On Resonant Excitations of High-n Magnetohydrodynamic Modes by Energetic/alpha Particles in Tokamaks PDF Download
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Author: Liu Chen
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ISBN:
Category :
Languages : en
Pages : 12
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Author: Liu Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Analytical theories for the excitations in tokamaks of magnetohydrodynamic (MHD) modes with large toroidal mode numbers (n”1) are presented. Specifically, only instability mechanisms due to resonances with energetic ions/alpha particles are considered. It is noted that, while trapped energetic particles contribute to the ideal region, circulating energetic particles contribute mainly to the singular layer dynamics. A unified dispersion relation manifesting both fishbone-like modes and beam transit-resonance modes is then driven. Finally, we also analyze the stability property of toroidicity-induced shear Alfven waves excited via transit resonances with alpha particles in ignited tokamaks. 11 refs.
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Languages : en
Pages :
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Analytical theories for the excitations in tokamaks of magnetohydrodynamic (MHD) modes with large toroidal mode numbers (n”1) are presented. Specifically, only instability mechanisms due to resonances with energetic ions/alpha particles are considered. It is noted that, while trapped energetic particles contribute to the ideal region, circulating energetic particles contribute mainly to the singular layer dynamics. A unified dispersion relation manifesting both fishbone-like modes and beam transit-resonance modes is then driven. Finally, we also analyze the stability property of toroidicity-induced shear Alfven waves excited via transit resonances with alpha particles in ignited tokamaks. 11 refs.
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Languages : en
Pages :
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It is shown that, in present-day large-size tokamaks, finite resistivity modifies qualitatively the stability properties of magnetohydrodynamic instabilities resonantly excited by the unfavorable processional drift of energetic-trapped particles, i.e., the so-called ''fishbone''-type instabilities. Specifically, it is found that (1) the n = 1 energetic-trapped particle-induced internal kink (''fishbone'') instability is strongly stabilized by resistive dissipation and (2) finite resistivity lowers considerably the threshold conditions for resonant excitations of high-n ballooning/interchange modes. The possibility of exciting fishbones by alpha particles in ignition experiments is also considered.
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Category :
Languages : en
Pages : 36
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The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small?{sub?}?{sub?}, and decreases as 1/n for?{sub?}?{sub?} {much gt} 1. The maximum growth rate is obtained at?{sub?}?{sub?} on the order of unity and is nearly constant for the range of 0.7
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Category : Power resources
Languages : en
Pages : 782
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Author: Hamid Biglari
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Category : Alpha rays
Languages : en
Pages : 8
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Category :
Languages : en
Pages : 19
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We have analyzed theoretically the resonant excitations of kinetic ballooning modes (KBM) by the energetic ions/alpha particles in tokamaks. Our theory includes finite-size orbit effects of both circulating and trapped particles. With energetic-particle contributions suppressed in the singular inertial layer, an analytic.dispersion relation can then be derived via an asymptotic matching analysis. The dispersion relation, in particular, demonstrates the existence of two types of modes; that is, the magnetohydrodynamic (MHD) gap mode and the energetic-particle continuum mode. Specific expressions for real frequencies, growth rates and threshold conditions are also derived for a model slowing-down beam ion distribution function.
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Category :
Languages : en
Pages : 14
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Author: C. Z. Cheng
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ISBN:
Category : Alpha rays
Languages : en
Pages : 36
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