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Journal Articles

Controlled growth of boron-doped epitaxial graphene by thermal decomposition of a B$$_{4}$$C thin film

Norimatsu, Wataru*; Matsuda, Keita*; Terasawa, Tomoo; Takata, Nao*; Masumori, Atsushi*; Ito, Keita*; Oda, Koji*; Ito, Takahiro*; Endo, Akira*; Funahashi, Ryoji*; et al.

Nanotechnology, 31(14), p.145711_1 - 145711_7, 2020/04

 Times Cited Count:6 Percentile:39.72(Nanoscience & Nanotechnology)

We show that boron-doped epitaxial graphene can be successfully grown by thermal decomposition of a boron carbide thin film, which can also be epitaxially grown on a silicon carbide substrate. The interfaces of B$$_{4}$$C on SiC and graphene on B$$_{4}$$C had a fixed orientation relation, having a local stable structure with no dangling bonds. The first carbon layer on B$$_{4}$$C acts as a buffer layer, and the overlaying carbon layers are graphene. Graphene on B$$_{4}$$C was highly boron doped, and the hole concentration could be controlled over a wide range of 2$$times$$10$$^{13}$$ to 2$$times$$10$$^{15}$$ cm$$^{-2}$$. Highly boron-doped graphene exhibited a spin-glass behavior, which suggests the presence of local antiferromagnetic ordering in the spin-frustration system. Thermal decomposition of carbides holds the promise of being a technique to obtain a new class of wafer-scale functional epitaxial graphene for various applications.

Journal Articles

Nanostructures and viscosities of nafion dispersions in water/ethanol from dilute to concentrated regimes

Gupit, C. I.*; Li, X.*; Maekawa, Ryosuke*; Hasegawa, Naoki*; Iwase, Hiroki*; Takata, Shinichi; Shibayama, Mitsuhiro*

Macromolecules, 53(4), p.1464 - 1473, 2020/02

Journal Articles

Droplet generation during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Aoyagi, Mitsuhiro; Takata, Takashi

Experimental Thermal and Fluid Science, 98, p.86 - 94, 2018/11

 Times Cited Count:11 Percentile:65.34(Thermodynamics)

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

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

Splash during liquid jet impingement onto a horizontal plate

Zhan, Y.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 6 Pages, 2017/07

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments are performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It is shown that the splash ratio can be correlated well as a function of the impact Weber number and dimensionless impact frequency.

Journal Articles

Production of droplets during liquid jet impingement onto a flat plate

Yi, Z.*; Oya, Naoki*; Enoki, Koji*; Okawa, Tomio*; Ohno, Shuji; Aoyagi, Mitsuhiro; Takata, Takashi

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

It is important to set the amount of sodium droplet mechanistically for appropriate numerical evaluations of sodium leak and fire behavior in a sodium-cooled fast reactor plant. In the present work, fundamental experiments were performed to measure the splash ratio during the vertical water jet impact onto a horizontal wall. It was shown that the splash ratio can be correlated well as a function of the impact Weber number, the Strouhal number and the Ohnesorge number of the droplets impinging the liquid film.

Journal Articles

Gelation process of polyacrylonitrile solutions as studied using small-angle neutron scattering techniques

Nakano, Shota*; Konno, Soken*; Tomita, Naoto*; Matsuba, Go*; Tominaga, Taiki*; Takata, Shinichi

Microsystem Technologies, 22(1), p.57 - 63, 2016/01

 Times Cited Count:2 Percentile:21.1(Engineering, Electrical & Electronic)

We studied the structural formation process of polyacrylonitrile (PAN) gelation in a wide-spatial scale with the small and wide angle neutron scattering in MLF, J-PARC. In micron-scale structure, light transmittance and gelation time were evaluated. The presence of water in the mixed solvent accelerated the phase separation and gelation. In the opaque-gel case, we observed the nanometer-scaled correlation of crystalline cross-linking points and smooth boundary of two micron-scaled phases due to liquid-liquid phase separation. The correlation length is independent of the annealing time, then the cross-linking point exists locally and micro-gelation occurs during phase separation. By contrast, in the transparent-gel case, the correlation length was found to increase throughout the gelation process, and the entanglements of the polymer chains play a role similar to that of cross-linking points.

Journal Articles

Quantitative magnetic field imaging by polarized pulsed neutrons at J-PARC

Shinohara, Takenao; Sakai, Kenji; Oi, Motoki; Kai, Tetsuya; Harada, Masahide; Oikawa, Kenichi; Maekawa, Fujio; Suzuki, Junichi; Oku, Takayuki; Takata, Shinichi; et al.

