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ABSTRACT: We developed a 15 kW synchronous motor with a fixed superconducting field winding. It was 8-pole type. Each field coil was a racetrack-shaped single pancake wound with a YBCO superconducting tape. It was fabricated by IBAD-PLD method and 10 mm in width. The rotating armature was composed of a copper winding and an iron core. The field coils were conduction-cooled down to 20 to 30 K through a copper pipe attached to the copper coil flange, in which helium gas was forced-flowed. The completed motor was first tested in the Suzuka factory of Japan motor and Generator Co. Ltd. before shipping as usual. Then it was moved to the test site of the Nagasaki shipyard of Mitsubishi Heavy Industry Ltd. and installed into a ship propulsion test system, which had a propeller with a diameter of 0.5 m. We verified the quite stable underwater operation and the output power of 15 kW-360 rpm as designed.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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T. Izumi,
M. Yoshizumi,
J. Matsuda,
K. Nakaoka,
Y. Kitoh,
Y. Sutoh,
T. Nakanishi,
A. Nakai,
K. Suzuki,
Y. Yamada,
A. Yajima, T. Saitoh
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ABSTRACT: Recent progresses in R&D of the TFA-MOD process for coated conductors are reviewed. On the efforts for high Ic tapes, the new process to prevent the crack formation in the thick film, which is the intermediate annealing between the calcination and the crystallization steps, was developed. Additionally, control of the starting composition, especially for the Ba-poor composition from the Y:Ba:Cu=1:2:3 stoichiometric one, is found to be effective to improve the Jc value of the films. Consequently, the extremely high Ic value of 735A was obtained. On the other hand, a reel-to-reel system has been applied to fabricate long tapes. A reasonable long tape of 25m with 100A was obtained by the increase of the gas flow rate which assists to enhance the conversion reaction rate. Additionally, it was found that the rigorous humidity control in the coating chamber is important to obtain the uniform characteristics in long tapes. The idea was applied to fabricate long tapes and a 56m tape with the end-to-end Ic value of 250A was realized.
Physica C-superconductivity and Its Applications - PHYSICA C. 01/2007; 463:510-514.
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ABSTRACT: Temperature dependence of the ac loss in YBCO superconducting tapes fabricated by IBAD-PLD technique was investigated. The ac loss was measured with a saddle-shaped pickup coil by applying magnetic field perpendicular to the tape. Temperature dependence of Ic-B characteristics was estimated from the observed magnetization curves. The Ic-B curves normalized by the zero-field Ic at the respective temperature coincided with one master curve regardless of temperature. Ic-B characteristics of YBCO superconducting tapes are scaled with temperature. According, when the magnetization curves and the ac loss vs field amplitude curves are normalized by using the zero field Ic at the respective temperature, they coincided with one master curve for any temperature from 4.2 to 77 K. It is verified that the magnetization and the ac loss are scaled with temperature.
Journal of Physics Conference Series 07/2006; 43(1):154.
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ABSTRACT: Three YBCO coated conductors with various critical currents, up to 189 A, were prepared. The magnetization losses without transport current and the total AC losses of the conductors carrying various transport currents in transverse magnetic fields with various orientations were measured electromagnetically to study the AC loss characteristics systematically. The measured total AC losses were compared with the numerical values using a one-dimensional FEM model
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
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ABSTRACT: Gd2Zr2O7 (GZO) layers were deposited on rolled, mirror like polished and electropolished Ni-based alloy (Inconel) tapes by the ion-beam-assisted deposition (IBAD) method and were investigated especially in terms of the effect of substrate roughness on the crystal grain alignment. Their surface roughness, Ra, was 7.6–12.3nm, 4.3–4.7nm and 1.4–3.4nm, respectively. The deposition time was varied from 1h to 6h. Crystalline alignment of these films was observed by X-ray diffraction (XRD) and cross-sectional transmission electron microscope (TEM). The grain alignment of the IBAD–GZO was improved by using flat surfaces. GZO film on the electropolished substrate got to align from closer point near the interface than that on rolled substrates.
