Ray-tracing simulations of lower hybrid current drive experiments in Tore Supra
LH current drive experiments in the Tore Supra tokamak have been simulated using an upgraded version of the Bonoli-Englade-Fuchs code. Aside from the usual ray-tracing and Fokker-Planck packages, the transport module in this code calculates the electron thermal diffusivity from the ITER global confinement scaling law. It also includes a theoretical model for calculating the perpendicular temperature of fast electrons, as well as a global model for the radial diffusion of the RF current in which the diffusion coefficient is found as an eigenvalue of a boundary value problem consistent with the conservation laws predicted by the Fokker-Planck equation. The simulations provide the RF current and power deposition profiles, and also the distribution function of fast electrons and other elements useful for interpreting and understanding the experiments. Quite good agreement can be obtained between the theoretical simulation and the experimental results, namely the drop in the loop voltage and the electron heating. In particular, in a shot where sawtooth stabilisation was achieved by injecting 1.85 MW of RF power, at a total plasma current of 1 MA and an average density of 1.4 x 1.0 E19/m3, the observed 60% drop in the loop voltage is reproduced well and so too is the increase in the central electron temperature from 3 to 4 keV. The response in the poloidal beta and in the plasma internal self inductance were simulated within the measurement uncertainties. The off-axis generation of suprathermal electrons up to 300 keV and their subsequent diffusion toward the centre of the discharge seem consistent with hard X-ray emission which is centrally peaked at average densities of about 1.0 to 1.5 x 1.0 E19/m3.
Bibliographic Reference: Paper presented: 18th European Conference of the EPS-Plasma Physics Division, Berlin (DE), June 3-7, 1991
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Record Number: 199110378 / Last updated on: 1994-12-02
Original language: en
Available languages: en