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Featured researches published by M. Igashira.


Journal of Nuclear Science and Technology | 1999

Measurements of keV-neutron capture cross sections and capture gamma-ray spectra of 161,162,163Dy

Satoshi Mizuno; M. Igashira; Koji Masuda

The neutron capture cross sections and capture γ-ray spectra of 161 162 163Dy 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 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 previous measurements and the evaluated values of ENDF/B-VI. Capture γ-ray spectra were obtained by unfolding observed capture γ-ray pulse-height spectra. An anomalous bump was observed around 2.5 MeV in the γ-ray spectra of each isotope, and the energy position of the bump was consistent with the systematics obtained in our previous work.


Nuclear Physics | 1986

Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

M. Igashira; H. Kitazawa; M. Shimizu; H. Komano; Nobuhiro Yamamuro

Abstract We have measured capture gamma-ray spectra of Pr, Tb, Ho, Lu, Ta and Au at neutron energies of 10 to 800 keV with an anti-Compton NaI(Tl) detector, employing a time-of-flight technique. An anomalous bump, so-called the pygmy resonance, was observed in all these spectra. Remarkable features of the pygmy resonance were found to be that the resonance energy and the electric-dipole strength exhausted in the resonance increase with neutron number but these quantities decrease precipitously around the neutron magic number of N = 82. Comparison with theoretical calculations suggests that the pygmy resonance is mainly made up of neutron particle-hole states decoupled from the giant electric-dipole resonance and is excited in a collective mode.


Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 1986

A heavy shield for the gamma-ray detector used in fast neutron experiments

M. Igashira; H. Kitazawa; Nobuhiro Yamamuro

Abstract The 80-20 wt.% mixture of paraffin and boric acid was proposed as a shielding material for the gamma-ray detector used in fast neutron experiments. Its neutron shielding capability was evaluated by neutron and gamma-ray transport calculations and compared with that of other materials. As a result, it was found that the borated paraffin will be an effective and economical shielding material against fast neutrons if it is used with a lead shield. Moreover, a heavy shield for the gamma-ray detector has been constructed, and the typical shield performance was investigated for keV-neutron capture experiments.


Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 1994

A Monte Carlo code for multiple neutron scattering events in a thick sample for (n, γ) experiments

K. Senoo; Y. Nagai; Tatsushi Shima; T. Ohsaki; M. Igashira

Abstract 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 neutrons 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.


The Astrophysical Journal | 1991

Capture rate of the Li-7(n, gamma)Li-8 reaction by prompt gamma-ray detection

Y. Nagai; M. Igashira; N. Mukai; T. Ohsaki; F. Uesawa; K. Takeda; T. Ando; H. Kitazawa; S. Kubono; T. Fukuda

The reaction 7 Li(n, γ) 8 Li is a trigger reaction which bridges the instability gap at mass 8 while producing heavy elements during the rapid process of primordial nucleosynthesis in the inhomogeneous big-bang models. The reaction rate was remeasured at the most probable neutron energy of 30 keV by detecting prompt γ-rays from a captured state; 39.3 ± 6.0 μb was obtained. This value is 2 times larger than that recently measured and agrees with the estimated value from the thermal neutron capture cross section by using the 1/v law. The result is discussed in terms of both nucleosynthesis and the solar neutrino problem


Journal of Nuclear Science and Technology | 2012

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

Atsushi Kimura; Toshiyuki Fujii; Satoshi Fukutani; K. Furutaka; Shinji Goko; K. Hara; H. Harada; K. Hirose; J. Hori; M. Igashira; Takashi Kamiyama; T. Katabuchi; Tadahiro Kin; Koichi Kino; Fumito Kitatani; Yoshiaki Kiyanagi; M. Koizumi; M. Mizumoto; Shoji Nakamura; Masayuki Ohta; M. Oshima; Koichi Takamiya; Yosuke Toh

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.


Progress in Nuclear Energy | 1995

Scientific feasibility of incineration in scnes

Hiroshi Akatsuka; Toshiro Ohsaki; Toru Obara; M. Igashira; Masaaki Suzuki; Y. Fujii-e

Abstract 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 (TRUs) produced in the core as fuel in the SCNES reactor. It is numerically found that the fission products (FPs) 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 FPs 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 FPs. 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.


The Astrophysical Journal | 1991

Measurement of the neutron capture rate of the (C-12)(n,gamma)(C-13) reaction at stellar energy

Y. Nagai; M. Igashira; K. Takeda; N. Mukai; S. Motoyama; F. Uesawa; H. Kitazawa; T. Fukuda

The reaction (C-12)(u,gamma)(C-13) at stellar energy plays important roles in the nucleosynthesis of intermediate-mass nuclei in inhomogeneous big bang models and in that of heavy elements during stellar evolution. In the present study, the reaction rate was measured by detecting gamma-rays emitted from a captured state; 16.8 + or {minus} 2.1 microbarn was obtained, about 5 times larger than the estimated value from the thermal-neutron capture cross section. The present result favors the nucleosynthesis of intermediate-mass nuclei in inhomogeneous big bang models and also of heavy elements in exploding supernovae. 19 refs.


Journal of Nuclear Science and Technology | 2013

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

K. Hirose; K. Furutaka; K. Hara; H. Harada; Atsushi Kimura; Tadahiro Kin; Fumito Kitatani; M. Koizumi; Shoji Nakamura; M. Oshima; Yosuke Toh; M. Igashira; T. Katabuchi; M. Mizumoto; Takashi Kamiyama; Koichi Kino; Yoshiaki Kiyanagi; J. Hori

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 .


Physical Review C | 1998

Nonresonant direct p - and d -wave neutron capture by 12 C

Takashi Kikuchi; Y. Nagai; T. Suzuki; Tatsushi Shima; T. Kii; M. Igashira; A. Mengoni; T. Otsuka

Discrete gamma-rays from the neutron capture state of 13C to its low-lying bound states have been measured using pulsed neutrons at En = 550 keV. The partial capture cross sections have been determined to be 1.7+/-0.5, 24.2+/-1.0, 2.0+/-0.4 and 1.0+/-0.4 microb for the ground (1/2-), first (1/2+), second (3/2-) and third (5/2+) excited states, respectively. From a comparison with theoretical predictions based on the non-resonant direct radiative capture mechanism, we could determine the spectroscopic factor for the 1/2+ state to be 0.80 +/- 0.04, free from neutron-nucleus interaction ambiguities in the continuum. In addition we have detected the contribution of the non-resonant d-wave capture component in the partial cross sections for transitions leading to the 1/2- and 3/2- states. While the s-wave capture dominates at En < 100 keV, the d-wave component turns out to be very important at higher energies. From the present investigation the 12C(n,gamma)13C reaction rate is obtained for temperatures in the range 10E+7 - 10E+10 K.

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Toshiro Ohsaki

Tokyo Institute of Technology

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T. Katabuchi

Tokyo Institute of Technology

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Atsushi Kimura

Japan Atomic Energy Agency

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H. Harada

Japan Atomic Energy Agency

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Shoji Nakamura

Japan Nuclear Cycle Development Institute

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M. Mizumoto

Tokyo Institute of Technology

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H. Kitazawa

Tokyo Institute of Technology

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