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47 巻 , 5 号
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研究論文
  • 川越 明史, 小坂 亮大, 濱田 佳志, 岡元 洋
    47 巻 (2012) 5 号 p. 268-275
    公開日: 2012/07/04
    ジャーナル フリー
    In our previous paper, we proposed a new indirect method of detecting normal transitions occurring in hightemperature superconducting coils. In this method, sets of pick-up coil pairs arranged outside the cryostat are used in order to electrically measure the occurrence of normal transitions during coil operations. This indirect method has benefits such as high reliability, safe detection and easy maintenance. The principle of locally detecting a normal transition is theoretically explained and the validity of this method is clarified experimentally using a Bi-2223 coil. In this paper, it is experimentally confirmed that this measuring method can be used to detect normal transitions in windings of a high-temperature superconducting transformer with 500 VA around which there are small leakage magnetic fields due to an iron core. In addition, a method for detecting normal transitions in windings of the transformer during transformer load changes is proposed and the validity of the method is demonstrated experimentally.
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  • 魏 一, 土井 俊哉, 勝目 彬人, 宮永 貴文, 稲田 満 , 白樂 善則, 嶋 邦弘, 窪田 秀一, 鹿島 直二, 長屋 重夫
    47 巻 (2012) 5 号 p. 276-281
    公開日: 2012/07/04
    ジャーナル フリー
    In this study, we attempted to install CeO 2 /Y2 O3 /CeO2 buffer layers, where the thicknesses of the CeO2 and Y 2O3 are10 and 250 nm respectively, instead of the CeO 2/YSZ (Y 2O3 stabilized ZrO 2)/CeO2 buffer layer architecture for YBCO (YBa 2 Cu3 O7 ) coated conductors using Ni-electroplated {100}<001> textured Cu and SUS316 laminated tape. Since the diffusion coefficient of oxygen in Y 2O3 is much smaller than that in YSZ and CeO 2, Y 2O3 seems to be a more favorable buffer layer material. We obtained a Jc of 1.0 MA/cm2 for the YBCO/Y 2 O3/Ni-electroplated Cu/SUS 316 laminated tape. However, the Δφvalue of the Y 2O3 layer deposited on the Ni layer increased by 1°compared with that of the Ni layer, and the Δφvalue of the YBCO layer on the Y 2O3 layer increased by 1.5°compared with that of the Y 2O3 layer. To avoid the degradation of the crystal orientations, we inserted very thin CeO2 layers of 10 nm between the Ni and the Y 2O3 layers, and between the Y 2O3 and the YBCO layers. The Jc of the 1 μm-thick YBCO layer prepared on the CeO 2 /Y2 O3 /CeO2 -buffered Ni-electroplated {100}<001> textured Cu/SUS316 laminated tape reached 2.1 MA/cm2 (Ic of 210 A-cm width) at 77 K in a self-field.
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