Instabilities in magnetized plasmas

Mathieu Jenny & Emmanuel Plaut

 

      This work is a co-operation with Étienne Gravier of the Institut Jean Lamour. We are interested in the transition to turbulence in magnetized plasmas. The contribution of the Lemta is a new spectral method for the analysis of cylindrical plasmas. This method has been set up and validated in [1], through a study of drift wave instabilities with a 2-fluid model. In [2], this method has been successfully applied to the analysis of a multi-fluid model, which describes drift wave and Ion Temperature Gradient instabilities, and incorporates some `kinetic' effects. The picture below is the figure 11 of [2].


[1] Transitions between drift waves in a magnetized cylindrical plasma: experiments and fluid model, solved with a spectral method É. Gravier, E. Plaut, X. Caron and M. Jenny Eur. Phys. J. D 67, 7 (2013).

A bifurcation scenario between collisional drift waves with different azimuthal wavenumbers m in a magnetized plasma column is experimentally studied, and compared with a linear two-fluid model solved with a new spectral method. The control parameter is the potential of an internal metallic tube in the experiments, the electron drift along the axis of the cylinder in the model. By increasing this parameter, we find bifurcations from azimuthal modes m = 5 to m = 1. The linear properties of the model agree well with the experimental observations.

[2] Kinetic water-bag model of global collisional drift waves and ion temperature gradient instabilities in cylindrical geometry É. Gravier and E. Plaut Phys. Plasmas 20, 042105 (2013).

Collisional drift waves and ion temperature gradient (ITG) instabilities are studied using a linear water-bag kinetic model [P. Morel et al., Phys. Plasmas 14, 112109 (2007)]. An efficient spectral method, already validated in the case of drift waves instabilities [E. Gravier et al., Eur. Phys. J. D 67, 7 (2013)], allows a fast solving of the global linear problem in cylindrical geometry. The comparison between the linear ITG instability properties thus computed and the ones given by the COLUMBIA experiment [R. G. Greaves et al., Plasma Phys. Controlled Fusion 34, 1253 (1992)] shows a qualitative agreement. Moreover, the transition between collisional drift waves and ITG instabilities is studied theoretically as a function of the ion temperature profile.


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Last modified: Fri Feb 19 16:17:15 CET 2016