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Journal Articles

Nonresonant $$p$$-wave direct capture and interference effect observed in the $$^{16}$$O$$(n,gamma)^{17}$$O reaction

Nagai, Yasuki*; Kinoshita, Mitsutaka*; Igashira, Masayuki*; Nobuhara, Yuriko*; Makii, Hiroyuki; Mishima, Kenji*; Shima, Tatsushi*; Mengoni, A.*

Physical Review C, 102(4), p.044616_1 - 044616_8, 2020/10

https://doi.org/10.1103/PhysRevC.102.044616
 Times Cited Count：4 Percentile：45.12(Physics, Nuclear)

Journal Articles

Measurement of neutron scattering cross section of nano-diamond with particle diameter of approximately 5 nm in energy range of 0.2 meV to 100 meV

Teshigawara, Makoto; Tsuchikawa, Yusuke*; Ichikawa, Go*; Takata, Shinichi; Mishima, Kenji*; Harada, Masahide; Oi, Motoki; Kawamura, Yukihiko*; Kai, Tetsuya; Kawamura, Seiko; et al.

Nuclear Instruments and Methods in Physics Research A, 929, p.113 - 120, 2019/06

https://doi.org/10.1016/j.nima.2019.03.038
 Times Cited Count：16 Percentile：86.05(Instruments & Instrumentation)

A nano-diamond is an attractive neutron reflection material below cold neutron energy. The total neutron cross section of a nano-diamond was derived from a neutron transmission measurement over the neutron energy range of 0.2 meV to 100 meV because total neutron cross section data were not available. The total cross section of a nano-diamond with particle size of approximately 5 nm increased with a decrease in neutron energy to 0.2 meV. It was approximately two orders of magnitude larger than that of graphite at 0.2 meV. The contribution of inelastic scattering to the total cross section was to be shown negligible small at neutron energies of 1.2, 1.5, 1.9, 2.6, and 5.9 meV in the inelastic neutron scattering measurement. Moreover, small-angle neutron scattering measurements of the nano-diamond showed a large scattering cross section in the forward direction for low neutron energies.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

https://doi.org/10.3390/qubs1030009

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

$$E1$$ and $$E2$$ cross sections of the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction at $$E_{rm{eff}}$$ $$sim$$ 1.2 MeV using pulsed $$alpha$$ beams

Makii, Hiroyuki; Ueda, Hitoshi*; Temma, Yasuyuki*; Nagai, Yasuki*; Shima, Tatsushi*; Fujimoto, Shinya*; Segawa, Mariko; Mishima, Kenji*; Nishiyama, Jun*; Igashira, Masayuki*

AIP Conference Proceedings 1269, p.283 - 288, 2010/10

https://doi.org/10.1063/1.3485149
 Times Cited Count：0 Percentile：0.02(Astronomy & Astrophysics)

The $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction cross section plays an important role in stellar evolution at the stage of helium-burning. However, the cross section at low energy still has a large uncertainty mainly due to the poor determination of the ratio of $$E2$$ cross section to $$E1$$ one. Hence, we have installed new system to make a precise measurement of the cross section. In this experiment, we used the high efficiency anti-Compton NaI(Tl) spectrometers with a large S/N ratio, an intense pulsed $$alpha$$ beams, and the monitoring system of target thickness. With use of the system we succeeded in removing a background due to neutron and could clearly detect the $$gamma$$-ray from the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction with high statistics. We determined the $$E1$$ and $$E2$$ cross section down to $$E_{rm{eff}} sim $$ 1.2 MeV, and thus obtained results are compared to recent theoretical calculations.

Journal Articles

$$E1$$ and $$E2$$ cross sections of the $$^{12}$$C$$(alpha,gamma_{0})^{16}$$O reaction using pulsed $$alpha$$ beams

Makii, Hiroyuki; Nagai, Yasuki*; Shima, Tatsushi*; Segawa, Mariko; Mishima, Kenji*; Ueda, Hitoshi*; Igashira, Masayuki*; Osaki, Toshiro*

Physical Review C, 80(6), p.065802_1 - 065802_16, 2009/10

https://doi.org/10.1103/PhysRevC.80.065802
 Times Cited Count：32 Percentile：83.95(Physics, Nuclear)

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

Journal Articles

Design of neutron beamline for fundamental physics at J-PARC BL05

Mishima, Kenji*; Ino, Takashi*; Sakai, Kenji; Shinohara, Takenao; Hirota, Katsuya*; Ikeda, Kazuaki*; Sato, Hiromi*; Otake, Yoshie*; Omori, Hitoshi*; Muto, Suguru*; et al.

