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Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:86 Percentile:0.14(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Development of beam scrapers using a 3-Mev linac at J-PARC

Hirano, Koichiro; Asano, Hiroyuki; Ishiyama, Tatsuya; Ito, Takashi; Okoshi, Kiyonori; Oguri, Hidetomo; Kondo, Yasuhiro; Kawane, Yusuke; Kikuzawa, Nobuhiro; Sato, Yoshikatsu; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.310 - 313, 2016/11

We have used a beam scraper with the incident angle of 65deg to reduce the beam power deposition density in the MEBT between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC linac. The 65$$^{circ}$$ scraper was irradiated by the H$$^{-}$$ beam up to particle number of 1.47E22. We observed a lot of surface projections with several hundred micrometers high in the beam irradiation damage on the scraper by using the laser microscope. In order to study the limits of scrapers, we constructed a new 3 MeV linac at J-PARC. We will conduct the scraper irradiation test at the end of this year.

Journal Articles

The Concept of dose system for radiological protection

Hirayama, Hideo*; Nakashima, Hiroshi; Sanami, Toshiya*; Yamaguchi, Yasuhiro; Sato, Osamu*; Takagi, Shunji*; Suzuki, Toshikazu*; Iwai, Satoshi*

Nippon Genshiryoku Gakkai-Shi, 55(2), p.83 - 96, 2013/02

Since the accident at the Fukushima Daiichi Power Plant, units of radiation doses such as Sv have been frequently reported by newspapers. However, it is not exactly understood even by experts on nuclear engineering that there are two different concepts which are the protection quantity such as the effective dose related to a radiation health risk and the practical quantity such as ambient dose equivalents related to measurements. In this special issue, Radiological Protection Quantity, and Operational Quantity and Radiological Protection Quantity, explain the radiation protection dose system including the protection and practical quantities established by ICRP and ICRU. Relation between Dosimeters used at Fukushima etc. and Radiological Protection Quantity describes a method and its problems to measure radiations from Cs on surface and underground using survey meters and personal dosimeters, and convert the measured values to effective doses.

Journal Articles

Magnetic structure and local lattice distortion in giant negative thermal expansion material Mn$$_{3}$$Cu$$_{1-x}$$Ge$$_{x}$$N

Iikubo, Satoshi*; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

Journal of Physics; Conference Series, 251, p.012014_1 - 012014_4, 2010/12

 Times Cited Count:3 Percentile:20.21

Journal Articles

Evaluation of susceptibility to stress corrosion cracking based on non-linear eddy current method

Oikawa, Ryota*; Uchimoto, Tetsuya*; Takagi, Toshiyuki*; Urayama, Ryoichi*; Nemoto, Yoshiyuki; Takaya, Shigeru; Keyakida, Satoshi*

International Journal of Applied Electromagnetics and Mechanics, 33(3-4), p.1303 - 1308, 2010/10

 Times Cited Count:4 Percentile:66.7(Engineering, Electrical & Electronic)

This paper discusses feasibility of non-linear eddy current method to evaluate material degradations of austenitic stainless steels associated with irradiation assisted stress corrosion cracking (IASCC). For the purpose, tensile test at elevated temperature was conducted using model alloys simulating radiation induced segregation (RIS), then magnetization curve of the specimens was measured by vibrating sample magnetometer (VSM), and microstructure of magnetization was observed by magnetic force microscopy (MFM). Moreover non-linear eddy current method was carried out. It was shown that the 3rd higher harmonic ration of the pick-up signal would relate to nominal strain of the specimens.

Journal Articles

Gradual development of $$Gamma^{5g}$$ antiferromagnetic moment in the giant negative thermal expansion material Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N ($$xsim$$ 0.5)

Kodama, Katsuaki; Iikubo, Satoshi*; Takenaka, Koshi*; Takigawa, Masashi*; Takagi, Hidenori*; Shamoto, Shinichi

Physical Review B, 81(22), p.224419_1 - 224419_8, 2010/06

 Times Cited Count:37 Percentile:17.47(Materials Science, Multidisciplinary)

Journal Articles

Microbeam irradiation facilities for radiobiology in Japan and China

Kobayashi, Yasuhiko; Funayama, Tomoo; Hamada, Nobuyuki*; Sakashita, Tetsuya; Konishi, Teruaki*; Imaseki, Hitoshi*; Yasuda, Keisuke*; Hatashita, Masanori*; Takagi, Keiichi*; Hatori, Satoshi*; et al.

