研究者詳細 - 木内　勝

論文 - 木内　勝

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Enhanced current-carrying capacity of three-layer cable composed of Bi-2223 tapes using the longitudinal field effect 査読有り

Vyatkin V., Vyatkin V., Kiuchi M., Kiuchi M., Otabe E., Otabe E., Ohya M., Matsushita T., Matsushita T.

IEEE Transactions on Applied Superconductivity 25 ( 3 ) 2015年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2014 IEEE.Innovative dc superconducting cables with higher current-carrying capacity than conventional cables were proposed in previous works. The superior property is brought about by the longitudinal magnetic field that enhances the critical current density. In this work, the current-carrying capacity of a three-layer cable composed of Bi-2223 tapes was theoretically calculated based on the measured critical current density in the longitudinal magnetic field. The obtained current-carrying capacity of the proposed cable is 13.2% higher in comparison with the conventional cable of the same size.

DOI： 10.1109/TASC.2014.2364607

Scopus

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Current-carrying capacity of HTS DC cables with the reduced Lorentz force 査読有り

Vyatkin V., Tanabe K., Otabe E., Kiuchi M., Matsushita T.

Journal of Physics: Conference Series 507 ( PART 2 ) 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The structure of superconducting DC cable made with high temperature superconducting tapes is designed to improve the current-carrying capacity by reducing the Lorentz force acting on flux lines. For this purpose an axial magnetic field is produced by the outer shield conductor. The analysis was performed for the optimum structure for various superconducting tapes with different Jc(B,θ) characteristics. It is found that the current-carrying capacity increases appreciably when the difference in the critical current density of the tape is large enough between normal and parallel magnetic fields.

DOI： 10.1088/1742-6596/507/2/022045

Scopus

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Fabrication of 1 T Bi-2223 superconducting magnet with 92 mm bore diameter at 77 K 査読有り

Otabe E., Vyatkin V., Kiuchi M., Matsushita T., Ni B., Kato T., Nishimura T., Uetsuki R.

AIP Conference Proceedings 1573 754 - 759 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2014 AIP Publishing LLC. A Bi-2223 superconducting magnet for practical use in liquid nitrogen is designed and fabricated. Bi-2223 tapes prepared by ConTrolled Over Pressure (CT-OP) process are used for the winding, and the critical current at 77.3 K and selffield is in the range of 174-185 A. 28 double-pancake coils are resistively connected in series by copper terminals. High critical current tape is used for top and bottom double-pancake coils, since the magnetic field normal to the tape surface is highest at the top and bottom of the magnet. Two iron plates at top and bottom of the magnet are used for reduction of the normal component of magnetic field to the Bi-2223 tape, since the total performance of the magnet is determined by the minimum critical current at maximum normal magnetic field component to the tape. The inner bore diameter of the magnet is 92 mm. And the homogeneity of magnetic field of long-axis direction in 50 mmø× 100 mm length is within 3%. The maximum magnetic field at the center of the bore is over 1.0 T at 77.3 K.

DOI： 10.1063/1.4860779

Scopus

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人工ピンニングによるREBCO 薄膜の臨界電流特性改善査読有り

松下照男, 木内勝

低温工学 ( 公益社団法人低温工学・超電導学会 (旧社団法人低温工学協会) ) 49 ( 3 ) 91 - 98 2014年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Nanorods and nanoparticles are commonly introduced to REBCO coated conductors as artificial pinning centers to improve the critical current density in high magnetic fields and to reduce the anisotropy with respect to the magnetic field angle. In this article the pinning properties are theoretically analyzed based on the classic condensation energy pinning interaction mechanism (δ<I>T</I><sub>c</sub> pinning) of these pinning centers and the results are compared with experimental results. The agreements show that the critical current density can be designed by controlling the microstructure of pinning centers and factors such as the size, number density and morphology. It is also pointed out that the upper critical field is enhanced via the electron scattering of the interface between the pinning center and the superconducting matrix. Hence, the upper critical field can also be controlled to enhance the irreversibility field by controlling the interface area in a unit volume of the superconductor. It is expected that the high field performance can be optimized by controlling the pinning strength and the upper critical field in the future.

