Journal of Advanced Science
Online ISSN : 1881-3917
Print ISSN : 0915-5651
ISSN-L : 0915-5651
4 巻 , 1 号
選択された号の論文の16件中1~16を表示しています
  • Sadao NAKAJIMA, Yoshimasa MURAYAMA
    1992 年 4 巻 1 号 p. 1-3,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Theoretical results of our own studies of the dp-model are briefly discussed, including the possibilities of a very narrow p-band in hole-doped cuprates and also of obtaining high-Tc superconductivity from the correlated hopping of doped carriers to be represented by the t-part of the tJ-model Hamiltonian.
  • Kyoji TACHIKAWA
    1992 年 4 巻 1 号 p. 4-9,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Nb-Ti and Nb3Sn conductors with different cross-sectional configurations are being produced for matching the specifications of different applications. Magnetic fields exceeding 18T have been so far generated at 4.2K by a superconducting magnet. In this article, recent progresses achieved in Nb-Ti, Nb3Sn and other metallic superconducting materials are reviewed. The developments of superconductors for AC use and those capable of generating fields over 20T are major topics in this area.
  • Osamu Motojima
    1992 年 4 巻 1 号 p. 10-17,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Large Helical Device (LHD) is a superconducting heliotron type device for advanced fusion experiments. The SC coil system is composed of a pair of helical coils and 3 sets of poloidal coils with a total stored magnetic energy of 1.63 GJ, which will be the world maximum. The main machine parameters, major radius (RC), coil minor radius (aC), magnetic field, plasma minor radius (aP), and plasma volume are 3.9m, 0.975m, 4T, 0.65m, and 30m3, respectively. The material of the super-conductor is NbTi, and the cooling systems are pool-boiling for helical coils and forced-flow for poloidal coils. Since the current density of the helical coils is as high as 53.3A/mm2 with the maximum experienced magnetic field strength of 9.6T, the refrigeration with the super-fluid helium is required. LHD is expected to demonstrate the viability of the helical magnetic configuration extrapolatable to the fusion reactor. The major contributions to fusion technology area are seen in the superconductivity research and development. The necessary R & D programs, detailed design, and construction of parts are now in progress. The construction will be completed in 1997.
  • D. K. Finnemore, Ming Xu, Qiang Li, J. E. Ostenson
    1992 年 4 巻 1 号 p. 18-21,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Composites having a very fine dispersion of Ag in a Bi2Sr2Ca2Cu3O10-δ matrix have been studied in order to provide a very robust conductor suitable for magnets. Conductors have a rather modest critical current density of 20, 000A/cm2 at 4.2K, zero magnetic field and zero bending strain but they degrade much less under bending strain having 3000A/cm2 at 20K, 20T for H perpendicular to the a-b plane and under 0.7% bending strain. The samples have typically had solder leads attached and removed a half dozen times, have been bent around different bending blocks, and have been quenched into liquid nitrogen, liquid helium, or liquid hydrogen many times before the measurements are made. These are very robust conductors.
  • Yuh Shiohara, Teruo Izumi, Yuichi Nakamura, Shoji Tanaka
    1992 年 4 巻 1 号 p. 22-29,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Directional steady-state solidification processes which are the Bridgman-type method and the zone melting method from the partial molten state, in which Y2BaCuO5 and liquid coexist in equilibrium, were performed under several different experimental conditions. In the Bridgman method, the temperature gradient (G) and the growth rate (R) were controlled independently at the same cooling rates. The degree of alignment of YBa2Cu3Oy crystals increased with increasing the G/R ratio even at the same cooling rate (6K/h). Higher G/R values were preferable for obtaining highly oriented crystal structures. The minimum limit for the continuous growth of YBa2Cu3Oy crystals exists between the G/R values of 301 and 482°Ch/cm2. The high Jc value of 1.9×104A/cm2 (77K, 1T), estimated from the magnetic measurement, was obtained in the sample grown under the high G/R of 482°Ch/cm2. The results of the samples grown by the zone melting method indicate that the continuous growth with large faceted solid/liquid interface can be achieved in the sample grown at 1mm/h and the volume fraction of 211 phase particles drasticaly decreases from in the liquid to the 123 phase solids at the interface. The proposed solidification model in which Y solute diffusion in the liquid limits the rate of the peritectic reaction agrees well with the experimental results.
  • Tomoko GOTO, Asaichi KAWANAKA, Takeshi HAYAKAWA, Ken-i-chi SAKAI, Masa ...
    1992 年 4 巻 1 号 p. 30-33,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    The contribution of the Y2Ba1Cu1O5 (211) phase and the effect of Pt addition on the critical current density (Jc) of the partial-melted Y-Ba-Cu-O filaments produced by suspension spinning and solution spinning are investigated. The Jc of the filament increases by adding the Pt element, whereas the Jc of decreases with increasing the Y-rich region from the stoichiometric composition of Y1Ba2Cu3Ox.
  • K. Togano, H. Kumakura, H. Kitaguchi, H. Maeda, J. Shimoyama, K. Nomur ...
    1992 年 4 巻 1 号 p. 34-39,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Partial melting and slow cooling process was applied for Bi2Sr2Ca1Cu2Ox/Ag tapes prepared by doctor blade and dip-coating processes. During slow cooling in molten state, plate-like 2212 crystals grow parallel to the tape surface, resulting in a highly oriented grain structure of c-axis alignment. Such a textured structure improves the intergrain coupling. We also found that the cooling condition after the solidification has a strong influence on the transport Jc and Tc. The transport Jc at 77K and 0T obtained so far is greater than 20, 000A/cm2, although it is very sensitive to the applied magnetic field. At the temperatures below 30K, the tapes show excellent high field performance. Jc at 4.2K reaches to the practical level (>105A/cm2) even in high magnetic fields. A 64 turn pancake coil was prepared from a 6m long tape produced by the continuous dip-coating process, which generated a central field of about 6, 000Gauss at 4.2K in a bias field of 12T.
