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Journal Articles

Step unbunching phenomenon on 4H-SiC (0001) surface during hydrogen etching

Sakakibara, Ryotaro*; Bao, J.*; Yuhara, Keisuke*; Matsuda, Keita*; Terasawa, Tomoo; Kusunoki, Michiko*; Norimatsu, Wataru*

Applied Physics Letters, 123(3), p.031603_1 - 031603_4, 2023/07

 Times Cited Count:0 Percentile:59.51

We here report a step unbunching phenomenon, which is the inverse of the phenomenon of step bunching. When a 4H-SiC (0001) surface is annealed at a high temperature, step bunching arises due to the different velocities of the step motion in adjacent steps, resulting in steps with a height of more than several nanometers. We found that the bunched steps, thus, obtained by hydrogen etching in an Ar/H$$_{2}$$ atmosphere were "unbunched" into lower height steps when annealed subsequently at lower temperatures. This unbunching phenomenon can be well explained by the consequence of the competition between energetics and kinetics. Our findings provide another approach for the surface smoothing of SiC by hydrogen etching and may give significant insight into the application of SiC power devices and two-dimensional materials growth techniques in general.

Journal Articles

Measurement of nuclide production cross sections for proton-induced reactions on $$^{rm nat}$$Ni and $$^{rm nat}$$Zr at 0.4, 1.3, 2.2, and 3.0 GeV

Takeshita, Hayato*; Meigo, Shinichiro; Matsuda, Hiroki*; Iwamoto, Hiroki; Nakano, Keita; Watanabe, Yukinobu*; Maekawa, Fujio

Nuclear Instruments and Methods in Physics Research B, 527, p.17 - 27, 2022/09

 Times Cited Count:0 Percentile:56.43(Instruments & Instrumentation)

To improve accuracy of nuclear design of accelerator driven nuclear transmutation systems and so on, nuclide production cross sections on Ni and Zr were measured for GeV energy protons. The measured results were compared with PHITS calculations, JENDL/HE-2007 and so on.

Journal Articles

Extended X-ray absorption fine structure spectroscopy measurements and ${it ab initio}$ molecular dynamics simulations reveal the hydration structure of the radium(II) ion

Yamaguchi, Akiko; Nagata, Kojiro*; Kobayashi, Keita; Tanaka, Kazuya; Kobayashi, Toru; Tanida, Hajime; Shimojo, Kojiro; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.

iScience (Internet), 25(8), p.104763_1 - 104763_12, 2022/08

 Times Cited Count:3 Percentile:54.33(Multidisciplinary Sciences)

no abstracts in English

JAEA Reports

Measurement of nuclide production cross-sections in high-energy proton-induced spallation reactions at J-PARC

Nakano, Keita; Matsuda, Hiroki*; Meigo, Shinichiro; Iwamoto, Hiroki; Takeshita, Hayato*; Maekawa, Fujio

JAEA-Research 2021-014, 25 Pages, 2022/03

JAEA-Research-2021-014.pdf:2.1MB

For the development of accelerator-driven transmutation system (ADS), measurement of nuclide production cross-sections in proton-induced reactions on $$^9$$Be, C, $$^{27}$$Al, $$^{45}$$Sc, and V have been performed. The measured data are compared with the calculations by the latest nuclear reaction models and with the nuclear data library to investigate the reproducibilities.

Journal Articles

Investigation of hydration and adsorption structures on clay minerals of radium by EXAFS

Yamaguchi, Akiko; Nagata, Kojiro*; Tanaka, Kazuya; Kobayashi, Keita; Kobayashi, Toru; Shimojo, Kojiro; Tanida, Hajime; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.

Hosha Kagaku, (45), p.28 - 30, 2022/03

no abstracts in English

Journal Articles

Nuclide production cross section of $$^{nat}$$Lu target irradiated with 0.4-, 1.3-, 2.2-, and 3.0-GeV protons

Takeshita, Hayato; Meigo, Shinichiro; Matsuda, Hiroki; Iwamoto, Hiroki; Nakano, Keita; Watanabe, Yukinobu*; Maekawa, Fujio

JAEA-Conf 2021-001, p.207 - 212, 2022/03

Prediction of nuclide production of spallation products by high-energy proton injection plays a fundamental and important role in shielding design of high-intensity proton accelerator facilities such as accelerator driven nuclear transmutation system (ADS). Since the prediction accuracy of the nuclear reaction models used in the production quantity prediction simulation is insufficient, it is necessary to improve the nuclear reaction models. We have measured nuclide production cross sections for various target materials with the aim of acquiring experimental data and improving nuclear reaction models. In this study, 1.3-, 2.2- and 3.0-GeV proton beams were irradiated to $$^{nat}$$Lu target, and nuclide production cross-section data were acquired by the activation method. The measured data were compared with several nuclear reaction models used in Monte Carlo particle transport calculation codes to grasp the current prediction accuracy and to study how the nuclear reaction model could be improved.

