35 results on '"Takeuchi, T."'
Search Results
2. Magnetic Microscopy Using a Circularly Polarized Hard-X-ray Nanoprobe at SPring-8.
- Author
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Suzuki, M., Yumoto, H., Koyama, T., Yamazaki, H., Takeuchi, T., Kawamura, N., Mizumaki, M., Osawa, H., Kondo, Y., Ariake, J., Yasui, A., Kotani, Y., Tsuji, N., Nakamura, T., Hirosawa, S., Yamada, K. T., Kim, S., Kim, K.-J., Ishibashi, M., and Ono, T.
- Subjects
MAGNETIZATION reversal ,MAGNETIC domain ,MICROSCOPY ,MAGNETIC circular dichroism ,MAGNETIC fields ,MAGNETIC structure ,MONOCHROMATORS ,FOCUS (Optics) - Published
- 2020
- Full Text
- View/download PDF
3. 14 MEV NEUTRON IRRADIATION EFFECT ON CRITICAL CURRENT AND CRITCAL MAGNETIC FIELD OF NB3SN AND NB3AL WIRES.
- Author
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Nishimura, A., Takeuchi, T., Nishijima, S., Ochiai, K., Nishijima, G., Watanabe, K., and Shikama, T.
- Subjects
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ALUMINUM wire , *MAGNETIC fields , *NEUTRONS , *IRRADIATION , *SUPERCONDUCTIVITY - Abstract
To investigate the effect of neutron irradiation on superconducting properties, a collaboration network was established among superconducting material engineering and neutronics fields. Within the framework, irradiation test of Nb3Sn and Nb3Al wires by 14 MeV fusion neutron was planned and carried out at Fusion Neutronics Source in Japan Atomic Energy Agency. After the irradiation, critical current and critical magnetic field were measured with 28 T hybrid magnet at Institute for Metals Research in Tohoku University. The irradiation to 3.52×1020 n/m2 showed a slight increase of the critical current of the Nb3Sn wire, and the irradiation to 1.78×1021 n/m2 made the critical current appreciably larger. Regarding the critical magnetic field, no clear change was observed. In the case of Nb3Al wire, a sample irradiated to 1.78×1021 n/m2 showed no increase of the critical current below 200 A which was the limit of the power supply. As for the critical magnetic field, there was no clear improvement similar to the Nb3Sn wire. The increase of the critical current would be caused by knock-on effect of the fast neutron. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
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4. 14 MeV Neutron Irradiation Effect on Superconducting Magnet Materials for Fusion Device.
- Author
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Nishimura, A., Hishinuma, Y., Seo, K., Tanaka, T., Muroga, T., Nishijima, S., Katagiri, K., Takeuchi, T., Shindo, Y., Ochiai, K., Nishitani, T., and Okuno, K.
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NEUTRON irradiation ,IRRADIATION ,NUCLEAR reactions ,SUPERCONDUCTING magnets ,ELECTROMAGNETS ,SUPERCONDUCTORS ,MAGNETIC fields ,FIELD theory (Physics) - Abstract
As a large-scale plasma experimental device is planned and designed, the importance of investigations on irradiation effect of 14 MeV neutron increases and an experimental database is desired to be piled up. Recently, intense streaming of fast neutron from ports are reported and degradation of superconducting magnet performance is anticipated. To investigate the pure neutron effect on superconducting magnet materials, a cryogenic target system was newly developed and installed at Fusion Neutronics Source in Japan Atomic Energy Research Institute. Although production rate of 14 MeV neutron is not large, only 14 MeV neutron can be supplied to irradiation test without gamma ray. Copper wires, superconducting wires, glass fiber reinforced composites are irradiated and the irradiation effects are characterized. At the same time, sensors for measuring temperature and magnetic field are irradiated and their performance was investigated after irradiation. This paper presents outline of the cryogenic target system and some irradiation test results. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2006
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5. First Trial to Fabricate Nb3(Al, Si) Multifilamentary Superconductors by Rapid-Heating and Quenching (RHQ) Process.
- Author
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Banno, N., Takeuchi, T., Kikuchi, A., Lijima, Y., Inoue, K., Yuyama, M., and Wada, H.
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NIOBIUM compounds , *SUPERCONDUCTORS , *HEATING , *CRITICAL currents , *MAGNETIC fields , *SUPERCONDUCTIVITY , *CRYOELECTRONICS - Abstract
Aiming at further improvement of high-field critical current density, Jc, in the Nb3Al conductors, Si addition was attempted. To fabricate the Nb3(Al,Si) conductors, we used two times the rapid-heating and quenching (RHQ) technique. First, drawability of the Nb/Al-Si composite wire has been improved by specially using the RHQ technique at an early stage of the precursor fabrication, where only the Al-alloy core is rapidly solidified from the molten state to form a fine microstructure of the core without any reaction with the Nb. This process makes the subsequent restacking and drawing process easier. Using this technique, multifilamentary Nb/Al-Si precursors with piece length of 30 m have been successfully fabricated at our laboratory workshop. For the prepared precursors, another RHQ was attempted for the formation of the high stoichiometric A15 phase. With increasing Si content, the upper critical field was enhanced, while providing the high Jc property in high magnetic fields such as 150 A/mm2 at 25 T, 4.2 K. Meanwhile, with Si additions of 2 at% to the core, metastable BCC Nb(Al,Si)ss phase was formed by the second RHQ process. This phase can be transformed to the A15 phase by a subsequent annealing around 800°C. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2004
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6. Conceptual Design of a Large-Aperture Dipole Magnet for HL-LHC Upgrade.
