電気学会論文誌A(基礎・材料・共通部門誌)
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
123 巻 , 3 号
選択された号の論文の17件中1~17を表示しています
解説
特集論文
論文
  • 豊田 光洋, 菊池 祐介, 上杉 喜彦, 高村 秀一
    原稿種別: 論文
    2003 年 123 巻 3 号 p. 285-293
    発行日: 2003年
    公開日: 2003/06/01
    ジャーナル フリー
    To achieve high confinement properties of a tokamak plasma, it is necessary to control the plasma position, current profile, shape of magnetic surface etc.. In addition to these, it has been found that a resistive wall mode (RWM) may limit the achievable plasma beta in present tokamak devices. Therefore, it is expected that an active feedback control using external coils is necessary to stabilize the RWM. A power supply for plasma control coils requires an accurate controllability and a fast response against such plasma disturbances. Recent development of high power and fast switching semiconductors, such as Insulated Gate Bipolar Transistor (IGBT) and MOSFET, improves the temporal response of power supply with a great extent. A small tokamak device, HYBTOK-II, is equipped with IGBT inverter power supplies for Joule and vertical field coils. In this paper a real-time feedback control of the plasma horizontal position has been employed with Digital Signal Processor (DSP). The experimental results on plasma response with such a feedback control have been compared with analysis of plasma column motion using transfer functions.
  • 佐藤 崇志, 森 夏樹, 中根 央, 山崎 貞郎, 吉澤 秀治, 山口 俊久
    原稿種別: 論文
    2003 年 123 巻 3 号 p. 294-300
    発行日: 2003年
    公開日: 2003/06/01
    ジャーナル フリー
    It is known that critical current density Jc in Bi-Based superconductors increases with the length of sintering time, and further increases with cold isostatic pressing (CIP) process. Analysis of excess conductivity due to the thermal fluctuation above Tc provides information about fluctuation amplitude and the dimensionality of conduction, and makes it possible to evaluate the superconducting correlation length. In this study, the mechanism of how Jc of Bi-based copper oxide improves by increasing sintering time is discussed on the basis of fluctuation-conductivity analysis. The temperature dependence of the resistance of Bi-based superconductors with various sintering time was measured. It was found that correlation length and effective cross-sectional area obtained from analysis systematically decrease with the sintering time, and that these parameters correlate well with Jc of the samples. It is widely accepted that the increase in Jc of the samples is due to the improvement in the crystallinity, (i.e., the increase in crystal density and better alignment of the crystal grains) which brings about decrease in correlation length and effective cross-sectional area. Therefore, the effect of the improvement in the density and alignment of the crystals, an important factor for increasing critical current density, was evaluated from the fluctuation conductivity analysis.
  • 山本 滋, 川上 親孝, 水寄 康雄
    原稿種別: 論文
    2003 年 123 巻 3 号 p. 301-314
    発行日: 2003年
    公開日: 2003/06/01
    ジャーナル フリー
    Polyethylene (PE) consists of non polar molecular chain having simple structure unit. Physically, it is so stable and flexible that this polymer is used widely for electric wire, electric power cable and various molding goods. Among the fundamental properties of PE, the crystalline texture, the formation of spherulite, has a pronounced influence on it's mechanical and electric properties. For the purpose of improving these properties of PE the spherulites is disappeared completely by heat mixing of PE with Li2CO3. Thus obtained PE has no spherulites, uniform structure, and excellent electrical and mechanical and thermal properties, e.g. short treeing length and high electric break down strength, and high tearing impact strength.
研究開発レター
feedback
Top