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Journal Articles

Out-of-plane strain induced in a Moir$'e$ superstructure of monolayer MoS$$_{2}$$ and MoSe$$_{2}$$ on Au(111)

Yasuda, Satoshi; Takahashi, Ryosuke*; Osaka, Ryo*; Kumagai, Ryota*; Miyata, Yasumitsu*; Okada, Susumu*; Hayamizu, Yuhei*; Murakoshi, Kei*

Small, 13(31), p.1700748_1 - 1700748_8, 2017/08

 Times Cited Count:17 Percentile:65.47(Chemistry, Multidisciplinary)

MoS$$_{2}$$ and MoSe$$_{2}$$ monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out-of-plane strain in both MoS$$_{2}$$ and MoSe$$_{2}$$ layers, whereas no strain generation is observed on polycrystalline Au or SiO$$_{2}$$/Si surfaces. Scanning tunneling microscopy analysis provides information regarding consequent specific adsorption sites between lower S (Se) atoms in the S-Mo-S (Se-Mo-Se) structure and Au atoms via unique moir$'e$ superstructure formation for MoS$$_{2}$$ and MoSe$$_{2}$$ layers on Au(111). This observation indicates that the specific adsorption sites give rise to out-of-plane strain in the TMDC layers. Furthermore, it also leads to effective modulation of the electronic structure of the MoS$$_{2}$$ or MoSe$$_{2}$$ layer.

Journal Articles

Simulation of discharge in insulating gas from initial partial discharge to growth of a stepped leader using the percolation model

Sasaki, Akira; Kato, Susumu*; Takahashi, Eiichi*; Kishimoto, Yasuaki*; Fujii, Takashi*; Kanazawa, Seiji*

Japanese Journal of Applied Physics, 55(2), p.026101_1 - 026101_10, 2016/02

 Times Cited Count:2 Percentile:9.97(Physics, Applied)

A percolation model of discharge, which can reproduce stochastic behaviors of initial partial discharge to the growth of a stepped leader, is presented. The model uses macroscopic cells, from which a network of electric circuits is defined, and the spatial and temporal evolutions of the electric field and current in the discharge medium are calculated. For each cell, one of two states, either insulator or conductor, which corresponds to neutral gas or ionized plasmas, respectively, is decided. The decision is made on the basis of probability for each calculation cell at each time step, taking the effects of local electric field and current, which enhance ionization and sustain the discharge channel, respectively, into account. The stochastic behavior of discharge is discussed, in conjunction with the characteristic feature of ionization, that is, the ionization occurs not only ahead of the streamer tip where the electric field is enhanced but randomly in the discharge medium.

Journal Articles

J-PARC E19 experiment; Pentaquark $$Theta^+$$ search in hadronic reaction at J-PARC

Takahashi, Tomonori*; Ekawa, Hiroyuki; Hayakawa, Shuhei; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi; Sako, Hiroyuki; Sato, Susumu; Sugimura, Hitoshi; Tanida, Kiyoshi; et al.

JPS Conference Proceedings (Internet), 8, p.022011_1 - 022011_6, 2015/09

Journal Articles

Detailed deposition density maps constructed by large-scale soil sampling for $$gamma$$-ray emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant accident

Saito, Kimiaki; Tanihata, Isao*; Fujiwara, Mamoru; Saito, Takashi*; Shimoura, Susumu*; Otsuka, Takaharu*; Onda, Yuichi*; Hoshi, Masaharu*; Ikeuchi, Yoshihiro*; Takahashi, Fumiaki; et al.

Journal of Environmental Radioactivity, 139, p.308 - 319, 2015/01

 Times Cited Count:216 Percentile:98.85(Environmental Sciences)

Journal Articles

Depth profiles of radioactive cesium in soil using a scraper plate over a wide area surrounding the Fukushima Dai-ichi Nuclear Power Plant, Japan

Matsuda, Norihiro; Mikami, Satoshi; Shimoura, Susumu*; Takahashi, Junko*; Nakano, Masakazu; Shimada, Kiyotaka*; Uno, Kiichiro; Hagiwara, Shigetomo; Saito, Kimiaki

Journal of Environmental Radioactivity, 139, p.427 - 434, 2015/01

 Times Cited Count:98 Percentile:94.55(Environmental Sciences)

Journal Articles

Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; Hasegawa, Shoichi; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.

Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04

 Times Cited Count:3 Percentile:16.37(Instruments & Instrumentation)

A TPC has been developed for J-PARC E42 experiment to search for H-dibaryon in ($$K^-$$, $$K^+$$) reaction. An event with 2 $$pi^-$$ and 2 protons decaying from H-dibaryon is searched for inside the TPC. The TPC has octagonal prism shape drift volume with about 50 cm diameter with 55 cm drift length filled with Ar-CH$$_{4}$$ (90:10) gas. At the end of the drift volume, 3-layer GEMs are equipped. In order to analyze momenta of produced particles, the TPC is applied with 1 T dipole magnetic field parallel to the drift electric field with a superconducting Helmholz magnet. In order to maximize the acceptance of H-dibaryon events, a diamond target is installed inside the TPC drift volume, in a cylindrical hole opened from the top to the middle of the drift volume. Since extremely high-rate $$K^-$$ beam is directly injected into the TPC drift volume to the target, a gating grid and GEMs are adopted to suppress positive-ion feedback.

Journal Articles

A Percolation model of the streamer discharges

Sasaki, Akira; Kato, Susumu*; Takahashi, Eiichi*; Kanazawa, Seiji*

JPS Conference Proceedings (Internet), 1, p.015029_1 - 015029_4, 2014/03

Although streamer discharges have long been studied, the mechanism of sudden formation of the complex discharge path has not been fully understood. We show that a simulation based on the percolation model reproduces such development of the streamer. In the model, the discharge medium is divided into cells and is considered to form an electrical circuit network, which is used to calculate the current. In contrast to the characteristic feature of a single electron avalanche is explained by the Townsend theory, when the size of the system becomes greater, random formation of the avalanche in the medium and connection between them determines the propagation of the steamer, which is analyzed using the percolation model. Figure shows the simulated discharge from the initial pre-discharge activity near the electrode to rapid growth of the stepped leader, which causes breakdown.

Journal Articles

Cryogenic structures of superconducting coils for fusion experimental reactor "ITER"

Nakajima, Hideo; Shimamoto, Susumu*; Iguchi, Masahide; Hamada, Kazuya; Okuno, Kiyoshi; Takahashi, Yoshikazu

Teion Kogaku, 48(10), p.508 - 516, 2013/10

JAEA is procuring both structural materials and structural design of Toroidal Field (TF) coil and Central Solenoid (CS) for ITER. Although 316LN is used in the most parts of the superconducting magnets system, the cryogenic stainless steels, JJ1 and JK2LB, which were newly developed by JAEA and Japanese steel companies, are used in the highest stress area of TF coil case and whole CS conductor jackets, respectively. These two materials became commercially available based on demonstration of productivity and weldability of materials, and evaluations of 4 K mechanical properties of trial products including welded parts. In order to simplify quality control in mass production, JAEA has used materials specified in the material section of "Codes for Fusion Facilities - Rules on Superconducting Magnet Structure (2008)" issued by the Japan Society of Mechanical Engineers (JSME). The design of structural materials, production technology and quality control are described in this paper.

Journal Articles

Evolution of cryogenic structural material development for superconducting coils in fusion reactor

Shimamoto, Susumu*; Nakajima, Hideo; Takahashi, Yoshikazu

Teion Kogaku, 48(2), p.60 - 67, 2013/03

JAEA started development of cryogenic structural material for Tokomak fusion reactor 30 years ago. Because, there was no specialized steel and mechanical data at 4K, JAEA settled target of mechanical characteristics which should satisfy requirements for coil structure at 4K and equipped evaluation facilities at 4K such as tensile test, fatigue test and so on. On the other hand JAEA initiated collaboration with steel industries in order to realize new cryogenic structural material and carried out mechanical evaluation at 4K on numerous samples which were supplied from industries. JAEA contributed standardization of these testing methods at 4K specified in the Japanese industrial standards (JIS). JAEA also supported to establish a construction code for structure of superconducting coil for fusion facility at the Japan Society of Mechanical Engineer (JSME), which is used in manufacture of the ITER toroidal field coil. This paper describes history over 30 years on the material development.

Journal Articles

Single-shot observation of growing streamers using an ultrafast camera

Takahashi, Eiichi*; Kato, Susumu*; Furutani, Hirohide*; Sasaki, Akira; Kishimoto, Yasuaki*; Takada, Kenji*; Matsumura, Satoshi*; Sasaki, Hiroyasu*

Journal of Physics D; Applied Physics, 44(30), p.302001_1 - 302001_4, 2011/08

 Times Cited Count:7 Percentile:31.56(Physics, Applied)

A recently developed ultrafast camera that can acquire $$10^8$$ frames per second was used to investigate positive streamer discharge. It enabled single-shot evaluation of streamer evolution without the need to consider shot-to-shot reproducibility. This camera was used to investigate streamers in argon. Growing branches, the transition when a streamer forms a return stroke, and related phenomena were clearly observed.