- Author
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Xu, Q., Nakamoto, T., Ogitsu, T., Sasaki, K., Terashima, A., Tsuchiya, K., Yamamoto, A., Todesco, E., Kikuchi, A., and Takeuchi, T.
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LUMINOSITY ,HADRON colliders ,SUPERCONDUCTORS ,MAGNETIC fields ,MAGNETIC dipoles ,COEFFICIENTS (Statistics) - Abstract
The development of a large-aperture (120–180 mm) dipole magnet is proposed in the framework of the CERN-KEK cooperation program. The application target is the D1 magnet (separation dipoles) replacement for the HL-LHC (High Luminosity—Large Hadron Collider) upgrade. The Cos-theta type coil cross section and the shell-based structure are adopted in the conceptual design of this magnet. The nominal field is estimated to be 6–10 T at 1.9 K with a 30-mm-width coil arranged in two layers. The candidates of superconductor are \Nb3\Al, \Nb3\Sn and Nb-Ti. We present the analytical estimation of the key parameters of this magnet and the simulation of the actual design which includes the field quality, the stray field, and the stress distribution in the coil. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
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7. Development of C6+ laser ion source and RFQ linac for carbon ion radiotherapy.
- Author
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Sako, T., Yamaguchi, A., Sato, K., Goto, A., Iwai, T., Nayuki, T., Nemoto, K., Kayama, T., and Takeuchi, T.
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RADIOTHERAPY ,ION beams ,CARBON ,ION sources ,PARTICLE beams ,MAGNETIC fields - Abstract
A prototype C6+ injector using a laser ion source has been developed for a compact synchrotron dedicated to carbon ion radiotherapy. The injector consists of a laser ion source and a 4-vane radio-frequency quadrupole (RFQ) linac. Ion beams are extracted from plasma and directly injected into the RFQ. A solenoid guides the low-energy beams into the RFQ. The RFQ is designed to accelerate high-intensity pulsed beams. A structure of monolithic vanes and cavities is adopted to reduce its power consumption. In beam acceleration tests, a solenoidal magnetic field set between the laser ion source and the RFQ helped increase both the peak currents before and after the RFQ by a factor of 4. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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8. Quench and Normal Zone Propagation Characteristics of RHQT-Processed Nb3Al Wires Under Cryocooler-Cooling Conditions.
- Author
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Murase, Satoru, Shimoyama, M., Nanato, N., Kim, S. B., Nishijima, G., Watanabe, K., Kikuchi, A., Banno, N., and Takeuchi, T.
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METAL quenching ,HEAT treatment of metals ,SUPERCONDUCTORS ,MAGNETIC fields ,CRYOELECTRONICS ,ELECTRIC conductivity ,COMBINATORIAL designs & configurations - Abstract
The minimum quench energy (MQE) and normal zone propagation velocity (NZPV) of three kinds of Nb
3 AI superconductors fabricated by the rapid heating, quenching and transformation (RHQT) process were measured under various conditions of applied magnetic field (10-14 T), temperature (7-11 K), and transport current (80-95% of the critical current), while cooled by a cryocooler for developing the over 20-T class cryogen-free magnet. As a result, MQE values were related to the critical current density (Jo); high MQE was obtained for low Jc . It is assumed that Jc has a stronger influence on the MQE than specific heat, thermal conductivity, resistivity, and other parameters of the composite superconductor including the matrix and the stabilizer. NZPV was mainly proportional to the transport current density varying with applied field and temperature. The second contribution to NZPV is assumed to be heat capacity depending on the wire configuration. [ABSTRACT FROM AUTHOR]- Published
- 2009
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9. Superfluid Density and Angular Dependence of the Energy Gap in Optimally Doped (BiPb)2(SrLa)2CuO6+ δ .
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Strässle, S., Khasanov, R., Kondo, T., Heron, D. O. G., Kaminski, A., Keller, H., Lee, S. L., and Takeuchi, T.
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DENSITY ,BAND gaps ,MAGNETIC fields ,SUPERCONDUCTIVITY ,FERMI surfaces - Abstract
We present a muon-spin rotation study of the optimally doped cuprate superconductor (BiPb)
2 (SrLa)2 CuO6+ δ . The measured magnetic field dependence of the in-plane magnetic penetration λab suggests superconductivity with a dominant d-wave order parameter. The comparison of the temperature dependence of λab with calculations, assuming the angular gap symmetry as obtained from photoemission measurements, is consistent with a partial suppression of the quasi-particle weight towards the anti-nodal region of the Fermi surface. This suggests that the superconducting and the pseudogap state are dominated by different parts of the Fermi surface. [ABSTRACT FROM AUTHOR]- Published
- 2009
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10. Status and perspective of the Nb3Al development
- Author
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Takeuchi, T., Kikuchi, A., Banno, N., Kitaguchi, H., Iijima, Y., Tagawa, K., Nakagawa, K., Tsuchiya, K., Mitsuda, C., Koizumi, N., and Okuno, K.
