Ion Temperature Gradient instability

2021-06-28T17:21:54Z

Sorah:

The ion temperature gradient (ITG) instability<ref> P. N. Guzdar, Liu Chen, W. M. Tang and P. H. Rutherford, ''Ion‐temperature‐gradient instability in toroidal plasmas'' [[doi:10.1063/1.864182|Phys. Fluids '''26''' (1983) 673]]</ref> is a microinstability in [[tokamak]]s relevant to turbulence and the associated [[anomalous transport]].

The instability occurs due to the nature of Grad-B drift. The Grad-B drift velocity of a particle (caused by a gradient in the magnetic field) is proportional to the particle's kinetic energy. Hotter particles drift further than colder particles.

Hence, if a temperature gradient is aligned with a magnetic field gradient (as occurs in a tokamak), particles in the hotter region will drift further. If there is a perturbation in the temperature gradient, then the difference in drift velocities will create charge separation. The charge separation creates an electric field. This electric field creates an <math>E\times B</math> drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.

Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the <math>E\times B</math> drift will suppress the perturbation rather than increase it. This situation occurs on the inner, "good-curvature" side of the tokamak.

See the figure for a graphical explanation.

[[File:ITG.png|600px|thumb|center|ITG mechanism]]

== See also ==

* [[Plasma instability]]

== References ==
<references/>

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Ion Temperature Gradient instability