Energetic Particle Stabilization of Ballooning Modes in Tokamaks

A theory describing the influence of energetic trapped particles on resistive interchange-ballooning modes in tokamaks is pre sented. It is shown that a population of hot particles trapped in the region of adverse curvature can resonantly interact with and destabilize the resistive interchange mode, which is stable in their absence because of favorable average curvature. The mode is different from the usual resistive interchange mode not only in its destabilization mechanism, but also in that it has a real component to its frequency comparable to the precessional drift frequency of the rapidly circulating energetic species. Corre sponding growth rate and threshold conditions for this trappedparticle-driven instability are derived and finite banana width effects are shown to have a stabilizing effect on the mode. Fi nally, the ballooning/tearing dispersion relation is generalized to include hot particles, so that both the ideal and the resistive .modes are derivable in the appropriate limits.

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“…It is for this reason that the hot particle stabilization scheme of Rosenbluth et a/. 7 cannot be recovered from this theory.…”

Section: U)-(;i)»-*» + (I)'mentioning

confidence: 93%

“…It will be seen that this 0 ordering will make the Rosehbluth et aJ. 7 stabilization scheme inaccessible from the point of view of this theory. We further assume very low density energetic particles, i.e., we take n k /n e ~ 0(£ 3 ) which, taken together with /?*//?,.…”

Section: A ~ O(j) < (And);r ~ O(o mentioning

confidence: 99%

Theory of energetic trapped particle-induced resistive interchange-ballooning modes

Biglari

Chen

1986

The Physics of Fluids

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“…Recalling that 6W C ~ 0{e^) ~ 10" 3 , we see that the resis tive contribution becomes comparable in magnitude to it for S.w Js 10 7 . Thus, the resistive correction to the ideal dispersion relation affects the growth rate only as an effective bW and this contribution is a stabilizing one.…”

mentioning

confidence: 99%

“…The conclusion is that even though energetic particles, at least at high 0 (where /? is the ratio of kinetic to magnetic pressure) and undergoing rapid precessional motion, can have a stabilizing influence on normal MHD modes when the mode frequency is strongly off-resonant with the hot particle precessional drift frequency 3 (i.e., w <£ wjf, = -JVjft-V, where v dh is the magnetic drift velocity), they become destabilizing when the wave structure starts to resonate with the precessional drift motion of the hot particle banana center (u c= <*>dh}-While the theory has been successful in explaining experimental observa tions, several issues remain. One is the validity of employing an ideal MHD description for the core plasma.…”

mentioning

confidence: 99%

Influence of resistivity on energetic trapped particle-induced internal kink modes

Biglari

Chen

1986

The Physics of Fluids

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The influence of resistivity on energetic trapped particle-induced internal kink modes, dubbed ‘‘fishbones’’ in the literature, is explored. A general dispersion relation, which recovers the ideal theory in its appropriate limit, is derived and analyzed. An important implication of the theory for present generation fusion devices such as the Joint European Torus [Plasma Physics and Controlled Nuclear Fusion Research (IAEA, London, 1984), Vol I, p.11] is that they will be stable to fishbone activity.

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“…For CT = -, Eq. (10) corresponds to the case studied by Rosenbluth et al [16]. For simplicity we let £ c = 0. nh(v)£b -oihPcCv).…”

Section: Effects Of Neutral-beam-injected Particles On the N=1 Internmentioning

confidence: 99%

Energetic particle effects on global MHD modes

Cheng¹

1990

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The effects of energetic particles on MHD type modes are studied by analytical theories and the nonvariational kinetic-MHD stability code (NOVA-K). In particular we address the problems of (1) the stabilization of ideal MHD internal kink modes and the excitation of resonant "fishbone" internal modes and (2) the alpha particle destabilization of toroidicityinduced Alfven eigenmodes (TAE) via transit resonances. Analytical theories are presented to help explaining the NOVA-K resufts.For energetic trapped particles generated by neutral-beam injection (NBI) or ion cyclotron resonant heating (ICRH), a stability window for the n*1 internal kink mode in the hot particle beta space exists even in the absence of core ion finite Larmor radius effect (finite to.i).On the other hand, the trapped alpha particles are found to resonantly excite instability of the n«1 internal mode and can lower the critical beta threshold. The circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha particlo pressure. 'This paper is presented as an invited talk at the Thirty-First Annual

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Energetic Particle Stabilization of Ballooning Modes in Tokamaks

Cited by 109 publications

References 11 publications

Theory of energetic trapped particle-induced resistive interchange-ballooning modes

Theory of energetic trapped particle-induced resistive interchange-ballooning modes

Influence of resistivity on energetic trapped particle-induced internal kink modes

Energetic particle effects on global MHD modes

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