Journal Articles

Controlling branching in streamer discharge by laser background ionization

Takahashi, Eiichi*; Kato, Susumu*; Sasaki, Akira; Kishimoto, Yasuaki*; Furutani, Hirohide*

Journal of Physics D; Applied Physics, 44(7), p.075204_1 - 075204_6, 2011/02

 Times Cited Count:20 Percentile:63.28(Physics, Applied)

Positive streamer branching in atmospheric argon gas was controlled by a KrF laser irradiation. This laser irradiation changes the amount of background ionization before the streamer discharge. Initial electron density formed by the KrF laser was evaluated by measuring ionization current. Characteristic "feather like" branching structure was observed and was suppressed only for the irradiated region. The threshold of ionization density which can influence to the branching was evaluated to be 5$$times$$10$$^{5}$$/cm$$^{3}$$. This suppression behavior was explained by the relation between a size of avalanche head and mean initial electron distance. These experimental results support the origin of the feather like structure comes from the branching model of Loeb-Meek that is probabilistic merging of individual avalanches.

Journal Articles

Percolation simulation of laser-guided electrical discharges

Sasaki, Akira; Kishimoto, Yasuaki*; Takahashi, Eiichi*; Kato, Susumu*; Fujii, Takashi*; Kanazawa, Seiji*

Physical Review Letters, 105(7), p.075004_1 - 075004_4, 2010/08

 Times Cited Count:10 Percentile:55.56(Physics, Multidisciplinary)

A three-dimensional simulation of laser guided-discharges based on the percolation is presented. The model includes both local growth of a streamer due to the enhanced electric field at the tip and propagation of a leader by remote ionization such that caused by runaway electrons. The stochastic behavior of the discharge through preformed plasma channel is reproduced by the calculation, which shows complex path with detouring and bifurcation. The probability of guiding is investigated with respect to the ionized, conductive fraction along the channel.

Journal Articles

Simulation of initial discharge path using combined percolation and electric circuit model

Sasaki, Akira; Takahashi, Eiichi*; Kato, Susumu*; Kishimoto, Yasuaki*

Denki Gakkai Parusu Pawa, Hoden Godo Kenkyukai Shiryo (PPT-09-95, ED-09-139), p.9 - 13, 2009/10

A new simulation model of the initiation of high pressure discharge is presented. The model reproduces branching and detouring properties of the discharge path. The model is based on combined random percolation and electric circuit models. We show that the idea of phase transition allows one to renormalize the effect of elementary atomic processes and to perform calculation of the discharge path with a realistic scale (mm to km). As a simple application of the model, discharge through a pre-ionized channel created by a laser irradiation, is investigated, which shows stochastic behaviors of the discharge guiding.

Journal Articles

Numerical modeling of atomic-molecule processes for discharge and lighting

Kato, Susumu*; Takahashi, Eiichi*; Sasaki, Akira; Kishimoto, Yasuaki*

Purazuma, Kaku Yugo Gakkai-Shi, 84(8), p.477 - 483, 2008/08

no abstracts in English

Journal Articles

The H-Invitational Database (H-InvDB); A Comprehensive annotation resource for human genes and transcripts

Yamasaki, Chisato*; Murakami, Katsuhiko*; Fujii, Yasuyuki*; Sato, Yoshiharu*; Harada, Erimi*; Takeda, Junichi*; Taniya, Takayuki*; Sakate, Ryuichi*; Kikugawa, Shingo*; Shimada, Makoto*; et al.

Nucleic Acids Research, 36(Database), p.D793 - D799, 2008/01

 Times Cited Count:51 Percentile:71.65(Biochemistry & Molecular Biology)

Here we report the new features and improvements in our latest release of the H-Invitational Database, a comprehensive annotation resource for human genes and transcripts. H-InvDB, originally developed as an integrated database of the human transcriptome based on extensive annotation of large sets of fulllength cDNA (FLcDNA) clones, now provides annotation for 120 558 human mRNAs extracted from the International Nucleotide Sequence Databases (INSD), in addition to 54 978 human FLcDNAs, in the latest release H-InvDB. We mapped those human transcripts onto the human genome sequences (NCBI build 36.1) and determined 34 699 human gene clusters, which could define 34 057 protein-coding and 642 non-protein-coding loci; 858 transcribed loci overlapped with predicted pseudogenes.

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

Innovative alpha-radioactivity monitor for clearance level inspection based on ionized air transportation technology, 1; Comparison with mass spectral analysis using uranium-attached samples

Aoyama, Yoshio; Miyamoto, Yasuaki; Yamaguchi, Hiromi; Sano, Akira*; Naito, Susumu*; Sumida, Akio*; Izumi, Mikio*; Maekawa, Tatsuyuki*; Sato, Mitsuyoshi*; Nambu, Kenichi*; et al.