DOI： 10.2221/jcsj.49.91

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130004457544

高性能超電導直流ケーブルの設計査読有り

松下照男, S. VYATKIN Vladimir, 木内勝, 小田部荘司

低温工学 = Cryogenic engineering ( 公益社団法人低温工学・超電導学会 (旧社団法人低温工学協会) ) 48 ( 11 ) 569 - 576 2013年11月

Effect of packing density on critical current density at high magnetic fields in polycrystalline MgB2 superconductors 査読有り

Matsushita T., Tanigawa J., Kiuchi M., Yamamoto A., Yamamoto A., Shimoyama J., Kishio K.

Japanese Journal of Applied Physics 51 ( 12 ) 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

It is well understood that the critical current density in polycrystalline MgB2 superconductors is severely restricted by porosities and wet insulating layers that cover superconducting grains. The relationship between critical current density and electrical connectivity is well explained by the prediction of the percolation theory. Recently, it has been found that the irreversibility field that directly influences the high-field performance of the critical current density is also dependent on electrical connectivity. This behavior is explained by the finding that superconducting grains with the c-axis tilted by a small angle from the direction of applied magnetic field lose their superconductivity at relatively low magnetic fields owing to the low irreversibility field, resulting in a decrease in the effective packing density. This phenomenon is theoretically investigated using the percolation theory and the theory of flux creep and flow. The obtained result explains the experimental result well. This shows that the packing factor of MgB2 is also important for improving the critical current density at high magnetic fields. © 2012 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.51.123103

Scopus

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Innovative superconducting force-free cable concept 査読有り

Matsushita T., Kiuchi M., Otabe E.

Superconductor Science and Technology 25 ( 12 ) 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

An innovative superconducting DC power cable using high-temperature superconducting wires is introduced. The new cable design is proposed to utilize the longitudinal magnetic field effect that was discovered about a half-century ago. It was shown that the critical current density of a superconducting wire could be significantly increased when the superconductor is in a parallel field configuration. It is empirically known that a force-free structure is attained for the current flowing in the superconductor in this case. In the new cable, the outer layer is twisted in such a way that the shielding current flowing in this region generates a magnetic field that is parallel to the inner conductor. As a result, a force-free structure is realized for the wiring in the inner conductor. It is shown that the current carrying capacity of the proposed cable is dramatically improved in comparison with other cables and that the improvement becomes more pronounced with the increase of the current level. © 2012 IOP Publishing Ltd.

DOI： 10.1088/0953-2048/25/12/125009

Scopus

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Improvement of flux pinning performance at high magnetic fields in GdBa <inf>2</inf>Cu <inf>3</inf>O <inf>y</inf> coated conductors with BHO nano-rods through enhancement of B <inf>c2</inf> 査読有り

Matsushita T., Nagamizu H., Tanabe K., Kiuchi M., Otabe E., Tobita H., Yoshizumi M., Izumi T., Shiohara Y., Yokoe D., Kato T., Hirayama T.

Superconductor Science and Technology 25 ( 12 ) 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Addition of BaHfO 3 (BHO) nano-rods as pinning centers into a GdBa 2Cu 3O y (GdBCO) coated conductor dramatically improves the critical current properties in high magnetic fields. This is partly ascribed to the strong flux pinning of these pinning centers. In this paper it is reported that this improvement is mainly caused by unexpected enhancement of the upper critical field, B c2. The mechanism of the enhancement of B c2 is not yet clear, although the strain around the interface between the pinning center and the superconducting matrix or the interface itself may scatter electrons. This result suggests that the critical current property of REBa 2Cu 3O y (RE: rare earth elements, REBCO) coated conductors could be designed not only by tailoring the microstructure of pinning centers but also by controlling the intrinsic superconducting property. Especially, the selection of pinning material and its content that determines B c2 is expected to be a key problem for further improvement of the pinning performance at high magnetic fields. © 2012 IOP Publishing Ltd.

