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Han, J.*; Uchimura, Tomohiro*; Araki, Yasufumi; Yoon, J.-Y.*; Takeuchi, Yutaro*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*
Nature Physics, 21 Pages, 2024/04
Times Cited Count：0Quantum metric and Berry curvature are two fundamental and distinct factors to describe the geometry of quantum eigenstates. While Berry curvature is known for playing crucial roles in several condensed-matter states, quantum metric, which was predicted to induce new classes of topological phenomena, has rarely been touched, particularly in an ambient circumstance. Using a topological chiral antiferromagnet Mn
Sn adjacent to Pt, at room temperature, we successfully manipulate the quantum-metric structure of electronic states through its interplay with the nanoscale spin texture at the MnSn/Pt interface. This is manifested by a time-reversal-odd second-order Hall effect that is robust against extrinsic electron scattering, in contrast to any transport effects from the Berry curvature. We also verify the flexibility of controlling the quantum-metric structure, as the interacting spin texture can be tuned by moderate magnetic fields or by interface engineering via spin-orbit interactions. Our work paves a way for harnessing the quantum-metric structure to unveil emerging topological physics in practical environments and to build applicable nonlinear devices.
Kusaka, Ryoji; Watanabe, Masayuki
Journal of Physical Chemistry Letters (Internet), 13(30), p.7065 - 7071, 2022/08
Times Cited Count：5 Percentile：67.52(Chemistry, Physical)Meigo, Shinichiro; Oi, Motoki; Fujimori, Hiroshi*
Physical Review Accelerators and Beams (Internet), 23(6), p.062802_1 - 062802_24, 2020/06
Times Cited Count：3 Percentile：35.72(Physics, Nuclear)As hadron accelerators for such as the ADS and spallation neutron source achieve increasing beam power, damage to targets is becoming increasingly severe. To mitigate this damage, nonlinear beam optics based on octupole magnets is attractive. Nonlinear optics can decrease the beam-focusing hazard due to failure of the rastering magnet. As a side effect of nonlinear optics, the beam size is known to expand drastically compared with linear optics. Nonlinear effects have been studied via a simplified filament model that ignores beam-divergence spread at the octupole magnet. In this study, a new generalized model is proposed for application to an octupole magnet, regardless of the filament-model approximation. It is found that the transverse distribution obtained by beam tracking can be specified by the introduction of only two parameters, namely the normalized octupole strength of 
and the 
of the phase advance. To achieve the two antagonistic requirements of reduction of the beam-peak density and minimization of the beam loss, the transverse distribution is surveyed for a large range of beam position. It is found that a bell-shaped distribution with 
1 and 
3 can satisfy requirements. This result is applied to beam transport in the spallation neutron source at J-PARC. The calculation result given by the present model shows good agreement with the experimental data, and the peak current density is reduced by 50% compared with the linear-optics case.
Kameda, Mai*; Hirobe, Daichi*; Daimon, Shunsuke*; Shiomi, Yuki*; Takahashi, Saburo*; Saito, Eiji
Journal of Magnetism and Magnetic Materials, 476, p.459 - 463, 2019/04
Times Cited Count：1 Percentile：4.65(Materials Science, Multidisciplinary)Hotchi, Hideaki; Harada, Hiroyuki
Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.371 - 375, 2018/08
no abstracts in English
Meigo, Shinichiro
Proceedings of 61st ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams (HB 2018) (Internet), p.99 - 103, 2018/07
As the increase of beam power, beam instruments play an essential role in the Hadron accelerator facility. In J-PARC, the pitting erosion on the mercury target vessel for the spallation neutron source is one of a pivotal issue to operate with the high power of the beam operation. Since the erosion is proportional to the 4th power of the beam current density, the minimization of the peak current density is required. To achieve low current density, the beam-flattening system by nonlinear beam optics in J-PARC, by which the peak density was successfully reduced by 30% than the density with the conventional case optics. Since the ADS requires a very powerful accelerator with the beam power such as 30 MW, a robust beam profile monitor is required, especially for the observation of the beam status on the target continuously. A candidate material for the beam monitor was developed by using heavy-ion of Ar beam to give the damage efficiently.
Meigo, Shinichiro; Oi, Motoki; Ikezaki, Kiyomi*; Kawasaki, Tomoyuki; Kinoshita, Hidetaka; Akutsu, Atsushi*; Nishikawa, Masaaki*; Fukuda, Shimpei
Proceedings of 12th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '15), p.255 - 260, 2016/00
Moribayashi, Kengo; Lee, K.*; Kagawa, Takashi*; Kim, D. E.*
Laser Physics, 16(2), p.322 - 324, 2006/02
Times Cited Count：1 Percentile：7.24(Optics)no abstracts in English
Inagaki, Shigeru*; Takenaga, Hidenobu; Ida, Katsumi*; Isayama, Akihiko; Tamura, Naoki*; Takizuka, Tomonori; Shimozuma, Takashi*; Kamada, Yutaka; Kubo, Shin*; Miura, Yukitoshi; et al.