Physica C-superconductivity and Its Applications - PHYSICA C. 01/2006; 445:608-610.
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ABSTRACT: YBCO tape is expected to be used in future HTS applications, because it has better J<sub>c</sub> characteristic in high temperatures and in high applied magnetic fields. It is important to consider the stability in superconducting applications. To establish the stability criterion for coated conductors, the characteristics of the transition to the normal state and normal-zone propagation in YBCO sample tapes were examined experimentally and numerically. The YBCO sample tapes were produced by IBAD/PLD method. Measurements were performed as a function of both heat input and operating current for operating temperatures of 55 K, 60 K, and 65 K in a background magnetic field of 5 T. The experimental results were compared with a simulation using a newly developed computer program based on the finite element method (FEM). In the computer program, the I-V characteristics of the YBCO sample tapes were taken into account. The computer program could simulate the normal transition and propagation phenomena and its validity was confirmed. The influence of the thickness of a Ag-stabilizer on the transient thermal behavior of YBCO tapes was examined experimentally and numerically and the results were presented here.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: Long length Y-123 superconducting tapes were produced by reel-to-reel continuous vacuum processing, by using Ion-Beam-Assisted Deposition (IBAD) and Pulsed-Laser-Deposition (PLD). Biaxially textured Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> buffer layers up to 255-m long were fabricated by IBAD with production speed of 0.5-1.0 m/h. Y-123 films were formed on them by PLD with production speed of 1.0-4.0 m/h. A 105-m long Y-123 film was fabricated with uniform thickness of 1.0 μm and Δφ of 3-4°. I<sub>c</sub> of 126 A was obtained in end-to-end at 77 K, 0 T, whose I-V curve had n-value of 28.5. I<sub>c</sub> times length reached 13,230 Am. Another 70-m long Y-123 tape with I<sub>c</sub> over 90 A (77 K, 0 T) was wound into a Solenoid type magnet whose inner diameter was 60 mm. The central field of 0.27 T was obtained at 66 K, with operating current of 130 A.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: The AC losses of YBCO coated conductors fabricated by the IBAD/PLD method were electromagnetically measured. Both the magnetization loss without transport current and the total AC loss during the simultaneous application of AC transport current and an AC external magnetic field were measured. The AC losses were numerically calculated using the one-dimensional FEM model. The magnetic field dependence and the spatial distribution of critical current density were taken into account in numerical calculations, and the calculated AC losses were compared with the measured AC losses. The critical current, the transport current, and the applied external magnetic field were varied in order to calculate the total AC loss systematically.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: We investigated the ac loss properties of YBCO superconducting tapes fabricated by IBAD-PLD technique. The thickness of a YBCO superconducting layer was 0.5 and 1 μm. Sample tapes of 60 mm in length and 10 mm in width were stacked into multilayers and inserted into a saddle-shaped pickup coil. The ac loss was measured at 64 K and 77 K by applying external ac magnetic field. The magnetic field angle was changed by rotating the sample stack around its longitudinal axis. The ac loss for the smaller amplitude than the effective penetration field strongly depended on the number of stacked tapes owing to the demagnetization effect. On the other hand, the ac loss for the much larger amplitude than that was independent of the number of tapes. In addition the ac loss decreased monotonically with decreasing field angle against the wide surface for any amplitude. We proposed the theoretical expression to estimate the ac losses for any field angle by using the observed ac losses in perpendicular magnetic field and confirmed the applicability by good agreement between theory and experiment.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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T. Izumi,