DOI： 10.1088/0953-2048/25/12/125003

Scopus

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Evaluation of critical current density of FeAs-based superconductors 査読有り

Otabe E., Kiuchi M., Matsushita T., Ni B., Qi Y., Wang L., Gao Z., Wang D., Zhang X., Ma Y., Nakajima Y., Tamegai T.

Journal of the Korea Institute of Applied Superconductivity and Cryogenics 14 ( 2 ) 1 - 7 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this review paper, we report the characteristics of the critical current density in FeAs based superconductors which is newly discovered by Hosono group of Tokyo Institute of Technology on 2008. Since the many specimens in present stage are not single crystals, there are two kinds of critical current density observed in the specimens which are so-called local and global critical current densities. Therefore, it is necessary to evaluate both kinds of critical current densities. The history effect in which the global critical current density shows different values in increasing and decreasing magnetic field is also observed when the specimens have the local and the global critical current densities. The wire which critical current is 180 A is successfully developed with using the knowledge of abovementioned characteristics of two kinds of critical current densities and the history effect.

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Estimation of critical current densities in polycrystalline Sr <inf>0.6</inf>K<inf>0.4</inf>Fe<inf>2</inf>As<inf>2</inf> Superconductors 査読有り

Ni B., Ge J., Tanaka Y., Otabe E., Kiuchi M., Matsushita T., Gao Z., Wang L., Qi Y., Zhang X., Ma Y.

IEEE Transactions on Applied Superconductivity 21 ( 3 PART 3 ) 2862 - 2865 2011年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

The superconducting Sr0.6K0.4Fe2As 2 (122 type) polycrystalline iron-based pnictides with Pb or Ag addition were prepared by a normal PIT method. The critical current densities were investigated by ac inductive (Campbell's) method. It was found that a fairly large critical current density over 1010 A/m2 even at the relatively high temperatures flows locally with the perimeter size similar to the average grain size of the bulk samples, while an extremely low global critical current density of 104106 A/m 2flows through the whole sample. Furthermore, a unique history dependence of global critical current density was observed, i.e., it shows a smaller critical current density in the increasing-field process than that in the decreasing-field process. Basing on the experimental results of the penetrating ac magnetic flux profile and the characteristic of ac magnetic field vs. penetration depth, the inter- and intra-granular super-current, the weak-link and the history effect in these materials were discussed. © 2010 IEEE.

DOI： 10.1109/TASC.2010.2088092

Scopus

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Critical current properties of Ag added Sr<inf>0.6</inf>K <inf>0.4</inf>Fe<inf>2</inf>As<inf>2</inf> 査読有り

Otabe E., Otabe E., Yoshida N., Kiuchi M., Kiuchi M., Matsushita T., Ge J., Ni B., Ni B., Wang L., Qi Y., Zhang X., Gao Z., Wang D., Ma Y., Ma Y.

Physica C: Superconductivity and its Applications 470 ( SUPPL.1 ) 2010年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The local and global critical current densities of polycrystalline bulks Sr0.6K0.4Fe2As2 were investigated by both the remnant magnetic moment and Campbell's methods. It was found that the global critical current density was improved by addition of Ag. It was speculated that the reason for the enhancement of the global critical current density was ascribed to the enlarged size of particle and the clean boundaries due to addition of Ag. It was also found that the critical current density estimated from usual magnetization measurement was a type of average value of both local and global critical current densities and can be explained by simple contributions from magnetic moments by local and global shielding currents. Therefore, the size of the grain was estimated by the present model and the agreement with the observation by SEM was obtained. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.01.033

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Three-dimensional analysis of BaZrO<inf>3</inf> pinning centers gives isotropic superconductivity in GdBa<inf>2</inf> Cu<inf>3</inf> O <inf>7-δ</inf> 査読有り

Kaneko K., Furuya K., Yamada K., Sadayama S., Sadayama S., Barnard J., Midgley P., Kato T., Hirayama T., Kiuchi M., Matsushita T., Ibi A., Yamada Y., Izumi T., Shiohara Y.