Nuclear Instruments and Methods in Physics Research A, 600, p.342 - 345, 2009/02

https://doi.org/10.1016/j.nima.2008.11.087
 Times Cited Count：27 Percentile：85.04(Instruments & Instrumentation)

A new beamline for a fundamental physics experiment is under construction at BL05 port in the Materials and Life Science Facility (MLF) at Japan Proton Accelerator Research Complex (J-PARC), this beamline is designed using novel techniques of neutron optics and it is termed "Neutron Optics and Physics". The beam from the moderator is deflected by multi-channel supermirrors and split into three branches for individual experiments. In this study, we have optimized the design of the beam optics and shields using the Monte Carlo simulation package PHITS. The neutron fluxes of beams are expected to be $$9.2 times 10^5/$$cm$$^2/mu$$str$$/$$s$$/$$MW, $$1.2 times 10^9/$$cm$$^2/$$s$$/$$MW, $$4.0 times 10^8/$$cm$$^2/$$s$$/$$MW, with polarization of 99.8%.

Journal Articles

$$E1$$ and $$E2$$ cross sections of the $$^{12}$$C($$alpha,gamma)^{16}$$O reaction at $$E_{cm} sim$$ 1.4 MeV using pulsed $$alpha$$ beams

Makii, Hiroyuki; Nagai, Yasuki; Mishima, Kenji*; Segawa, Mariko; Shima, Tatsushi*; Ueda, Hitoshi; Igashira, Masayuki*

AIP Conference Proceedings 1016, p.215 - 220, 2008/05

https://doi.org/10.1063/1.2943575

The $$^{12}$$C($$alpha,gamma)^{16}$$O reaction plays an important role in stellar evolution at the stage of helium-burning. However, the cross section at low energy still has a large uncertainty mainly due to the poor determination of the $$sigma_{E2}/sigma_{E1}$$ ratio. We have installed a new system to measure the $$gamma$$-ray angular distribution of the $$^{12}$$C($$alpha,gamma)^{16}$$O reaction to accurately determine the $$sigma_{E1}$$ and $$sigma_{E2}$$. In this experiment, we used high efficiency anti-Compton NaI(Tl) spectrometers to detect a $$gamma$$-ray from the reaction with a large S/N ratio, intense pulsed $$alpha$$ beams to discriminate true events from neutron induced background with a time-of-flight method, and the monitoring system of target thickness. We succeeded in removing a background due to neutrons and could clearly detect the $$gamma$$-ray from the $$^{12}$$C($$alpha,gamma)^{16}$$O reaction with high statics.

Journal Articles

Neutron capture and inelastic scattering cross sections for $$^{186}$$Os, $$^{187}$$Os, and $$^{189}$$Os and the Re-Os chronology

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Temma, Yasuyuki*; Shima, Tatsushi*; Mishima, Kenji*; Igashira, Masayuki*; Goriely, S.*; Koning, A.*; Hilaire, S.*

AIP Conference Proceedings 1016, p.448 - 450, 2008/05

https://doi.org/10.1063/1.2943622

$$^{187}$$Re-$$^{187}$$Os pair is known as the most promising nuclear cosmochronometer with considerable potential. However, there remains non-trivial problems related to an excited neutron capture reaction of $$^{187}$$Os at a stellar temperature. Firstly, $$^{187}$$Os is produced and depleted by the slow process nucleosynthesis. Hence, it is necessary to obtain both the production and depletion rates of $$^{187}$$Os. Secondly, $$^{187}$$Os is depleted not only by its ground state neutron capture reaction but also by an excited state neutron capture reaction of $$^{187}$$Os in a stellar temperature. In the present study, we have measured the neutron capture reaction cross sections for $$^{186}$$Os, $$^{187}$$Os and $$^{189}$$Os accurately and neutron inelastic scattering reaction cross section for $$^{187}$$Os off the ground state of $$^{187}$$Os to its 9.75 keV first excited state in the neutron energy range from 10 to 100 keV.