Journal Articles

Measurement of nuclide production cross sections for proton-induced reactions on Mn and Co at 1.3, 2.2, and 3.0 GeV

Takeshita, Hayato*; Meigo, Shinichiro; Matsuda, Hiroki*; Iwamoto, Hiroki; Nakano, Keita; Watanabe, Yukinobu*; Maekawa, Fujio

Nuclear Instruments and Methods in Physics Research B, 511, p.30 - 41, 2022/01

 Times Cited Count:1 Percentile:66.98(Instruments & Instrumentation)

Nuclide production cross sections for proton-induced reactions on Mn and Co at incident energies of 1.3, 2.2, and 3.0 GeV were measured by the activation method at the J-PARC. In total, 143 production cross sections of reaction products were obtained. Among them, the cross sections of $$^{55}$$Mn(p,X)$$^{38}$$S and $$^{55}$$Mn(p,X)$$^{41}$$Ar were measured for the first time. The stable proton beam and well established beam monitoring system contributed to the reduction of the systematic uncertainties to typically less than 5%, which was better than those of the previous data. To examine the prediction capabilities of spallation reaction models and evaluated data library, the measured data were compared with the spallation reaction models in PHITS (INCL4.6/GEM, etc.), INCL++/ABLA07, and the JENDL/HE-2007 library. The comparison of the mean square deviation factors indicated that both INCL4.6/GEM and JENDL/HE-2007 showed better agreement with the measured data than the others.

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

Magnetic excitation in totally symmetric staggered ordered phase of PrFe$$_4$$P$$_{12}$$

Iwasa, Kazuaki*; Hao, L.*; Kogi, Masafumi*; Kuwahara, Keitaro*; Mignot, J.-M.*; Sugawara, Hitoshi*; Aoki, Yuji*; Matsuda, Tatsuma; Sato, Hideyuki*

Journal of the Physical Society of Japan, 81(9), p.094711_1 - 094711_9, 2012/09

 Times Cited Count:9 Percentile:52.99(Physics, Multidisciplinary)

Journal Articles

Neutron scattering study on the field-induced $$O_{xy}$$-type antiferroquadrupolar ordering of the heavy-fermion superconductor PrOs$$_4$$Sb$$_{12}$$

Kaneko, Koji; Metoki, Naoto; Shiina, Ryosuke*; Matsuda, Tatsuma; Kogi, Masafumi*; Kuwahara, Keitaro*; Bernhoeft, N.*

Physical Review B, 75(9), p.094408_1 - 094408_7, 2007/03

 Times Cited Count:21 Percentile:64.85(Materials Science, Multidisciplinary)

Neutron scattering experiments have revealed a field-induced antiferroquadrupolar order parameter in the Pr-based heavy-fermion superconductor PrOs$$_4$$Sb$$_{12}$$. We observed the field-induced antiferromagnetic dipole moment with the propagation vector $$q$$ = (1 0 0) for the applied field direction both $$H parallel$$ [1 1 0] and [0 0 1]. For $$H parallel$$ [1 1 0] at 8 T, it should be noted that the induced antiferromagnetic moment of 0.16 $$mu_{rm B}$$/ Pr orients parallel to the field within our experimental accuracy. This observation is strong evidence that the $$O_{xy}$$ electric quadrupole to be the primary order parameter for $$H parallel$$ [1 1 0]. A mean-field calculation, based on $$Gamma_1$$ singlet and $${Gamma}_4^{(2)}$$ excited triplet with the $$O_{xy}$$ quadrupolar interaction, reproduces the induced moment direction and its field response. These facts indicate the predominance of $$O_{xy}$$-type antiferroquadrupolar interaction in PrOs$$_4$$Sb$$_{12}$$.

Journal Articles

Field-induced antiferroquadrupolar order in the heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$

Kaneko, Koji; Metoki, Naoto; Matsuda, Tatsuma; Kuwahara, Keitaro*; Kogi, Masafumi*; Shiina, Ryosuke*; Mignot, J.-M.*; Gukasov, A.*; Bernhoeft, N.*

Physica B; Condensed Matter, 378-380, p.189 - 191, 2006/05

 Times Cited Count:1 Percentile:6.65(Physics, Condensed Matter)

Neutron diffraction experiments under magnetic fields were carried out on the heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$ in order to reveal the origin of the field-induced ordered phase (FIOP) for $$H$$$$Vert$$[1,1,0]. The application of magnetic field induces the weak superlattice peaks with the ordering vector $$q$$=(1,0,0) in FIOP, which is the same as for $$H{parallel}$$[0,0,1]. The observed superlattice reflections for $$H$$$$Vert$$[1,1,0] result from the antiferromagnetic component of $$J_x$$+$$J_y$$; the induced tiny antiferromagnetic moments orient parallel to the applied field. This result cannot be explained by magnetic interactions and strongly evidences the underlying AFQ order with $$O_{xy}$$ as a primary order parameter. These facts clarify the dominant role of $$O_{xy}$$-type antiferroquadrupolar interaction in PrOs$$_4$$Sb$$_{12}$$.

