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Your search keyword '"Miyashita, Katsumi"' showing total 20 results
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20 results on '"Miyashita, Katsumi"'

1. AC loss of multifilamentary superconducting AC wire caused by longitudinal and azimuthal AC magnetic field components

Author

Fukui, Satoshi, Negishi, Kazuaki, Tsukamoto, Osami, Miyashita, Katsumi, and Fukuda, Kunihiro

Subjects
Alternating current -- Research, High temperature superconductors -- Research, Magnetic fields -- Research, Superconductors -- Electric properties, Business, Electronics, Electronics and electrical industries
Abstract

Experimental and theoretical investigations of alternating current loss characteristics of multifilamentary NbTi alternating current wires under alternating current external magnetic field were conducted. Alternating transport current losses of alternating current wires having different twist pitches under the alternating current external magnetic field were measured. Results show that the alternating current losses can be significantly reduced by proper selection of the twist pitch and the external longitudinal field component.

Published
1999

2. Difference of Irreversible Strain Limit in Technical RHQT Nb3Al Superconductors

Author

Banno, Nobuya, Nishijima, Gen, Kitaguchi, Hitoshi, and Miyashita, Katsumi

Abstract

Strain limit for critical current degradation in various technical rapid-heating, quenching, and transformation-processed Nb3 Al strands has been studied with respect to the matrix material and filament diameter. This property is one important factor as well as the strain sensitivity to Jc characteristics, especially when we consider to apply the so-called react and wind technique to large magnets such as DEMO reactors.We compared five strands, including a standard Nb matrix, standard Ta matrix, Nb/Ag/Nb three-layered barrier structure, and other two fine filament diameter strands prepared by the restackingmethod. In normal Nb and Ta matrix strands with a filament diameter of more than 30 μm, the irreversible strain limit is about 0.3%. Refinement of the filament diameter enables us to significantly improve the irreversible strain limit up to more than 0.7%. The Nb/Ag/Nb three-layered barrier structure appearsmore attractive from a practical point of view. The irreversible strain limit was improved up to nearly 0.6%, even if the filament diameter is more than 20 μm. The Ag layer between the Nb3 Al filaments seems to act as a cushion to mitigate the stress concentration in the wire. The Ag barrier also seems to be effective for current bypass in existence of cracks, resulting in suppressing Ic degradation in a higher strain range.

Published
2018

6. Mass Production and Quality Control of Nb3Sn Superconducting Strands for ITER Toroidal Field Coils

Author

NABARA, Yoshihiro, primary, NUNOYA, Yoshihiko, additional, ISONO, Takaaki, additional, HAMADA, Kazuya, additional, UNO, Yasuhiro, additional, TAKAHASHI, Yoshikazu, additional, NAKAJIMA, Hideo, additional, TSUZUKU, Seiji, additional, TAGAWA, Kouhei, additional, MIYASHITA, Katsumi, additional, MURAKAMI, Yukinobu, additional, MIYATAKE, Takayuki, additional, and YOSHIKAWA, Masatoshi, additional

Published
2012
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16. Development of Single-Stacked Internal-Tin Nb3Sn Superconducting Wire.

Author

Ohata, Katsumi, Miyashita, Katsumi, Wadayama, Yoshihide, Kimura, Morio, and Nakagawa, Kazuhiko

Subjects
*SUPERCONDUCTING wire, *CURRENT density (Electromagnetism), *FABRICATION (Manufacturing), *MAGNETIC fields, *NUCLEAR magnetic resonance, *HEAT treatment
Abstract

The internal-tin technique is an excellent method of fabricating Nb3Sn superconducting wires with high critical current densities. We have developed an internal-tin Nb3Sn wire in which the multi-filamentary wire is fabricated by assembling mono-filamentary Nb elements and mono-filamentary Sn elements. The simple fabrication process allows a reduction in the fabrication cost of the wires. By optimizing the spacing of the Nb3Sn filaments, a 600 m long wire with a high critical current density of 400 A/mm^2 at 18 T and no flux jumping was fabricated. [ABSTRACT FROM PUBLISHER]

Published
2012
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17. Calibration of Inductive Heater for Stability Test of Cable in Conduit Conductor.

Author

Seo, Kazutaka, Takahata, Kazuya, Mito, Toshiyuki, Hayashi, Hidemi, Terazono, Kanichi, Semba, Tomoyuki, and Miyashita, Katsumi

Subjects
SUPERCONDUCTING magnets, CALIBRATION, PHYSICAL measurements, SUPERCONDUCTORS, SUPERCONDUCTIVITY, ELECTRIC currents, HEAT transfer
Abstract

Stability tests employing inductive heaters are useful to evaluate stability margins of cable in conduit conductors (CICC's). The inductive heater, which consists of the resistive induction-coil and the AC or pulse power supply, can introduce eddy currents in the CICC. The frequency is more than one hundred Hz and it can introduce the heat pulse with the duration of several ms. The stability test using the inductive heaters had been reported. However, the ratio of the deposited energies to the components; superconducting strands, conduit and induction-coil, have not been discussed exactly. By the inductive heater, the coupling and eddy current losses are introduced in the strand. In addition, inter-strand coupling loss, eddy current loss in the conduit and joule and/or eddy current losses in the induction-coil itself are introduced. We evaluated these kinds of losses by both experimental and numerical methods. Finally, we evaluated the quench energy margin of the cable in conduit conductor quantitatively. [ABSTRACT FROM AUTHOR]

Published
2005
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19. Influence of Indentation on the Critical Current of Nb3Sn Strands

Author

Nunoya Yoshihiko, Soun Pil Kwon, Miyashita Katsumi, Oshikiri Masayuki, Takahashi Yoshikazu, Shibutani Kazuyuki, Suwa Tomone, Murakami Yukinobu, Nabara Yoshihiro, Tsutsumi Fumiaki, and Ki-Hong Sim

Subjects
Superconductivity, Materials science, Critical depth, Solenoid, Physics and Astronomy(all), deformation before heat treatment, Current sharing, Indentation, ITER, Critical current, Twist, Composite material, Nb3Sn strand, Electrical conductor, critical current, degradation
Abstract

The Japan Atomic Energy Agency (JAEA) is procuring Central Solenoid (CS) conductorsfor all modules forITER. The superconducting properties of the Nb 3 Sn CS conductors will have to sustain 60,000 electromagnetic (EM) cycles. The current sharing temperatures ( T cs ) were stable with EM cycles in short twist pitch conductors.However, the short twist pitch and tight cabling increases indented strands at the contact point between strands before heat treatment. The results of I c measurement on artificially indented Nb 3 Sn strands indicate that I c was almost constant within a critical depth of the indentations.

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