| Project/Area Number |
11680502
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | National Institute for Fusion Science |
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Principal Investigator |
OKAMURA Shoichi National Institute for Fusion Science, Professor, 大型ヘリカル研究部, 教授 (60115540)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIMURA Shin National Institute for Fusion Science, Research associate, 大型ヘリカル研究部, 助手 (60311205)
NOMURA Izumi National Institute for Fusion Science, Research associate, 大型ヘリカル研究部, 助手 (20280597)
MATSUOKA Keisuke National Institute for Fusion Science, Professor, 大型ヘリカル研究部, 教授 (70023736)
FUJIWARA Masami National Institute for Fusion Science, Professor, 大型ヘリカル研究部, 教授 (10023722)
ISOBE Mitsutaka National Institute for Fusion Science, Research associate, 大型ヘリカル研究部, 助手 (00300731)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | toroidal viscosity / quasi-axisymmetry / MHD stability / optimization / plasma rotation / Boozer coordinate / torsatron / CHS-qa |
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| Research Abstract |
The most important characteristics of the magnetic field configuration which has been studied in this research project is the quasi-axisymmetry (QA symmetry). This symmetry gives the magnetic field structure which does not depend on the toroidal coordinate when expressed in the Boozer coordinates. This characteristics is called as a two dimensional field structure. However the geometric structure is still three dimensional which is necessary to create the rotational transform without a toroidal plasma current. This point is important difference between tokamaks and QA stellarators. One of solutions we found for QA configurations is called 2b32 which has toroidal periods N=2 and the average aspect ratio 3.2. This aspect ratio is relatively very low among all family of helical systems and is considered to be advantageous for the design of compact helical reactors in the future. 2b32 configuration has a flat profile of rotational transform (iota=0.4) and gives good MHD stability for the a
… More
verage beta 4% against various ideal MHD modes (Mercier and global ballooning modes). It has a magnetic well for all positions of radius and all range of beta which is very different from the conventional helical systems. The neoclassical transport coefficients are reduced by about two orders of magnitudes in the low collisionality from the conventional helical systems. Besides these advantageous features in the classical evaluations of confinement properties, this new configuration has possibilities of giving improved confinement modes against anomalous transport phenomena. An important modeling of the improved confinement in toroidal systems is the reduction of the turbulence due to a sheared flow caused by the sharp gradient of the radial electric field. In order to create such a condition, low viscosity for the plasma rotating motion is necessary. Our new configuration has a two orders smaller neoclassical viscosities compared with conventional helical systems. The engineering design was also made for 2b32 configuration which has 20 modular coils with 1.5 m major radius for 1.5 Tesla magnetic field. Less
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