荒谷 秀和*; 中谷 泰博*; 藤原 秀紀*; 川田 萌樹*; 金井 惟奈*; 山神 光平*; 藤岡 修平*; 濱本 諭*; 久我 健太郎*; 木須 孝幸*; et al.
Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09
We present a detailed study on the ground state symmetry of the pressure-induced superconductor CeCuGe probed by soft X-ray absorption and hard X-ray photoemission spectroscopy. The revised Ce ground states are determined as with in-plane rotational symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCuSi, we propose that the charge distribution along the -axis plays an essential role in driving the system into a superconducting phase.
諏訪 友音*; 辺見 努*; 齊藤 徹*; 高橋 良和*; 小泉 徳潔*; Luzin, V.*; 鈴木 裕士; Harjo, S.
IEEE Transactions on Applied Superconductivity, 28(3), p.6001104_1 - 6001104_4, 2018/04
NbSn strands, whose properties are very sensitive to stress/strain, are utilized for ITER cable-in-conduit conductor (CICC) of the central solenoids. The NbSn strands experience temperature range of 1000 K from the temperature of the heat treatment with the initiation of the NbSn reaction to the operation temperature of 4 K. Due to this large temperature range, large thermal strain is induced in the NbSn filaments due to the differences between the coefficients of thermal expansion and Young's moduli of the components of the strand. Therefore, it is considered that initial performance of the CICC is influenced by the thermal strain on the NbSn, and it is important to evaluate the strain state of the NbSn strand at low temperature. In this study, the thermal strain of the components of free NbSn strand was measured by neutron diffraction and stress/strain state was assessed from room temperature to low temperature. As the results of diffraction measurements, it was found that 0.111 % and 0.209 % compressive strain were generated in NbSn filaments at 300 and 10 K, respectively.
上野 恭裕*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 啓一*; 伊藤 孝; 岩崎 雅彦*; et al.
Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11
MuSEUM is an international collaboration aiming at a new precise measurement of the muonium hyperfine structure at J-PARC (Japan Proton Accelerator Research Complex). Utilizing its intense pulsed muon beam, we expect a ten-fold improvement for both measurements at high magnetic field and zero magnetic field. We have developed a sophisticated monitoring system, including a beam profile monitor to measure the 3D distribution of muonium atoms to suppress the systematic uncertainty.
Shand, C. M.*; Podolyk, Zs.*; Grska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.
Physics Letters B, 773, p.492 - 497, 2017/10
Low-lying states in neutron-rich Zn nuclei were measured for the first time via in-beam -ray spectroscopy at RIKEN. These include the 4 to 2 in Zn and the 2 to 0 and 4 to 2 in Zn. The reduced E() energies and increased E(4)/E(2) ratios at =52,54 compared to Zn attest that the magicity is confined just on the neutron number =50 only. The levels observed in Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.
伊藤 大介*; Rivera, M. N.*; 齊藤 泰司*; 青柳 光裕; 神山 健司; 鈴木 徹*
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 10 Pages, 2017/09
Two-phase flow through porous media must be well understood to develop a severe accident analysis code not only for light water reactor (LWR) but also sodium-cooled fast reactor (SFR). When a core disruptive accident occurs in SFR, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. Thus, as first step, the present work focuses on the characteristics of pressure drop in two-phase flows in different porous media conditions (porous size, liquid and gas flow velocity). To construct an experimental database, the measured pressure drop under different conditions was compared with existing correlations. In addition, X-ray radiography, which is very helpful to understand the two-phase structure inside the porous media, was applied to measure porosity and void fraction distribution in the packed bed of spheres.
Nava, M.*; 伊藤 大介*; 齊藤 泰司*; 青柳 光裕; 神山 健司; 鈴木 徹*
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 5 Pages, 2017/07
Two-phase flow through porous media should be well understood to develop a severe accident analysis code not only for light water reactor but also sodium cooled fast reactor (SFR). When a core disruptive accident occurs in SFR, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. Thus, as first step, the present work focuses on the characteristics of pressure drop in single and two-phase flows in different porous media conditions (porous size, liquid and gas flow velocity). In addition, in order to construct an experimental database, the measured pressure drop under different conditions was compared with existing correlations.