Nuclear Instruments and Methods in Physics Research A, 651(1), p.121 - 125, 2011/09

 Times Cited Count:26 Percentile:88.02(Instruments & Instrumentation)

no abstracts in English

Journal Articles

ACS cavity for J-PARC LINAC

Ao, Hiroyuki; Asano, Hiroyuki; Ouchi, Nobuo; Tsubota, Naoaki; Hasegawa, Kazuo; Hirano, Koichiro; Morishita, Takatoshi; Takata, Koji*; Naito, Fujio*; Yamazaki, Yoshishige

Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.552 - 554, 2010/08

The energy upgrade of the J-PARC linac was started from March 2009. In this project 20 Annular Coupled Structure (ACS) modules will be fabricated. The resonant frequency of the ACS module has to be tuned with mechanical machining before the final brazing. Therefore the test cells were fabricated to accumulate frequency tuning parameters. We fixed the final dimensions and the machining amount of the frequency tuning using these results. So far, the cell parts for the five ACS modules were tuned within 71.93 $$pm$$ 0.05 MHz. At the moment the first ACS module is being assembled and it will be completed in autumn 2010.

Journal Articles

Imaging experiments on NOBORU at MLF

Harada, Masahide; Oikawa, Kenichi; Oi, Motoki; Kai, Tetsuya; Sakai, Kenji; Maekawa, Fujio; Watanabe, Noboru*; Shinohara, Takenao; Takata, Shinichi

Proceedings of 19th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-19) (CD-ROM), 10 Pages, 2010/07

A neutron beam line NOBORU built at MLF in J-PARC is suitable for imaging experiments due to a large beam size, a short distance from the moderator to the sample position and an adequate experimental room. In order to evaluate suitability for the imaging experiments, we measured neutron spectral intensities and flux distributions at the sample position of NOBORU. We also measured those quantities with use of some filters, collimators and slits equipped on NOBORU. As preliminary experiments for imaging, we measured Bragg edge transmission of some alloys and resonance absorption of some elements. The result showed welded and non-welded areas in an alloy could be clearly distinguished by the Bragg edge transmission. It was also found that several elements in the sample could be distinguished clearly by the resonance absorption method. It could be concluded that NOBORU was very suitable for the imaging experiments at J-PARC.

Journal Articles

Status of mass production of the ACS cavity for the J-PARC linac energy upgrade

Ao, Hiroyuki; Asano, Hiroyuki; Ouchi, Nobuo; Tsubota, Naoaki; Hasegawa, Kazuo; Hirano, Koichiro; Morishita, Takatoshi; Takata, Koji*; Naito, Fujio*; Yamazaki, Yoshishige

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.618 - 620, 2010/05

The mass production of the ACS (Annular-ring Coupled Structure) cavity started from March 2009 for the J-PARC linac energy upgrade from 181 MeV to 400 MeV. This upgrade project requires 18 ACS accelerating modules and two debunchers additionally within three years. The schedule is so tight that we have to optimize the fabrication process. Thus the test cells were fabricated for the all geometrical beta before the mass production to confirm the initial design and the frequency tuning procedure. This paper describes our approach for the mass production and the current status.

Journal Articles

New development in nanostructure analysis by smaller-angle neutron scattering instrument of J-PARC

Suzuki, Junichi; Shinohara, Takenao; Takata, Shinichi; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; Otomo, Toshiya*; Sugiyama, Masaaki*

Nihon Kessho Gakkai-Shi, 50(1), p.24 - 28, 2008/02

no abstracts in English

Oral presentation

High-q performance of the J-PARC small-angle neutron scattering instrument (HI-SANS) for observation of biological molecules with atomic resolution

Takata, Shinichi; Suzuki, Junichi; Shinohara, Takenao; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Otomo, Toshiya*; Arai, Masatoshi

no journal, , 

For the clarification and enhancement of function of biological molecules with nm size, we believe that small-angle neutron scattering measurement in wide-q range giving structural information of the molecules with atomic resolution is important. We have thus designed the high-intensity small-angle neutron scattering instrument HI-SANS for the J-PARC in order to carry out the efficient measurement in wide-q range including high-q range of 1-100 nm$$^{-1}$$. In the design work we have performed Monte Carlo simulation of neutron scattering from typical proteins in solution using the scattering function based on the Debye formula. In this paper we present the q-resolution required from the simulation and then show detector arrangement to realize the q-resolution and counting efficiency expected with the detector arrangement.

