Nonlinear Coupling of Lower-Hybrid Waves at the Edge of Tokamak Plasmas

Krapchev, V.B.; Theilhaber, K.; Ko, Kwang-Cheol; Bers, A.

doi:10.1103/physrevlett.46.1398

Cited by 8 publications

(8 citation statements)

References 10 publications

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“…The density term is A 0 (x) = co p e0 (x)/a> 2 , which is proportional to the ' ' equilibrium density. Equations (3,4) become: dxdz = 0 (10) where Eis the normalized electric field. Finally, we simplify Eqs (10,11) by eliminating E x .…”

Section: Basic Equationsmentioning

confidence: 99%

“…(28) is used by Krapchev et al [10] in thcir treatment of waveguide coupling, but it is assumed in their derivation that 9,(E) = constant. We retain here the E dependence of 9 1 , while ignoring the effect of hannonic generation on the waveguide loading.…”

Section: A Coupling Equationmentioning

confidence: 99%

“…To do this, we must solve the "Nonlinear Klein Gordon Equation", derived by Krapchev and Bers [9]. An analytic treatment of this equation has been given by Krapchev et al [10], but under the assumption that the perpendicular dependence of the density modulation can be neglected. The numerical results of the present paper indicate that this assumption may not be valid.…”

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confidence: 99%

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Non-linear coupling to lower-hybrid waves in a tokamak plasma

Theilhaber

1982

Nucl. Fusion

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AbstmatThe nonlinear coupling of lower hybrid waves excited by a waveguide array is examined numerically and analytically in a model of a Tokamak plasma. The nonlinearity considered is the ponderomotive force and the fields are evolved self-consistently in time to the steady-state. Simplified coupling models are derived for the loading of large and small arrays and for different phasings of the waveguides. It is found that the reflection coefficient can be modified considerably by the nonlinear effects. It is also found that the nonlinear modification of the power spectrum is especially large when the array excites two resonance cones. The fields filament and the spectrum is broadened and upshifted. The travelling-wave excitation, which excites a single resonance cone and is considered for current drive, is less affected nonlinearly; the fields do not filament and the spectrum remains narrow.

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Section: Basic Equationsmentioning

confidence: 99%

Section: A Coupling Equationmentioning

confidence: 99%

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confidence: 99%

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Non-linear coupling to lower-hybrid waves in a tokamak plasma

Theilhaber

1982

Nucl. Fusion

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“…Secondly, non-linear effects in the edge plasma, due to pondermotive forces [9], can modify the plasma dynamics and hence the coupling problem. Much attention has been given to this recently for coupling in the LHRF [10][11][12][13].…”

Section: Summary and Discussionmentioning

confidence: 99%

“…2, the waveguide transverse electric and magnetic fields at x = 0 must match onto the plasma fields, i.e. and (12) Using Eqs (1), ( 2), ( 8), (9), and (10), we can write expressions (11) and ( 12) as…”

Section: The Waveguide-plasma Couplingmentioning

confidence: 99%

Three-dimensional theory of waveguide-plasma coupling

Bers

Theilhaber

1983

Nucl. Fusion

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ABSTRACT. A general, linear theory of coupling electromagnetic fields from free-space waveguide arrays to an inhomogeneous plasma in a magnetic field is presented. In contrast to previous analyses, which assumed parallel-plate waveguides, waveguides having closed cross-sections of arbitrary shape are considered; full account is taken of all the waveguide modes. Far away from the coupling region, the plasma is assumed to be absorptive and the waveguides to propagate only their dominant modes. The formulation is geared to obtain the reflection coefficients in the waveguides and the excitation of waves in the plasma. The results are applicable to RF heating of plasmas whose size is large compared to the waveguide array, as would be the case in a fusion reactor, and valid for the frequency regimes of either ion-cyclotron (harmonic), or lower-hybrid, or electron-cyclotron (harmonic) heating.

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