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成果報告書詳細
管理番号20170000000387
タイトル*平成28年度中間年報 高温超電導実用化促進技術開発 高磁場マグネットシステム開発 高温超電導高磁場コイル用線材の実用化技術開発(株式会社フジクラ 国立研究開発法人産業技術総合研究所)
公開日2017/7/7
報告書年度2016 - 2016
委託先名株式会社フジクラ 国立研究開発法人産業技術総合研究所
プロジェクト番号P16006
部署名省エネルギー部
和文要約
英文要約 REBCO films doped with artificial pinning centers (APC) by Hot-Wall PLD method on IBAD template tape substrates were prepared. The highest Jc of 13 MA/cm^2 was obtained for a 1.0 um thick BaHfO3 doped EuBCO sample at 30 K, 2 T where Ic of 291 A, Je of 358 A/mm^2 were obtained at 30K, 7T. However, the Jc decreased to 9 to 11 MA/cm^2 at 30 K, 2 T for the same thickness samples prepared with from 2.4 to 3.6 times faster tape speed. Rod-like BaHfO structures with diameter of several nanometers were observed by transmission electron micrographs, where the density of rods was denser for the lower tape speed . It is revealed that high Jc must be obtained for thicker films with higher growth rate conditions to meet with final program target of Je > 400 A/mm^2 at 30 K, 7 T. The possibility of cross-sectional area reduction of REBCO wire was also argued.
Also origin of intermittent Ic degradations of REBCO coated conductors was surveyed by two dimensional magnetization viewgraphs using a magneto-optical sensor introduced by the program. Process cleaning devices were developed in order to obtain end-to-end uniform samples over the length of 1 km with Ic degradation ratio being limited within 15 %, which is second final target of this program.
Finally, we investigated longitudinal and out-of-plane mechanical strength of REBCO conductors at low temperature operating environment, which should be important to understand basic parameters for long length and long-time mechanical reliability. It was revealed that the longitudinal tensile strain dependence of Ic reduction at 77 K was getting prominent for APC introduced samples, but was suppressed with properly controlled planer crystalline axes. Furthermore, we compared the delamination strength data obtained by out-of-plane tensile test using an anvil with large contact area, and the delamination strength evaluated by degradation of epoxy impregnated coils. It was revealed that the degradation probability of both results were quite consistent assuming Weibull statistical theory was valid considering the size effect.
We derived analytical formula describing the explicit relationship between the magnetic field in a coil and the magnetization due to the screening current in HTS tapes. It is theoretically clarified that the reduction of the magnetization of striated tapes are effective in suppression of screening-current-induced magnetic field.
The influence of APC doping to coated conductors (CC) on uniformity of Ic characteristics has been investigated for high performance of the scribed tape. It was found that Ic distribution of CC with BHO doping is larger than that of pure one. As typical values, the filament Ic distribution in the scribed CC (the filament width of 440 um) with BZO was 10.4 % in contrast to that of pure CC of 7.0 %.
As for investigation of twisting structure with HTS tape conductors, we investigated feasibility of various twisting structures of HTS tape conductors such as ROEBEL, CORC and twisted-stacked striated conductors as low-loss conductors for high magnetic field coils.
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