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  • 1
    Electronic Resource
    Electronic Resource
    Calculations of wave excitation and dissipation in Tokamak Chauffage Alfvén wave heating experiment in Brazil (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2437-2442 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of numerical calculations of Alfvén wave absorption are discussed for the experimental conditions foreseen for the Tokamak Chauffage Alfvén wave heating experiment in Brazil (TCABR) [Nucl. Fusion 30, 503 (1996)]. In particular, the effect of toroidal mode coupling on the power deposition of Global Alfvén Wave (GAW) eigenmodes is carefully investigated. Resonant absorption of the toroidally coupled sidebands causes a broad power deposition close to the plasma boundary which can surpass the power deposition of the main GAW at the plasma center. However, the wave absorption can be somewhat optimized by a proper choice of mode spectrum. The excitation of a pure mode spectrum centered at the toroidal mode numbers n=−4 and −6 leads to better plasma coupling than a spectrum centered at n=−2. Finally, it is shown that a small population of light impurities in a hydrogen plasma can strongly modify the dispersion of the GAW and the toroidal Alfvén continuum.© 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873515
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  • 2
    Electronic Resource
    Electronic Resource
    Anomalous electron precipitation near the Earth's auroral zone induced by the wave–particle interaction (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2269-2275 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of a numerical simulation of anomalous electron precipitation in the Earth's auroral zone induced by waves are discussed. In order to study the plasma electron–wave interaction, a two-dimensional quasilinear code has been used. A quasilinear operator models the electron Landau damping of any plasma eigenmodes: kinetic Alfvén waves, whistlers, lower hybrid waves, etc. The distribution function structure was analyzed. The electron current induced by waves, the density, and the plasma energy decay, which stimulates the electron precipitation, have also been investigated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872390
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  • 3
    Electronic Resource
    Electronic Resource
    Alfvén ion–ion hybrid wave heating in the Phaedrus-T tokamak (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1331-1339 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the Phaedrus-T tokamak [R. A. Breun et al., Fusion Technol. 19, 1327 (1991)], Alfvén waves are indirectly driven by a fast wave antenna array. Small fractions of minority ions are shown to have a large effect on the Alfvén spectrum, as measured at the edge. An ion–ion hybrid Alfvén mode has been identified by measuring dispersion properties. Landau damping is predicted to be large and spatially localized. These Alfvénic waves are experimentally shown to generate correlated electron heating and changes in density near the core of the tokamak plasma. Fast wave antenna fields can mode convert at a hybrid Alfvén resonance and provide a promising route to spatially localized tokamak heating and current drive, even for low effective ionic charge Zeff≈1.3–2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871786
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of trapped electrons on the dielectric properties of the Earth's radiation belts (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3798-3808 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric tensor of an axisymmetric magnetosphere is derived by solving the Vlasov equations for trapped particles for a two-dimensional plasma model with circular magnetic field lines. Because of the nonuniformity of the geomagnetic field any Fourier harmonic of the perturbed current density (after its Fourier expansion over the geomagnetic latitude) is proportional to the sum over all harmonics of the oscillating electric field; that leads to additional wave dissipation effects. The resonant conditions for wave–particle interactions are discussed taking into account the cyclotron and bounce resonances; these conditions in magnetospheric plasmas are entirely different from the Landau damping resonant factor in the uniform magnetic field. The numerical calculations of the longitudinal permeability in the Earth's radiation belts (the equatorial distance of the magnetic field line is five Earth's radii) are carried out for short-period oscillations with the frequency ω∼2 s−1 and longitudinal wave numbers n=1,...,15. The different energy levels of the trapped electrons, T∼40–4000 eV, are considered. It is shown that, in the low-frequency region, the imaginary part of the longitudinal permeability decreases as ∼T−2.5 whereas the electron temperature increases. This decrease is stronger than ∼T−1.5 for plasmas in a straight magnetic field. For a given wave frequency, the basic contribution of trapped electrons to the imaginary part of longitudinal permeability is associated with the low numbers of bounce resonances and the low longitudinal wave numbers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871512
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  • 5
    Electronic Resource
    Electronic Resource
    Alfvén wave current drive in the Phaedrus-T tokamak (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2263-2271 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first experimental evidence of Alfvén Wave Current Drive (AWCD) in a tokamak is shown. In a low-density experiment, an estimated 20–35 kA out of 65 kA total current, or 30%–55% of the total current has been driven. The estimated efficiency for current driven per unit RF input power is approximately ICD/PRF≈0.2 A/W, which is near the predicted efficiency, and corresponds to the commonly used figure of merit, neR0ICD/PRF≈0.4×1018 A m−2 W−1, where ne is plasma density and R0 is the major radius. The significant 30%–40% drop in loop voltage observed cannot be explained by any plausible increase in electron temperature Te, or decrease in inductive plasma energy, or changes in plasma resistivity. Independently measured loop voltage, Te, effective ionic charge Zeff, and plasma inductance and resistance are all consistent with this conclusion. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871249
