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  • 1985-1989  (12)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Magnetic field line ergodicity in the edge plasma due to an ion-Bernstein wave antenna (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1293-1295 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large ponderomotive forces can occur near a high-power ion cyclotron range of frequency antenna, particularly for the parallel electric field polarization used to excite ion-Bernstein waves (IBW). The magnetohydrodynamic (MHD) equilibrium of the edge plasma is modified by these forces when the antenna is highly localized poloidally and toroidally. Magnetic islands develop at the edge, near q=m/n, where ||m||≤πa/wa and ||n||≤πR/la, with wa and la the width and length of the antenna, respectively. Ergodicity of the magnetic field lines may be expected when the islands overlap. Numerical calculations of the island overlap criteria are presented for two examples relevant to present day (IBW) heating experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866760
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Induced azimuthal electric fields in a tandem mirror with throttle coils (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2751-2752 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A tandem mirror with an axisymmetric center cell separated from quadrupole regions by a large mirror ratio throttle coil is considered. Passing particles induce an azimuthal electric field in the center cell that destroys the axisymmetry of the guiding center orbits. It is shown that the resulting neoclassical resonant-plateau transport is small if dielectric resonances can be avoided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865518
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comments on "Bifurcation phenomena and the radial electric field in a nonaxisymmetric plasma'' [Phys. Fluids 29, 536 (1986)] (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2760-2761 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The smallest total collisional entropy production rate technique of choosing among multiple ambipolar roots is contrasted with a linearized stability method in which only the ambipolar potential is perturbed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865522
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Quasilinear theory of the ponderomotive force: Induced stability and transport in axisymmetric mirrors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1895-1905 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A kinetic theory of the ponderomotive force density produced by an electromagnetic cyclotron wave is developed within the quasilinear approximation. The theory is applied to identify the effects of the rf-plasma interaction in equilibrium, stability and transport in paraxial, axisymmetric mirror geometry. The force caused by nonresonant particles is shown to modify the usual magnetohydrodynamic interchange stability drive, and the corresponding arbitrary-m ballooning equation is derived. Resonant particle contributions to the force are shown to arise from the absorption of photon momentum and spin. This effect produces a radial particle flux, modifies the radial ambipolar potential profile, and couples transport and stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864933
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Two- and three-dimensional tokamak equilibrium modifications driven by the localized ponderomotive force of applied radio frequency waves (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1190-1201 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large ponderomotive forces can occur when waves in the ion cyclotron range of frequencies (ICRF) are employed in stabilization or high power heating schemes. It is shown that the magnetohydrodynamic (MHD) equilibrium of the plasma is modified when the rf antenna is localized poloidally and/or toroidally. In the two-dimensional (2-D) problem (toroidally uniform rf) a modified Grad–Shafranov equation describes ponderomotively driven magnetic surface distortions. At electric field strengths of interest for ICRF stabilization, the equilibrium distortions are small provided that Lrf(very-much-less-than)a and the poloidal localization of the rf is not severe. The character of the 3-D problem (toroidally and poloidally varying rf) depends on whether or not the ponderomotive force couples to rational surfaces within the plasma. For the case without rational surfaces, the 3-D component of the distortions is found to be small by 1/q2a relative to the 2-D component. In the case where rational surfaces are excited, magnetic islands result. A threshold condition for island overlap determines the rf electric field at which ergodicity may be expected. It is shown that ergodicity of the edge plasma may occur for some cases of interest for heating and stabilization, but should be controllable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866748
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    A computational study of ion cyclotron frequency stabilization of the m=1 interchange mode in mirror geometry (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 148-159 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A cylindrical plasma model is used to study the stabilizing effect of electromagnetic ion cyclotron frequency range (ICRF) waves on the m=1 magnetohydrodynamic interchange mode. The fast wave eigenmodes of the column and the near-field antenna pattern are calculated numerically for a diffuse plasma profile when ω〉Ωi. The resulting ponderomotive force and sideband contributions to global interchange stability are then determined using a rigid shift trial function. For far-field stabilization it is verified that the direct ponderomotive and sideband contributions cancel exactly as the conducting wall supporting the fast wave eigenmode moves out to infinity. The near-field stabilization effect is related numerically to the driven k(parallel) spectrum of the waves and their radial profiles. The numerical model is employed to calculate threshold ICRF wave amplitudes for the stabilization experiments in the Phaedrus tandem mirror [Phys. Rev. Lett. 51, 1955 (1983)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866163
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: "Stability of mirrors with inverted pressure profiles'' [Phys. Fluids 27, 2256 (1984)] (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 438-438 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865430
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Pressure surface distortion by applied ion cyclotron waves and magnetic field asymmetries (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 149-157 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In magnetic confinement devices the pressure surfaces must obey the parallel current constraint. In a tandem mirror, nonquadrupole magnetic field components or ion cyclotron range of frequencies (ICRF) ponderomotive effects enter the parallel current equation in a nontrivial way. The extra terms cause a shift of the plasma column and/or distortion of the pressure surface shape. These effects are examined for three cases of interest: magnetic error fields due to misaligned coils, axial asymmetries in the quadrupole or solenoidal fields, and azimuthally asymmetric ponderomotive effects associated with applied ICRF waves. The ambipolar potential can compensate for asymmetries and permit lowest order isorrhopic equilibria in some cases, but if the passing density between cells is too small (np/na〈rTa/eΦRc) this cannot occur and the flux surfaces of the cells disconnect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866555
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Comments on "Stability of the radial electric field in a nonaxisymmetric torus'' [Phys. Fluids 27, 1567 (1984)] (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2020-2020 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The validity of a stability argument in which only the ambipolar potential is perturbed to select a suitable solution when multiple ambipolar roots occur is questioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865582
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  • 10
    Electronic Resource
    Electronic Resource
    A quiver-kinetic formulation of radio-frequency heating and confinement in collisional edge plasmas (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1193-1204 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The near fields in the collisional edge plasma of a radio-frequency-heated tokamak can cause one or more charged species to oscillate in the applied field with a quiver (or jitter) speed comparable to its thermal speed. By assuming the quiver motion dominates over drifts and gyromotion a completely new kinetic description of the flows in an edge plasma is formulated that retains Coulomb collisions and the relevant atomic processes. Moment equations are employed to obtain a description in which only a lowest-order quiver-kinetic equation need be solved to evaluate the slow time particle fluxes and current induced by the applied fields. The electron heating by collisional randomization of their quiver motion (inverse bremsstrahlung) is balanced by impact excitation losses since equilibration with the ions is too weak. A model plasma of electrons, neutrals, and a single cold ion species is considered to illustrate the utility of the quiver-kinetic formulation. The model predicts local electrostatic potential changes and a local E×B convective flux that is of the same magnitude and scaling as would be predicted by Bohm diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858995
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    Paper (German National Licenses)
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