低温工学
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
57 巻, 1 号
選択された号の論文の9件中1~9を表示しています
巻頭言
特集:MgB2 超伝導体:材料開発と応用の現状と展望(2)
解説
  • 山本 明保
    2022 年 57 巻 1 号 p. 3-8
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    MgB2 superconducting bulk materials have excellent potential for various applications. In this review, the characteristics and challenges of MgB2 as a bulk material, and the recent research trends, such as the synthesis of dense MgB2 bulks using high pressure process, atmospheric pressure synthesis process using liquid and gas diffusion, are introduced.

  • 松本 明善, Patel Dipak
    2022 年 57 巻 1 号 p. 9-16
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    Magnesium diboride (MgB2) has a high critical temperature (Tc = 39 K) as a metal-based superconductor and is expected to be used as a superconducting material for liquid helium-free applied equipment. The superconducting joint between MgB2 wires is an important technology when considering applications of superconducting magnets. In this commentary, we will review the joint techniques that have been applied to MgB2 wires, and show the results. There are several methods for producing MgB2 wires, and various methods using wires produced by the in-situ method, ex-situ method, and IMD method were obtained from information from patents and treatises. Some typical methods and problems of some typical ones will be explained. The superconducting joint of MgB2 wire is relatively easy to accomplish compared to that of other high-temperature superconducting wires, but Ic has not been obtained easily. This is due to the microstructure of the joint interface, and the improvement of those microstructures is considered to be important for the creation of a reliable superconducting joint for MgB2 in the future.

テーマ解説
  • 山本 明
    2022 年 57 巻 1 号 p. 17-22
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    Advances in applications of MgB2 superconductor for particle accelerators are reviewed. The MgB2 superconductor provides its unique features of much higher critical temperature and critical field than that of NbTi with a potential for the competitive cost for the production. It may contribute to expand superconducting technology applications with improved energy balance with hither temperature operation combined with conduction cooling technology. The recent advances in MgB2 applications for particle accelerators and associated devices are overviewed in this paper.

  • TAJIMA Tsuyoshi
    2022 年 57 巻 1 号 p. 23-30
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    Advances in the research and development on MgB2 toward the application to superconducting radio-frequency (SRF) cavities for particle accelerators are reviewed. Evaluations using small flat thin film samples have shown promising results and the techniques to coat the interior of SRF cavities with MgB2 are being developed. We will probably see some results of standard 1.3-GHz cavities coated with MgB2 within 5 years. If MgB2 coated cavities are successfully developed, a new class of SRF cavities operated at ~20 K with cryocoolers will be possible. Such accelerators can be used more easily at 20 K than at 4 K since higher capacity cryocoolers are available and the static heat load is more tolerable. Future applications of such accelerators include, but not limited to, environmental remediation and national security in addition to physics and material science.

研究論文
  • 菱沼 良光, 嶋田 雄介, 波多 聰, 田中 照也, 菊池 章弘
    2022 年 57 巻 1 号 p. 31-38
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    MgB2 compound is one of the low activation superconducting materials because the half-life time of the MgB2 phase is much shorter than that of the Nb-based superconductors, such as Nb-Ti and Nb3Sn. The natural boron powder as the boron source of the in-situ MgB2 wire and bulk consists of two kinds of stable isotope materials, which are B-10 (10B:19.78 %) and B-11 (11B: 80.22 %) isotopes. The 11B isotope is a promising raw material for the further improvement of the neutron irradiation effect on the low activation MgB2 wire. This study focused on the quality effect of the 11B isotope raw powder on the superconducting properties of the 11B isotope-originated MgB2 (Mg11B2) wire. We found that the nano-order particle size and the higher purification of the 11B isotope raw powder would be efficient in the improvement of the superconducting properties of the low activation Mg11B2 wire.

  • 福本 祥一, 高田 芳宏, 武田 実, 前川 一真, 熊倉 浩明
    2022 年 57 巻 1 号 p. 39-45
    発行日: 2022年
    公開日: 2022/01/20
    ジャーナル フリー

    Research and development of superconducting magnesium diboride (MgB2) level sensor for liquid hydrogen have been conducted actively. Recently, the remarkably high performance of the external-heating-type MgB2 level sensor has been recognized. However, the performance of the long MgB2 level sensor based on a 100-m-long class MgB2 wire has not yet been tested, although the test is needed to produce the MgB2 level sensor for the large liquid hydrogen tank. Thus, we have fabricated 100-m-long class MgB2 wires, and evaluated their superconducting characteristics. Homogeneous elongation in the total length and uniform superconducting characteristics of the MgB2 wires were obtained. Using these MgB2 wires, we made 500-mm-long MgB2 level sensors and tested them. We obtained good level-detecting characteristics from those MgB2 level sensors. Thus, the production of the long MgB2 level sensor for the large liquid hydrogen tank is expected to be feasible.

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