(TH/P8-7) Validity of Quasi-Linear Transport Model

C. Bourdelle1), A. Casati1), X. Garbet1), F. Imbeaux1), J. Candy2), F. Clairet1), G. Dif-Pradalier1), G. Falchetto1), T. Gerbaud1), V. Grandgirard1), P. Hennequin3), R. Sabot1), Y. Sarazin1), L. Vermare3), R. Waltz2)
1) CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
2) General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
3) Laboratoire de Physique et Technologie des Plasmas, CNRS-Ecole Polytechnique,
91128 Palaiseau Cedex, France

Abstract.  In order to gain reliable predictions on turbulent fluxes in tokamak plasmas, physics based transport models have to be improved. On a confinement time scale, nonlinear gyrokinetic electromagnetic simulations for all species are still too costly in terms of computing time. On the other hand, interestingly, quasi-linear approximation seems to retain the relevant physics for fairly reproducing both experimental results and nonlinear gyrokinetic simulations. Quasi-linear fluxes are made of two parts, the quasi-linear weight and the saturated squared electrostatic potential. The first one is shown to follow well nonlinear predictions; the second one is based on both nonlinear simulations and turbulence measurements. The resulting quasi-linear fluxes are shown to agree with the nonlinear ones when varying various dimensionless parameters such as the ion to electron temperature ratio, the collisionality and the temperature gradients, ranging from Ion Temperature Gradient (ITG) to Trapped Electron Modes (TEM) turbulence.

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