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  • Full radius linear and nonlinear gyrokinetic simulations for tokamaks and stellarators: zonal flows, applied ExB flows, trapped electrons and finite beta
FP5

Full radius linear and nonlinear gyrokinetic simulations for tokamaks and stellarators: zonal flows, applied ExB flows, trapped electrons and finite beta

Funded under: FP5-EAECTP C

Abstract

The aim of this paper is to report on recent advances made on global gyrokinetic simulations of Ion Temperature Gradient modes (ITG) and other microinstabilities. The nonlinear development and saturation of ITG modes and the role of ExB zonal flows are studied with a global nonlinear delta f formulation that retains parallel nonlinearity and thus allows for a check of the energy conservation property as a means to verify the quality of the numerical simulation. Due to an optimised loading technique the conservation property is satisfied with an unprecedented quality well into the nonlinear stage. The zonal component of the perturbation establishes a quasi-steady state with regions of ITG suppression, strongly reduced radial energy flux and steepened effective temperature profile alternating with regions of higher ITG mode amplitudes, larger radial energy flux and flattened effective temperature profile. A semi-Lagrangian approach free of statistical noise is proposed as an alternative to the nonlinear delta f formulation. An Asdex-Upgrade experiment with an Internal Transport Barrier (ITB) is analysed with a global gyrokinetic code that includes trapped electron dynamics. The weakly destabilizing effect of trapped electron dynamics on ITG modes in an axisymmetric bumpy configuration modelling W7-X is shown in global linear simulations that retain the full electron dynamics. Finite beta effects on microinstabilities are investigated with a linear global spectral electromagnetic gyrokinetic formulation. The radial global structure of electromagnetic modes shows a resonant behaviour with rational q values.

Additional information

Authors: NUHRENBERG J, Max-Planck-Institut fur Plasmaphysik, Euratom-IPP, Greifswald (DE);VILLARD L ET AL, Centre de Recherches en Physique des Plasmas, Association EURATOM-Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne (CH);HATZKY R, Max-Planck-Institut für Plasmaphysik, Euratom-IPP, Garching (DE);PEETERS A G, Max-Planck-Institut für Plasmaphysik, Euratom-IPP, Garching (DE);NÜHRENBERG J, Max-Planck-Institut für Plasmaphysik, Euratom-IPP, Greifswald (DE);SORGE S, Max-Planck-Institut für Plasmaphysik, Euratom-IPP, Greifswald (DE);FALCHETTO G L, Departement de Recherches sur la Fusion Contrôlée, Association EURATOM-CEA, CEA Cadarache, Saint Paul-lez-Durance (FR);GRANDGIRARD V, Departement de Recherches sur la Fusion Contrôlée, Association EURATOM-CEA, CEA Cadarache, Saint Paul-lez-Durance (FR)
Bibliographic Reference: A paper presented at: 19th IAEA Fusion Energy Conference. Organised by: International Atomic Energy Agency (IAEA). Held at: Lyon, France, October 14-19 2002.
Availability: Available online at: http://crppwww.epfl.ch/conferences/IAEA02/ Also published in EPFL Internal Report LRP 738/02, available free of charge from: École Polytechnique Fédérale de Lausanne, Ecublens, CH-1015 Lausanne. Fax: +41-21-6934747.
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