutrons from $^{13}\mathrm{C}$($\ensuremath{\alpha},n$)$^{16}\mathrm{O}$. The obtained $\ensuremath{\gamma}$-ray spectrum with anti-Compton NaI(Tl) spectrometers showed a characteristic line shape from $^{12}\mathrm{C}$$(\ensuremath{\alpha},{\ensuremath{\gamma}}_{0})$$^{16}\mathrm{O}$: the Doppler broadening and energy loss of $\ensuremath{\alpha}$ particles in $^{12}\mathrm{C}$ targets. A Rutherford backscattering spectrum of $\ensuremath{\alpha}$ particles from enriched $^{12}\mathrm{C}$ targets was measured during beam irradiation to obtain the target thickness and incident $\ensuremath{\alpha}$-beam intensities. The astrophysical $S$ factors for $E1$ and $E2,{S}_{E1}({\ensuremath{\gamma}}_{0}:{E}_{\mathrm{eff}})$ and ${S}_{E2}({\ensuremath{\gamma}}_{0}:{E}_{\mathrm{eff}})$, derived from the present cross sections are in excellent agreement with the values derived by $R$-matrix calculation of the $\ensuremath{\beta}$-delayed $\ensuremath{\alpha}$ spectrum of $^{16}\mathrm{N}$, and by using the asymptotic normalization constant in the $R$-matrix fit.

Neutron radiative capture cross sections of 7 Li and 12 C were measured at a neutron energy of 30 keV to study the production rate of intermediate-mass nuclei in primordial nucleosynthesis. The reaction cross sections were obtained by using pulsed neutrons and by observing prompt γ-rays from the captured state. The present results favor the nucleosynthesis of intermediate-mass nuclei in the early universe.

Fast neutrons play crucial roles as a probe to trace the history of the universe. The present paper describes our recent work on the measurement of the neutron capture and neutron inelastic scattering cross sections of various nuclei from primordial and stellar nucleostyntheses point of view, which have been carried out by developing a high sensitive measurement system. The obtained results are compared to previous works and theoretical calculations.

Neutron capture cross sections of minor actinides and long-lived fission products are important for the R&D of innovative nuclear reactors. However, those data are rather poor both in quality and in quantity at present. Thus, we have started projects for neutron cross section measurements. We have constructed an 4π Ge spectrometer consisting of Ge crystals and BGO shields. The neutron cross section measurements have been done at KURRI electron linac and JAEA JRR-3 facilities, which will be extended at the high-intensity neutron source at J-PARC.

The neutron capture cross sections and capture gamma-ray spectra of Sn ( 116�119 Sn) and Gd ( 155�158 Gd) isotopes have been measured in the incident neutron energy region from 10 to 100keV and at 550keV. PulsedkeV neutrons were produced by the 7 Li(p,n) 7 Be reaction. Capture gamma rays were detected with a large anti-Compton NaI(Tl) spectrometer by means of a time-of-flight method. A pulse-height weighting technique was applied to the observed capture gamma-ray pulse-height spectra to obtain capture yields. Using the standard capture cross sections of 197 Au, the capture cross sections of the Sn and Gd isotopes were derived. The capture gamma-ray spectra were obtained by unfolding the observed capture gamma-ray pulse-height spectra. The present cross section results were compared with other experimental data and evaluated values.

A distortion of pulse‐height spectra of neutron capture γ‐rays caused by γ‐flash at neutron time‐of‐flight (TOF) measurement using a pulse neutron source has been investigated. Pulses from C6D6 detectors accumulated by flash‐ADC were processed with both traditional analog‐to‐digital converter (ADC) and flash‐ADC operational modes. A correction factor of γ‐ray yields, due to baseline shift, was quantitatively obtained by comparing the pulse‐height spectra of the two data‐collecting modes. The magnitude of the correction factor depends on the time, which passed after γ‐flash, and has complicated time dependence with a changing sign.