Journal of Applied Physics 108 ( 6 ) 2010年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

BaZrO3 doped GdBa2 Cu3 O 7-δ superconductor was prepared by pulsed layer deposition using a KrF excimer laser, which showed isotropic characteristics of critical current density, JC, for magnetic-field orientations, ∼4.0× 109 A m-2 at 1.0 T. Microstructural and morphological characterization of resulting artificial pinning centers were conducted by transmission electron microscopy and electron tomography, which confirmed the presence of one-dimensional artificial pinning centers, BaZrO3 nanorods. Since there is noticeable anisotropy from GdBa2 Cu 3 O7-δ superconductor without doping BaZrO 3, the pinning observed for all magnetic-field orientations are due to the high density and high dispersion of these BaZrO3 nanorods with very wide angular distributions. © 2010 American Institute of Physics.

DOI： 10.1063/1.3486213

Scopus

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Influence of nanoparticles on critical current properties in TFA-MOD processed YGdBCO coated conductor 査読有り

Masaru Kiuchi,Fumiya Matsutani,Yuji Takahashi,Edmund S. Otabe,Teruo Matsushita,Masashi Miura,Teruo Izumi,Yuh Shiohara

Journal of Physics: Conference Series 234 022018 - 022018 2010年04月

Evaluation of geometrical effect on magnetization loss in GdBCO coated conductor 査読有り

Y. Nakayama,M. Kiuchi,E.S. Otabe,T. Matsushita,H. Okamoto,T. Saito,T. Izumi

Physica C 470 1315 - 1317 2010年04月

Critical current characteristics and history dependence in superconducting SmFeAsOF bulk 査読有り

B. Ni,J. Ge,M. Kiuchi,E.S. Otabe,Z. Gao,L. Wang,Y. Qi,X. Zhang,Y. M

Journal of Physics: Conference Series 234 012028 - 012028 2010年04月

Estimation of magnetic relaxation property for CVD processedYBCO-coated conductors 査読有り

Y. Takahashi,M. Kiuchi,E.S. Otabe,T. Matsushita,K. Shikimachi,T. Watanabe ,N. Kashima,S. Nagaya

Physica C 470 1284 - 1287 2010年04月

Critical current density properties in polycrystalline Sr0.6K0.4Fe2As2 superconductor 査読有り

N. Yoshida,M. Kiuchi,E.S. Otabe,T. Matsushita,J. Ge,B. Ni,L. Wang,Y. Qi ,X. Zhang,Z. Gao,Y. Ma

Physica C 470 1216 - 1218 2010年04月

Influence of nanoparticles on flux pinning properties in TFA-MOD processed YGdBCO coated conductor 査読有り

F. Matsutani,Y. Takahashi,M. Kiuchi,E.S. Otabe,T. Matsushita,M. Miura,T. Izumi,Y. Shiohara

Physica C 470 1411 - 1414 2010年04月

Critical current properties at high magnetic fields in polycrystallineMgB2 superconductors 査読有り

T. Matsushita,M. Kiuchi,E.S. Otabe,A. Yamamoto,J. Shimoyama,K. Kishio

Physica C 470 1406 - 1410 2010年04月

Bi-2223 superconducting magnet generating over 1T in liquid nitrogen 査読有り

E. S. Otabe,S. Nemoto,M. Kiuchi,T. Matsushita,T. Hayashi,K. Fujino,B. Ni

Journal of Physics: Conference Series 234 032046 - 032046 2010年04月

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