Expansion of parameter space for toroidal Alfven eigenmode experiments in TFTR

Wong, K. L.; Wilson, J. R.; Chang, Z.; Fu, G. Y.; Fredrickson, E.; Hammett, G. W.; Bush, C. E.; Phillips, C. K.; Snipes, J. A.; Taylor, G.

doi:10.1088/0741-3335/36/5/009

Cited by 49 publications

(28 citation statements)

References 22 publications

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“…On the other hand, ICRH-driven modes in the Alfvén frequency range, similar to those observed in [4,7], show predominantly the first three types of mode evolution on TFTR [15], JT-60U [16], DIII-D [17], and C-MOD [18]. Taking into account that the distribution function of NBIproduced ions establishes itself due to electron dynamical friction (also called drag and slowing down) [19], while the distribution function of ICRH-accelerated ions [20] is formed via a quasilinear diffusive process, a comparison between dynamical friction and velocity-space diffusion becomes an important issue for kinetic instabilities.…”

supporting

confidence: 63%

Destabilizing Effect of Dynamical Friction on Fast-Particle-Driven Waves in a Near-Threshold Nonlinear Regime

2009

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The nonlinear evolution of waves excited by the resonant interaction with energetic particles, just above the instability threshold, is shown to depend on the type of relaxation process that restores the unstable distribution function. When dynamical friction dominates over diffusion in the phase space region surrounding the wave-particle resonance, an explosive evolution of the wave is found to be the only solution. This is in contrast with the case of dominant diffusion when the wave may exhibit steady-state, amplitude modulation, chaotic and explosive regimes near marginal stability. The experimentally observed differences between Alfvénic instabilities driven by neutral beam injection and those driven by ion-cyclotron resonance heating are interpreted.

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supporting

confidence: 63%

Destabilizing Effect of Dynamical Friction on Fast-Particle-Driven Waves in a Near-Threshold Nonlinear Regime

2009

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“…There are typically two distinct groups of modes detected in the AlfvŽn range of frequencies, one which displays the characteristic density (n e ) -1/2 dependence of the Toroidal AlfvŽn Eigenmodes (TAE) [7], the other characterized by a chirping frequency [8] (Figure 2). …”

Section: Alfvƒn Instabilitiesmentioning

confidence: 99%

Role of Alfv?n Instabilities in Energetic Ion Transport

Bell¹,

Bernabei²,

Budny³

et al. 1998

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Experiments of plasma heating at the ion cyclotron resonance of a minority specie have shown that the heating efficiency degrades above a certain power threshold. It is found that this threshold is due to the destabilization of a branch of shear AlfvŽn waves which causes a diffusive loss of fast ions, the Energetic Particle Modes. These modes not only play a fundamental role in the transport of the fast ions, but appear closely related to the formation of the giant sawteeth.

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“…Figure 2 shows the frequency spectrum of the mode compared with the TAE modes driven by the energetic tail ions in the ICRF-heated plasmas [6]. The frequency band width of the AFM is typically about EiOkHz, while a single n (the toroidal mode number) TAE mode has a width 5 1 kHz.…”

Section: Characteristics Of the Alfvkn-f'requency-modementioning

confidence: 99%