Maumi Kawashima

Electromagnetic Properties and Structures of BiPbSrCaCuO Superconducting Wires

High-Jc silver-sheathed BiPbSrCaCuO superconducting wires were fabricated through the solid reaction method. These wires showed the maximum Jc of 2.5X 104 A/cm2 (77. 3K) in a zero magnetic field and 1.2X104 A/cm2 at 0.1 Tesla. Key factors for high-Jc wires are: dominant high-Tc phase, highly oriented structures, good bonding at grain boundaries and fine dispersion of non- superconducting phases. When the wire was immersed in liquid helium, maximum Jc of 3.8X104 A/cm2 at 23 Tesla was achieved. 50cm length conductors were fabricated. These conductors were tested and proved to have Ic of practical levels; 170 A at 77.3K and 1000 A at 4.2K. These results show the promising potential of silver-sheathed BiPbSrCaCuO superconducting wires.

Development of High Tc Superconducting Wire by Powder Method

Ag-sheathed high Tc superconducting wires of YBa2Cu3O7-x and Bi0.8Pb0.2SrCaCU1.5Ox were developed. Improvements in the density and the orientation of crystals brought about by press processing have been investigated, and by adopting adequate processing procedures the critical current densities were increased up to 4140A/ cm2 and 4400A/ cm2 for Ag-sheathed YBa2Cu3O7-x and Bi0.8Pb0.2SrCaCu1.5Ox superconductors, respectively.

DEVELOPMENT OF A 3 MJ-CLASS PULSED SUPERCONDUCTING COIL

One double pancake coil for a 3.8 MJ pulsed coil is under construction at Sumitomo Electric Industries according to Electrotechnical Laboratorys specification, and all pancake coils will be completed around August, 1982. The cable structure, the double pancake coil module and discussions on stability and ac losses are described. The conductor is so-called built-up cable and the first-level cable is stabilized with high purity aluminum. It shows very stable performances and extremely low ac losses. Since Youngs modulus of the cable against compressive load is very small in low stress level, it is shown that the coil windings have to be pre-compressed edgewise.

Growth and Structure of (Tl,Bi,Pb)Sr2CaCu2OX Single Crystal

Crystal growth and structural analysis of (Tl,Bi,Pb)Sr2CaCu2Ox single crystals were performed. A single crystal with superconducting onset transition temperature of 85K was grown in a sealed gold tube by the slow-cooling method. The crystal structure was determined to be tetragonai(P4/mmm) with lattice constants of a=3.80A and c=12.09A. The refinement of the crystal structure was carried out based on the single-crystal X-ray diffraction data.

Preparation of Y-Ba-Cu-O Superconducting Films by Excimer Laser Ablation

Y-Ba-Cu-O films were deposited on MgO substrates by KrF excimer laser ablation of a stoichioietric Y1Ba2Cu3Ox target. The substrate temperature was kept at 700 ~800 °C. The best superconducting properties of as-deposited films were end point of transition temperature Tc(R=0) of 89K and critical current density Jc(77.3K) of 1.9×106A/cm2. The microscopic structures of the films were studied using cross-section transmission electron microscopy. Different images were clearly observed between the high Jc and the low Jc film. We also tried high speed deposition using a high repetition rate of laser pulses. At the deposition rate of 300 A /min, a film with Jc(77.3K) of 2.3 × 105A/cm2 was obtained. Up to the rate of 700 A /min, Tc(R=0) was as high as 80K. Even at the rate of 2200 A /min, films were found to have the almost perfect c-axis orientation normal to the substrate surface.

GaAs Solar Cell Test Facility

A hybrid type (electricity and heat) GaAs solar cell test facility has been made to evaluate total characteristics of GaAs cell and to study the energy conversion system. The size of solar collector is 3.4 m ×2.1 m and 60 GaAs cells with Fresnel lenses are attached on it. The solar collector is controlled by a microcomputer to track up the sun. Electric energy produced by the cells is stored in a lead-acid battery and then supplied to the load through a DC-AC inverter. The microcomputer also controls the data acquisition in parallel with tracking. This paper presents an overview of our facility and experimental results of power generation obtained to date.