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P: Plasmaphysik

P 10: Poster II

P 10.18: Poster

Dienstag, 18. März 2003, 17:30–19:15, Foyer

Influence of the non-linearity of the collision operator on ion cyclotron resonance heating of a tokamak plasma. — •Fabrice Louche — Laboratory for Plasma Physics - Association "Euratom-Belgian State" - Trilateral Euregio Cluster - ERM/KMS - Brussels - Belgium

The distribution functions of ions heated in the Ion Cyclotron Range of Frequencies is obtained by the resolution of the Fokker-Planck equation. For non-minority heating scenarios, the full non-linear Coulomb collision operator must be used in this equation. A method of resolution accounting for the complexity of this operator is presented. We consider a plasma immersed in a homogeneous magnetic field. The adopted method of resolution is based on an expansion of the distribution function in a series of Legendre polynomials. Results of the corresponding code (NLFP-2D) are discussed for experimentally important JET parameters. The convergence of the Legendre expansion has been tested and the importance of the non-linear effects has been shown. Three different regimes, characterized by different modes of indirect ion heating and depending on the absorbed RF power density as well as the minority concentration, were identified. The NLFP-2D code has been used to study the validity of the Maxwellian approximation of the self-collision operator. One finds that this model is only correct in a very limited range of parameters, and leads mostly to an overestimation of the indirect ion heating.