辺見 努*; Harjo, S.; 梶谷 秀樹*; 諏訪 友音*; 齊藤 徹*; 相澤 一也; 長村 光造*; 小泉 徳潔*
IEEE Transactions on Applied Superconductivity, 27(4), p.4200905_1 - 4200905_5, 2017/06
The superconducting property of NbSn strands is very sensitive to strain. The transverse electromagnetic loading has been considered as a major origin of the degradation of NbSn cable-in-conduit conductors (CICCs) due to the local bending. Since the bending pitch is around 5 mm due to contacting of strands compacted by the electromagnetic transverse loading, there is a possibility of a large bending strain with small deflection of strands. The bending strain of the strands cannot be evaluated from only the small deflection obtained visually. Measuring bending strain of NbSn strand in CICCs is important for evaluating the conductor performance. Neutrons, which have a large penetration depth, are a powerful tool to evaluate the internal strain of NbSn in the CICC. This paper shows that the bending strain in NbSn strands of CICCs can be determined by the neutron diffraction profile nondestructively and quantitatively.
Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; Baba, H.*; Calvet, D.*; et al.
Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06
The first -ray spectroscopy of very neutron rich Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.
伊藤 大介*; Nava, M.*; 齊藤 泰司*; 青柳 光裕; 神山 健司; 鈴木 徹*
Proceedings of 2017 Japan-US Seminar on Two-Phase Flow Dynamics (JUS 2017), 4 Pages, 2017/06
Two-phase flow through porous media should be well understood to develop a severe accident analysis code not only for light water reactor but also sodium-cooled fast reactor (SFR). When a core disruptive accident occurs in SFR, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. Thus, as first step, the present work focuses on the characteristics of pressure drop in two-phase flows in different porous media conditions (porous size, liquid and gas flow velocity). In addition, to construct an experimental database, the measured pressure drop under different conditions was compared with existing correlations.
Vaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; Ncher, E.*; Sahin, E.*; 志賀 慶明*; et al.
Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05
Excited states in Sn were populated following one-neutron knockout reaction from an unstable Sn beam at the RIBF laboratory in RIKEN. In addition to the already known rays, additional strength was observed for the first time in the excitation-energy range 3.5-5.5 MeV. Since the neutron separation energy of Sn is low, this observation provides direct evidence for the radioactive decay of neutron-unbound states in this nucleus. The ability of decay to compete with neutron emission was attributed to a mismatch between the wave functions of the initial and final states in the neutron emission case. These findings suggest that in the region south-east of Sn, nuclear structure effects play a significant role in the decay of unbound states, which are instead usually ignored in the evaluation of neutron-emission probabilities in astrophysical simulations.
Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Rodriguez, T. R.*; Authelet, G.*; Baba, H.*; Calvet, D.*; Chteau, F.*; Corsi, A.*; Delbart, A.*; et al.
Physical Review C, 95(4), p.041302_1 - 041302_6, 2017/04
Neutron-rich isotopes of selenium, Se, where studied via in beam -ray spectroscopy after nucleon removal reactions at RIBF in RIKEN. The low-energy excitations of these nuclei were investigated using - coincidences, and the first and second excited 2 states were found at remarkably low energies. The analysis and comparison with self-consistent beyond-mean field calculations suggest that both shape coexistence and triaxiality are needed to describe these isotopes.
Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; Baba, H.*; Bally, B.*; Bender, M.*; Calvet, D.*; Chteau, F.*; et al.
Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01
The first measurement of rays emitted by the very neutron rich nuclei Mo (Z=42) and Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state Mo and Zr, respectively 235(7) keV and 185(11) keV, and their E(4)/E(2) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.
Strasser, P.*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 啓一*; 伊藤 孝; 岩崎 雅彦*; et al.
Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12
At the Muon Science Facility (MUSE) of J-PARC (Japan Proton Accelerator Research Complex), the MuSEUM collaboration is planning new measurements of the ground state hyperfine structure (HFS) of muonium both at zero field and at high magnetic field. The previous measurements were performed both at LAMPF (Los Alamos Meson Physics Facility) with experimental uncertainties mostly dominated by statistical errors. The new high intensity muon beam that will soon be available at MUSE H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation, and the results of a first commissioning test experiment at zero field are presented.