Journal Articles

Neutron-induced reactions using a $$gamma$$-ray detector in a $$^{12}$$C($$alpha,gamma$$)$$^{16}$$O reaction study

Makii, Hiroyuki; Nagai, Yasuki*; Mishima, Kenji*; Segawa, Mariko; Shima, Tatsushi*; Igashira, Masayuki*

Physical Review C, 76(2), p.022801_1 - 022801_5, 2007/08

https://doi.org/10.1103/PhysRevC.76.022801
 Times Cited Count：14 Percentile：67.84(Physics, Nuclear)

Neutron-induced background events occurring within a $$gamma$$-ray detector in the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction study are discussed by comparing a spectrum taken by a NaI(Tl) detector with a pulsed $$alpha$$-beam with that taken previously by a Ge detector using a continuous $$alpha$$-beam. Both spectra contain such background events induced by neutrons from the $$({alpha},n)$$ reaction on $$^{13}$$C and/or $$^{9}$$Be contained in enriched $$^{12}$$C targets. These observations together with a calculated $$gamma$$-ray spectrum of the neutron-induced reaction by Ge isotopes indicate the thus-produced background events, which would be hardly reduced by using shield materials, become significant background in the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction study at low $$alpha$$-beam energy.

Journal Articles

Neutron capture cross sections of $$^{186}$$Os, $$^{187}$$Os, and $$^{189}$$Os for the Re-Os chronology

Segawa, Mariko; Masaki, Tomohiro*; Nagai, Yasuki*; Temma, Yasuyuki*; Shima, Tatsushi*; Mishima, Kenji*; Igashira, Masayuki*; Goriely, S.*; Koning, A.*; Hilaire, S.*

Physical Review C, 76(2), p.022802_1 - 022802_5, 2007/08

https://doi.org/10.1103/PhysRevC.76.022802
 Times Cited Count：17 Percentile：72.66(Physics, Nuclear)

Discrete as well as continuum $$gamma$$-ray energy spectra from the neutron capture by $$^{186}$$Os, $$^{187}$$Os, and $$^{189}$$Os have been taken for the first time at 5 $$leq$$ En $$leq$$ 90 keV by an anti-Compton NaI(Tl) spectrometer. The detection of a weak discrete $$gamma$$-ray, about 0.5% of total $$gamma$$-ray strength, demonstrates the high sensitivity of the present measurement. The energy spectra enabled us to accurately determine the reaction cross sections with a small systematic uncertainty. Based on the new cross sections, we re-estimate on the basis of a careful reaction cross section calculation the correction factor F$$_{sigma}$$ for the neutron capture on the 9.75-keV first excited state in $$^{187}$$Os as a function of stellar temperature, as required to derive the age of the Galaxy within the Re-Os chronology.

Journal Articles

Highly polarized cold neutron beam obtained by using a quadrupole magnet

Oku, Takayuki; Yamada, Satoru; Shinohara, Takenao; Suzuki, Junichi; Mishima, Kenji*; Hirota, Katsuya*; Sato, Hiromi*; Shimizu, Hirohiko

Physica B; Condensed Matter, 397(1-2), p.188 - 191, 2007/07

https://doi.org/10.1016/j.physb.2007.02.055
 Times Cited Count：5 Percentile：27.18(Physics, Condensed Matter)

We have studied a neutron polarization method by means of a quadrupole magnet. By passing through the aperture of the quadrupole magnet (QM), positive and negative polarity neutrons are accelerated in opposite directions and spatially separated due to the magnetic field gradient. Then, by extracting one spin component, we can obtain a highly polarized neutron beam. Since polarized neutrons do not interact with any substances in this method, we can obtain the polarized neutron beam free from neutron attenuation. As a result of a cold neutron beam polarization experiment by using the QM, we obtained extremely high neutron polarization degree P0.999. In this paper, we show some experimental results of the neutron polarization experiment and discuss the application of the QM-based polarizing device to neutron scattering experiments.

Oral presentation

Development of a neutron polarizer based on a quadrupole magnet

Oku, Takayuki; Yamada, Satoru; Suzuki, Junichi; Mishima, Kenji*; Shinohara, Takenao*; Ikeda, Kazuaki*; Hirota, Katsuya*; Sato, Hiromi*; Shimizu, Hirohiko*

no journal, , 

no abstracts in English

Oral presentation

Neutron Beta Decay experiment(NBD) at JRR-3; Measurement of beta decay events

Yamada, Satoru; Mishima, Kenji*; Sato, Hiromi*; Hirota, Katsuya*; Shinohara, Takenao*; Morishima, Takahiro*; Ono, Masashi*; Oku, Takayuki; Suzuki, Junichi; Shimizu, Hirohiko*

no journal, , 

no abstracts in English

Oral presentation

$$sigma$$$$_{E2}$$ and $$sigma$$$$_{E1}$$ of the $$^{12}$$C($$alpha$$, $$gamma$$)$$^{16}$$O reaction obtained at E$$_{cm}$$ = 1.6 and 1.4 MeV