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 6 Pages, 2007/04

no abstracts in English

Journal Articles

The Japanese approach to developing clay-based repository concepts; An Example of design studies for the assessment of sealing strategies

Sugita, Yutaka; Fujita, Tomoo; Takahashi, Yoshiaki*; Kawakami, Susumu; Umeki, Hiroyuki; Yui, Mikazu; Uragami, Manabu*; Kitayama, Kazumi*

Physics and Chemistry of the Earth, 32(1-7), p.32 - 41, 2007/00

 Times Cited Count:6 Percentile:20.97(Geosciences, Multidisciplinary)

The H12 repository concept for vitrified high-level radioactive waste was developed based on a multi-barrier system with the emphasis on robust engineered barrier performance to ensure its feasibility for a wide range of geological conditions typically observed in Japan. The buffer is clay-based and plays a very important role in the engineered barrier system (EBS). The decision to use a volunteer siting process requires maximum flexibility of the repository concept to allow it to be adapted to potential sites and hence a wide range of variants of the basic H12 repository design has been developed. In order to evaluate the feasibility and the applicability of different repository options to specific siting environments, NUMO has established a set of "design factors" which classify the aspects that need to be considered when evaluating the pros and cons of different repository options. A Na-type bentonite from Japan is used as the reference material for all clay-based repository components (buffer, backfill, clay plug, etc.). The characteristics of this bentonite (thermal, mechanical, chemical, hydraulic) have been examined with consideration of various practical constraints (limitation on the repository footprint, the influence of saline water, the interaction of hyperalkaline leachates and practical working environment, etc.). Clay-based seals, which close off the tunnels after emplacement of the EBS, may also be key components for assessment of the repository. Full analyses considering all engineered barrier components (buffer, backfill, clay plug, concrete lining, tunnel, concrete plug, host rock) that may be used in a repository will be an essential future task. As a first step towards this goal, a numerical analysis focusing on hydraulic behaviour at the intersections of the disposal tunnels and the main tunnel is presented to illustrate how the design requirements of clay-based seals can be determined.

Journal Articles

"ITER" International Thermonuclear Experimental Reactor; From the engineering design activity to the construction phase

Shimamoto, Susumu*; Takahashi, Yoshikazu; Okuno, Kiyoshi

Teion Kogaku, 41(12), p.542 - 552, 2006/12

The purpose of this paper is to explain, from the aspect of superconducting coil system, the concept of ITER (International Thermonuclear Experimental Reactor) to be constructed in France by means of international collaboration of the seven parties. The specifications and results of R&D on superconducting model coils, which were performed during the Engineering Design Activity, were compared with the final design of ITER. The identification of the relevance of model coils to full scale ITER coils and their limitations as well are discussed from the technical and project manage point of view.

JAEA Reports

Discussion on sealing performance required to disposal system; Hydraulic analysis considering intersections of tunnels

Sugita, Yutaka*; Fujita, Tomoo; Takahashi, Yoshiaki*; Kawakami, Susumu; Umeki, Hiroyuki; Yui, Mikazu; Uragami, Manabu*

JNC TN8400 2005-016, 49 Pages, 2005/09


The sealing performance of a repository should be considered in the safety assessment of the geological disposal system of the high level radioactive waste. Nuclear Waste Management Organization of Japan and Japan Nuclear Cycle Development Institute are examining the sealing performance of the closure components (backfilling material and clay plug) to present the concept on the sealing performance required to the disposal system, and to develop the direction for the future R&D programme for the design requirements of the closure components of the presented concepts.The first step of this examination reviewed the current status of the domestic and the international sealing technologies, summarized the repository components and the repository environments, and performed the hydraulic analysis considering components on the intersections of a main tunnel and a disposal tunnel in a disposal panel and in and around the engineered barrier system (EBS). Since all tunnels connect in the underground facility, understanding of hydraulic behaviour at the intersections of the tunnels is the important issue to estimate migration of radionuclides from the EBS, and to evaluate the required sealing performance for the disposal system. The considering components in the analysis model are the intersections of the disposal tunnel and the main tunnel, the waste package, the EBS, the backfilling material, the clay plug, the concrete plug, the excavated disturbed zone, the tunnel lining and the host rock. Alteration of the concrete material (tunnel lining and concrete plug) is described as variation of the hydraulic conductivity of it. Sites of emplacement of the clay plug are the disposal tunnel and the main tunnel. No clay plug condition is also analysed. Effect of the clay plug is discussed by the results of these analyses.

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