1PO6-21 Fabrication of (Hg_1-xRe_x)Ba₂Ca₂Cu₃O_y Tapes

T. Murakami, J. Shimoyama, K.D. Otzschi and K. Kishio, Department of Superconductivity, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Presenting Author: T. Murakami

We reported that (Hg_1-xRe_x)Ba₂Ca₂Cu₃O_y [(Hg_1-xRe_x)1223] superconductor is chemically stable with T_c higher than 130K [1]. In addition, its intragrain J_c under magnetic field was found to be dramatically enhanced with increasing amount of Re-doping up to x = 0.25, suggesting that (Hg_1-xRe_x)1223 can be considered as a candidate material for practical high-field applications at high temperatures. In the present study, we have attempted to fabricate c-axis oriented (Hg_0.75Re_0.25)1223 tapes on a Ni substrate with a buffer layer of Cr.

(Hg_0.75Re_0.25)1223 thick films were formed on the substrate by painting method using a slurry containing calcined powder of (Hg_0.75Re_0.25)1223. The green tapes were sintered at 1073 ~ 1193K in a quartz ampoule together with Hg-containing pellets having various compositions.

When either Hg_0.6Re_0.4Ba₂CaCu₂O_y, or Hg_0.75Re_0.25Ba₂Ca₃Cu₄O_y was used as the nominal composition of Hg-containing pellets, platelet crystals were found to grow on the substrate by sintering, but grain alignment was poor. Intermediate uniaxial press between sinterings at 1163K improved the grain alignment and strongly c-axis oriented (Hg_0.75Re_0.25)1223 tape was obtained. The best tape exhibited T_c(zero) = 127K and H_irr = 5T at 77K under magnetic fields applied perpendicular to the tape surface (H//~c).

[1] J. Shimoyama et al., Proc. 10th Anniversary HTS Workshop on Physics, pp.85-88 (1996).

1PO6-22 HTS Coil Techniques

Jian X. Jin and Shi X. Dou, Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia

Presenting Author: J.X. Jin

A high temperature superconducting (HTS) coil has been made using a Ag-clad Bi-2223 HTS multifilament wire. The small prototype unit basically consists of (1) HTS winding which has been made using a Ag-clad Bi-2223 27-core HTS wire, (2) Ag-clad flexible Bi-2223 HTS current lead, (3) textured bulk Bi-2223 HTS current lead, (4) cooling finger, and (5) normal Cu winding. The Ag-clad Bi-2223 HTS wire has been verified with basic concerns of how to form a coil with the HTS wires, critical current, magnetic field, large current lead, HTS wire insulation, losses, and HTS cryogenic cooling techniques. Consequently this HTS wire can be fully justified for practical applications. The prototype HTS coil will be introduced and practical results will be presented in this paper.

1PO6-23 HTS-LTS Superconducting Joint with I_c > 500 A

Keiji Fukushima 1, Michiya Okada 1, Tsukasa Kiyoshi 2, Shinji Matsumoto 2, and Hitoshi Wada 2. 1 Hitachi Research Laboratory, Hitachi, Ltd., Hitachi, Ibaraki 319-1292, Japan. 2 National Research Institute for Metals, Tsukuba, Ibaraki 305-0047, Japan.

Presenting Author: Keiji Fukushima

We developed a novel superconducting joint between Bi-2212/Ag multifilamentary wire and NbTi/Cu-matrix conductor. The superconducting joint showed an excellent transport current carrying capacity of over 500A at 4.2K, self field condition. A closed circuit was tried to fabricate by means of a solenoid magnet and a persistent current switch of NbTi/Cu-Ni, including a Bi-2212/Ag and NbTi/Cu joint. Persistent-mode operation of the closed circuit have been tested and proved the excellent transport performance of the joint. We also investigated the magnetic field dependence of J_c of the joint, and found the joint is available below 1T. The details of the dissipation of persistent current in the closed circuit will also be discussed.