Anisotropic ion temperature gradient instabilities.
Item
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Title
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Anisotropic ion temperature gradient instabilities.
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Identifier
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AAI9510721
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identifier
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9510721
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Creator
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Song, Hao.
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Contributor
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Adviser: Amiya K. Sen
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Fluid and Plasma
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Abstract
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The effects of anisotropic temperature gradient and collisions on the ion-temperature-gradient (ITG) instabilities have been investigated by using kinetic theory. In the slab limit, the ITG mode is driven unstable by coupling between the transit resonance and ion temperature gradients. While {dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar} ({dollar}\eta\sb{lcub}\rm i\perp{rcub} \equiv \partial{dollar}lnT{dollar}\sb{lcub}i\perp{rcub}{dollar}/{dollar}\partial{dollar}lnn, where T{dollar}\sb{lcub}\rm i\perp{rcub}{dollar} is the perpendicular ion temperature and n is the plasma density) only affects the mode through the finite Larmor radius effect, {dollar}\eta\sb{lcub}\rm i\Vert{rcub}{dollar} ({dollar}\eta\sb{lcub}\rm i\Vert{rcub} \equiv \partial{dollar}lnT{dollar}\sb{lcub}\rm i\Vert{rcub}{dollar}/{dollar}\partial{dollar}lnn) is needed to trigger the instability. With electron collisions, the mode propagating in the electron diamagnetic drift direction becomes more unstable at small {dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar} but a second stability regime is found at large {dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar} for the branch propagating in the ion diamagnetic drift direction. In the toroidal limit, the ion branch is driven unstable by coupling between the magnetic drift resonance and temperature gradients and it can be stabilized by electron collisions. The electron branch destabilized by the interchange effect from bad magnetic curvature can be further destabilized by electron collisions. For the trapped ion toroidal ITG mode, the perpendicular ion temperature gradient is crucial to drive the instability. However, the critical temperature gradient is increased by a factor of 1/{dollar}\varepsilon\sp{lcub}1/2{rcub}{dollar}, where {dollar}\varepsilon\sp{lcub}1/2{rcub}{dollar} is the trapped fraction, and it can be further enlarged by ion or electron collisions. For the mixed slab and toroidal ITG mode, a coupling between the ion and electron branches was found to cause the stability regime to break into two separated regions in the {dollar}\eta\sb{lcub}\rm i\Vert{rcub}{dollar}-{dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar} plane. Electron collisions can significantly reduce the first stability regime at small {dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar} but expand the second stability regimes at large {dollar}\eta\sb{lcub}\rm i\perp{rcub}{dollar}. The non-local correction has a stabilizing effect on the ion branch but a destabilizing effect on the electron branch. This effect is so strong that it can overcome the coupling effect and so the second stability regime is not separated from the first one. The new second stability regime may provide a possible stabilization scheme for the ITG instability via intense ion cyclotron resonance heating and neutral beam injection.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
