Casson, F. J. (Francis James), Peeters, A. G., Angioni, C., Camenen, Y., Hornsby, W. A., Snodin, A. P. and Szepesi, G. (2010) Gyrokinetic simulations including the centrifugal force in a rotating tokamak plasma. Physics of Plasmas, Vol.17 (No.10). Article no. 102305. doi:10.1063/1.3491110 ISSN 1070-664X.

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Abstract

Tokamak experiments operate with a rotating plasma, with toroidal velocity which can be driven externally but can also arise spontaneously. In the frame that corotates with the plasma, the effects of the centrifugal force are felt through a centrifugal drift and an enhanced mirror force [Peeters et al., Phys. Plasmas 16, 042310 (2009)]. These inertial terms become important in the case of strong rotation, as is common in spherical devices, and are also important for heavy impurity ions even at small toroidal velocities. In this work, the first gyrokinetic simulations including the centrifugal force in a strongly rotating plasma are presented. The enhanced mirror force redistributes density over a flux surface and modifies the trapping condition, destabilizing trapped electron modes. At intermediate scales this can result in promotion of the trapped electron mode over the ion temperature gradient (ITG) mode as the dominant instability, which under marginal conditions could result in an enhanced electron heat flux. The centrifugal drift acts to damp the residual zonal flow of the geoacoustic mode, while its frequency is increased. For nonlinear ITG dominated turbulence, increased trapped electron drive and reduced zonal flow lead to an increase in ion heat diffusivity if the increased rotation is not accompanied by rotational shear stabilization. An increased fraction of slow trapped electrons enhances the convective particle pinch, leading to an increase in the steady state density gradient with strong rotation. Linear ITG mode results show an increased pinch of heavy trace impurities due to their strong centrifugal trapping. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3491110]

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Journal or Publication Title:	Physics of Plasmas
Publisher:	American Institute of Physics
ISSN:	1070-664X
Official Date:	October 2010
Dates:	Date Event October 2010 Published
Volume:	Vol.17
Number:	No.10
Number of Pages:	11
Page Range:	Article no. 102305
DOI:	10.1063/1.3491110
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), CCFE, HECTOR U.K.
Grant number:	EP/H002081/1 (EPSRC)

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