Journal Articles

Electrical and magnetic properties of a single crystal UCu$$_2$$Si$$_2$$

Matsuda, Tatsuma; Haga, Yoshinori; Ikeda, Shugo; Galatanu, A.; Yamamoto, Etsuji; Shishido, Hiroaki*; Yamada, Mineko*; Yamaura, Junichi*; Hedo, Masato*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 74(5), p.1552 - 1556, 2005/05

 Times Cited Count:23 Percentile:72.2(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of UCu$$_2$$Si$$_2$$ with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu$$_2$$Si$$_2$$ is found to order antiferromagnetically below $$T_{rm N}$$ = 106 K, and follows a successive ferromagnetic ordering at $$T_{rm C}$$ = 100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ($$c$$-axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction ($$a$$-axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes smoothly into a ferromagnetic magnetization curve below $$T_{rm C}$$ = 100 K. The saturation moment is determined as 1.75$$mu_{rm B}$$/U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/K$$^2$$$$cdot$$mol.

Journal Articles

Development of environment for remote participation in fusion research on JT-60

Oshima, Takayuki; Naito, Osamu; Hamamatsu, Kiyotaka; Iba, Katsuyuki; Sato, Minoru; Sakata, Shinya; Tsugita, Tomonori; Matsuda, Toshiaki; Iwasaki, Keita*; Karube, Yukihiro*; et al.

Fusion Engineering and Design, 71(1-4), p.239 - 244, 2004/06

 Times Cited Count:5 Percentile:35.33(Nuclear Science & Technology)

In the JT-60 tokamak at JAERI, environment for remote participation is planned to be developed by concentrating experts of nuclear fusion research of another research organizations and universities distributed all over the country. We are constructing a hierarchical remote research system, which consists of remote experiment, remote analysis, and remote diagnostic. In a remote collaboration, it is important to maintain the security of the system, as well as to share the information, atmosphere and presence between the participants. For the latter purpose, we developed a video conferencing system, and a video streaming system that can deliver the images of the JT-60 control room. Furthermore, a development of the remote analysis system called "VizAnalysis" has been started. And to assist the remote analysis, we developed a web based software system called "VizSquare". In the JT-60 tokamak at JAERI, security and authentication methods on a computer network and a new communication tool are developed, and probably they will be applied to the remote participation of ITER.

Journal Articles

Development of workstation-based CAMAC data acquisition system for JT-60 data processing system

Sato, Minoru; Tsugita, Tomonori; Oshima, Takayuki; Sakata, Shinya; Iwasaki, Keita*; Matsuda, Toshiaki; Iba, Katsuyuki; Ozeki, Takahisa

Fusion Engineering and Design, 71(1-4), p.145 - 149, 2004/06

 Times Cited Count:7 Percentile:45.16(Nuclear Science & Technology)

Data processing system in JT-60 has been used CAMAC widely for control and data acquisition of plasma diagnostic. However, it has passed over fifteen years from the operation, and the problem is caused for maintenance and function enhancement by the deterioration. Then, Mini-computer and microcomputer ,which control the CAMAC system were replaced workstation based on UNIX-OS, and these system were remodeled by developing the application software for screen control by GUI and for constructing environment of remote diagnostic through the network. In addition, CAMAC device driver for Linux has been developed in for next CAMAC control system.

Journal Articles

Proposal for a chopper spectrometer with very high energy resolution

Oyama, Kenji*; Ito, Shinichi*; Otomo, Toshiya*; Osakabe, Toyotaka; Suzuki, Junichi; Matsuda, Masaaki; Kuwahara, Keitaro*; Arai, Masatoshi*

Applied Physics A, 74(Suppl.1), p.S1598 - S1600, 2002/12

 Times Cited Count:2 Percentile:11.52(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Data processing and analysis systems for JT-60U

Matsuda, Toshiaki; Totsuka, Toshiyuki; Tsugita, Tomonori; Oshima, Takayuki; Sakata, Shinya; Sato, Minoru; Iwasaki, Keita*

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.512 - 520, 2002/09

 Times Cited Count:3 Percentile:23.44(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Recent changes of JT-60 data processing system

Matsuda, Toshiaki; Tsugita, Tomonori; Oshima, Takayuki; Sakata, Shinya; Sato, Minoru; Iwasaki, Keita*

Fusion Engineering and Design, 60(3), p.235 - 239, 2002/06

 Times Cited Count:5 Percentile:34.65(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Video srteaming system for remote participation JT-60 experiment

Oshima, Takayuki; Matsuda, Toshiaki; Iwasaki, Keita*; Ishikawa, Kazuya*

NIFS-MEMO-36, p.463 - 466, 2002/06

no abstracts in English

Journal Articles

Development of new ACM-A utilizing UNIX workstations, 2

Iwasaki, Keita*; Sato, Minoru; Matsuda, Toshiaki

NIFS-MEMO-36, p.479 - 482, 2002/06

no abstracts in English

Journal Articles

Development of new ACM-A utilizing UNIX workstations, 1

Sato, Minoru; Iwasaki, Keita*; Matsuda, Toshiaki

NIFS-MEMO-36, p.475 - 478, 2002/06

no abstracts in English

27 (Records 1-20 displayed on this page)