Journal of Radiation Research, 50(Suppl.A), p.A29 - A47, 2009/03

 Times Cited Count:32 Percentile:27.32(Biology)

Journal Articles

Local lattice distortion in the giant negative thermal expansion material Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N

Iikubo, Satoshi*; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Takigawa, Masashi*; Shamoto, Shinichi

Physical Review Letters, 101(20), p.205901_1 - 205901_4, 2008/11

 Times Cited Count:140 Percentile:3.34(Physics, Multidisciplinary)

Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering is broadened by substitution. In this Letter, we address the unique role of the "magic" element, Ge, for such broadening in Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N. We present evidence for a local lattice distortion well described by the low-temperature tetragonal (${it T$_{4}$}$) structure of Mn$$_3$$GeN for a range of $$x$$, where the overall structure remains cubic. This structural instability shows a strong correlation with the broadness of the growth of the ordered magnetic moment and, hence, is considered to trigger the broadening of the volume change.

Journal Articles

Angle-correlated spectrum measurement for two neutrons emitted from (n,2n) reaction with the coincidence detection technique using a pencil-beam DT neutron source

Murata, Isao*; Takagi, Satoshi*; Kondo, Keitaro; Shiken, Kimiaki*; Miyamaru, Hiroyuki*; Mitsuda, Motoyuki; Maekawa, Fujio; Ochiai, Kentaro; Nishitani, Takeo

Nuclear Instruments and Methods in Physics Research A, 595(2), p.439 - 446, 2008/10

 Times Cited Count:3 Percentile:69.48(Instruments & Instrumentation)

A technique was developed to measure the angle-correlated neutron energy spectrum with the coincidence detection technique using a pencil-beam DT neutron source at the Fusion Neutronics Source (FNS) of the Japan Atomic Energy Agency (JAEA). Triple differential cross-sections of the $$^{55}$$Mn(n,2n) reaction were measured first, from which the total $$^{55}$$Mn(n,2n) reaction cross-section was deduced and compared with JENDL-3.3. The agreement was sufficient to prove the validity of the technique. With the present measuring technique, a complete measurement of a medium-heavy or heavy element such as manganese would become possible through several measurements, because the angle dependence of the emitted neutrons from it is normally weak. The technique will be a useful tool for measuring the angle-correlated neutron spectrum of light elements such as beryllium for investigation of their complicated nuclear reaction mechanism.

Journal Articles

Measurement of the angle-correlated neutron spectrum for the $$^{9}$$Be(n,2n) reaction with a pencil-beam DT neutron source

Murata, Isao*; Takagi, Satoshi*; Shiken, Kimiaki*; Kondo, Keitaro; Miyamaru, Hiroyuki*; Ochiai, Kentaro; Nishitani, Takeo; Konno, Chikara

Proceedings of International Conference on Nuclear Data for Science and Technology (ND 2007), Vol.2, p.999 - 1002, 2008/05

The (n,2n) reaction plays a very important role in the design of fusion reactor. In the present study, using a pencil-beam DT neutron source, angle-correlated two neutrons emitted through (n,2n) reaction have directly been measured to determine (n,2n) reaction cross section with the coincidence detection technique for beryllium which is the most important element in the fusion reactor. In the experiment, two NE213 detectors were arranged very close to the sample to efficiently measure the two neutrons. The measured spectra were unfolded by FORIST with the detector response matrix evaluated by SCINFUL. As a relust, comparing with the evaluations of ENDF/B-VI and JENDL-3.3 for energies above 800 keV of the lower measurable limit energy, the shape of derived angula-differential cross-section fits JENDL-3.3 better than ENDF/B-VI. However, agreement of the cross section of (n,2n) above 800 keV was acceptable within 10 percents for both libraries.