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NIOBIUM , *ALUMINUM , *STRAINS & stresses (Mechanics) , *MAGNETIC fields - Abstract
Abstract: Nb3Al has advantages of better tolerance to strain/stress and a higher critical magnetic field (30T at 4.2K) for stoichiometric composition over Nb3Sn. The rapid-heating, quenching and transformation annealing (RHQT) process enables to form a stoichiometric Nb3Al with fine grain structures via metastable bcc supersaturated-solid-solution. As a result a large critical current density of Nb3Al is achieved over the whole range of magnetic fields without trading off the excellent strain tolerance. A long-length of RHQ processing has been established, and a rectangular but Cu stabilized Nb3Al strand is about be commercially available for NMR uses. Ag or Cu internal stabilization and Cu ion-plating/electroplating techniques have been also developed to enable the stabilized round wire for accelerator and fusion magnets. Successfully energized test coils that were manufactured with a wind-and-react technique have demonstrated that a long piece of Cu stabilized RHQT Nb3Al wire is really available for practical applications. [Copyright &y& Elsevier]
- Published
- 2008
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11. Reduction of the Matrix Ratio for Improvement of the Non-Cu Jc of Nb3A1 Wires.
- Author
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Banno, N., Takeuchi, T., Iijima, Y., Kikuchi, A., and Tagawa, K.
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ALUMINUM wire , *PLASMA sheaths , *SUPERCONDUCTIVITY , *ELECTRIC currents , *SUPERCONDUCTING magnets , *SUPERCONDUCTING composites , *SUPERCONDUCTORS , *MAGNETIC fields , *CRYOELECTRONICS - Abstract
We attempted to reduce the matrix ratio down to 0.5 and 0.25 for RHQT (rapid-heating, quenching and transformation) Nb3 Al wires, which is directly related to improvement of the non-Cu Jc. The Ta matrix was chosen to improve the wire strength. It was found that the matrix ratio of 0.25 is too small to carry out RHQ treatment although drawing was possible by using cassette-roller dies (CRDs) as well as conical dies. The reduction of the matrix ratio down to 0.5 can also be achieved. However, the scale-up would make the drawing very difficult. It would be necessary for the scale-up to improve adhesion among the jelly-roll (JR) cores and also the outer Ta sheath in the multi-billet. The RHQ treatment was possible for the wire with a matrix ratio of 0.5. However, it was successful only when the wire diameter was less than 1.13 mm. It is necessary to suppress the experienced bend strain in the operation. The non-Cu Jc was found to be improved by about 20% by the reduction of the matrix ratio, compared to conventional Nb3Al wires. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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12. Quench Tests of Nb3A1 Small Racetrack Magnets.
- Author
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Yamada, R., Kikuchi, A., Tartaglia, M., Ambrosio, G., Andreev, N., Barzi, E., Carcagno, R., Feher, S., Kashikin, V. V., Kotelnikov, S., Lamm, M., Novitski, I., Orris, D., Pischalnikov, Y., Takeuchi, T., Tompkins, J. C., Turrioni, D., Wake, M., Wands, R., and Xiao, J.
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SUPERCONDUCTIVITY ,SUPERCONDUCTING magnets ,SUPERCONDUCTING composites ,SUPERCONDUCTORS ,MAGNETIC fields ,CRYOELECTRONICS ,ELECTRIC currents ,FIELD theory (Physics) ,MAGNETIC flux ,ELECTROMAGNETIC induction - Abstract
Two Cu stabilized Nb
3 Al strands, F1 (Nb matrix) and F3 (Ta matrix), fabricated at NIMS were wound into Rutherford cables at Fermilab in collaboration with NIMS. A Small Race-track magnet using F! Rutherford cable, the first Nb3 Al dipole magnet in the world, was constructed and tested to full current at Fermilab. This magnet was tested extensively to full short sample data and its quench characteristics were studied and reported. The 3-D magnetic field calculation was done with ANSYS to find the peak field. The quench characteristics of the magnet are explained with the characteristics of the Nb3 Al strand and Rutherford cable. The Small Racetrack magnet built using Ta matrix F3 strand was constructed and will be tested in the near future. The advantages and disadvantages of these Nb3 Al cables are briefly discussed. [ABSTRACT FROM AUTHOR]- Published
- 2008
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13. Development of RHQT-Processed Nb3A1 Wire for High-Field Accelerator Magnet Applications.
- Author
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Tsuchiya, K., Mitsuda, C., Terashima, A., Yamamoto, A., Takeuchi, T., Banno, N., Nimori, S., Kikuchi, A., Iijima, Y., Okamoto, K., Fukuda, T., Takenaka, K., Takao, T., and Tagawa, K.
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SUPERCONDUCTIVITY ,ELECTRIC currents ,SUPERCONDUCTING magnets ,SUPERCONDUCTING composites ,SUPERCONDUCTORS ,MAGNETIC fields - Abstract
In the development of RHQT-processed Nb
3 Al wires for high-field accelerator magnet applications, one of the major objectives is to increase the non-copper critical current density in the field range of 12-15 T. To pursue this goal, a low-matrixratio wire was fabricated, and the effects of the RHQ conditions and the area reduction after the RHQ treatment on the properties of the wire were investigated. This paper describes the details and results of this study. [ABSTRACT FROM AUTHOR]- Published
- 2008
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14. Cu Stabilized Nb3A1 Strands for the High Field Accelerator Magnet.
- Author
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Kikuchi, A., Yamada, R., Barzi, E., Lamm, M., Takeuchi, T., Turrioni, D., and Ziobinb, A. V.
