Nonlinear Saturation of the Collisional Trapped-Particle Instability

Jablon, C.

doi:10.1103/physrevlett.28.880

Cited by 16 publications

(32 citation statements)

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“…Since proposed operating parameters of PLT, T -10, and future generation tokamaks fall in the regime where the trappedion instability is theoretically predicted to appear, understanding the nonlinear saturation and the concomitant anomalous transport is very important. However, comparatively little research has been done on the nonlinear saturation [9,10,13].…”

Section: ~I T'mentioning

confidence: 99%

“…It is well known that microinstabilities involving magnetically trapped particles [1][2][3][4][5][6][7][8][9][10] represent a potentially serious threat to efficient plasma confinement in toroidal systems.…”

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“…Under these conditions it is predicted that unstable drift waves, called dissipative trapped-ion modes, will be generated. The threat of anomalously large transport [11,12] due to this instability has motivated detailed theoretical study of its linear [1~8] and, to a .lesser extent, its nonlinear [9,10,13] properties. The purpose of this paper is to consider mode-coupling mechanisms for saturation, in much more breadth and detail than previously [10].…”

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confidence: 99%

“…Jablon proposed that electrostatic detrapping of marginally trapped ions can nonlinearly saturate the instability at a fluctuation level low enough to give substantially less transport than the Kadomtsev-Pogutse estimate [9]. LaQuey, Mahajan, Rutherford and Tang (LMRT) [10] considered a slab model first proposed by Kadomtsev and Pogutse [11,12], and demonstrated that the instability can be saturated by the nonlinear E x• ~ coupling of energy from unstable long-wavelength modes to short-wavelength modes which are stabilized by ion Landau damping for sufficiently weak temperature gradients:…”

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Nonlinear saturation of the dissipative trapped-ion mode by mode coupling

Cohen¹,

Krommes²,

Tang³

et al. 1976

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The nonlinear saturation of the dissipative trapped-ion mode is analyzed. . I The basic mechanism considered is the process whereby energy in long wavelength th unstable modes is nonlinearly coupled via E x B convection to short wavelength modes stabilized by Landau damping due to both circulating and trapped ions. In the usual limit of the mode frequency small relative to the effective electron collision frequency, a one-dimensional nonlinear partial differential equation for the potential can be derived, as first shown by LaQuey, Mahajan, Tang, and Rutherford. The stability and accessibility of the possible equilibria for this equation are examined in detail, both analytically and numerically. The equilibrium emphasized by LaQuey et al. is shown to be unstable. However, a class of nonlinear saturated states which are stable to linear perturbations is found. Included in the analysis are the effects of both ion collisions and dispersion due to finite ion bananawidth effects. Cross-field transport is estimated and the scaling of the results is considered for tokamak parameters (specifically those for the'• Princeton Large Torus). It is concluded that the anomalous• cross-field transport can be much lower than the estimate of Kadomtsev and Pogutse, for relevant parameters.

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confidence: 99%

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confidence: 99%

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Nonlinear saturation of the dissipative trapped-ion mode by mode coupling

Cohen¹,

Krommes²,

Tang³

et al. 1976

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“…39 collisionless detrapping mechanism differs from mechanisms considered by earlier authors. [121,122] In this section we clarify those differences.…”

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confidence: 99%