Effects of trapped alpha particles on ballooning modes in tokamaks

D. A. Spong; D. J. Sigmar; W. A. Cooper; D. E. Hastings; K. T. Tsang

doi:10.1063/1.865257

Effects of trapped alpha particles on ballooning modes in tokamaks

D. A. Spong, D. J. Sigmar, W. A. Cooper, D. E. Hastings, K. T. Tsang

Plasma Theory and Modeling

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Abstract

The effects of a trapped, precessing alpha particle population on ballooning modes are examined for a large aspect ratio, shifted circular flux surface tokamak equilibrium. The alphas are modeled in the deeply trapped limit and with a Maxwellian distribution in energy. The resulting kinetic ballooning equation is solved numerically, and the dependence of the eigenvalues and stability boundaries on shear, background pressure gradient, and ratio of hot-to-background temperatures (and densities) is investigated. In the low-frequency regime (ω ≪ ω_dH = alpha processional drift frequency), the alpha component has a stabilizing influence, while in the intermediate frequency range (ω≲ω_dH) the alphas destabilize ballooning modes through interaction with the trapped particle precessional drift resonance. Parameter ranges which should be typical of alpha production in near term tokamak devices such as the Tokamak Fusion Test Reactor (TFTR) [Phys. Rev. Lett. 52, 1492 (1984)] are considered.

Original language	English
Pages (from-to)	2494-2501
Number of pages	8
Journal	Physics of Fluids
Volume	28
Issue number	8
DOIs	https://doi.org/10.1063/1.865257
State	Published - 1985

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title = "Effects of trapped alpha particles on ballooning modes in tokamaks",

abstract = "The effects of a trapped, precessing alpha particle population on ballooning modes are examined for a large aspect ratio, shifted circular flux surface tokamak equilibrium. The alphas are modeled in the deeply trapped limit and with a Maxwellian distribution in energy. The resulting kinetic ballooning equation is solved numerically, and the dependence of the eigenvalues and stability boundaries on shear, background pressure gradient, and ratio of hot-to-background temperatures (and densities) is investigated. In the low-frequency regime (ω ≪ ωdH = alpha processional drift frequency), the alpha component has a stabilizing influence, while in the intermediate frequency range (ω≲ωdH) the alphas destabilize ballooning modes through interaction with the trapped particle precessional drift resonance. Parameter ranges which should be typical of alpha production in near term tokamak devices such as the Tokamak Fusion Test Reactor (TFTR) [Phys. Rev. Lett. 52, 1492 (1984)] are considered.",

author = "Spong, {D. A.} and Sigmar, {D. J.} and Cooper, {W. A.} and Hastings, {D. E.} and Tsang, {K. T.}",

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T1 - Effects of trapped alpha particles on ballooning modes in tokamaks

AU - Spong, D. A.

AU - Sigmar, D. J.

AU - Cooper, W. A.

AU - Hastings, D. E.

AU - Tsang, K. T.

PY - 1985

Y1 - 1985

N2 - The effects of a trapped, precessing alpha particle population on ballooning modes are examined for a large aspect ratio, shifted circular flux surface tokamak equilibrium. The alphas are modeled in the deeply trapped limit and with a Maxwellian distribution in energy. The resulting kinetic ballooning equation is solved numerically, and the dependence of the eigenvalues and stability boundaries on shear, background pressure gradient, and ratio of hot-to-background temperatures (and densities) is investigated. In the low-frequency regime (ω ≪ ωdH = alpha processional drift frequency), the alpha component has a stabilizing influence, while in the intermediate frequency range (ω≲ωdH) the alphas destabilize ballooning modes through interaction with the trapped particle precessional drift resonance. Parameter ranges which should be typical of alpha production in near term tokamak devices such as the Tokamak Fusion Test Reactor (TFTR) [Phys. Rev. Lett. 52, 1492 (1984)] are considered.

AB - The effects of a trapped, precessing alpha particle population on ballooning modes are examined for a large aspect ratio, shifted circular flux surface tokamak equilibrium. The alphas are modeled in the deeply trapped limit and with a Maxwellian distribution in energy. The resulting kinetic ballooning equation is solved numerically, and the dependence of the eigenvalues and stability boundaries on shear, background pressure gradient, and ratio of hot-to-background temperatures (and densities) is investigated. In the low-frequency regime (ω ≪ ωdH = alpha processional drift frequency), the alpha component has a stabilizing influence, while in the intermediate frequency range (ω≲ωdH) the alphas destabilize ballooning modes through interaction with the trapped particle precessional drift resonance. Parameter ranges which should be typical of alpha production in near term tokamak devices such as the Tokamak Fusion Test Reactor (TFTR) [Phys. Rev. Lett. 52, 1492 (1984)] are considered.

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Effects of trapped alpha particles on ballooning modes in tokamaks

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