M. Mizumoto

Neutron-capture cross-sections of 244Cm and 246Cm measured with an array of large germanium detectors in the ANNRI at J-PARC/MLF

The neutron neutron-capture cross cross-sections of 244Cm and 246Cm were measured by the time-of-flight method in the energy range of 1–300 300 eV with an array of large germanium detectors in the Accurate Neutron-Nucleus Reaction measurement InstrumentANNRI at Material and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research ComplexJ-PARC/MLF. The 244Cm resonances at around 7.7 and 16.8 8 eV and the 246Cm resonances at around 4.3 and 15.3 3 eV were observed in the capture reactions for the first time. The uncertainties of the obtained cross cross-sections are 5.8% at the top of the first resonance of 244Cm and 6.6% at that of 246Cm. The rResonance analyses were performed for low-energy ones using the code SAMMY. The prompt γ-ray spectra of 244Cm and 246Cm were also obtained. Eight and five new prompt γ-ray emissions were observed in the 244Cm(n, γ) and 246Cm(n, γ) reactions, respectively.

Cross-section measurement of 237Np (n, 𝛄) from 10 meV to 1 keV at Japan Proton Accelerator Research Complex

The cross-section of the 237Np reaction has been measured in the energy range from 10 meV to 1 keV using the ANNRI-NaI(Tl) spectrometer at the Japan Proton Accelerator Research Complex (J-PARC). The cross-section was obtained relative to that of the 10B reaction. The absolute value of the cross-section was deduced by normalizing the relative cross-section to the evaluated value of JENDL-4.0 at the first resonance. The thermal cross-section was obtained to be ( ) b. The Maxwellian-averaged cross-section for meV was derived as ( ) b by referring the cross-section below 10 meV from JENDL-4.0. These results lead to the Westcotts g-factor of .

Measurements of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 77Se

The neutron capture cross sections and capture γ-ray spectra of 77Se were measured in a region from 15 to 100 keV and at around 510 keV. A neutron time-of-flight method was used with a ns-pulsed neutron source based on the 7Li(p,n)7 Be reaction and with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to the observed γ-ray pulse-height spectra to obtain capture yields. The capture cross sections were derived with errors less than 5%, by using the standard capture cross sections of 197Au. The present results were the first experimental ones above the resolved resonance region, and compared with the evaluated values in JENDL-3.3, ENDF/B-VI.8, and ENDF/B-VII.0. The evaluated values in those libraries were smaller than the present results by 10–20% in the region from 15 to 100 keV. At around 510 keV, the values in JENDL-3.3 and ENDF/B-VII.0 were smaller than the present result by about 20%, but those in ENDF-VI.8 were larger than the present result by about 20%. The capture γ-ray spectra of 77Se were derived by unfolding the observed capture γ-ray pulse-height spectra. The present results were the first experimental ones in the keV region.

Development of a 4π germanium spectrometer for nuclear data measurements at J-PARC

A 4π germanium spectrometer was developed for measurements of neutron capture cross sections of minor ac-tinides and long-lived-fission products. It was installed on the Beam Line No. 04 of the MLF in the J-PARC. We measured its full-energy peak efficiency and gamma-energy resolution at 1.3-MeV with a 60Co standard source (10kBq). As an example of a result of TOF measurements with the spectrometer, preliminary TOF and energy spectra of 108Pd are shown in this paper.

Measurement of Neutron Capture Cross Section Ratios of 244Cm Resonances Using NNRI

Measurement of Neutron Capture Cross Section Ratios of Cm Resonances Using NNRI Shinji GOKO a , Atsushi KIMURA a , Hideo HARADA a , Masumi OSHIMA a , Masayuki OHTA a , Kazuyoshi FURUTAKA a , Tadahiro KIN a , Fumito KITATANI a , Mitsuo KOIZUMI a , Shoji NAKAMURA a , Yosuke TOH a , Masayuki IGASHIRA b , Tatsuya KATABUCHI b , Motoharu MIZUMOTO c , Yoshiaki KIYANAGI c , Koichi KINO c , Michihiro FURUSAKA c , Fujio HIRAGA c , Takashi KAMIYAMA d , Jun-ichi HORI d , Toshiyuki FUJJI d , Satoshi FUKUTANI d & Koichi TAKAMIYA a a Nuclear Science and Engineering Directorate , Japan Atomic Energy Agency , Tokaimura, Naka-gun, Ibaraki , 319-1195 , Japan b Research Laboratory for Nuclear Reactors , Tokyo Institute of Technology , O-okayama, Meguro-ku, Tokyo , 152-8550 , Japan c Faculty of Engineering , Hokkaido University , Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido , 060-8628 , Japan d Research Reactor Institute , Kyoto University , Asashiro Nishi, Kumatori-cho, Sennangun, Osaka , 590-0494 , Japan Published online: 05 Jan 2012.

A dead-time correction method for multiple gamma-ray detection

To correct dead time in TOF experiments with multi-detector gamma-ray detection method, we have tested a dead-time correction method. In this dead-time correction method, random timing pulses generated by a random pulse generator are input to every pre-amplifier via test-signal inputs. Both the random timing pulses and the other pulses originated from gamma rays are measured with a data acquisition system (DAQ). At the same time, a number of the input random timing pulses are counted with another fast system. Because dead time affects similarly both the pulses from the random pulse generator and the measured gamma rays, we can calculate the dead time by comparing the number of the input random timing pulses counted by the fast system with an area count of the peak due to the random timing pulses measured with the DAQ.

Precise Measurements of Neutron Capture Cross Sections for LLFPs and MAs

To evaluate the feasibility of development of nuclear transmutation technology and an advanced nuclear system, precise nuclear data of neutron capture cross sections for long-lived fission products (LLFPs) and minor actinides (MAs) are indispensable. In this chapter, we present our research activities for the measurements of neutron capture cross sections for LLFPs and MAs.

Measurement of keV‐Neutron Capture Gamma Rays for Se Isotopes

Neutron capture gamma rays were measured for all stable Se isotopes in an incident neutron energy region from 15 to 100 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 gamma‐ray pulse‐height spectra to obtain the capture yields. Using the standard capture cross sections of 197Au, the capture cross sections of stable Se isotopes were derived with an error of about 5%. The capture gamma‐ray spectra were obtained by unfolding the observed capture gamma‐ray pulse‐height spectra. The present results for the capture cross sections are compared with the previous measurements and the evaluations of JENDL‐3.3 and ENDF/B‐VI.8 and VII.0.