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  • 1
    Electronic Resource
    Electronic Resource
    Collisionless m=1 reconnection in tokamaks (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2411-2422 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In high temperature tokamak regimes, the m=1 reconnecting mode is governed by two fluid effects associated with the electron skin-depth de=c/ωpe and the ion sound radius ρs=cs/Ωci. To clarify the early nonlinear dynamics of this mode, numerical simulations of a two fluid model are presented. To simulate physically reasonable parameters in a tokamak geometry, an efficient approach is used in which only a narrow layer surrounding the q=1 surface and m=1 magnetic island must be simulated. In the usual tokamak case ρs(approximately-greater-than)de, as well as the limit ρs=0, the early nonlinear growth of the mode is faster than exponential due a broadening of the flow layer. This broadening appears to result from tension in the magnetic field lines, which acts to pull the layer open as the island grows. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871925
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  • 2
    Electronic Resource
    Electronic Resource
    Electron temperature gradient driven turbulence : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1904-1910 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Collisionless electron-temperature-gradient-driven (ETG) turbulence in toroidal geometry is studied via nonlinear numerical simulations. To this aim, two massively parallel, fully gyrokinetic Vlasov codes are used, both including electromagnetic effects. Somewhat surprisingly, and unlike in the analogous case of ion-temperature-gradient-driven (ITG) turbulence, we find that the turbulent electron heat flux is significantly underpredicted by simple mixing length estimates in a certain parameter regime (s(circumflex)∼1, low α). This observation is directly linked to the presence of radially highly elongated vortices ("streamers") which lead to very effective cross-field transport. The simulations therefore indicate that ETG turbulence is likely to be relevant to magnetic confinement fusion experiments. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874014
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  • 3
    Electronic Resource
    Electronic Resource
    Diamagnetic stabilization of ideal ballooning modes in the edge pedestal (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2797-2801 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of the tokamak edge pedestal to ballooning modes is addressed using three-dimensional simulations of the Braginskii equations and simple analytic models. The effects of ion diamagnetic drift and the finite radial localization of the pedestal pressure gradient are found to be strongly stabilizing when δ〈δR, where δ is the pedestal half-width and δR∼ρi2/3R1/3 in the center of the pedestal. In this limit, conventional ballooning modes within the pedestal region become stable, and a stability condition is obtained in the two fluid system α/αc〈(4/3)δR/δ (stable) which is much less stringent than that predicted by local magnetohydrodynamic (MHD) theory (α/αc〈1). Given α∼q2Rβ/δ, this condition implies a stability limit on the pedestal β: β〈βc, where βc=(4αc/3q2)δR/R. This limit is due the onset of an ideal pressure driven "surface" instability that depends only on the pressure drop across the pedestal. Near marginal conditions, this mode has a poloidal wavenumber kθ∼1/δR, a radial envelope ∼δR(〉δ), and real frequency ω∼cs/δRR. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873237
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  • 4
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Collisionless m=1 reconnection in tokamaks' " [Phys. Plasmas 3, 2411 (1996)] (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1175-1175 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Our numerical simulation of collisionless m = 1 reconnection in tokamaks do not support the Wang and Bhattacharjee theory of explosive growth of plasma instabilities. We disagree with their assumptions link-ing the poloidal flow to the plasma pressure. (AIP) © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872216
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  • 5
    Electronic Resource
    Electronic Resource
    Nonlinear ω*-stabilization of the m=1 mode in tokamaks (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3420-3428 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Earlier studies of sawtooth oscillations in Tokamak Fusion Test Reactor (TFTR) supershots [Levinton et al., Phys. Rev. Lett. 72, 2895 (1994); Zakharov et al., "Onset and stabilization of sawtooth oscillations in tokamaks,'' in Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 15th International Conference, Seville, 1994 (International Atomic Energy Agency, Vienna, in press)] have found an apparent contradiction between conventional linear theory and experiment: even in sawtooth-free discharges, the theory typically predicts instability due to a nearly ideal m=1 mode. Here, the nonlinear evolution of such mode is analyzed using numerical simulations of a two-fluid magnetohydrodynamic (MHD) model. We find the mode saturates nonlinearly at a small amplitude provided the ion and electron drift-frequencies ω*i,e are somewhat above the linear stability threshold of the collisionless m=1 reconnecting mode. The comparison of the simulation results to m=1 mode activity in TFTR suggests additional, stabilizing effects outside the present model are also important. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871124
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  • 6
    Electronic Resource
    Electronic Resource
    A method for production of cheap, reliable Pt–Ir tips (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1702-1705 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method of producing Pt–Ir tips for use in scanning tunneling microscopy is described. This reproducible method is simple, cheap, fast, and avoids the use of hazardous chemicals common in many other methods. Scanning electron microscopy, time of flight–secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy have been applied to understand both the chemical and morphological changes that occur as a result of the etching. The method has been demonstrated on both stock Pt–Ir wire and commercial tips and has been found to dramatically enhance image quality. It is also reusable on the same tip extending the lifetime of a single tip indefinitely. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150523
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  • 7
    Electronic Resource
    Electronic Resource
    Rubber as Lining for Grinding Mills1: Solution of a Long-Standing Problem of Chemical Grinding (1927)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 19 (1927), S. 139-141 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50205a046
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  • 8
    Electronic Resource
    Electronic Resource
    The Effect of Photoperiod on Androgen-Binding Protein and Sperm Fertilizing Ability in the Hamster (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 513 (1987), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1987.tb25069.x
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  • 9
    Electronic Resource
    Electronic Resource
    Two-fluid magnetohydrodynamic description of the internal kink mode in tokamaks (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3285-3301 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The two-fluid linear magnetohydrodynamic (MHD) theory of the internal kink mode is studied in finite β regimes relevant to recent high-temperature tokamak experiments. It is found that the scale length of the plasma motion decouples due to the Hall term from the scale length of the current layer and becomes the "ion-sound Larmor radius'' ρs=cs/Ωci, where cs=(square root of)(Te+γiTi)/mi is the ion-sound speed (γi=5/3 for adiabatic ions), and Ωci is the ion-cyclotron frequency. The predictions of two-fluid MHD for the m=1 reconnection mode are shown to be in good quantitative agreement with analogous results of kinetic studies. An important nonlinear consequence of this relatively large scale length for the plasma motion is that the reconnection time in Kadomtsev's model becomes τ = τ*Aa1/1/ρs∝ a1/1R(square root of)n/[(1 − q0)(square root of)Te+(5/3)Ti], which seems able to account for the fast sawtooth crash.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860384
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  • 10
    Electronic Resource
    Electronic Resource
    The theory of the early nonlinear stage of m=1 reconnection in tokamaksf| (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2498-2505 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The theory of the early nonlinear stage of reconnection, when the plasma central core displacement ξ0 is still small with respect to the q=1 radius r1 but exceeds the characteristic width of the singular layer, is considered. The two-dimensional magnetic geometry of m=1 reconnection is determined by solving Waelbroeck's equations [Phys. Fluids B 1, 2372 (1989)]. Fast nonlinear exponential growth of the mode in contemporary high-temperature experiments is explained on the basis of the nonlinear two-fluid magnetohydrodynamic theory. It is shown that the stabilization of the reconnecting m=1 mode by ω*-effects is in qualitative agreement with experimental observations. A nonlinear cancellation of the ω*-stabilization is proposed as explanation of the triggering of the sawtooth crash.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860735
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