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SUPERCONDUCTING magnets ,SUPERCONDUCTING composites ,SUPERCONDUCTING generators ,SUPERCONDUCTORS ,SUPERCONDUCTIVITY ,MAGNETIC fields ,ELECTROPLATING chemicals ,TANTALUM ,ELECTROCHEMISTRY - Abstract
Characteristics of recently developed Nb
3 Al strand though the RHQT (rapid heating/quenching and transformation) process are described. One kilometer-long copper stabilized Nb3 Al round strands were economically fabricated with ion-plating and electroplating. The copper electroplating was successfully done with the high velocity of 5 m/h. A strong bonding between the copper and the precursor was achieved, and the mechanical rolling test did not show the separation of the copper stabilizer from the precursor. The rolled Nb3 Al strands showed no degradation both in critical current density and RRR value. Magnetic instability at 4.2 K at low fields was apparently improved on the recent F3 strand, relative to the previously F1 stand because a tantalum was used for the interfilament matrix of precursor. The large magnetic flux jumps, which were observed with the F! strand, were suppressed at 4.2 K, although appeared again below 3.0 K. The twisted strands are shown to be effective to reduce the time-dependent eddy current coupling. It was obtained 48 μm of Deff on F3 strand with twist pitch of 45 mm. In addition, the transverse pressure test for the F1 Nb3 Al strand was performed at 4.2 K and 12 T. The critical, current did not degrade with the transverse pressure up to 210 MPa. [ABSTRACT FROM AUTHOR]- Published
- 2008
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15. Optimization of the Sn-Ta Sheet Composition in Jelly Roll Processed (Nb, Ta)3Sn Wires.
- Author
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Tachikawa, K., Koyata, Y., Tsuyuki, T., Kawanabe, M., and Takeuchi, T.
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MATHEMATICAL optimization ,SUPERCONDUCTORS ,MAGNETIC fields ,MAGNETICS ,ELECTRIC currents ,SUPERCONDUCTIVITY ,ELECTRICAL conductors ,METAL castings ,INDUSTRIAL costs - Abstract
Tightly shrunk Sn-Ta ingots with good workability were prepared by the reaction at 750°C–800°C from the mixed powder of Sn and Ta containing 25–30at%Ta. Then Jelly Roll processed wires were fabricated starting from Sn-Ta/Nb composites in which thick (Nb, Ta)
3 Sn layers were produced after the heat treatment. A few wt% Cu addition to the Sn-Ta mixed powder reduces the heat treatment temperature. Moreover, a few at% Ti substitution for Sn + Ta enhances the formation of (Nb, Ta)3 Sn layer, and improves the non-Cu Jc of the wire. In the present study, effect of the Sn-Ta-Ti-Cu sheet composition on the structure and high-field performance of the wire has been studied. It has been found that a small amount of Ti and Cu addition decreases the amount of Ta in the sheet from 25–30at% to 10at%, which is favorable for the material cost reduction. Moreover, it has been revealed that thick (Nb, Ta)3 Sn layers are synthesized even if the Cu concentration in the sheet is decreased less than lwt% when a few at% Ti is substituted. A non-Cu Jc of ∼ 150 A/mm2 has been obtained at 22 T and 4.2 K in the wires with different sheet composition after the heat treatment at 725°–750°C. [ABSTRACT FROM AUTHOR]- Published
- 2007
- Full Text
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16. Feasibility Study of Nb3Al Rutherford Cable for High Field Accelerator Magnet Application.
- Author
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Yamada, R., Kikuchi, A., Ambrosio, G., Andreev, N., Barzi, E., Cooper, C., Feher, S., Kashikin, V. V., Lamm, M., Novitski, I., Takeuchi, T., Tartaglia, M., Turrioni, D., Verweij, A. P., Wake, M., Willering, G., and Zlobin, A. V.
- Subjects
COPPER ,CABLES ,POWER transmission ,MAGNETS ,MAGNETICS ,MAGNETIC fields ,ELECTRIC currents ,ELECTRON accelerators - Abstract
Feasibility study of Cu stabilized Nb3AI strand and Rutherford cable for the application to high field accelerator magnets are being done at Fermilab in collaboration with NIMS. The Nb3A1 strand, which was developed and manufactured at NIMS in Japan, has a non-copper Jc of about 844 A/mm² at 15 Tesla at 4.2 K, a copper content of 50%, and filament size of about 50 microns. Rutherford cables with 27 Nb
3 Al strands of 1.03 mm diameter were fabricated and tested. Quench tests on a short cable were done to study its stability with only its self field, utilizing a high current transformer. A pair of 2 meter long Nb3 Al cables was tested extensively at CERN at 4.3 and 1.9 K up to 11 Tesla including its self field with a high transport current of 20.2 kA. In the low field test we observed instability near splices and in the central region. This is related to the flux-jump like behavior, because of excessive amount of Nb in the Nb3 Al strand. There is possibility that the Nb in Nb3 Al can cause instability below 2 Tesla field regions. We need further investigation on this problem. Above 8 Tesla, we observed quenches near the critical surface at fast ramp rate from 1000 to 3000 A/sec, with quench velocity over 100 m/sec. A small racetrack magnet was made using a 14 m of Rutherford cable and successfully tested up to 21.8 kA, corresponding to 8.7 T. [ABSTRACT FROM AUTHOR]- Published
- 2007
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17. Trial Manufacture of a 2.5 km Class Long-Length of Nb-Matrix Jelly-Roll Nb/Al Precursor Wire for RHQT Process.
- Author
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Tagawa, K., Takeuchi, T., Banno, N., Lijima, Y., Kikuchi, A., Kitaguchi, H., Iwaki, G., and Sakurai, Y.
