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1997 Fiscal Year Final Research Report Summary

Study on measurement of disturbed magnetic surfaces of stellarators ant its robustness

Research Project

Project/Area Number 07680543
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Nuclear fusion studies
Research InstitutionScience University of Tokyo

Principal Investigator

KOGOSHI Sumio  Science University of Tokyo, Science and Technology, Professor, 理工学部, 教授 (60134459)

Project Period (FY) 1995 – 1997
Keywordsmagnetic surface / fractal dimension / rotational transform / Lyapunov exponent / stellarator / circle mapping / chaos / magnetic island
Research Abstract

The purpose of this study is to devise the ways to measure disturbances of magnetic surfaces of stellarators and to discuss their robustness. It is said that for stellarators magnetic islands grow at rational surfaces when helical symmetry is destroyed by toroidicity. Then magnetic surfaces are disturbed. When magnetic islands grow so that adjacent islands overlap, the behavior of the magnetic field lines is chaotic.
Commonly, the degrees of the disturbance of magnetic surfaces are estimated with the width of magnetic islands. However, this method needs extensive calculation time. In addition, it can not estimate chaotic magnetic field lines. To improve these points, we propose new methods. One is (1) a fractal dimension method and others are (2) a rotational transformation method and (3) a circle mapping method. We compared these three methods with the common method. Then the followings are confirmed. These methods are all available to estimate the degree of disturbed magnetic surfaces. The method (1), however, can only evaluate chaotic magnetic field lines and the method (2) needs the least calculation time. Also we show at first that Poincare maps of chaotic magnetic field lines have non-integer fractal dimensions and positive Lyapunov exponents.These indicate strongly the behaviors of chaotic magnetic field lines are really chaos.

  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] 福島 雅弘: "ヘリカル巻き戻し法によるモジュール形ステラレータの平衡安定解析" 電気学会論文誌A. 117. 775-776 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] S.Mishimagi: "EVALUATION OF DISTURBED MAGNETIC SURFACES WITH FRACTAL DIMENSION" Proc.of Joint Conf.ISC-11 & ITC-8. 123-123 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] S.Kogoshi: "Chaotic Approach to Evaluation of Disturbed Magnetic Surfaces" J.of the Physical Society of Japan. 67. (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 長部 行秀: "ヘリカルヘリアックの最適化の検討" 電気学会論文誌A. 118. (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] M.Fukushima, J.Maeda, S.Kogoshi and M.Katsurai: "Equilibrium and Stability Analisis of Modular Stellarators" Trans.IEE of Japan. Vol.177-A. 775-776 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] S.Mishimagi, K.Yoshii, S.Kogoshi and J.Maeda: "EVALUATION OF DISTURBED MAGNETIC SURFACES WITH FRACTAL DIMENSION" Proc.of Joint Conf.ISC-11&ITC-8. 123 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] S.Kogoshi, S.Mishimagi, K.Yoshii and J.Maeda: "Chatic Approch to Evaluation of Disturbed Magnetic Sur Faces" J.of the Physical Society of Japan. Vol.67(in press).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Y.Osabe, S.Kogoshi, J.Maeda, M.Katsurai, H.Yamada and K.Sato: "Investigation of the optimum parameters for a Heliacal Heliac" Trans.IEE of Japan. Vol.178-A(in press).

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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