Scenarios for the nonlinear evolution of alpha-particle-induced Alfvén wave instability

Berk, H. L.; Breǐzman, B. N.; Ye, Huanchun

doi:10.1103/physrevlett.68.3563

Cited by 147 publications

(142 citation statements)

References 9 publications

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“…The nonlinear regime The effect of the double-resonance in the nonlinear regime is clearly visible in figure 5 (∆s = 0.2): in the double mode scenario, the modes not only grow faster (in the case of the TAE), but also saturate at a higher level compared to the single mode case (by about a factor of five to ten). This is due to the orbit stochasticization at δB/B ≈ 2 · 10 −3 already discovered in single mode simulations: The stochastic threshold [8] is only reached in the double mode scenario, not in the single mode case. To visualize the effect of stochasticization, an representative particle orbit and the particle's energy evolution before and after the stochasticization sets in is shown in figure 6.…”

Section: Simulation Resultsmentioning

confidence: 75%

“…[8]) predicts that conversion of free energy to wave energy is enhanced in a multiplemode scenario, i.e., the interaction of multiple modes produces energy conversion rates higher than that which would be achieved with each mode acting independently. This can be partially explained by the principle of gradient (of the radial particle distribution) driven mode growth -according to ‡ γ ∝ ∇ f (s) [9] -which can be extended to multiple modes [8,[10][11][12]. This picture of gradient driven doubleresonance is based on the precondition that modes share resonances in the same phase space area.…”

Section: Theoretical Picture Of Double-resonancementioning

confidence: 99%

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Double-resonant fast particle-wave interaction

Schneller¹,

Lauber²,

Brüdgam³

et al. 2012

Nucl. Fusion

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Abstract. In future fusion devices fast particles must be well confined in order to transfer their energy to the background plasma. Magnetohydrodynamic instabilities like Toroidal Alfvén Eigenmodes or core-localized modes such as Beta Induced Alfvén Eigenmodes and Reversed Shear Alfvén Eigenmodes, both driven by fast particles, can lead to significant losses. This is observed in many ASDEX Upgrade discharges. The present study applies the drift-kinetic HAGIS code with the aim of understanding the underlying resonance mechanisms, especially in the presence of multiple modes with different frequencies. Of particular interest is the resonant interaction of particles simultaneously with two different modes, referred to as "doubleresonance". Various mode overlapping scenarios with different q profiles are considered. It is found that, depending on the radial mode distance, double-resonance is able to enhance growth rates as well as mode amplitudes significantly. Surprisingly, no radial mode overlap is necessary for this effect. Quite the contrary is found: small radial mode distances can lead to strong nonlinear mode stabilization of a linearly dominant mode.

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Section: Simulation Resultsmentioning

confidence: 75%

Section: Theoretical Picture Of Double-resonancementioning

confidence: 99%

Double-resonant fast particle-wave interaction

Schneller¹,

Lauber²,

Brüdgam³

et al. 2012

Nucl. Fusion

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show abstract

“…This chirping was seen in particle simulations to be associated with the dynamics of energetic particles and the formation of coherent structures in the phasespace, moving in the momentum direction 3-5 . Such dynamics in phase space have been studied, not only for the bump-on-tail case, but also for various Energetic Particle Modes (EPMs), be it for specific modes such as the Alfvén waves 6 or in a more general way 7 .…”

Section: Introductionmentioning

confidence: 99%

Linear study of the precessional fishbone instability

et al. 2016

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The precessional fishbone instability is an m = n = 1 internal kink mode destabilized by a population of trapped energetic particles. The linear phase of this instability is studied here, analytically and numerically, with a simplified model. This model uses the reduced magneto-hydrodynamics (MHD) equations for the bulk plasma and the Vlasov equation for a population of energetic particles with a radially decreasing density. A threshold condition for the instability is found, as well as a linear growth rate and frequency. It is shown that the mode frequency is given by the precession frequency of the deeply trapped energetic particles at the position of strongest radial gradient. The growth rate is shown to scale with the energetic particle density and particles energy while it is decreased by continuum damping.

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“…Of particular concern in multiple modes case is whether the TAE amplitudes becomes large enough to cause resonance overlap, which can lead to global particle diffusion and energy loss. As shown previously [23], resonance overlap is greatly facilitated by the simultaneous excitation of multiple modes. In the following simulation we use ITER-like parameters: R = 800cm, a = 300cm, B = 6T, Sr = a / 3 .…”

Section: Nonlinear Particle/mhd Hybrid Simulationsmentioning

confidence: 73%

Recent progress in linear and nonlinear studies of toroidal Alfven eigenmode

Fu¹,

Chen²,

Budny³

1997

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DISCLAIMER Portions of this document may be illegiblein electronic image products. Images are produced from the best available original document. AbstractTAE modes studied in linear and nonlinear regimes using several kinetic/MHD hybrid models. It is shown that the stability of TAE mode is largely determined by its radial mode structure. The calculated stability thresholds are correlated well with observations, including the recently observed alpha-driven TAE modes in the TFTR D T experiments. In the nonlinear regime, quasilinear simulations with multiple modes show that the saturation level is enhanced by nonlinear wave-particle resonance overlapping when the linear growth rate exceeds a critical value. A fully self-consistent Sf noise reduction method for the 3D particle/MHD hybrid model is developed.

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Scenarios for the nonlinear evolution of alpha-particle-induced Alfvén wave instability

Cited by 147 publications

References 9 publications

Double-resonant fast particle-wave interaction

Double-resonant fast particle-wave interaction

Linear study of the precessional fishbone instability

Recent progress in linear and nonlinear studies of toroidal Alfven eigenmode

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