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MAGNETIC fields , *ELECTRICAL conductors , *BUS conductors (Electricity) , *NUCLEAR magnetic resonance , *ELECTRIC coils , *MAGNETIC circuits - Abstract
Since the RHQT-Nb3Al conductor shows excellent superconducting characteristics in high magnetic fields, its application to a 1 GHz NMR insert coil is in particular expected. For such an application, the development of a long-length of RHQT-Nb3Al wire is indispensable. However, the unit length of wire achieved was no more than 400 m so far, due to a restricted size of the multi-billet, while about a 2.5 km-length of wire is necessary for the NMR insert coil application. Thus, an attempt was made to produce a 2.5 km-length of precursor wire by using a large-sized billet, and we have succeeded in producing such a long-length of precursor wire (2.6 km) without any breaking of wire during hydrostatic extrusion and subsequent drawing processes. [ABSTRACT FROM AUTHOR]
- Published
- 2005
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- View/download PDF
18. Fabrication of V-Based Laves Phase Compound Multifilamentary Wires by Applying a Rapidly-Heating/Quenching Process to PIT Precursors and Using a V Tube.
- Author
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Hishinuma, Y., Kikuchi, A., Lijima, Y., Yoshida, Y., Takeuchi, T., Nishimura, A., and Inoue, K.
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MAGNETIC fields ,VACUUM ,METAL quenching ,HEAT treatment of metals ,ALLOYS ,TANTALUM isotopes - Abstract
We fabricated V-based Laves phase compound such as V
2 (Hf, Zr) multifilamentary wire by applying a rapidly-heating/quenching (RHQ) process. Pure Hf and Zr metal powders were mixed and it put in high pure V tube composed with tantalum (Ta), and it was drawn in order to make lire (powder-in-tube (PIT) method). The wires were heat-treated by RHQ process, and some were annealed additionally in vacuum. Since Ta has a higher melting point than V, it is expected that the alloying prevents from breakage of the precursor wire during RHQ treatment because the maximum temperature exceeds 2500 K. SEM observation confirmed that the thick reaction layer within about 10 microns was formed on the boundary of the powder mixture filament and the V matrix after the RHQ. Tc values of the as-quenched samples increased with increasing maximum temperature during RHQ process, and the maximum mid point Tc value was about 8.0 K. The transport Jc properties under magnetic fields were also investigated. [ABSTRACT FROM AUTHOR]- Published
- 2005
- Full Text
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19. In-Situ Resistance Measurements of RHQT Processed Nb3Al Superconductors.
- Author
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Tan, K. S., Hopkins, S. C., Pong, I., Steam, R. J., Glowacki, B. A., Kikuchi, A., Takeuchi, T., and Inoue, K.
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SUPERCONDUCTIVITY ,ELECTRIC currents ,SOLID state electronics ,MAGNETIC fields ,CRYSTALLIZATION ,ELECTRIC resistance - Abstract
The bcc supersaturated solid solution, Nb(Al)
ss obtained by rapid heating and quenching of a multifilamentary Nb/Al composite wire has shown a change from a disordered to an ordered structure before finally transforming to the A15 Nb3 Al phase. It is believed that such ordering is responsible for suppressing the critical temperature, Tc , the upper critical magnetic field, Bc2 , and the critical current density, Jc . The ordering of the bcc phase can be suppressed by increasing the heating rate, and therefore this should improve the superconducting properties of the resulting Nb3 Al wires. Enhancement of Jc can also be achieved if the Nb(Al)ss phase is mechanically deformed before transformation. The transformation process was studied in as-quenched and mechanically deformed Nb/Nb(Al)ss wires by in-situ resistance measurement under heating at two different rates, 200°C/h and 800°C/h. The electrical resistivities of the wires decrease abruptly during the transformation from bcc to A15 phases and the process is much faster for mechanically deformed wires. Also, the healing rate affects the onset temperature of the A15 transformation. The results also show that the Jc of the transformed Nb3 Al wires increases with increasing reduction in area. [ABSTRACT FROM AUTHOR]- Published
- 2005
- Full Text
- View/download PDF
20. New High-Field (Nb, Ta)3Sn Superconductors Prepared From Sn-Ta Matrix.
- Author
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Tachikawa, K., Izawa, H., Ikeda, Y., Koyata, T., and Takeuchi, T.
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SUPERCONDUCTORS ,VACUUM ,MATRICES (Mathematics) ,SOLID state electronics ,MAGNETIC fields ,ELECTRIC currents - Abstract
Structure and high-field performance of(Nb, Ta)
3 Sn conductors fabricated by using ductile Sn-Ta matrix are reported. A mixed powder of Sn and Ta with or without a small amount of Cu addition was melted at 800° C in vacuum. The resulting Sn-Ta alloy was rolled into a sheet 100 μm in thickness. The Sn-Ta sheet was laminated with a Nb foil of the same thickness, and wound around a Nb-4at%Ta rod forming a Jelly Roll composite. The composite was encased in a Nb-4at%Ta tube, and then fabricated into a wire without intermediate annealing. The wire with no Cu addition to the Sn-Ta sheet and reacted at 900°C showed a non-Cu Jc of 100 A/mm2 at 23 T and 4.2 K. The non-Cu Jc of the wire at 2.1 K and 25 T reached 100 A/mm<2 , the upper critical field of the wire being 28.4 T. A small amount of Cu addition to the Sn-Ta sheet appreciably reduced the reaction temperature, and produced a non-Cu Jc of 100 A/mm2 at 22 T and 4.2 K after the reaction at 800° C. Another process for fabricating multifilamentary-type (Nb, Ta)3 Sn conductors using ductile Sn-Ta/Nb composite is also being studied. [ABSTRACT FROM AUTHOR]- Published
- 2004
- Full Text
- View/download PDF
21. Microstructure and Jc - B Performance of DRHQ Processed Nb3A1 Tape with Ag Stabilizer.
- Author
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Kikuchi, A., Iijima, Y., Banno, N., Takeuchi, T., Inoue, K., Nimori, S., Kosuge, M., and Yuyama, M.