Oral presentation

Optics and shieldings designs of HI-SANS for J-PARC

Shinohara, Takenao; Takata, Shinichi; Suzuki, Junichi; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Otomo, Toshiya*; Sugiyama, Masaaki*; Arai, Masatoshi

no journal, , 

no abstracts in English

Oral presentation

Research of data analysis and detector arrangement for HI-SANS in J-PARC

Takata, Shinichi; Suzuki, Junichi; Shinohara, Takenao; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Otomo, Toshiya*; Sugiyama, Masaaki*; Arai, Masatoshi

no journal, , 

For the clarification and enhancement of function of biological molecules with nm size, we believe that small-angle neutron scattering measurement in wide-$$q$$ range giving structural information of the molecules with atomic resolution is important. We have thus designed the high-intensity small-angle neutron scattering instrument HI-SANS for the J-PARC in order to carry out the efficient measurement in wide-$$q$$ range including high-q range of 1$$sim$$100 nm$$^{-1}$$. In order to use effectively the information on the structure over wide-$$q$$ rang, we have performed the simulation of neutron scattering function from typical proteins in solution using Debye formula. The result showed that change of the scattering function from $$q$$ = 0.1 to 5$$[AA $$$$^{-1}$$$$]$$ is important for the new structural analysis which added the information on an internal structure.

Oral presentation

Conceptual design of the smaller-angle neutron scattering instrument HI-SANS for J-PARC

Suzuki, Junichi; Shinohara, Takenao; Takata, Shinichi; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; Otomo, Toshiya*; Sugiyama, Masaaki*

no journal, , 

no abstracts in English

Oral presentation

Development of nanostructure analysis method using data to wide range of q for HI-SANS at J-PARC

Takata, Shinichi; Shinohara, Takenao; Suzuki, Junichi; Oku, Takayuki; Suzuya, Kentaro; Aizawa, Kazuya; Otomo, Toshiya*; Sugiyama, Masaaki*; Arai, Masatoshi

no journal, , 

The high-intensity smaller-angle neutron scattering instrument (HI-SANS) is designed for efficient measurements in wide-q range including higher q range of 1$$times$$10$$^{-3}$$ to 50 [$AA$^{-1}$$]. By obtaining structural information from such wide-q range, the instrument is expected to contribute significantly to clarify hierarchical structures such as protein, polymer, and metal nanoparticles. Heretofore, the analysis method used in conventional SANS instruments was enough to treat the data measured in the q range limited below about 0.2 [$AA$^{-1}$$]. However, for the HI-SANS, it is important to develop a new analysis method, which is taken into account the information of the material structure in atomic scale to micrometer scale. We will present the development of such wide-q analysis method along with the contrast variation analysis of proteins in hydrated water and the reverse Monte Carlo analysis.

Oral presentation

Smaller-angle neutron scattering instrument of J-PARC with polarizing and magnetic focusing options

Suzuki, Junichi; Shinohara, Takenao; Takata, Shinichi; Oku, Takayuki; Kira, Hiroshi; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; Otomo, Toshiya*; Sugiyama, Masaaki*

no journal, , 

Small-angle neutron scattering (SANS) technique has been indispensable in research of microstructures and hierarchical structures in materials science and life science. However, recent progress in nanotechnology and research of complex multi-component or multi-phase systems and non-equilibrium systems has required the SANS technique to enable to produce structural information more efficiently with higher structural and time resolution. The time-of-flight SANS instrument HI-SANS constructed at the 1MW neutron source of J-PARC has potential to satisfy such requirements by simultaneous coverage of wide q-range with high q-resolution by using large area detectors located at positions with short total flight path of neutrons and with polarizing and magnetic focusing devices.

Oral presentation

A High performance neutron polarizer using magnetic super mirrors

Shinohara, Takenao; Takata, Shinichi; Suzuki, Junichi; Oku, Takayuki; Kira, Hiroshi; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; Otomo, Toshiya*; Sugiyama, Masaaki*

no journal, , 

no abstracts in English

Oral presentation

Research of detector arrangement for HI-SANS in J-PARC and wide-range structure analysis with Reverse Monte Carlo method

Takata, Shinichi; Shinohara, Takenao; Suzuki, Junichi; Oku, Takayuki; Kira, Hiroshi; Suzuya, Kentaro; Aizawa, Kazuya; Arai, Masatoshi; Otomo, Toshiya*; Sugiyama, Masaaki*

no journal, , 

no abstracts in English

61 (Records 1-20 displayed on this page)