H. Fuji,
Y. Aoki,
R. Teranishi,
K. Nakaoka,
J. Matsuda,
Y. Kitoh,
Y. Yamada,
Y. Shiohara,
Y. Iijima, T. Saitoh,
T. Goto,
A. Yoshinaka,
A. Yajima
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ABSTRACT: Recent progress in the research and development of the TFA-MOD processing for the coated conductors in Japan was reviewed. For the higher Ic performance, the optimizations both in the calcinations and crystallization steps have taken place. Consequently, the extremely high Ic value of 413 A was achieved by the combination of the information from the above investigations and the use of highly textured CeO<sub>2</sub> cap layered substrates. Concerning the development of long tapes, a 8.6-m-long tape with its end-to-end Ic value of 119 A was successfully grown by a reel-to-reel system. Additionally, improvement of the production rate in the calcination step was realized by designing a multi-turn system.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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M. Inoue,
T. Kiss,
Y. Tsuda,
H. Sawa,
M. Takeo,
S. Awaji,
K. Watanabe,
Y. Iijima,
K. Kakimoto, T. Saitoh,
J. Matsuda,
Y. Tokunaga,
T. Izumi,
Y. Shiohara
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ABSTRACT: Current transport characteristics in a Y<sub>1</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> (YBCO) coated conductor fabricated by a trifluoroacetates-metal organic deposition (TFA-MOD) process were investigated over a wide range of temperature and magnetic field up to 25 T. Improved TFA-MOD process was successfully introduced for the better property of critical current density, J<sub>c</sub>, at high magnetic fields. The J<sub>c</sub> and critical current, I<sub>c</sub>, values of multi-coated film with 1.2 μm thickness and 1 cm width were 2.1 MA/cm<sup>2</sup> and 251 A at 77 K in self-field. Additionally, the superior J<sub>c</sub> properties remained even at high magnetic fields over 20 T and lower temperature, e.g. J<sub>c</sub> value at 30 K in 25 T was 1.0 MA/cm<sup>2</sup>. The J<sub>c</sub> value was about 2.5 times higher than those of previous TFA-MOD process at wide range of magnetic field. Moreover, the statistical distribution of J<sub>c</sub> in the conductor was also estimated within a framework of the percolation model. The uniformity in the YBCO coated conductor was improved by optimizing the TFA-MOD process.
IEEE Transactions on Appiled Superconductivity 07/2005; · 1.04 Impact Factor
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ABSTRACT: 100-m class Y-123 coated conductors were demonstrated by using reel-to-reel vacuum apparatuses of ion-beam-assisted-deposition (IBAD) and pulsed-laser-deposition (PLD). The window for Gd2Zr2O7 deposition condition was quite wide and 100-m long IBAD-Gd2Zr2O7 template films were routinely obtained with Δφ of 10° on non-textured Ni-alloy tapes. 100-m long second buffer layers of Y2O3 or CeO2 were grown by PLD on the IBAD templates with Δφ of 7–8°, or 5–6°, respectively. Y-123 films with Δφ of 7° were formed on the substrate of Y2O3//IBAD-Gd2Zr2O7//Hastelloy by PLD. End-to-end Ic of 38 A and Jc of 0.76 MA/cm2 (77 K, self-field) were obtained in a 100-m long sample. On the other hand, Δφ of 3° was obtained on the substrate of CeO2//IBAD-Gd2Zr2O7//Hastelloy. Jc of 2.9 MA/cm2 were obtained in a 0.1-m long Y-123 film, and Jc was improved to 1.6 MA/cm2 for an 80-m long Y-123 tape.
Physica C-superconductivity and Its Applications - PHYSICA C. 01/2004; 412:801-806.
