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Author(s):
T.Hayashi, A.Takei, N.Ohyabu, T.Sato, M.Wakatani, H.Sugama, M.Yagi, K.Watanabe, B.G.Hong and W.Horton
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Title:
Equilibrium Beta Limit and Anomalous Transport Studies of Helical Systems
Date of publication:
Sep. 1990
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Key words:
helical system, equilibrium, beta limit, magnetic surface breaking, suppression of surface breaking, heliotron, helias, anomalous transport, FLR-MHD, resistive interchange mode, g mode, ion temperature gradient mode
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Abstract:
Equilibrium magnetic surfaces and anomalous transport of helical systems are studied. The equilibrium beta limit, which is defined by the breaking of magnetic surfaces due to the finite beta effect, is investigated for two types of helical systems. The results indicate that the breaking often imposes severer limitation on beta than the Shafranov shift. However, if we properly choose controllable parameters, such as the vertical field B_upsilon, we can obtain a high beta equilibrium, such as bar{beta} geq 5%. Furthermore, a simple method is proposed, by which the breaking can be actively suppressed and fairly high beta equilibria with clearly nested magnetic surfaces can be realized. In order to study anomalous transport based on the fluid type turbulence in heliotron/torsatron six-field equations are derived from the two fluid model. A new type of the eta_i mode coupled to the g mode is found in the presence of unfavalable magnetic curvature. For the drift resistive interchange turbulence the Botzmann relation between the density and the potential fluctuation spectrum is observed in the weak collisional regime.
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