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  • 6
    Electronic Resource
    Electronic Resource
    Anomalous and neoclassical transport suppression by the radial electric field, induced by Alfvén waves in tokamaks (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3548-3553 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The suppression of anomalous transport and/or reduction of neoclassical transport caused by the Alfvén-wave-induced shear of the radial electric field in tokamaks is investigated. The simple quantitative estimates reported in previous papers are checked by a consistent evaluation of the profile of the radial electric field created by the resonant absorption of Alfvén waves. The radial variations of the ion viscosity and heat conductivity across the mode conversion layer are evaluated both in the banana and potato regions. In agreement with previous analytical results, it is shown that the kinetic Alfvén waves may play the role of a convenient mechanism for reduction of anomalous and neoclassical transport and formation of transport barriers in tokamaks. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873615
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  • 7
    Electronic Resource
    Electronic Resource
    Alfvén and fast wave forces, affecting ions in magnetic traps with closed magnetic surfaces (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1378-1381 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: General expressions for time- and surface-averaged radio frequency forces, affecting ions in closed toroidal devices, are obtained in this paper. Toroidal effects are included in these forces. These effects can, for example, be important to calculate Alfvén or fast wave forces in stellarators, spheromaks, or for toroidicity induced Alfvén wave eigenmodes (TAE) in axially symmetric tokamaks. The further simplification of obtained expressions should be fulfilled for the proper kind of rf waves and toroidal devices. It is hoped that these rf force expressions can, for example, be useful for the computer simulations of the transport barrier formation by Alfvén and fast waves in toroidal devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873377
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  • 8
    Electronic Resource
    Electronic Resource
    Discrete spectrum of Alfvén ion–ion hybrid waves (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1054-1063 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the Phaedrus-T tokamak [R. Majeski et al., Phys Fluids B 5, 2506 (1993)], Alfvén waves are indirectly driven by a fast wave antenna array. Small fractions of minority ions can couple Alfvén and ion–ion hybrid waves and have a large effect on the wave numbers accessible for a given launched frequency. A discrete spectrum and toroidal damping for these modes has been identified by measuring dispersion properties at the edge. Landau damping is predicted to be large and spatially localized and to be responsible for the experimentally observed electron heating (T. Intrator et al., "Alfvén ion–ion hybrid wave heating in the Phaedrus-T tokamak,'' to appear in Phys. Plasmas) and current drive near the core of the tokamak plasmas. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871761
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrodynamic description of Alfvén and fast wave current drive in weakly collisional plasmas of magnetic traps (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2784-2789 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, general aspects of the Alfvén and fast wave nonresonant and resonant current-drive problem are considered both for collisional and weakly collisional plasmas. The magnetohydrodynamic approach is used for all collisional regimes and Landau damping is taken into account in the weakly collisional plasma case. Averaged in time and over magnetic surface, the general form of current-drive forces are derived, including the viscosity and collision frequency perturbation terms. As an example, a weakly collisional plasma cylinder case is discussed and some disagreements on this problem between different authors results are eliminated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871176
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  • 10
    Electronic Resource
    Electronic Resource
    The Coulomb scattering effect on trapped particles bounce-resonance dissipation in magnetized toroidal plasmas (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1547-1553 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The solution of the Vlasov equation with a simplified Fokker–Planck collision operator is presented for axially symmetric tokamak plasmas with a circular cross section of magnetic surfaces. The analytical expression for the parallel component of the dielectric permittivity tensor of trapped particles is obtained. This expression is used for theoretical analyses of the collision effect on the bounce-resonance wave dissipation. Conditions for a collisionless description of radio-frequency (rf) oscillations are found. This dielectric tensor components can be used for computer calculations of the rf field structure and the rf dissipated power related to trapped electrons in tokamak plasmas. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873408
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