Fishbone Instability Excited by Barely Trapped Electrons

Wang, Zhongtian; Yong-Xing, Long; Dong, J. Q.; Long, Wang; Zonca, F.

doi:10.1088/0256-307x/23/1/046

Cited by 13 publications

(1 citation statement)

References 8 publications

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“…11 and 12) with LHW injection. Some authors have proposed several theoretical models: the dominant notion proposed by Wong et al, 9 Zonca et al, 8 and Wang et al [13][14][15][16][17] is that the ideal kink mode resonates with barely trapped energetic electrons for they spend longer time on the high field side, resulting in their precessional direction reversing to the same as that of energetic ions.…”

Section: Introductionmentioning

confidence: 99%

Nonideal fishbone instability excited by trapped energetic electrons

2013

Physics of Plasmas

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It is shown that trapped energetic electrons can resonate with the collisionless m ¼ 1 nonideal kink mode, therefore exciting the nonideal e-fishbone, which would often lead to a drop in soft x-ray emissivity and frequency chirping. The theory predictions agree well with the experimental observations of e-fishbone on HL-2A. It is also found that the effects of MHD energy of background plasma might be the reason for the observed phenomena: frequency chirping up and down, and V-font-style sweeping. V C 2013 American Institute of Physics.

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Section: Introductionmentioning

confidence: 99%

Nonideal fishbone instability excited by trapped energetic electrons

2013

Physics of Plasmas

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Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure

Delgado‐Aparicio

Sugiyama²,

Shiraiwa

et al. 2015

Phys. Plasmas

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New experimental observations are reported on the structure and dynamics of short-lived periodic (1, 1) "fishbone"-like oscillations that appear during radio frequency heating and current-drive experiments in tokamak plasmas. For the first time, measurements can directly relate changes in the high energy electrons to the mode onset, saturation, and damping. In the relatively high collisionality of Alcator C-Mod with lower hybrid current drive, the instability appears to be destabilized by the non-resonant suprathermal electron pressure -rather than by wave-particle resonance, rotates toroidally with the plasma and grows independently of the (1, 1) sawtooth crash driven by the thermal plasma pressure. The economic feasibility of a fusion reactor can be measured in terms of β ≡ p/ B 2 /2µ 0 , where p is the plasma pressure and B 2 /2µ 0 is the magnetic field energy density. The presence of magnetohydrodynamic (MHD) instabilities can distort the orbits of fast ions and electrons compared to the equilibrium, causing an off-axis redistribution of the fusion heating and current density to the detriment of the central β, reducing the fusion power and the production of fast neutrons for tritium breeding. Therefore, understanding the stability and behavior of 3D helical modes in the core of an axisymmetric toroidal configuration remains one of the challenges of fusion research 1-6 . It is doubly significant for burning plasmas such as ITER, where the q = 1 radius that bounds these instabilities may reach half the minor radius.A helical internal kink-like mode 7-9 with dominant poloidal and toroidal mode numbers m = 1, n = 1 has recently been observed in the Alcator C-Mod tokamak 10

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Electron fishbones: theory and experimental evidence

et al. 2007

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We discuss the processes underlying the excitation of fishbone-like internal kink instabilities driven by supra-thermal electrons generated experimentally by different means: Electron Cyclotron Resonance Heating (ECRH) and by Lower Hybrid (LH) power injection. The peculiarity and interest of exciting these electron fishbones by ECRH only or by LH only is also analyzed. Not only the mode stability is explained, but also the transition between steady state nonlinear oscillations to bursting (almost regular) pulsations, as observed in FTU, is interpreted in terms of the LH power input. These results are directly relevant to the investigation of trapped alpha particle interactions with low-frequency MHD modes in burning plasmas: in fact, alpha particles in reactor relevant conditions are characterized by small dimensionless orbits, similarly to electrons; the trapped particle bounce averaged dynamics, meanwhile, depends on energy and not mass.

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Fishbone Instability Excited by Barely Trapped Electrons

Cited by 13 publications

References 8 publications

Nonideal fishbone instability excited by trapped energetic electrons

Nonideal fishbone instability excited by trapped energetic electrons

Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure

Electron fishbones: theory and experimental evidence

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