  • Ichiroh NAKADA, Yasuo KANAI, Keizo MATSUDA, Yasuo MIYAMOTO, Iwao OGURA ...
    1992 年 4 巻 1 号 p. 40-49,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Bi-2201 system oxide superconducting crystals with or without doped La are grown by Verneuil method and travelling melt zone method by CO2-laser heating. Single crystals though tiny reveal microstep line structures on their surfaces produced by lateral crystal growth mechanism. The fundamental step height is measured as 12Å which is equal to the half unit cell dimension. Bi, Cu and O, respectively, distribute nearly uniformly in the crystal, while Sr and La do not display uniform distribution. As an interesting characterics the concentration of Sr and La is complementary between the two. This suggests the a replacement of Sr in the crystal lattice by La is taking place. Occasionally magnetic susceptibility and electrical resistivity proved the occurrence of superconductivity but the reproducibility is rather inferior.
  • J. JUNG, M. A.-K. MOHAMED
    1992 年 4 巻 1 号 p. 50-53,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    We have studied intergranular flux depinning in Y1Ba2Cu3O7-δ ceramics. We measured do magnetization as a function of temperature at different applied magnetic fields for field-cooled ceramic and pressed-powder samples. Fast cooling of the ceramic sample down to low temperatures causes more intergrain flux trapping than slow cooling. During warming the flux depins which is associated with an increased Meissner expulsion. Two characteristic temperatures indicating the onset and completion of depinning allowed to develop a (H, T) magnetic phase diagram for the intergrain flux depinning, that occurs for magnetic fields and temperatures over a range 0-1500G and 92-30K, respectively.
  • Koji YAMAGUCHI, Masato MURAKAMI, Hiroyuki FUJIMOTO, Naoki KOSHIZUKA, S ...
    1992 年 4 巻 1 号 p. 54-57,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Microstructures of high-Jc YBaCuO material fabricated by Melt-Powder-Melt-Growth process were studied by transmission electron microscopy to clear the most effective pinning center in the material. It turns out that the interface between the YBa2Cu3O7 matrix and Y2BaCuO5 inclusion is sharp. Such an interface may act as a strong pinning center, and the large Jc value of the MPMG processed material is thought to be brought by the 211 inclusions with sharp interfaces.
  • V. M. PAN, G. G. KAMINSKY, A. L. KASATKIN, M. A. KUZNETSOV, Y. A. PETR ...
    1992 年 4 巻 1 号 p. 58-63,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Direct measurements of transport critical current and resistive state in YBCO single crystal microbridges and thin films have been performed, using pulse technique with microsecond current pulses. We have obtained critical currents values up to 105A/cm2 at 80K in zero field for single crystals and more than 106A/cm2 for thin films. Data on field dependence of ρf are presented and preliminary assumptions on the difference in flux flow mechanism in YBCO single crystals and thin films are made.
  • David T. Shaw
    1992 年 4 巻 1 号 p. 64-68,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Multilayered YBa2Cu3O6.8/YBa2(Cu1-xNix)3O7-y and YBa2Cu3O6.8/Bi2Sr2Can-1CunOx (n=1, 2, 3) superconducting films have been grown by laser deposition technique. Critical currents were measured in the external magnetic field up to 5 tesla with different thicknesses of the interlayers. Results show that control of the number of layers as well as the thickness in multilayer structures could provide an effective means for improving the critical current in magnetic fields.
  • S. Jin
    1992 年 4 巻 1 号 p. 69-74,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Major bulk applications of the high Tc superconductors depend on their current-carrying capability. In order to achieve the desired critical current density of 105A/cm2 or higher, the enhancement of flux pinning is essential. In this paper, various techniques for flux pinning enhancement in bulk high Tc superconductors will be reviewed, and the chemical, microstructural, and processing parameters for introducing desirable flux pinning sites will be discussed.
  • M. Murakami, H. Fujimoto, K. Yamaguchi, N. Nakamura, N. Koshizuka, S. ...
    1992 年 4 巻 1 号 p. 75-80,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    It is possible to disperse Y2BaCuO5(211) inclusions into YBa2Cu3O7 (123) matrix by melt processes. Since nonsuperconducting particles are known to act as pinning centers, the 211 inclusions are expected to provide flux pinning. In this paper we give evidence that the 211/123 interfaces are effective in flux pinning in melt grown YBaCuO.
  • David O. Welch
    1992 年 4 巻 1 号 p. 81-85,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    Various issues involved in the development of phenomenological models of flux pinning and motion in high-Tc oxides are discussed. A simplified model is presented for the critical current density and is used to examine the question of whether flux flow results from an instability due to plasticity of the flux-line array or from pin breaking.
  • Hiroaki MYOREN, Takatoshi ISHIKAWA, Yukio OSAKA
    1992 年 4 巻 1 号 p. 86-89,f3
    発行日: 1992/03/15
    公開日: 2010/02/25
    ジャーナル フリー
    The capacitance-voltage (C-V) characteristics were measured at various temperatures by using the Ag-MgO-high-Tc superconductor (Ba2YCu3Ox and Bi2Sr2CaCu2Ox) MIS diode structure. With decreasing temperature, the capacitance of Ba2YCu3Ox films decreases. This temperature dependence of the capacitance will be discussed based on a marginal Fermi liquid theory.
feedback
Top