日本金属学会誌

J. Japan Inst. Metals, Vol. 71, No. 11 (2007),
pp. 972-976

Transport Performance and Structures of Bi2212 Oxide Superconductors Prepared by Diffusion Process

Yutaka Yamada1, Takuya Shimohiro1, Takeshi Ohtani1, Kyoji Tachikawa1, Hitoshi Tamura2, Toshiyuki Mito2, Masafumi Ogata3 and Masaru Iwamatsu3

1School of Engineering, Tokai University, Hiratsuka 259-1292
2National Institute for Fusion Science, Toki 509-5292
3Railway Technical Research Institute, Tokyo 185-8540

Abstract:

Bi2212 HTS conical tubular conductors have been prepared by diffusion process for current lead. The Bi2212 HTS layers are synthesized through the diffusion reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. The HTS diffusion layers about 150 μm in thickness are formed around both outside and inside of the conical tubes 34/29 mm in outside/inside diameter at the larger end, 24/19 mm in outside/inside diameter at the smaller end, and 100 mm in length. The Ag added to the coating enhances the diffusion reaction, and precipitates on the surface of the specimen decreasing its contact resistance. The transport current properties were evaluated by measuring system using two cryocoolers at Railway Technical Research Institute. The critical temperature of transport current of 1000 A at 0.5 T for the specimen is 57.4 K, which corresponds to the current density of 33 A/mm2 for the Bi2212 layer. The transport current decreases with increasing temperature at the warm end of the conical specimen, and is about 800 A at 60.2 K and 600 A at 62.5 K. The joint voltage of 20 μV at cold end was generated at 50 K and 0.5 T with transport current of 1000 A, which corresponds to the small heat load of 20 mW resulted from the Joule heating. Present Bi2212 conical tubes seem to be promising as current leads with small heat loads for superconducting magnets.


(Received 2007/6/1)

Keywords:

Bi2212 oxide superconductor, diffusion process, current lead, critical current, heat leakage, contact resistance


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