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Global gyrokinetic ion temperature gradient turbulence simulations of ITER
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Villard, L., Angelino, P., Bottino, A., Brunner, S., Jolliet, S., McMillan, Ben F., Tran, T. M. and Vernay, T. (2013) Global gyrokinetic ion temperature gradient turbulence simulations of ITER. Plasma Physics and Controlled Fusion, Volume 55 (Number 7). Article number 074017. doi:10.1088/0741-3335/55/7/074017 ISSN 0741-3335.
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Official URL: http://dx.doi.org/10.1088/0741-3335/55/7/074017
Abstract
Global gyrokinetic simulations of ion temperature gradient (ITG) driven turbulence in an ideal MHD ITER equilibrium plasma are performed with the ORB5 code. The noise control and field-aligned Fourier filtering procedures implemented in ORB5 are essential in obtaining numerically healthy results with a reasonable amount of computational effort: typical simulations require 109 grid points, 109 particles and, despite a particle per cell ratio of unity, achieve a signal to noise ratio larger than 50. As compared with a circular concentric configuration with otherwise similar parameters (same ρ* = 1/720), the effective heat diffusivity is considerably reduced for the ITER MHD equilibrium. A self-organized radial structure appears, with long-lived zonal flows (ZF), modulating turbulence heat transport and resulting in a corrugated temperature gradient profile. The ratio of long-lived ZF to the fluctuating ZF is markedly higher for the ITER MHD equilibrium as compared with circular configurations, thereby producing a more effective ITG turbulence suppression, in spite of a higher linear growth rate. As a result, the nonlinear critical temperature gradient, R/LTcrit,NL, is about twice the linear critical temperature gradient, R/LTcrit,lin. Moreover, the heat transport stiffness above the nonlinear threshold is considerably reduced as compared with circular cases. Plasma elongation is probably one of the essential causes of this behaviour: indeed, undamped ZF residual levels and geodesic acoustic mode damping are both increasing with elongation. Other possible causes of the difference, such as magnetic shear profile effects, are also investigated.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | Plasma Physics and Controlled Fusion | ||||
Publisher: | Institute of Physics Publishing Ltd. | ||||
ISSN: | 0741-3335 | ||||
Official Date: | 2013 | ||||
Dates: |
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Volume: | Volume 55 | ||||
Number: | Number 7 | ||||
Page Range: | Article number 074017 | ||||
DOI: | 10.1088/0741-3335/55/7/074017 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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