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This paper presents self-consistent simulations over a wide range of plasma parameters, to obtain the dependence of characteristic features of the sawteeth on the transport coefficients. The simulations are based on the standard, straight cylinder, low-beta, reduced-MHD equations with self-consistent evolution of the electron temperature, including a highly anisotropic thermal diffusivity and ohmic heating. Comparison of the simulation results concerning e.g. period, growth-time of the instability and collapse time with experimental data shows excellent agreement for Lundquist numbers up to about 1.0 E7 (corresponding to machines of the size of Frascati Tokamak). An important effect found in these self-consistent simulations is that the current profile is significantly modified by the sawteeth, leading to a very flat distribution in a central region accompanied by a sharp drop outside the reconnection layer. This profile makes it possible to turn on the resistive kink instability with a large growth-rate by a minute change in central q. Thus, the Kadomtsev model, with some modification of the current profile, appears to describe the sawtoothing in, at least, small and medium sized tokamaks very well.

Additional information

Authors: VLAD G, ENEA, C.R.E Frascati, C.P. 65 - 00044 - Frascati, Roma (IT);BONDESON A, Centre de Recherches en Physique des Plasmas, École Polytechnique Fédérale de Lausanne, 21 avenue des Bains, CH-1007 Lausanne (CH)
Bibliographic Reference: Paper presented: 16th European Conference on Controlled Fusion and Plasma Physics, Venezia (IT), March 13-17, 1989
Availability: Available from (1) as Paper EN 34976 ORA
Record Number: 198911105 / Last updated on: 1994-12-01
Original language: en
Available languages: en