小貫 祐介*; 星川 晃範*; 佐藤 成男*; 徐 平光; 石垣 徹*; 齋藤 洋一*; 轟 秀和*; 林 眞琴*
Journal of Applied Crystallography, 49(5), p.1579 - 1584, 2016/10
The authors have developed texture measurement system on a time-of flight neutron diffractometer, iMATERIA (BL20, MLF/J-PARC, Japan). Quantitative Rietveld texture analysis for a duplex stainless steel was possible with one neutron beam exposure for several minutes without sample rotation. The minimum number of diffraction spectra required for the Rietveld texture analysis was experimentally determined as 100. The suggested rapid measurement scheme used 132 spectra and determined volume fractions of texture components in both ferrite and austenite phases, quantitatively. This quantitative and rapid measurement scheme was established by utilizing the features of iMATERIA as a powder diffractometer, i.e. fairly high resolution in d-spacing and numerous detectors equipped in a wide range of scattering angle.
高橋 遼*; 松尾 衛; 小野 正雄; 針井 一哉; 中堂 博之; 岡安 悟; 家田 淳一; 高橋 三郎*; 前川 禎通; 齊藤 英治
Nature Physics, 12, p.52 - 56, 2016/01
Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.
小野 正雄; 中堂 博之; 針井 一哉; 岡安 悟; 松尾 衛; 家田 淳一; 高橋 遼*; 前川 禎通; 齊藤 英治
Physical Review B, 92(17), p.174424_1 - 174424_4, 2015/11
We report the observation of the Barnett effect in paramagnetic states by mechanically rotating gadolinium (Gd) metal with a rotational frequency of up to 1.5 kHz above the Curie temperature. An in situ magnetic measurement setup comprising a high-speed rotational system and a fluxgate magnetic sensor was developed for the measurement. Temperature dependence of the observed magnetization follows that of paramagnetic susceptibility, indicating that any emergent magnetic field is proportional to the rotational frequency and is independent of temperature. From the proportionality constant of the emergent field, the gyromagnetic ratio of Gd is calculated to be -29 5 GHz/T. This study revisits the primordial issue of magnetism with modern technologies to shed new light on the fundamental spin-rotation coupling.
齊藤 徹; 大久保 暁一*; 泉 敬介*; 大川 慶直*; 小林 宣博*; 山崎 亨; 河野 勝己; 礒野 高明
低温工学, 50(8), p.400 - 408, 2015/08
尾関 秀将; 齊藤 徹; 河野 勝己; 高橋 良和; 布谷 嘉彦; 山崎 亨; 礒野 高明
Physics Procedia, 67, p.1010 - 1015, 2015/07
JAEA is responsible for procurement of the central solenoid (CS) conductor for ITER. The CS conductor is assembled by inserting NbSn superconductor cable into circular-in-square jacket whose material is JK2LB high manganese stainless steel developed by JAEA, and then heat treatment is carried out. In the recent study of NbSn strand, heat treatment for 250 hours at 570 degrees Celsius and 100 hours at 650 degrees is adopted. The effect of 250 hours at 570 degree for JK2LB has not studied yet although the region of 650 degree has already studied, and might be a cause of sensitization. So the characteristics of JK2LB jacket after heat treatment for 250 hours at 570 degree and then 200 hours at 650 degree was studied in terms of mechanical tests at 4K and metallographic tests. The mechanical test results satisfied the requirement of ITER and metallographic tests result showed no remarkable degradation. This study proved JK2LB jacket can be applicable to the heat treatment above.
齊藤 徹; 河野 勝己; 山崎 亨; 尾関 秀将; 礒野 高明; 濱田 一弥*; Devred, A.*; Vostner, A.*
Physics Procedia, 67, p.1016 - 1021, 2015/07
A suite of advanced austenitic stainless steels are used for the superconductor jacket, magnet casing and support structure in the ITER TF, CS and PF coil systems. These materials will be exposed to cyclic-stress environment at cryogenic temperature. The CS jacket suffers high electromagnetic force with 60,000 cycles during its life time. Therefore, high manganese austenitic stainless steel JK2LB, which has high tensile strength, high ductility, and high resistance to fatigue at 4K has been chosen for the CS conductor. The cryogenic temperature mechanical property data of this material are very important to ITER magnet design but not much data were available. This study is focused on mechanical characteristics of JK2LB and its weld joint. We present results from tensile tests, fracture toughness, fatigue crack growth rate and fatigue at 4K. Test result of tensile tests, fracture toughness, fatigue crack growth rates and fatigue satisfy the ITER requirements.
櫻井 武尊; 井口 将秀; 中平 昌隆; 斎藤 徹*; 森本 将明*; 稲垣 隆*; Hong, Y.-S.*; 松井 邦浩; 辺見 努; 梶谷 秀樹; et al.
Physics Procedia, 67, p.536 - 542, 2015/07