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Author(s):
K. Itoh, S.-I. Itoh and L. Giannone
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Title:
Modelling of Density Limit Phenomena in Toroidal Helical Plasmas
Date of publication:
Mar. 2000
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Key words:
density limit, radiation loss, anomalous transport, L-mode scaling law, helical systems
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Abstract:
The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling low of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycyle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the W7-AS stellarator.
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