| Co-Investigator(Kenkyū-buntansha) |
VALENTINO Antoni Institute of Ionized Gases, CNR PADOVA Researcher, 欧州原子力共同体, 主任研究員
SELGEO Ortolani Institute of Ionized Gases, CNR PADOVA Researcher, 欧州原子力共同体, 主任研究員
GAETANO Malesani Institute of Ionized Gases, CNR PADOVA Researcher, 欧州原子力共同体, 所長
SHINOHARA Shunjiro University of Kyushu, Associate Professor, 大学院総合理工学研究科, 助教授 (10134446)
TOYAMA Hiroshi University of Tokyo, Professor, 理学部, 教授 (50023718)
YOSHIDA Zensho University of Tokyo, Associate Professor, 工学部, 助教授 (80182765)
OGAWA Yuichi University of Tokyo, Associate Professor, 工学部, 助教授 (90144170)
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| Research Abstract |
Anomalous transport phenomena in RFP plasma were studied experimentally and theoretically, and their implications for the future RFP research have been discussed.
Deviation from the classical diffusion directly implies an enhancement of the ohmic dissipation. The classical diffusion yields the current profile which minimizes the ohmic dissipation. The Taylor relaxed state, such as an RFP or a ULQ, has a striking difference in the formation of the current profiles. The internal electric field, which is called the dynamo effect, should be included in Ohm's law to modify it as E=etaj+E_D, where the additional term E_D may be expressed by the ensemble average-<upsilon*B>within the framework of MHD. This term strongly modifies the current profile, and hence the ohmic dissipation rate. Since the classical diffusion, which occurs without the dynamo internal electric field E_D, minimizes P_<oh>, it is clear that the dynamo effect increases the ohmic dissipation. In a tokamak which is close to t
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he classical model, the global resistance, and hence the global confinement time, is determined by the minimum of eta, which occurs in the core region of the plasma. In an RFP, which is close to the Taylor relaxed state, the global resistance is dominated by the outer region where eta is large. Many of nonideal effects may deteriorate the confinement of the outer region, and they directly influence the global confinement of an RFP.
Reversed-field-pinch(RFP)plasmas are characterized by high level electromagnetic fluctuations associated with the dynamo effect. Since the poloidal beta is typically of order 0.1, the magnetic free energy is predominant, and hence the magnetic fluctuation dominates various anomalous transport phenomena, in contrast to the tokamak plasma where electrostatic fluctuation dominates. Because of a very low safety factor q, the magnetic-field connection length, which is of order q* major radius, is small, so the collision-less interactions are important. Observations of direct ion heating through fluctuations, production of superthermal electrons, and appearance of magnetic fluctuations in the range of the ion cyclotron frequency are current interests invoking kinetic theory of plasma turbulence. We summarized kinetic processes which are relevant in recent and future high-temperature RFP experiments. Less
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