- Subjects
MAGNETIC fields ,FIELD theory (Physics) ,MAGNETICS ,ELECTRICAL engineering ,ELECTRICAL conductors ,MATERIALS - Abstract
The DRHQ process was applied to the jelly-rolled Nb
3 Al precursors having internal Ag stabilizers. The Ag internal stabilizer is effective to improve the superconducting stability of the DRHQ processed conductor with the Ag-stabilizer/non-Ag ratio of 0.32. The DRHQ process needs a reduction of a bending strain of the precursors, such as tape-formed specimen. The maximum Tc and Bc2 (4.2 K) of the DRHQ-processed tape with Ag stabilizer are 18.4 K and 29.7 T, respectively. Large transport core-Jc (4.2 K) of 210 A/mm2 was obtained at high magnetic field of 25 T, which is 20 times larger than that of the typical RHQT-processed wires. On the other hand, Jc in fields below 20 T apparently decreased with increasing the peak heating temperature during the second-RHQ. According to the TEM observation, the stacking faults were still formed in the DRHQ-processed Nb3 Al, but their density becomes very small compared with that of the RHQT-processed Nb3 Al. In addition, the stacking faults gradually vanished with increasing the peak heating temperature. The grain size of several hundred nanometers for the DRHQ-Nb3 Al is still rather small. Thus, these results support that the stacking faults should be dominant as the effective pinning center for the both of RHQT- and DRHQ-processed Nb3 Al conductors. [ABSTRACT FROM AUTHOR]- Published
- 2004
- Full Text
- View/download PDF
22. Stabilization and Coil Performance of RHQT-Processed Nb[sub 3]Al Conductors.
- Author
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Takeuchi, T., Banno, N., Fukuzaki, T., Kiyoshi, T., Matsumoto, S., Wada, H., Aihara, K., Wadayama, Y., Okada, M., Tagawa, K., and Nakagawa, K.
- Subjects
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MAGNETIC properties of superconductors , *MAGNETIC fields - Abstract
Examines the stabilization and magnetic field performance of Nb[sub 3]Al superconductors. Critical current enhancement by deformation during cladding; X-ray diffraction patterns of the superconductors; Specifications of wind and react Nb[sub 3]Al solenoid coils.
- Published
- 2001
- Full Text
- View/download PDF
23. Magnetic properties and B–T phase diagram in the heavy-fermion superconductor CePt3Si
- Author
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Takeuchi, T., Shiimoto, M., Kohara, H., Hashimoto, S., Yasuda, T., Matsuda, T.D., Haga, Y., Settai, R., and Ōnuki, Y.
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SUPERCONDUCTORS , *MAGNETIC fields , *FERMIONS , *MAGNETOSTRICTION , *THERMAL expansion - Abstract
Abstract: Magnetic and superconducting properties have been investigated on a single crystal of CePt3Si which is the recently discovered heavy-fermion superconductor. The effect of magnetic field on the antiferromagnetic transition temperature was studied by the iso-field thermal expansion coefficient. From these results, together with the results of the electrical resistivity under magnetic fields, magnetostriction and magnetization measurements, we have constructed the magnetic and superconducting phase diagrams for and [001]. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
24. Stable barium compounds in YBa2Cu3O y superconductors
- Author
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Kita, R., Suzuki, K., Takeuchi, T., Iwasa, T., Miura, O., Ichino, Y., Yoshimura, T., Yoshida, Y., Yamada, K., Kaneko, K., and Ichinose, A.
- Subjects
- *
COPPER oxide superconductors , *BARIUM compounds , *SINTERING , *TEMPERATURE effect , *CRITICAL currents , *MAGNETIC fields , *X-ray diffraction , *PHYSICAL constants - Abstract
Abstract: The stability of various amounts of Ba3Cu3In4O12 (334) or BaTbO3 (BTO) in a sintered YBa2Cu3O y (YBCO) matrix was examined. Samples with added 334 or BTO exhibited critical temperatures (T c) above 90K for up to 20vol.% addition and improved critical current densities (J c) under a magnetic field. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis indicated that 334 and BTO did not react with the YBCO matrix under the sintering conditions used. The normalized J c under a magnetic field of 1T reached a maximum at 14vol.% of 334 addition and 20vol.% BTO addition. YBCO thin films with added BTO showed a gradual decrease in the T c with increasing BTO content. YBCO films with added 334 showed a constant T c of 87K up to a 334 content of 4vol.%. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
25. Magneto-mechanical evaluation for twinning plane movement driven by magnetic field in ferromagnetic shape memory alloys
- Author
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Kakeshita, T., Fukuda, T., and Takeuchi, T.
