1998 Fiscal Year Final Research Report Summary
Physics of anomalous transport and confinement improvement
| Project/Area Number |
09044111
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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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 |
IDA Katsumi National Institute for Fusion Science Associate Professor, 大型ヘリカル研究部, 助教授 (00184599)
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| Co-Investigator(Kenkyū-buntansha) |
WAGNER F IPP-Garhing vise director, 副所長
FUKUYAMA Atsushi Kyoto-Univ.Professor, 大学院・工学研究科, 教授 (60116499)
YAGI Masatoshi Kyusu-University Associate Professor, 応用力学研究所, 助教授 (70274537)
ITOH Sanae Kyusu-University Professor, 応用力学研究所, 教授 (70127611)
FUJISAWA Akihide National Institute for Fusion Science Associate Professor, 大型ヘリカル研究部, 助教授 (60222262)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Self sustained transport model / Theory of confinement improvement / Theory of collapse phenomena / Non local transport model / Helical system / Momentum Transport / Spontaneous potential Bifurcation / Internal Transport Barrier |
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| Research Abstract |
Theoretical research results are (1) Development of self sustained transport model (critical turbulence characteristics, spectral. turbulence), (2) Theory of confinement improvement and guideline for helical system (3) Theory of collapse phenomena.(4)Development of non local transport model. Experimental results are (5) Finding of confinement improvement in Helical system (6) Research of momentum transport (7) Bifurcation of radial electric field. Experimental evidence of micro turbulence in the scale of collisionless electron decay length.
The bifurcation surface of radial electric field is predicted theoretically in the structure of radial electric field in torus plasma. The radial electric field bifurcation surface is the surface between the strong positive radial electric field and negative (orweak positive) radial electric field. It is theoretically predicted that the anomalous transport is reduced in the region where the gradient of radial electric field is strong. Theoretically i
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nternal transport barrier is predicted to be produced by this mechanism in helical system.
In the conventional anomalous transport mode, the hat flux crossing the magnetic flux is expressed with local plasma parameter at the magnetic flux surface. In the theoretical frame work, it is difficult to explain the fast response for external trigger observed in W7AS device.New non-local transport model is proposed by analyzing the observation in W7AS.The heat flux across the magnetic flux surface is affected by the radial profile of plasma because of the turbulence of long wavelength comparable to the plasma size, In the self sustained transport model, the transition of one turbulence to the other is predicted and theory of collapse phenomena such as ELMs and internal transport barrier collapse is proposed.
There is significant development of experiment research. In CHS the transition between the two different profiles of electric potential was observed. This is the first observation for spontaneous electric potential bifurcation in toroidal plasma and supports the hypnosis of bifurcation of radial electric field. The transition between two profiles are continuous and give the impact to steady state helical plasma.
These bifurcation is predicted in tokamak plasma as well as helical plasma and plasma flow due to the plasma pressure is theoretically predicted in the momentum transport. The detail experiments on this issue has been done and the relation between the gradient of flow velocity and momentum flux is studied. It is clearly demonstrated that the momentum flux not due to the gradient of flow but the gradient of ion pressure or ion temperature exists in the momentum transport. Less
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