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Ion Temperature Gradient instability

2016-10-18T14:01:03Z

Alschei:

The ion temperature gradient (ITG) instability is a microinstability in tokamaks 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 a electric field. This electric field creates an ExB 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 ExB 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]]

Ion Temperature Gradient instability

2016-10-18T13:58:23Z

Alschei:

The ion temperature gradient (ITG) instability is a microinstability in tokamaks 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 a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.

See the figure for a graphical explanation.

[[File:ITG.png | width=10 | image-width=10]]

Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it. This situation occurs on the inner, "good-curvature" side of the tokamak.

Ion Temperature Gradient instability

2016-10-18T13:51:26Z

Alschei:

The ion temperature gradient (ITG) instability is a microinstability in tokamaks 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 a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.

See the figure for a graphical explanation.

[[File:ITG.png|width=100px|Caption A cartoon sketch of the Ion Temperature Gradient instability]]

Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it. This situation occurs on the inner, "good-curvature" side of the tokamak.

Ion Temperature Gradient instability

2016-10-18T13:48:14Z

Alschei:

The ion temperature gradient (ITG) instability is a microinstability in tokamaks 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 a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.

See the figure for a graphical explanation.

[[File:ITG.png]]

Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it. This situation occurs on the inner, "good-curvature" side of the tokamak.

File:ITG.png

2016-10-18T13:46:29Z

Alschei: A graphic explanation of the ion temperature gradient (ITG) instability. Created by: Aaron Scheinberg

A graphic explanation of the ion temperature gradient (ITG) instability.

Created by: Aaron Scheinberg

Ion Temperature Gradient instability

2016-10-18T13:44:14Z

Alschei: Created page with "The ion temperature gradient (ITG) instability is a microinstability in tokamaks relevant to turbulence and the associated anomalous transport. The instability occurs due to ..."

The ion temperature gradient (ITG) instability is a microinstability in tokamaks 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 a electric field. This electric field creates an ExB drift which increases the perturbation's amplitude. The positive-feedback nature of this loop leads to exponential growth of the instability.

See the figure to see the geometric setup.

Note that if the temperature gradient is anti-parallel to the magnetic field gradient, the ExB drift will suppress the perturbation rather than increase it. This situation occurs on the inner, "good-curvature" side of the tokamak.

[[File:ITG.eps]]