- Subjects
- *
MAGNETIC fields , *ALLOYS , *METALLIC composites , *MAGNETICS - Abstract
Abstract: Rearrangement of martensite variants under magnetic field has been investigated by using single crystals of three ferromagnetic shape memory alloys: a disordered Fe–31.2at.% Pd alloy, an ordered (degree of order ∼0.8) Fe3Pt, and stoichiometric Ni2MnGa. Each alloy transforms from a cubic parent phase to a tetragonal or pseudotetragonal martensite phase whose tetragonality is about 0.94 at low temperatures. We evaluated the magnetic shear stress τ mag acting across the twinning plane under magnetic field, by using magnetic anisotropy constant and twinning shear, and compared it with the shear stress required for the rearrangement τ req, which is obtained from tensile or compressive tests. As a result, we confirmed that τ mag is larger than τ req when the rearrangement of variants occurs by magnetic field and vice versa regardless of temperature and field direction. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
26. PROCESSING OF HIGH-PERFORMANCE Nb{sub 3}Sn WIRES THROUGH A NEW DIFFUSION REACTION USING Sn BASED ALLOYS
- Author
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Takeuchi, T [National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan)]
- Published
- 2010
- Full Text
- View/download PDF
27. STRUCTURE AND HIGH-FIELD PERFORMANCE OF JELLY ROLL PROCESSED Nb{sub 3}Sn WIRES USING Sn-Ta AND Sn-Ti BASED ALLOY SHEET
- Author
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Takeuchi, T [National Institute for Materials Science Tsukuba, Ibaraki 305-0047 (Japan)]
- Published
- 2008
- Full Text
- View/download PDF
28. Observation of Modulated Quadrupolar Structures in PrPb{sub 3}
- Author
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Takeuchi, T [Low Temperature Center, Osaka University, Toyonaka 560-0043 (Japan)]
- Published
- 2005
- Full Text
- View/download PDF
29. Development of a 56 GHz ECH system for deuterium plasma experiments of a low magnetic field in LHD.
- Author
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Yanai, R., Ii Tsujimura, T., Kubo, S., Yoshimura, Y., Takeuchi, T., Ito, S., Mizuno, Y., Nishiura, M., Igami, H., Kenmochi, N., Takahashi, H., Shimozuma, T., Osakabe, M., and Morisaki, T.
- Subjects
- *
DEUTERIUM plasma , *DEUTERIUM , *ELECTRON cyclotron resonance heating , *MAGNETIC fields , *NEUTRAL beams - Abstract
• 56 GHz ECH system was newly designed and constructed in LHD. • The dependences of plasma startup on the polarization and ECH power were obtained. • Pure deuterium plasma experiment in a low magnetic field was succeeded in the LHD. We have completed establishing a 56 GHz electron cyclotron heating (ECH) system with a new gyrotron to realize high β plasma experiments with pure deuterium gas in the Large Helical Device (LHD). This new ECH system made it possible to conduct the relatively low magnetic field experiment around 1 T with pure deuterium gas because tangential neutral beam injection (NBI) systems of deuterium beams did not have enough power to initiate plasma in the LHD. We succeeded in initiating and sustaining pure deuterium plasma in the magnetic field of 1 T by using the 56 GHz ECH system and the deuterium NBI (D-NBI). This new ECH system contributed to expanding the new experimental regime in the LHD. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
30. Quick screening for new flux pinning materials in YBCO films with the combinatorial-PLD method
- Author
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Yoshimura, T., Ichino, Y., Yoshida, Y., Takai, Y., Kita, R., Suzuki, K., and Takeuchi, T.
- Subjects
- *
FLUX pinning , *COPPER oxide superconductors , *ELECTRIC properties of thin films , *PULSED laser deposition , *MAGNETIC fields , *PERFORMANCE evaluation , *SUBSTRATES (Materials science) , *ND-YAG lasers - Abstract
Abstract: An effective way to improve the superconducting properties in REBa2Cu3O y (REBCO) films under a magnetic field is to dope artificial pinning centers (APC). The pinning performance depends on the content of the APC materials. Usually, the optimal APC content is explored by preparing films one at a time from the REBCO target using different APC material content, which is an extremely time-consuming process. The combinatorial-PLD (C-PLD) method allowed us to prepare films that continuously changed in composition across a single substrate. In this study, we used the C-PLD method to prepare BaSnO3 (BSO)-doped YBCO films. The films were deposited on SrTiO3 substrate using a fourth-harmonic Nd:YAG laser. From the results of the J c–B curves at 77K and B//c, the film that contained 3.2vol.% of BSO exhibited the best pinning performance in this study. We showed that the C-PLD method was efficient for quick screening of the optimal APC content with only one deposition. We also used the C-PLD method to explore new APC materials, and proved that it can quickly evaluate the new APC materials Ba3Cu3In4O12 and BaTbO3. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
31. Superfluid Density and Angular Dependence of the Energy Gap in Optimally Doped (BiPb)2(SrLa)2CuO6+ δ .
- Author
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Strässle, S., Khasanov, R., Kondo, T., Heron, D. O. G., Kaminski, A., Keller, H., Lee, S. L., and Takeuchi, T.