Makii, Hiroyuki; Nagai, Yasuki*; Shima, Tatsushi*; Segawa, Mariko; Ueda, Hitoshi*; Masaki, Tomohiro*; Mishima, Kenji*; Igashira, Masayuki*; Osaki, Toshiro*

no journal, , 

no abstracts in English

Oral presentation

Highly polarized neutron beam produced by a quadrupole magnet and its application to fundamental physics

Yamada, Satoru; Oku, Takayuki; Mishima, Kenji*; Sato, Hiromi*; Hirota, Katsuya*; Morishima, Takahiro*; Ono, Masashi*; Shinohara, Takenao; Suzuki, Junichi; Shimizu, Hirohiko*

no journal, , 

no abstracts in English

Oral presentation

Neutron induced reaction and Re/Os cosmochronometer, 3

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Shima, Tatsushi*; Makii, Hiroyuki; Mishima, Kenji*; Ueda, Hitoshi*; Temma, Yasuyuki*; Igashira, Masayuki*; Osaki, Toshiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of a highly efficient neutron polarizing device based on a quadrupole magnet

Oku, Takayuki; Yamada, Satoru*; Shinohara, Takenao; Suzuki, Junichi; Mishima, Kenji*; Hirota, Katsuya*; Sato, Hiromi*; Shimizu, Hirohiko

no journal, , 

no abstracts in English

Oral presentation

Nuclear astrophysics study with pulsed neutrons

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Temma, Yasuyuki*; Shima, Tatsushi*; Mishima, Kenji*; Igashira, Masayuki*; Goriely, S.*; Koning, A.*; Hilaire, S.*

no journal, , 

The $$^{187}$$Re nucleus is known to be a good chronometer to derive the stellar duration of the r-process nuceosyntheis and deduce the age of universe. However, there are several problems inherent to this chronometer. In order to solve these problems, one must know both the production and depletion rates (via the excited state as well as the ground state) of $$^{187}$$Os and inelastic scattering cross section off the ground state (J$$^{pi}$$= 1/2$$^{-}$$) of $$^{187}$$Os to its excited 10 keV state (J$$^{pi}$$= 3/2$$^{-}$$) are needed. Hence, in the present study we aimed to accurately measure the neutron capture cross sections of $$^{186}$$Os, $$^{187}$$Os and $$^{189}$$Os, and the inelastic scattering cross section for $$^{187}$$Os for neutrons between 10 and 90 keV by developing a new experimental method.

Oral presentation

Neutron induced reaction and Re/Os chronometer

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Temma, Yasuyuki*; Shima, Tatsushi*; Makii, Hiroyuki*; Mishima, Kenji*; Ueda, Hitoshi*; Nakayoshi, Akira*; Ota, Takeshi*; et al.

no journal, , 

$$^{187}$$Re-$$^{187}$$Os pair is known as the most promising nuclear cosmochronometer with considerable potential. However, there remains non-trivial problems related to an excited neutron capture reaction of $$^{187}$$Os at a stellar temperature. Firstly, $$^{187}$$Os is produced and depleted by the slow process nucleosynthesis. Hence, it is necessary to obtain both the production and depletion rates of $$^{187}$$Os. Secondly, $$^{187}$$Os is depleted not only by its ground state neutron capture reaction but also by an excited state neutron capture reaction of $$^{187}$$Os in a stellar temperature. In the present study, we have measured the neutron capture reaction cross sections for $$^{186}$$Os, $$^{187}$$Os and $$^{189}$$Os accurately and neutron inelastic scattering reaction cross section for $$^{187}$$Os off the ground state of $$^{187}$$Os to its 9.75-keV first excited statein the neutron energy range from 10 to 100 keV. The measurements of the neutron capture reactions have been carried out by detecting a prompt $$gamma$$-ray by means fan anti-Compton NaI(Tl) spectrometer. The (n, n') reaction cross section for $$^{187}$$Os has been measured with use of four $$^{6}$$Li-glass scintillation detectors. Based on these new capture cross sections, we reestimate on the basis of a careful reaction cross section calculation the correction factor F for the neutron capture on the 9.75-keV first excited state in $$^{187}$$Os as a function of stellar temperature, as required to derive the age of the galaxy within the Re-Os chronology.

Oral presentation

Present status of experimental apparatus for neutron optics and physics at J-PARC BL05

Sakai, Kenji; Muto, Suguru*; Ino, Takashi*; Yoshioka, Tamaki*; Mishima, Kenji*; Taketani, Kaoru*; Shimizu, Hirohiko*

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)