Nuclear Fusion, 46(1), p.133 - 141, 2006/01
Times Cited Count：55 Percentile：85.19(Physics, Fluids & Plasmas)no abstracts in English
Moribayashi, Kengo; Kagawa, Takashi*; Kim, D. E.*
Journal of Physics B; Atomic, Molecular and Optical Physics, 38(13), p.2187 - 2194, 2005/07
Times Cited Count：6 Percentile：31.16(Optics)no abstracts in English
Sato, Kenji*; Ninomiya, Shiro*; Miyawaki, Nobumasa; Fukuda, Mitsuhiro; Obata, Shuji*
Proceedings of 2nd Annual Meeting of Particle Accelerator Society of Japan and 30th Linear Accelerator Meeting in Japan, p.159 - 161, 2005/07
It is possible to transform three equations of motion into a convenient form which is expressed by terms up to 2nd differential of variables of the Lorentz factor and angular velocity by the use of a field index of magnetic field distribution. The expression plays a vital role in a two-step nonlinear acceleration theory of spiral orbital motions in cyclotrons because this single equation of motion refers to both longitudinal motion and transverse motion.
n eigenmodes driven by negative-ion-based neutral beams in JT-60UShinohara, Koji; Ishikawa, Masao; Takechi, Manabu; Kusama, Yoshinori; Todo, Yasushi*; Gorelenkov, N. N.*; Cheng, C. Z.*; Fukuyama, Atsushi*; Kramer, G.*; Nazikian, R. M.*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 81(7), p.547 - 552, 2005/07
In the bursting instabilities in the frequency range of Alfven Eigenmode, we observed two types of modes phenomenologically. In one type, the time scale of the mode was 
1ms and the mode amplitude was so large that we were able to detect apparent enhanced transport of the energetic ions. The enhanced transport showed the clear energy dependence by using new diagnostics, natural diamond detector. In another type, the mode amplitude is not so large, compared with the first type. The frequency up-down chirping is clearly observed with the time-scale of a few ms. This frequency chirping was reproduced by the newly developed simulation code, MEGA To demonstrate this model of Reversed-Shear-induced Alfven Eigenmode, RSAE, we have performed experiments in the condition where we can have q profile with a good signal-to-noise ratio. We observed the slow up-frequency sweeping of RSAE due to the down evolution of qmin, We have analyzed this experiment by using NOVA-K code. We observed that the most unstable mode localized around qmin.
Inagaki, Shigeru*; Takenaga, Hidenobu; Ida, Katsumi*; Isayama, Akihiko; Tamura, Naoki*; Takizuka, Tomonori; Shimozuma, Takashi*; Kamada, Yutaka; Kubo, Shin*; Miura, Yukitoshi; et al.
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
no abstracts in English
Machida, Masahiko; Koyama, Tomio*
Physical Review B, 70(2), p.024523_1 - 024523_6, 2004/07
Times Cited Count：64 Percentile：89.35(Materials Science, Multidisciplinary)no abstracts in English
Suzuki, Takahiro; Ide, Shunsuke; Hamamatsu, Kiyotaka; Petty, C. C.*; Lao, L. L.*; Isayama, Akihiko; Fujita, Takaaki; Ikeda, Yoshitaka; Seki, Masami; Moriyama, Shinichi; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 80(6), p.511 - 515, 2004/06
no abstracts in English
Atanasiu, G. M.*; Hazama, Osamu; Guo, Z.; Yagawa, Genki*
Proceedings of 2nd International Conference Lifetime Oriented Design Concepts (ICLODC 2004), p.449 - 458, 2004/03
Some strategies in monitoring the structural seismic performance for a class of RC multistory buildings using linear and nonlinear dynamic analysis. New concepts and visions, considering the seismic input models based on probabilistic hazard level, will be presented. Numerical simulations of RC structures with different topologies are carried out as case studies, to search for a suitable strategy of seismic monitoring based on structural performance. For comparison, equivalent single degree of freedom models are also taken into account. The seismic input is based on the 1994 Northridge earthquake acceleration time histories. For comparison, the unscaled Kobe ground motion were also considered as input.
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki
Theory of Fusion Plasmas, ISPP21, p.213 - 226, 2004/00
no abstracts in English
characteristics and optical properties in high-
superconductors with alternating junction parametersKoyama, Tomio*; Machida, Masahiko
Physica C, 392-396(1-4), p.145 - 148, 2003/10
no abstracts in English
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*
Nuclear Fusion, 43(7), p.539 - 546, 2003/07
no abstracts in English
Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*
Nuclear Fusion, 43(7), p.539 - 546, 2003/07
Times Cited Count：27 Percentile：61.29(Physics, Fluids & Plasmas)no abstracts in English
