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  • 1
    Electronic Resource
    Electronic Resource
    Instability of an expanding charged-particle beam (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7682-7689 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that a uniform collisionless charged-particle beam expanding under the influence of electrostatic and internal pressure forces is linearly unstable. The instability, which tends to cause spreading and change the radial profile of the beam, implies a limit on the achievable focusing even when the lens system corrects for expansion. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357941
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  • 2
    Electronic Resource
    Electronic Resource
    High-frequency electrostatic modes in non-neutral plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1398-1403 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fluid description is employed to derive the dispersion relation for cyclotron modes in a cylindrical non-neutral plasma of radius R confined by a uniform magnetic field B=B0ez inside a chamber with conducting walls of radius R0. In contrast to the theory of Gould and LaPointe [Phys. Rev. Lett. 67, 3685 (1991); Phys. Fluids B 4, 2038 (1992)] the model includes the diamagnetic drift but omits finite Larmor radius effects. The density and the temperature of the unperturbed state are taken to be n(r)=n0(1−r2/R2) and T(r)=T0(1−r2/R2)γ−1, where γ is the adiabatic index, so that the r-dependent slow rotation frequency is ωr≈−[δ(1−r2/2R2)+ε(1−r2/R2)γ−2]Ω/2, where Ω=qB0/Mc is the ion gyrofrequency, δ=4πn0q2/MΩ2, and ε=4γT0/MΩ2R2. For the linearized fluid equations together with the Poisson equation the eigenvalue problem is solved in the limit δ(very-much-less-than)1, ε(very-much-less-than)1. The eigenfrequencies for high-frequency electrostatic modes with wave vectors satisfying k⋅B=0 (Bernstein modes) are found in the form ω=−Ω+Δω, where Δω/Ω contains terms proportional to δ and ε. Solutions are obtained and compared with experiment and the theory of Gould and LaPointe. The present theory predicts that at a given T0 modes with m(approximately-greater-than)1 propagate only when the density is less than a critical value that increases with m, and that Δω normalized by the diocotron frequency depends only on the ratio of the Debye length to the plasma radius and hence is independent of B and M. The predictions of the two theories differ in several other respects; future observations may serve to decide between them. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871460
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  • 3
    Electronic Resource
    Electronic Resource
    Suppression of the Rayleigh–Taylor instability through accretion (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 354-359 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear growth of the Rayleigh–Taylor instability in an accelerated shell can be reduced by arranging for the shell to sweep up material as it moves. Momentum conservation preferentially slows the thinner "bubble'' portions of the perturbed shell, which lead the "spikes.'' Results are presented from calculations based on the spherical thin-shell model. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871859
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  • 4
    Electronic Resource
    Electronic Resource
    Extensions and applications of the Bogema–Davidson inversion theorem (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2090-2094 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For a single particle species confined by a uniform magnetic field B, the Bogema–Davidson inversion theorem determines a self-consistent rigid-rotor equilibrium distribution function F(H⊥−ωrPθ) as the derivative of the given radial density profile n(r) with respect to the corresponding generalized potential ψ(r). Aside from the quadratic density profile, most forms one can choose for n(r), even if integrable, yield potentials ψ(r) that cannot be inverted. The function F can be found parametrically, however, by writing the derivative of n with respect to ψ as the ratio of the radial derivatives of n and ψ. Several nontrivial examples of physical interest are studied. Numerical methods for calculating F are presented, its asymptotic form and integration are investigated, and applications to experiment are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872375
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  • 5
    Electronic Resource
    Electronic Resource
    Linearized geometrical-dynamics treatment of the stability of converging shocks (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 635-637 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The approximation of geometrical shock dynamics has been used to study the stability of radially converging shocks of arbitrary initial strength. The equations of motion are linearized about the symmetric solution, using the shock Mach number as the independent variable, and solved numerically. Perturbations with angular dependence given by pure cylindrical (in two-dimensional) or spherical (in three-dimensional) harmonics exhibit damped oscillatory behavior for all but the lowest mode numbers. Relative to the decreasing shock radius R, however, they grow without bound. The solutions can be approximated by hypergeometric functions. The limiting behavior as R→0 is found using the asymptotic properties of the latter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857714
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  • 6
    Electronic Resource
    Electronic Resource
    Variation in the amplitude of perturbations on the inner surface of an imploding shell during the coasting phase (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 367-376 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In some inertial confinement fusion target designs a spherical shell collapses on a void or compresses a small amount of gaseous material. There can be a period during which both the outside (driver) pressure and the inside pressure have a negligible effect on the implosion dynamics, and the motion is essentially ballistic. The changes in the aspect ratio occur mainly because of geometrical convergence. For reasonable parameters the inner surface does not begin to decelerate until shortly before convergence is complete. An approximate description of this "coasting'' phase has been developed and applied to study the evolution of perturbations on the inner and outer surfaces of the shell in the limit where the fluid is incompressible. The two surfaces are strongly coupled as long as the shell remains thin. When the shell becomes thick compared to the inner radius, the inner and outer surface perturbations decouple. Under these conditions the surface wave action is a good adiabatic invariant, which can be used to estimate the change in the amplitude of a perturbation as a function of the shell inner radius R1. Detailed analysis confirms the adiabatic invariance argument and extends the results. The adiabatic invariant may also be applicable in the case of compressible fluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866387
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  • 7
    Electronic Resource
    Electronic Resource
    Disproof of a conjectured inequality arising in the theory of magnetic flux diffusion (1989)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 2947-2950 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The conjecture that the magnetic field energy introduced into an imperfectly conducting medium by diffusion is less than the thermal energy produced by the associated Joule heating is shown to imply the positivity of a certain integral operator with an indefinite kernel. Counterexamples are found by means of a variational calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528482
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  • 8
    Electronic Resource
    Electronic Resource
    Quantifying residual numerical diffusion in flux-corrected transport algorithms (1991)
    Springer
    Journal of scientific computing 6 (1991), S. 323-343 
    Details
    ISSN: 1573-7691
    Keywords: Numerical diffusion ; flux corrected transport ; antidiffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Residual diffusion in fluid-dynamics calculations results from the finite order of approximation in the underlying linear algorithm, including the effect of smoothing sometimes added for numerical reasons, and, in the case of monotonicity-preserving algorithms such as flux-corrected transport (FCT), the nonlinear action of the flux limiter on steep profiles. Some widely used FCT algorithms contain a multiplicative constant that reduces the antidiffusion coefficient by ∼0.01%–0.1%. Replacing this constant with a smoothly varying function of velocity which equals unity when the Courant number vanishes causes the linear diffusion to go to zero when the flow velocity does. The use of a velocity-dependent antidiffusion coefficient minimizes numerical smearing of discontinuities and associated effects in the neighboring flow. Computational examples are presented. The residual diffusion for nonzero flow speeds is nonlinear and problem dependent. A method is presented for calibrating it in any given code in the context of a particular problem, and is applied to the FCT algorithms described here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01062816
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  • 9
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    Reconnecting reconnection with its current roots (2018)
    American Institute of Physics
    Details
    Publication Date: 2018-03-01
    Print ISSN: 0031-9228
    Electronic ISSN: 1945-0699
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Acoustic Amplification in Imploding Spherical Shells (1978)
    American Physical Society
    Details
    Publication Date: 1978-11-27
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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