Journal Articles

Magnetovolume effect in Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N related to the magnetic structure; Neutron powder diffraction measurements

Iikubo, Satoshi; Kodama, Katsuaki; Takenaka, Koshi*; Takagi, Hidenori*; Shamoto, Shinichi

Physical Review B, 77(2), p.020409_1 - 020409_4, 2008/01

 Times Cited Count:91 Percentile:5.57(Materials Science, Multidisciplinary)

Magnetic structures in an antiperovskite system Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N with a large magneto-volume effect above $$x$$=0.15 have been studied by neutron powder diffraction measurement. The present neutron study revealed that not only a cubic crystal structure, but also a $$Gamma^{5g}$$ antiperovskite spin structure, is a key ingredient of the large magneto-volume effect in this itinerant electron system. The large magneto-volume effect is possibly ascribed to the geometrical frustration originating from the corner-shared octahedra of the antiperovskite sturucture.

Journal Articles

Verification of nuclear data for DT neutron induced charged-particle emission reaction of light nuclei

Kondo, Keitaro; Murata, Isao*; Ochiai, Kentaro; Kubota, Naoyoshi; Miyamaru, Hiroyuki*; Takagi, Satoshi*; Shido, Shoichi*; Konno, Chikara; Nishitani, Takeo

Fusion Engineering and Design, 82(15-24), p.2786 - 2793, 2007/10

 Times Cited Count:2 Percentile:79.6(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Current status of the control system for J-PARC accelerator complex

Yoshikawa, Hiroshi; Sakaki, Hironao; Sako, Hiroyuki; Takahashi, Hiroki; Shen, G.; Kato, Yuko; Ito, Yuichi; Ikeda, Hiroshi*; Ishiyama, Tatsuya*; Tsuchiya, Hitoshi*; et al.

Proceedings of International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS '07) (CD-ROM), p.62 - 64, 2007/10

J-PARC is a large scale facility of the proton accelerators for the multi-purpose of scientific researches in Japan. This facility consists of three accelerators and three experimental stations. Now, J-PARC is under construction, and LINAC is operated for one year, 3GeV synchrotron has just started the commissioning in this October the 1st. The completion of this facility will be next summer. The control system of accelerators established fundamental performance for the initial commissioning. The most important requirement to the control system of this facility is to minimize the activation of accelerator devices. In this paper, we show that the performances of each layer of this control system have been achieved in the initial stage.

Journal Articles

Charged-particle spectrometry using a pencil-beam DT neutron source for double-differential cross-section measurement

Kondo, Keitaro; Murata, Isao*; Ochiai, Kentaro; Miyamaru, Hiroyuki*; Kubota, Naoyoshi; Takagi, Satoshi*; Shido, Shoichi*; Takahashi, Akito*; Nishitani, Takeo

Nuclear Instruments and Methods in Physics Research A, 568(2), p.723 - 733, 2006/12

 Times Cited Count:14 Percentile:27.6(Instruments & Instrumentation)

Deuteron-tritium (DT) neutron induced charged-particle emission double-differential cross section (DDXc) is quite important to estimate nuclear heating, material damages for a fusion reactor. In order to realize the accurate measurement of the DDXc data especially for light nuclei, we propose a unique spectrometer system and a data processing method in this paper. The spectrometer overcomes the fundamental difficulty of the DDXc measurement with a pencil-beam neutron source and a counter telescope consisting of silicon surface barrier detectors. A superior S/N ratio, fine energy and angular resolutions, a wide detection energy range, and a excellent particle discrimination are realized. In order to confirm the validity of the spectrometer, measurements of the emitted $$alpha$$-particle from $$^{27}$$Al(${it n,x$alpha$}$) reaction and the recoiled proton from $$^{1}$$H(${it n,n}$) reaction are carried out. Based on the results, we conclude the validity and the superiority of the present spectrometry technique.

