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The origin of the reduced electron heat diffusivity X(e) and the diffusion coefficient D in the core of H-mode plasmas is explored. By statistical analyses of 38 H-mode discharges in ASDEX it is shown that in the L- and H-regimes the electron temperature profile shape is invariant in the outer half of the plasma. On the basis of this profile invariance and the edge temperatures in the L- and H-phases, the magnitude, the weak radial dependence and the short time-scale of the reduction of X(e) in the bulk plasma are explained. The constancy of the T(e) profile shape yields a non-local contribution to the anomalous transport and accounts for the regime dependent factors in the empirical scalings of X(e) and D used up to now. It is also shown that T(e) profile invariance can explain the power dependence of X(e) and of the energy confinement time in the intermediate regime between ohmic heating (OH) and pure L-mode confinement and the delayed L-OH transition after neutral beam injection.

Additional information

Authors: BECKER G, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Article: Nuclear Fusion, Vol. 31 (1991) No. 4, pp. 663-671
Record Number: 199110910 / Last updated on: 1994-12-02
Original language: en
Available languages: en
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