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ABSTRACT: We investigated calcining conditions for YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> (YBCO) films by metalorganic deposition using trifluoroacetates. We measured residual carbon content by secondary ion mass spectroscopy (SIMS) and critical current density J<sub>c</sub> values of the films calcined with various heat treatments. Precursor films are decomposed in calcining duration at 200 to 250°C, and simultaneously harmful residue such as carbon content is generated. SIMS results of carbon intensity show calcination is more effective than extension of the duration at 200 to 250°C to reduce carbon content. J<sub>c</sub> values of films with the calcination varied with the duration, reaching a maximum at about 10 hours. The J<sub>c</sub> values of the films depend on decomposition of trifluoroacetates and CuO nanocrystallites growth, rather than the influence of carbon content. We have succeeded in fabricating the YBCO films of 217 to 241 nm thickness with high J<sub>c</sub> values; 1.7 to 2.9 MA/cm<sup>2</sup> (77 K, 0 T) on CeO<sub>2</sub>/Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub>/hastelloy -C.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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T. Araki,
T. Kato,
T. Muroga,
T. Niwa,
T. Yuasa,
H. Kurosaki,
Y. Iijima,
Y. Yamada,
T. Hirayama, T. Saitoh,
Y. Shiohara,
I. Hirabayashi
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ABSTRACT: High critical current density (J<sub>c</sub>) YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> films were routinely prepared by metalorganic deposition using trifluoroacetates (TFA-MOD). Although the growth scheme of the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> films has been studied, we still have two or more unsolved problems during heat-treatments. The first problem is chemical reaction, including the carbon-expelling scheme during the calcining process. Considering Gibbs free energy changes in the related chemical reactions and electronegativity of atoms, we explain the expelling scheme. During the calcining process metal-oxygen bonds remain after the decomposition. The fluorine partially attacks and replaces oxygen linked to Y and Ba. Consequently, these metal compounds become an amorphous matrix of metal oxyfluorides. Only CuO grows to be nanocrystalline. These results are consistent with the present precursor films derived from highly purified coating solution by the Solvent-Into-Gel method. The second problem is clarification of the required conditions to obtain high J<sub>c</sub> YBCO film by TFA-MOD. Transmission electron microscopy revealed the existence of isolated Ba and Y oxides besides CuO grains within the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> layer, which are derived from the normally purified coating solution. Optimal calcining processing, which certainly suppresses only the CuO grains, never improves the J<sub>c</sub> of the films containing Ba and Y oxides. Thus the required condition for high J<sub>c</sub> YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> films is a combination of a highly purified coating solution and an optimized calcining process. With that combination, we prepared 210 - 230 nm thick YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> films on CeO<sub>2</sub> buffered YSZ for which the J<sub>c</sub>'s were 10.5 - 11.4 MA/cm<sup>2</sup> (77 K, 0 T) by four-probe transport measurement.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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T. Kiss,
M. Inoue,
S. Egashira,
T. Kuga,
M. Ishimaru,
M. Takeo,
T. Matsushita,
Y. Iijima,
K. Kakimoto, T. Saitoh,
S. Awaji,
K. Watanabe,
Y. Shiohara
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ABSTRACT: We have investigated extended electric field-vs.-current density E-J characteristics in YBCO coated IBAD tapes. The results of a Monte-Carlo study on the depinning in a random pin medium were compared with measurements. Using a low temperature scanning laser microscope, we examined the percolative behavior of the local resistive transition in the YBCO tape. It was also shown that the depinning probability, which is proportional to the dynamic resistance of the E-J curves, is scaled as a function of reduced current density with the aid of a power index. Consequently, the E-J characteristics in the tapes can be described by the combination of the two kinds of scaling laws: one is the scaling law of the depinning probability predicted in a random network and the other is the scaling law for the flux pinning force. These properties agree well with the percolation model of depinned clusters.