The γ rays from the neutron capture reaction by 90,94Zr were measured in an incident neutron energy region from 15 to 100 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) spectrometer. A pulse‐height weighting technique was applied to observed capture γ‐ray pulse‐height spectra to derive capture yields. Using the standard capture cross sections of 197Au in ENDF/B‐VI, the capture cross sections of 90, 94Zr were obtained with the errors from 6 to 8%. The present results were compared with previous measurements and the evaluations of JENDL‐3.3 and ENDF/B‐VI. The capture γ‐ray spectra of 90, 94Zr 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.

The capture γ rays from the 46‐keV d‐wave and 84‐keV p‐wave neutron resonances of 24Mg were measured by using a large anti‐Compton HPGe γ‐ray spectrometer . A neutron time‐of‐flight method was adopted with a 1.5‐ns pulsed neutron source by the 7Li(p,n)7Be reaction. The standard capture cross sections of 197Au were used to determine the incident neutron flux. Twenty‐one and twenty‐six primary γ‐ray transitions were identified for the 46‐ and 84‐keV resonances, respectively. The corresponding capture kernels were derived for both the resonances, and the radiative widths were obtained for the 84‐keV broad resonance.

We develop a 4pi Ge spectrometer consisting of large-volume Ge detectors and BGO scintillators for capture cross section measurement of minor actinides such as 241,243Am and 237Np. By using this spectrometer we can extract summed gamma-ray energy, which corresponds to excitation energy of the residual nucleus after neutron capture reaction. The high energy resolution achieved by Ge crystals will enable us to distinguish between the nucleus of interest and impurity nucleus: we can eliminate the contribution from the impurity nucleus in the cross section measurements, enabling us to derive accurate cross section data. In this paper we will describe detailed design study of the spectrometer and its performance based on the Monte-Carlo simulation code GEANT4.5.0.

There are many common features in nuclear data for energy applications and nuclear cosmology/astrophysics, especially the neutron‐capture nucleosynthesis. Therefore it is a natural consequence to think that many of the tools that we have developed for the conventional nuclear‐data applications can be applied for a development of a database for nuclear cosmology/astrophysics. However, there are also many features that are uncommon to these fields, so new development is necessary when we think about a database for nuclear cosmology and astrophysics. Such new development will then give us a new horizon for the conventional nuclear data activities as well. In this paper we will show the present status of our activities in this direction, putting emphasis on data relevant to neutron capture nucleosynthesis, namely s‐ and r‐processes.

We are developing a 4π Ge‐spectrometer for the measurement of neutron capture cross sections of minor actinides. The 4π Ge‐spectrometer consists of Ge detectors that cover a large solid angle of a sample; the spectrometer has high efficiency and good energy resolution for γ‐ray detection. This feature enables us to discriminate desired events from backgrounds based on the measurement of total excitation energy following the neutron capture reaction. In this work, we determined an optimal configuration and evaluated performances of 4π Ge‐spectrometer using a Geant4 simulation. From comparison of performances, two configurations that have uniform count rates or a high efficiency were determined. Therefore one of the two configurations is used properly to reduce an experimental error for the neutron capture cross section. Further simulations were made with a full geometry including BGO shields; absolute efficiency for the high‐efficiency configuration was estimated to be 15% for a 1‐MeV γ ray.

The response function of a high-resolution high-energy photon spectrometer (HHS), consisting of a twin Ge detector and BGO (Bi 3 Ge 4 O 12 ) anti-coincidence shields, has been measured for 10.763 MeV monochromatic γ-rays generated in a resonant reaction 27 Al(p,γ) 28 Si. The experimental response functions measured with and without the anti-coincidence were compared with results by Monte Carlo simulations, in which a pulse-height degradation effect associated with a surface channel of the twin Ge detector has been included. Excellent agreement was obtained between the experimental response functions and the simulations.

We measured the cross section of the 186,187,189 Os(n, γ ) reactions at the stellar energy by detecting a prompt gamma ray with an anti-Compton NaI(Tl) spectrometer. Currently, we are consructing a detecting system to measure inelastically scattered neutrons from 187 Os(n, n') and 189 Os(n, n') reactions with Li-glass detectors.