TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan)
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
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Volume 41, Issue 10
Displaying 1-4 of 4 articles from this issue
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Preface
Fundamental Cryogenic Engineering
  • Cryocooler [2]
    — Fundamental Review of Cryogenic Refrigerators —
    Yoichi MATSUBARA
    2006 Volume 41 Issue 10 Pages 420-427
    Published: 2006
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2221/jcsj.41.420
    JOURNAL FREE ACCESS
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    Part II of this study covers the variations of loss mechanisms for not only cryocoolers, but also compressors. To do so, it is inevitable to understand the efficiency of a system in terms of percent Carnot and/or a coefficient of performance. Once readers review these concepts, the next step is how to minimize the losses and optimize the entire refrigeration cycle. As described in part I of this study, a GM cryocooler is employed to study the loss mechanisms in detail. By introducing the concepts of energy flow, work flow, enthalpy flow and entropy flow, it is fairly straight-forward to visualize the refrigeration process. This approach is effective to optimize the refrigeration cycle, and a numerical method is used to demonstrate optimization of the GM cooler. To review the historical background of GM coolers, the Solvay cycle is also described to compare efficiencies.
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Originals
  • Superconducting Properties in LTG-Sm1+xBa2-x Cu3Oy + Low-Tc Nanoparticle Films under Low Temperature and High Magnetic Field
    Masashi MIURA, Yutaka YOSHIDA, Toshinori OZAKI, Yusuke ICHINO, Masakaz ...
    2006 Volume 41 Issue 10 Pages 428-438
    Published: 2006
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2221/jcsj.41.428
    JOURNAL FREE ACCESS
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    We have reported high-Jc Sm1+xBa2-xCu3Oy (SmBCO) films prepared by a low-temperature growth (LTG) technique. The LTG-SmBCO films showed a Jc of 0.28 MA/cm2 (77 K, B//c, B=5 T). However, the Jc of these films in the magnetic fields above 5 T dropped and were lower than that of NbTi wire (4.2 K). In this study, we introduced nanoparticles with low Tc (low-Tc-nanoparticles) into LTG-SmBCO films to improve the Jc at the high magnetic field. The LTG-SmBCO + 1.4 vol.% nanoparticle film result in a Jc of 0.37 MA/cm2 (77 K, B//c, B = 5 T) and 0.10 MA/cm2 (77 K, B//c, B = 8 T). Furthermore, the Jc at 65 K in a field of 16 T (B//c) reached 0.05 MA/cm2. Elemental mapping clarified that LTG-SmBCO + 1.4 vol.% nanoparticle film had nanosized low-Tc particles with an x of 0.15-0.30 and low-Tc network with an x of 0.05-0.15, which were dispersed in the high-Tc matrix. We speculate that the Jc under high magnetic field conditions depends not only on the distribution and size of low-Tc regions, but also on the Sm/Ba composition within the low-Tc regions.
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Errata
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