Journal Articles

Structural transformation on the pressure-induced metal-insulator transition in PrFe$$_{4}$$4P$$_{12}$$

Kawana, Daichi*; Kuwahara, Keitaro*; Sato, Masashi*; Takagi, Masatoshi*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*; Sagayama, Hajime*; Osakabe, Toyotaka; Iwasa, Kazuaki*; et al.

Journal of the Physical Society of Japan, 75(11), p.113602_1 - 113602_4, 2006/11

 Times Cited Count:11 Percentile:41.41(Physics, Multidisciplinary)

We report the first X-ray diffraction experiments of PrFe$$_{4}$$P$$_{12}$$ under high pressure. We discovered a symmetry lowering from cubic to orthorhombic or lower at the metal-insulator transition temperature, accompanied by a jump in the lattice constant, which indicates a first-order phase transition. The superlattice reflections at q=(1,0,0) observed in the low-pressure nonmagnetic ordered phase are found to disappear in the insulating phase. The temperature dependence of the lattice constant and the absence of the superlattice reflections are well explained by taking into account an antiferromagnetic ordering.

Journal Articles

New approach to measure double-differential charged-particle emission cross sections of several materials for a fusion reactor

Kondo, Keitaro; Takagi, Satoshi*; Murata, Isao*; Miyamaru, Hiroyuki*; Takahashi, Akito*; Kubota, Naoyoshi; Ochiai, Kentaro; Nishitani, Takeo

Fusion Engineering and Design, 81(8-14), p.1527 - 1533, 2006/02

 Times Cited Count:12 Percentile:32.43(Nuclear Science & Technology)

In a fusion reactor development, double-differential charged-particle emission cross sections(DDXc) are necessary to estimate nuclear heating and material damages of candidate materials irradiated with neutrons. Especially in light nuclei such as Be, Li, and C, nuclear reactions are complicated and difficult to estimate energy spectra of emitted particles based only on theoretical calculations Therefore development of a new technique for precise measurements of DDXc is quite important. Recently we successfully developed a new spectrometer for measurement of DDXc using a pencil-beam DT neutron source of FNS in JAERI. In the present study we carried out measurements of DDXc of $$^{9}$$Be, $$^{12}$$C, $$^{19}$$F, and $$^{27}$$Al using the spectrometer. The present technique was valid from the result of measurement for the $$^{27}$$Al(n,x$$alpha$$) reactions. Slight differences appeared between measured data and evaluation or previous experimental values for $$^{9}$$Be(n,x$$alpha$$) reactions at backward scattering angle and in lower energy region.

Journal Articles

Research of disease onset mechanism by determining the distribution of intracellular trace elements using an in-air micro-PIXE analyzer system

Nakano, Takashi*; Arakawa, Kazuo; Sakurai, Hideyuki*; Hasegawa, Masatoshi*; Yuasa, Kazuhisa*; Saito, Etsuko*; Takagi, Hitoshi*; Nagamine, Takeaki*; Kusakabe, Takahiko*; Takada, Hisashi*; et al.

International Journal of PIXE, 16(1-2), p.69 - 76, 2006/00

A new program was started out to create a new medical scientific field, which is consisting of radiation oncology and nuclear medicine, utilizing the advanced accelerator and ion beam technology. An in-air micro-PIXE analyzer system, which is among the most important technical basis of the program, was upgraded to improve accuracy of elemental mapping for samples having thickness variation in a scope of microbeam scanning. In the program, on the other hand, in order to approach important bio-medical problems on cancer, intracellular dynamics of the trace elements according to mechanism of development of diseases were studied using this system. This paper outlines this program and shows the system upgraded, and results of preliminary studied about the problems.

Journal Articles

Progress in physics and technology developments for the modification of JT-60

Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.

Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02

 Times Cited Count:2 Percentile:92.85(Physics, Fluids & Plasmas)

The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-$$beta$$. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

no abstracts in English

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

 Times Cited Count:33 Percentile:27.44(Physics, Fluids & Plasmas)

no abstracts in English

41 (Records 1-20 displayed on this page)