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45 巻 , 5 号
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  • 太刀川 恭治
    45 巻 (2010) 5 号 p. 226-237
    公開日: 2010/06/18
    ジャーナル フリー
    Continuing on from part one, this article describes different fabrication processes of Nb3Sn wires. The PIT process using Nb-Sn compound powder, Ta-Sn powder and Cu5Sn4 powder has been commercialized. The Nb tube process, originally developed in Japan, has been recently revived in US. A MJR process using Nb mesh sheet has been also developed. The Nb3Sn wires fabricated through these processes show nearly the same high non-Cu Jc at 12 T as that of the RRP internal Sn processed wire described in the last article. The JR Nb3Sn wires using Sn-based alloy sheet indicate enough potential to be used in fields over 20 T at 4.2 K. The stoichiometric Sn concentration and the homogeneous grain structure are the key factors to produce high performance in the Nb3Sn layers. In addition Nb3Sn wires with ultra-thin filaments have been developed for AC use. In the study of V3Ga wires, pioneering works have been performed, such as the effect of Cu for the synthesis of A15 layer, which yielded a breakthrough in the wire fabrication. The V3Ga wires have also been used for high-field superconducting magnets. Further progress may be expected in the processing and performance of these compound wires based on the informations obtained so far.
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技術ノート
  • 木村 誠宏, 高田 卓, 後藤 修一, 川又 弘史, 飯田 真久, 村上 正秀, 永井 秀明, 間宮 幹人
    45 巻 (2010) 5 号 p. 238-243
    公開日: 2010/06/18
    ジャーナル フリー
    In order to study the film boiling phenomena in saturated superfluid helium (He IIs) under a microgravity environment, a very compact visualization system has been fabricated and tested at KEK. It consists of a cryostat, a vacuum pump, a high-speed video camera and electrical circuits for measurement. The cryostat in the system is equipped with optical windows for the visualization of film boiling in He IIs. The system was tested to verify the thermal and safety performances under a microgravity environment using a 10 m-drop tower at the Hokkaido Center of the National Institute of Advanced Industrial Science and Technology (AIST). Successful system operation from 1.94 to 2.05 K under microgravity conditions below 1 × 10-3 g was confirmed. The design and test results are described in this technical note.
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