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: For the development of the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> (YBCO) coated conductors, processing of the thicker film and long tape have been investigated using the metal organic deposition (MOD) method with the trifluoroacetates solution. About 1 micro-meter thick MOD film was realized by the control of the P<sub>H2O</sub> condition during annealing for the formation of the YBCO layer. The improvement was explained by the competition between the nucleation of the undesirable grains and the epitaxial growth up to the surface. By applying the suitable condition to the metallic substrate system, high critical current density (Jc) and critical current corresponding to 1 cm wide tape (Ic<sup>*</sup>) were realized as to be 1.6 MA/cm<sup>2</sup> and 153 A/cm-w in the film with 1 micrometer thickness, respectively. For the fundamental investigation of long tape processing, influence of the gas flow direction during annealing for the YBCO formation was investigated. Although nonuniformities in the X-ray diffraction (XRD) intensities and Jc values were recognized in the film grown under the gas flow parallel to the long direction of the tape, both of them was improved by changing the gas flow direction to the transverse one.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: Tapes of 30-m length high-J<sub>c</sub> Y-123 were processed by using ion-beam-assisted deposition (IBAD) and pulsed-laser deposition (PLD). Biaxially textured Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> buffer layers up to 60-m length were fabricated by IBAD with production speed of 0.5 - 1.0 m/h. Y-123 films were processed on them by PLD with production speed of 1.0 - 4.0 m/h. A 30-m Y-123 film was obtained with uniform thickness of 0.5 μm and Δφ of 8 - 11°. I<sub>c</sub> of 49 A (J<sub>c</sub> = 0.99 MA/cm<sup>2</sup>) was obtained in 10-m length part end-to-end, whose I-V curve had high n-value of 46. The 30-m length end-to-end I<sub>c</sub> value was 40 A (J<sub>c</sub> = 0.8 MA/cm<sup>2</sup>), where I<sub>c</sub> times length reached 1200 Am.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: Continuous deposition of Y-123 tapes was performed by
ion-beam-assisted deposition (IBAD) and pulsed laser deposition (PLD)
method. YSZ template films were deposited by IBAD on Ni-based alloy
tapes with tape shifting speeds of 0.1-0.3 m/h. They were uniformly
coated with an in-plane mosaic spread of 12-13 degrees in 5 m length. In
order to overcome the low deposition rate of the IBAD process, large
area ion sources with inductively coupled discharge plasma were applied.
Y-123 films were deposited by PLD on the YSZ templates with a tape
shifting speed of 1.0 m/h. The degradation of Y-123 targets for the PLD
process was effectively restricted by combined motion of rapid rotation
and linear shifting. I<sub>c</sub> of 84.0 A and J<sub>c</sub> of
0.76MA/cm<sup>2</sup> were obtained at 77 K, 0 T in the length of 1.0 m
when the in-plane mosaic spread for the Y-123 film was 7 degrees.
I<sub>c</sub> of 35.0 A and J<sub>c</sub> of 0.25MA/cm<sup>2</sup> were
obtained in a 4.6 m long sample at the length of 4.0 m, when the
in-plane mosaic spread for the Y-123 film was 11 degrees
IEEE Transactions on Appiled Superconductivity 04/2001; · 1.04 Impact Factor
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ABSTRACT: We present new synthesis and applications of fully-sulfonated polyaniline(SPAN), a self-doped conducting polymer. It is difficult to make polymers of aniline sulfonic acids(ASA) with a high molecular weight, since reactivity of ASA as a monomer is low due to the presence of an electron attractive sulfonic group. We prepared a high molecular weight poly(aniline sulfonic acid)(PAS) with a high yield by polymerizing the ASA having an electron donative group under basic conditions. The conducting polymer materials based on this polymer were developed for a variety of applications including;Over Coated Film for Resists (aquaSAVE®) — Charge prevention for e-beam lithography and improvement of post-exposure delay(PED) latitude for Chemical amplified resists.Conductive Bottom Layers of Multi level Resists — Reduction of gate oxide damage in metal etching, etc.
Synthetic Metals - SYNTHET METAL. 01/1997; 85(1):1337-1338.
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ABSTRACT: Thick YBa2Cu3O7−δ (YBCO) films have been successfully formed by the liquid phase epitaxy (LPE) method on Ni–Cr alloy tape. A buffer layer of yttria stabilized zirconia and seed layer of YBCO were formed by the ion beam assisted deposition and by the pulsed laser deposition method, respectively. YBCO films have been grown from the solution of BaO–CuO–Ag–BaF2 at 820, 845 and 860 °C under low oxygen partial pressure of 2% to prevent the metallic substrate from reacting with the solution. Good YBCO films are obtained by the growth at 820 °C, and the best one shows high critical current density of 1.9 MA/cm2. A cross-sectional observation by high resolution scanning electron microscopy shows neither reaction layer nor damaged region at the substrate/YBCO film interface. θ–2θ and pole figure X-ray diffraction of the seed layer and the YBCO LPE layer show that in-plane orientation distribution is highly improved by the LPE process.
Physica C Superconductivity · 1.01 Impact Factor