- Subjects
- *
DENSITY , *BAND gaps , *MAGNETIC fields , *SUPERCONDUCTIVITY , *FERMI surfaces - Abstract
We present a muon-spin rotation study of the optimally doped cuprate superconductor (BiPb)2(SrLa)2 CuO6+ δ . The measured magnetic field dependence of the in-plane magnetic penetration λ ab suggests superconductivity with a dominant d-wave order parameter. The comparison of the temperature dependence of λ ab with calculations, assuming the angular gap symmetry as obtained from photoemission measurements, is consistent with a partial suppression of the quasi-particle weight towards the anti-nodal region of the Fermi surface. This suggests that the superconducting and the pseudogap state are dominated by different parts of the Fermi surface. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
32. Magnetocrystalline anisotropy constant and twinning stress in martensite phase of Ni–Mn–Ga
- Author
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Okamoto, N., Fukuda, T., Kakeshita, T., and Takeuchi, T.
- Subjects
- *
MARTENSITE , *MAGNETIC fields , *SHAPE memory alloys , *ANISOTROPY - Abstract
Abstract: We have examined rearrangement of martensite variants driven by magnetic field for 10M martensite in Ni2MnGa and 2M martensite in Ni2.14Mn0.92Ga0.94 in a wide temperature range below each transformation temperature. The following results are obtained: (i) the twinning plane of the 10M martensite moves by the application of magnetic field, but that of 2M martensite does not at any temperature, (ii) in order to explain such difference, we have evaluated the maximum of the magnetic shear stress acting across the twinning plane (), which is calculated by using the magnetocrystalline anisotropy constant (K u) measured in this study, and the twinning shear stress (τ req) obtained by compressive test in this study for the 10M and 2M martensites, and have confirmed whether or not the relation of is satisfied for 10M martensite and that of is satisfied for 2M martensite. As a result, the above condition is satisfied at any temperatures for 10M and 2M martensites. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
33. Pressure- and field-induced magnetic instabilities in a heavy-fermion antiferromagnet Ce7Ni3
- Author
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Umeo, K., Motoya, K., Kadowaki, H., Aso, N., Tayama, T., Sakakibara, T., Kurita, N., Hedo, M., Uwatoko, Y., Takeuchi, T., and Takabatake, T.
- Subjects
- *
PARTICLES (Nuclear physics) , *NEUTRON diffraction , *MAGNETIC fields , *HIGH pressure (Science) - Abstract
Abstract: We investigated ground state properties of a heavy-fermion antiferromagnet Ce7Ni3 under hydrostatic pressures and magnetic fields. This compound undergoes two antiferromagnetic phase transitions at T N1 =1.9K and T N2 =0.7K. Below T N1, a spin-density-wave (SDW) develops. Upon applying rather weak pressure 0.39GPa= P c, both T N1 and T N2 vanish, and non-Fermi liquid behavior appears in the specific heat and magnetic susceptibility. The enhancement of residual resistivity along the a axis near P c is attributed to the increased spin fluctuations along the a axis. By applying fields B along the c axis, T N1 is suppressed and vanishes at 0.3T. Magnetoresistance, specific-heat, and magnetization measurements revealed another field-induced magnetic (FIM) phase in the region B || c >0.7T and T <0.5K. Neutron diffraction experiments indicate that the magnetic unit cell in the c-plane for the FIM phase is treble that of the chemical unit cell. Moreover, this magnetic reflection intensity remains even in the region between the FIM phase and SDW phase. This observation indicates the presence of large spin fluctuations in the c-plane associated with the magnetic frustration, which should be responsible for the magnetic instability of Ce7Ni3. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
34. Measurement of <f>V–I</f> characteristics of commercial multifilamentary NbTi wires
- Author
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Tsuchiya, K., Kobayashi, T., Shintomi, T., Banno, N., Itoh, K., Nimori, S., and Takeuchi, T.
- Subjects
- *
MAGNETIC fields , *GLASS fibers , *ELECTRIC fields , *ELECTROMAGNETIC fields - Abstract
The voltage–current characteristics of commercial multifilamentary NbTi wires have been examined in the magnetic fields from 0 to 10 T. The measurements were performed using a specimen holder made of a fiberglass epoxy cylinder of 50 mm in diameter. The specimens of 300 mm length were spirally wound on it and the normal-state transition was measured over the central 150 mm of the specimen. The results show that in the field above 3 T the
n -values determined from theV–I traces for the electric field higher than 10 μV/m increase with decreasing field, but below 2 T then -values begin to decrease and take a minimum at about 0.5 T. [Copyright &y& Elsevier]- Published
- 2004
- Full Text
- View/download PDF
35. Magnetic-field-enhanced aniferromagnetism in the noncentrosymmetric heavy-fermion superconductor CePt3Si.
- Author
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Kaneko, K., Stockert, O., Fåk, B., Raymond, S., Skoulatos, M., Takeuchi, T., and Ōnuki, Y.
- Subjects
- *
MAGNETIC fields , *ANTIFERROMAGNETISM , *SYMMETRY (Physics) , *SUPERCONDUCTORS , *SILICON compounds , *PLATINUM compounds - Abstract
The effect of magnetic field on the static and dynamic spin correlations in the noncentrosymmetric heavy-fermion superconductor CePt3Si was investigated by neutron scattering. The application of a magnetic field B increases the antiferromagnetic (AFM) peak intensity. This increase depends strongly on the field direction: for B‖[0 0 1] the intensity increases by a factor of 4.6 at a field of 6.6 T, which corresponds to more than a doubling of the AFM moment, while the moment increases by only 10% for B‖[1 0 0] at 5 T. This is in strong contrast to the inelastic response near the antiferromagnetic ordering vector, where no marked field variations are observed for B‖[0 0 1] up to 3.8 T. The results reveal that the AFM state in CePt3Si, which coexists with superconductivity, is distinctly different from other unconventional superconductors. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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